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3222 3223 3224 3225 3226 3227 | <?xml version="1.0"?>
<!DOCTYPE gsdoc PUBLIC "-//GNUstep//DTD gsdoc 1.0.4//EN" "http://www.gnustep.org/gsdoc-1_0_4.dtd">
<gsdoc base="SQLClient">
<head>
<title>SQLClient documentation</title>
<author name="Richard Frith-Macdonald">
<email address="rfm@gnu.org">
rfm@gnu.org
</email>
</author>
<version>38114</version>
<date>2014-10-13 11:47:06 +0100 (Mon, 13 Oct 2014)</date>
<copy>2004 Free Software Foundation, Inc.</copy>
</head>
<body>
<front><contents /></front>
<chapter>
<heading>The SQLClient library</heading>
<section>
<heading>What is the SQLClient library?</heading>
<p>
The SQLClient library is designed to provide a simple
interface to SQL databases for GNUstep
applications. It does not attempt the sort of
abstraction provided by the much more
sophisticated GDL2 library, but rather allows
applications to directly execute SQL queries and
statements.
</p>
<p>
SQLClient provides for the Objective-C programmer
much the same thing that JDBC provides for the Java
programmer (though SQLClient is a bit faster,
easier to use, and easier to add new database backends
for than JDBC).
</p>
<p>
The major features of the SQLClient library are -
</p>
<list>
<item>
Simple API for executing queries and statements... a
variable length sequence of comma separated
strings and other objects (NSNumber, NSDate,
NSData) are concatenated into a single SQL
statement and executed.
</item>
<item>
Simple API
<ref type="class" id="SQLTransaction">SQLTransaction</ref>
)for combining multiple SQL statements into a single
transaction which can be used to minimise
client-server interactions to get the best
possible performance from your database.
</item>
<item>
Supports multiple sumultaneous named connections
to a database server in a thread-safe manner. <br />
</item>
<item>
Supports multiple simultaneous connections to
different database servers with backend driver
bundles loaded for different database engines.
Clear, simple subclassing of the abstract base
class to enable easy implementation of new backend
bundles.
</item>
<item>
Configuration for all connections held in
one place and referenced by connection name for ease
of configuration control. Changes via NSUserDefaults
can even allow reconfiguration of client instances
within a running application.
</item>
<item>
Thread safe operation... The base class supports
locking such that a single instance can be shared
between multiple threads.
</item>
<item>
Support for standalone web applications... eg to
allow data to be added to the database by people
posting web forms to the application.
</item>
<item>
Supports notification of connection to and
disconnection from the database server.
</item>
</list>
</section>
<section>
<heading>
What backend bundles are available?
</heading>
<p>
Current backend bundles are -
</p>
<list>
<item>
ECPG - a bundle using the embedded SQL interface for
postgres. <br /> This is based on a similar
code which was in production use for over eighteen
months, so it should be reliable, but
inefficient.
</item>
<item>
Postgres - a bundle using the libpq native
interface for postgres. <br /> This is the
preferred backend as it allows 'SELECT FOR
UPDATE', which the ECPG backend cannot support
due to limitations in the postgres implementation of
cursors. The code is now well tested and known
to be efficient.
</item>
<item>
MySQL - a bundle using the mysqlclient library for
*recent* MySQL. <br /> I don't use MySQL... but
the test program ran successfully with a vanilla
install of the MySQL packages for recent Debian
unstable.
</item>
<item>
SQLite - a bundle using the sqlite3 library which
supports an SQL-like API for direct access to a
database file (rather than acting as a client of
a database server process). <br /> Not as functional as
the other backends (doesn't support dates for
instance), but good enough for many purposes
and very 'lightweight'. See http://www.sqlite.org
</item>
<item>
Oracle - a bundle using embedded SQL for Oracle.
<br /> Completely untested... may even need some
work to compile... but this *is* based on code which
was working about a year ago. <br /> No support for
BLOBs yet.
</item>
</list>
</section>
<section>
<heading>
Where can you get it? How can you install it?
</heading>
<p>
The SQLClient library is currently only available via
CVS from the GNUstep CVS repository. <br /> See
<https://savannah.gnu.org/cvs/?group=gnustep>
<br /> You need to check out
<code>gnustep/dev-libs/SQLClient</code>
</p>
<p>
To build this library you must have a basic GNUstep
environment set up...
</p>
<list>
<item>
The gnustep-make package must have been built and
installed.
</item>
<item>
The gnustep-base package must have been built and
installed.
</item>
<item>
The Performance library (from the dev-libs area in
GNUstep CVS) must have been built and installed.
</item>
<item>
If this environment is in place, all you should need
to do is run 'make' to configure and build the
library, 'make install' to install it.
</item>
<item>Then you can run the test programs.</item>
<item>
Your most likely problems are that the configure
script may not detect the database libraries you
want... Please figure out how to modify
<code>configure.ac</code> so that it will detect
the required headers and libraries on your system,
and supply na patch.
</item>
<item>
Once the library is installed, you can include the
header file
<code><SQLClient/SQLClient.h%gt;</code> and
link your programs with the <code>SQLClient</code>
library to use it.
</item>
</list>
<p>
Bug reports, patches, and contributions (eg a backend
bundle for a new database) should be entered on the
GNUstep project page
<http://savannah.gnu.org/projects/gnustep>
and the bug reporting page
<http://savannah.gnu.org/bugs/?group=gnustep>
</p>
</section>
</chapter>
<chapter>
<heading>
Software documentation for the SQLClient class
</heading>
<class name="SQLClient" super="NSObject">
<declared>SQLClient.h</declared>
<desc>
<p>
The SQLClient class encapsulates dynamic SQL access to
relational database systems. A shared instance
of the class is used for each database (as identified by
the name of the database), and the number of
simultanous database connections is managed
too.
</p>
<p>
SQLClient is an abstract base class... when you
create an instance of it, you are actually creating
an instance of a concrete subclass whose implementation
is loaded from a bundle.
</p>
</desc>
<ivariable type="GSCache*" name="_cache" validity="protected">
<desc>
The cache for query results <br /> <em>Warning</em> the
underscore at the start of the name of this
instance variable indicates that, even though it
is not technically <em>private</em>, it is intended for
internal use within the package, and you should
not use the variable in other code.
</desc>
</ivariable>
<ivariable type="NSThread*" name="_cacheThread" validity="protected">
<desc>
Thread for cache queries <br /> <em>Warning</em> the
underscore at the start of the name of this
instance variable indicates that, even though it
is not technically <em>private</em>, it is intended for
internal use within the package, and you should
not use the variable in other code.
</desc>
</ivariable>
<ivariable type="NSString*" name="_client" validity="protected">
<desc>
Identifier within backend <br />
<em>Warning</em> the underscore at the start of the
name of this instance variable indicates that, even
though it is not technically <em>private</em>, it is
intended for internal use within the package, and
you should not use the variable in other code.
</desc>
</ivariable>
<ivariable type="unsigned int" name="_connectFails" validity="protected">
<desc>
The count of connection failures <br />
<em>Warning</em> the underscore at the start of the
name of this instance variable indicates that, even
though it is not technically <em>private</em>, it is
intended for internal use within the package, and
you should not use the variable in other code.
</desc>
</ivariable>
<ivariable type="NSString*" name="_database" validity="protected">
<desc>
The configured database name/host <br />
<em>Warning</em> the underscore at the start of the
name of this instance variable indicates that, even
though it is not technically <em>private</em>, it is
intended for internal use within the package, and
you should not use the variable in other code.
</desc>
</ivariable>
<ivariable type="unsigned int" name="_debugging" validity="protected">
<desc>
The current debugging level <br /> <em>Warning</em> the
underscore at the start of the name of this
instance variable indicates that, even though it
is not technically <em>private</em>, it is intended for
internal use within the package, and you should
not use the variable in other code.
</desc>
</ivariable>
<ivariable type="NSTimeInterval" name="_duration" validity="protected">
<desc>
Duration logging threshold <br /> <em>Warning</em>
the underscore at the start of the name of this
instance variable indicates that, even though it
is not technically <em>private</em>, it is intended for
internal use within the package, and you should
not use the variable in other code.
</desc>
</ivariable>
<ivariable type="void*" name="_extra" validity="protected">
<desc>
Allow for extensions by allocating memory and
pointing to it from the _extra ivar. That way we
can avoid binary incompatibility between minor
releases. <br /> <em>Warning</em> the underscore
at the start of the name of this instance variable
indicates that, even though it is not technically
<em>private</em>, it is intended for internal use
within the package, and you should not use the
variable in other code.
</desc>
</ivariable>
<ivariable type="BOOL" name="_inTransaction" validity="protected">
<desc>
A flag indicating whether this instance is currently
within a transaction. This variable must
<em>only</em> be set by the
<ref type="method" id="-begin">
-begin
</ref>
, <ref type="method" id="-commit">-commit</ref> or
<ref type="method" id="-rollback">
-rollback
</ref>
methods. <br /> Are we inside a transaction?
<br /> <em>Warning</em> the underscore at the start
of the name of this instance variable indicates that,
even though it is not technically <em>private</em>, it
is intended for internal use within the package, and you
should not use the variable in other code.
</desc>
</ivariable>
<ivariable type="NSTimeInterval" name="_lastOperation" validity="protected">
<desc>
Timestamp of completion of last operation. <br />
Maintained by
<ref type="method" id="-simpleExecute:">
-simpleExecute:
</ref>
<ref type="method" id="-simpleQuery:recordType:listType:">
-simpleQuery:recordType:listType:
</ref>
and
<ref type="method" id="-cache:simpleQuery:recordType:listType:">-cache:simpleQuery:recordType:listType:</ref> Also set for a failed connection attempt, but not reported by the <ref type="method" id="-lastOperation">-lastOperation</ref> method in that case. <br /> <em>Warning</em> the underscore at the start of the name of this instance variable indicates that, even though it is not technically <em>private</em>, it is intended for internal use within the package, and you should not use the variable in other code.
</desc>
</ivariable>
<ivariable type="NSTimeInterval" name="_lastStart" validity="protected">
<desc>
Last op start or connect <br /> <em>Warning</em> the
underscore at the start of the name of this
instance variable indicates that, even though it
is not technically <em>private</em>, it is intended for
internal use within the package, and you should
not use the variable in other code.
</desc>
</ivariable>
<ivariable type="NSString*" name="_name" validity="protected">
<desc>
Unique identifier for instance <br />
<em>Warning</em> the underscore at the start of the
name of this instance variable indicates that, even
though it is not technically <em>private</em>, it is
intended for internal use within the package, and
you should not use the variable in other code.
</desc>
</ivariable>
<ivariable type="NSCountedSet*" name="_names" validity="protected">
<desc>
Track notification names <br /> <em>Warning</em> the
underscore at the start of the name of this
instance variable indicates that, even though it
is not technically <em>private</em>, it is intended for
internal use within the package, and you should
not use the variable in other code.
</desc>
</ivariable>
<ivariable type="NSMapTable*" name="_observers" validity="protected">
<desc>
Observations of async events <br />
<em>Warning</em> the underscore at the start of the
name of this instance variable indicates that, even
though it is not technically <em>private</em>, it is
intended for internal use within the package, and
you should not use the variable in other code.
</desc>
</ivariable>
<ivariable type="NSString*" name="_password" validity="protected">
<desc>
The configured password <br /> <em>Warning</em> the
underscore at the start of the name of this
instance variable indicates that, even though it
is not technically <em>private</em>, it is intended for
internal use within the package, and you should
not use the variable in other code.
</desc>
</ivariable>
<ivariable type="SQLClientPool*" name="_pool" validity="protected">
<desc>
The pool of the client (or <code>nil</code>) <br />
<em>Warning</em> the underscore at the start of the
name of this instance variable indicates that, even
though it is not technically <em>private</em>, it is
intended for internal use within the package, and
you should not use the variable in other code.
</desc>
</ivariable>
<ivariable type="BOOL" name="_shouldTrim" validity="protected">
<desc>
A flag indicating whether leading and trailing white
space in values read from the database should
automatically be removed. <br /> This should
only be modified by the
<ref type="method" id="-setShouldTrim:">
-setShouldTrim:
</ref>
method. <br /> Should whitespace be trimmed? <br />
<em>Warning</em> the underscore at the start of the
name of this instance variable indicates that, even
though it is not technically <em>private</em>, it is
intended for internal use within the package, and
you should not use the variable in other code.
</desc>
</ivariable>
<ivariable type="NSMutableArray*" name="_statements" validity="protected">
<desc>
Uncommitted statements <br /> <em>Warning</em>
the underscore at the start of the name of this
instance variable indicates that, even though it
is not technically <em>private</em>, it is intended for
internal use within the package, and you should
not use the variable in other code.
</desc>
</ivariable>
<ivariable type="NSString*" name="_user" validity="protected">
<desc>
The configured user <br /> <em>Warning</em> the
underscore at the start of the name of this
instance variable indicates that, even though it
is not technically <em>private</em>, it is intended for
internal use within the package, and you should
not use the variable in other code.
</desc>
</ivariable>
<ivariable type="BOOL" name="connected" validity="protected">
<desc>
A flag indicating whether this instance is currently
connected to the backend database server. This
variable must <em>only</em> be set by the
<ref type="method" id="-backendConnect">
-backendConnect
</ref>
or
<ref type="method" id="-backendDisconnect">
-backendDisconnect
</ref>
methods.
</desc>
</ivariable>
<ivariable type="void*" name="extra" validity="protected">
<desc>
For subclass specific data
</desc>
</ivariable>
<ivariable type="NSRecursiveLock*" name="lock" validity="protected">
<desc>
Maintain thread-safety
</desc>
</ivariable>
<method type="NSArray*" factory="yes">
<sel>allClients</sel>
<desc>
Returns an array containing all the SQLClient
instances.
</desc>
</method>
<method type="SQLClient*" factory="yes">
<sel>clientWithConfiguration:</sel>
<arg type="NSDictionary*">config</arg>
<sel>name:</sel>
<arg type="NSString*">reference</arg>
<desc>
Return an existing SQLClient instance (using
+existingClient:) if possible, or creates
one, initialises it using
<ref type="method" id="-initWithConfiguration:name:">
-initWithConfiguration:name:
</ref>
, and returns the new instance (autoreleased). <br />
Returns <code>nil</code> on failure.
</desc>
</method>
<method type="SQLClient*" factory="yes">
<sel>existingClient:</sel>
<arg type="NSString*">reference</arg>
<desc>
Return an existing SQLClient instance for the
specified name if one exists, otherwise returns
<code>nil</code>.
</desc>
</method>
<method type="unsigned int" factory="yes">
<sel>maxConnections</sel>
<desc>
Returns the maximum number of simultaneous database
connections permitted (set by
<ref type="method" id="+setMaxConnections:">
+setMaxConnections:
</ref>
and defaults to 8) for connections outside of
SQLClientPool instances.
</desc>
</method>
<method type="void" factory="yes">
<sel>purgeConnections:</sel>
<arg type="NSDate*">since</arg>
<desc>
<p>
Use this method to reduce the number of database
connections currently active so that it is
less than the limit set by the
<ref type="method" id="+setMaxConnections:">
+setMaxConnections:
</ref>
method. This mechanism is used internally by the
class to ensure that, when it is about to open a
new connection, the limit is not exceeded.
</p>
<p>
If <var>since</var> is not <code>nil</code>, then any
connection which has not been used more
recently than that date is disconnected anyway.
<br /> You can (and probably should) use this
periodically to purge idle connections, but
you can also pass a date in the future to close all
connections.
</p>
<p>
Purging does not apply to connections made by
SQLClientPool instances.
</p>
</desc>
</method>
<method type="void" factory="yes">
<sel>setMaxConnections:</sel>
<arg type="unsigned int">c</arg>
<desc>
<p>
Set the maximum number of simultaneous database
connections permitted (defaults to 8 and may
not be set less than 1).
</p>
<p>
This value is used by the
<ref type="method" id="+purgeConnections:">
+purgeConnections:
</ref>
method to determine how many connections should be
disconnected when it is called.
</p>
<p>
Connections used by SQLClientPool instances
are not considered by this maximum.
</p>
</desc>
</method>
<method type="void">
<sel>begin</sel>
<desc>
Start a transaction for this database client. <br />
You <strong>must</strong> match this with either a
<ref type="method" id="-commit">
-commit
</ref>
or a <ref type="method" id="-rollback">-rollback</ref>.
<br />
<p>
Normally, if you execute an SQL statement
without using this method first, the
<em>autocommit</em> feature is employed, and the
statement takes effect immediately. Use of this
method permits you to execute several statements
in sequence, and only have them take effect (as a
single operation) when you call the
<ref type="method" id="-commit">
-commit
</ref>
method.
</p>
<p>
NB. You must <strong>not</strong> execute an SQL
statement which would start a transaction
directly... use only this method.
</p>
<p>
Where possible, consider using the
<ref type="class" id="SQLTransaction">SQLTransaction</ref>class rather than calling <ref type="method" id="-begin">-begin</ref> <ref type="method" id="-commit">-commit</ref> or <ref type="method" id="-rollback">-rollback</ref> yourself.</p>
</desc>
</method>
<method type="NSString*">
<sel>buildQuery:</sel>
<arg type="NSString*">stmt</arg>
<vararg />
<desc>
<p>
Build an sql query string using the supplied
arguments.
</p>
<p>
This method has at least one argument, the string
starting the query to be executed (which must
have the prefix 'select ').
</p>
<p>
Additional arguments are a <code>nil</code>
terminated list which also be strings, and
these are appended to the statement. <br /> Any
string arguments are assumed to have been quoted
appropriately already, but non-string
arguments are automatically quoted using the
<ref type="method" id="-quote:">
-quote:
</ref>
method.
</p>
<example>
sql = [db buildQuery: @"SELECT Name FROM ", table, nil];
</example>
<p>
Upon error, an exception is raised.
</p>
<p>
The method returns a string containing sql suitable
for passing to the
<ref type="method" id="-simpleQuery:recordType:listType:">-simpleQuery:recordType:listType:</ref> or <ref type="method" id="-cache:simpleQuery:recordType:listType:">-cache:simpleQuery:recordType:listType:</ref> methods.
</p>
</desc>
</method>
<method type="NSString*">
<sel>buildQuery:</sel>
<arg type="NSString*">stmt</arg>
<sel>with:</sel>
<arg type="NSDictionary*">values</arg>
<desc>
Takes the query statement and substitutes in
<var>values</var> from the dictionary where markup of
the format {key} is found. <br /> Returns the resulting
query string.
<example>
sql = [db buildQuery: @"SELECT Name FROM {Table} WHERE ID = {ID}"
with: values];
</example>
<p>
Any non-string <var>values</var> in the dictionary
will be replaced by the results of the
<ref type="method" id="-quote:">
-quote:
</ref>
method. <br /> The markup format may also be
{key?default} where <em>default</em> is a
string to be used if there is no value for the
<em>key</em> in the dictionary.
</p>
<p>
The method returns a string containing sql suitable
for passing to the
<ref type="method" id="-simpleQuery:recordType:listType:">-simpleQuery:recordType:listType:</ref> or <ref type="method" id="-cache:simpleQuery:recordType:listType:">-cache:simpleQuery:recordType:listType:</ref> methods.
</p>
</desc>
</method>
<method type="NSString*">
<sel>clientName</sel>
<desc>
Return the client name for this instance. <br />
Normally this is useful only for
debugging/reporting purposes, but if
you are using multiple instances of this class in your
application, and you are using embedded SQL,
you will need to use this method to fetch the
client/connection name and store its
C-string representation in a variable
'connectionName' declared to the sql
preprocessor, so you can then have statements
of the form - 'exec sql at :connectionName...'.
</desc>
</method>
<method type="void">
<sel>commit</sel>
<desc>
Complete a transaction for this database client.
<br /> This <strong>must</strong> match an earlier
<ref type="method" id="-begin">
-begin
</ref>
.
<p>
NB. You must <strong>not</strong> execute an SQL
statement which would commit or rollback a
transaction directly... use only this method
or the
<ref type="method" id="-rollback">
-rollback
</ref>
method.
</p>
<p>
Where possible, consider using the
<ref type="class" id="SQLTransaction">SQLTransaction</ref>class rather than calling <ref type="method" id="-begin">-begin</ref> <ref type="method" id="-commit">-commit</ref> or <ref type="method" id="-rollback">-rollback</ref> yourself.</p>
</desc>
</method>
<method type="BOOL">
<sel>connect</sel>
<desc>
If the <em>connected</em> instance variable is
<code>NO</code>, this method calls
<ref type="method" id="-backendConnect">
-backendConnect
</ref>
to ensure that there is a connection to the database
server established. Returns the result. <br />
Performs any necessary locking for thread safety.
<br /> This method also counts the number of
consecutive failed connection attempts. A delay
is enforced between each connection attempt, with the
length of the delay growing with each failure. This
ensures that applications which fail to deal with
connection failures, and just keep trying to
reconnect, will not overload the system/server.
<br /> The maximum delay is 30 seconds, so when the
database server is restarted, the application can
reconnect reasonably quickly.
</desc>
</method>
<method type="BOOL">
<sel>connected</sel>
<desc>
Return a flag to say whether a connection to the
database server is currently live (the value of
the 'connected' instance variable). <br /> This is
mostly useful for debug/reporting.
</desc>
</method>
<method type="NSString*">
<sel>database</sel>
<desc>
Return the database name for this instance (or
<code>nil</code>).
</desc>
</method>
<method type="void">
<sel>disconnect</sel>
<desc>
If the <em>connected</em> instance variable is
<code>YES</code>, this method calls
<ref type="method" id="-backendDisconnect">
-backendDisconnect
</ref>
to ensure that the connection to the database server is
dropped. <br /> Performs any necessary locking for
thread safety.
</desc>
</method>
<method type="NSInteger">
<sel>execute:</sel>
<arg type="NSString*">stmt</arg>
<vararg />
<desc>
Perform arbitrary operation
<em>which does not return any value.</em> <br /> This
arguments to this method are a <code>nil</code>
terminated list which are concatenated in the
manner of the
<ref type="method" id="-query:,...">
-query:,...
</ref>
method. <br /> Any string arguments are assumed to
have been quoted appropriately already, but non-string
arguments are automatically quoted using the
<ref type="method" id="-quote:">
-quote:
</ref>
method.
<example>
[db execute: @"UPDATE ", table, @" SET Name = ",
myName, " WHERE ID = ", myId, nil];
</example>
Where the database backend support it, this method
returns the count of the number of rows to which
the operation applied. Otherwise this returns -1.
</desc>
</method>
<method type="NSInteger">
<sel>execute:</sel>
<arg type="NSString*">stmt</arg>
<sel>with:</sel>
<arg type="NSDictionary*">values</arg>
<desc>
Takes the statement and substitutes in
<var>values</var> from the dictionary where markup of
the format {key} is found. <br /> Passes the result to
the
<ref type="method" id="-execute:,...">
-execute:,...
</ref>
method.
<example>
[db execute: @"UPDATE {Table} SET Name = {Name} WHERE ID = {ID}"
with: values];
</example>
Any non-string <var>values</var> in the dictionary will
be replaced by the results of the
<ref type="method" id="-quote:">
-quote:
</ref>
method. <br /> The markup format may also be
{key?default} where <em>default</em> is a
string to be used if there is no value for the
<em>key</em> in the dictionary. <br /> Where the
database backend support it, this method returns
the count of the number of rows to which the operation
applied. Otherwise this returns -1.
</desc>
</method>
<method type="id">
<sel>initWithConfiguration:</sel>
<arg type="NSDictionary*">config</arg>
<desc>
Calls
<ref type="method" id="-initWithConfiguration:name:">
-initWithConfiguration:name:
</ref>
passing a <code>nil</code> reference name.
</desc>
</method>
<method type="id">
<sel>initWithConfiguration:</sel>
<arg type="NSDictionary*">config</arg>
<sel>name:</sel>
<arg type="NSString*">reference</arg>
<desc>
Calls
<ref type="method" id="-initWithConfiguration:name:pool:">
-initWithConfiguration:name:pool:
</ref>
passing <code>NO</code> to say the client is not in
a pool.
</desc>
</method>
<method type="id">
<sel>initWithConfiguration:</sel>
<arg type="NSDictionary*">config</arg>
<sel>name:</sel>
<arg type="NSString*">reference</arg>
<sel>pool:</sel>
<arg type="SQLClientPool*">pool</arg>
<desc>
Initialise using the supplied configuration, or
if that is <code>nil</code>, try to use values from
NSUserDefaults (and automatically update
when the defaults change). <br /> Uses the
<var>reference</var> name to determine configuration
information... and if a <code>nil</code> name
is supplied, defaults to the value of SQLClientName in
the configuration dictionary (or in the standard user
defaults). If there is no value for
SQLClientName, uses the string 'Database'.
<br /> If <var>pool</var> is <code>nil</code> and a
SQLClient instance already exists with the name
used for this instance, the receiver is deallocated
and the existing instance is retained and returned...
there may only ever be one instance for a particular
<var>reference</var> name which is not in a
<var>pool</var>. <br /> <br /> The <var>config</var>
argument (or the SQLClientReferences user default)
is a dictionary with names as keys and dictionaries as
its values. Configuration entries from the dictionary
corresponding to the database client are used
if possible, general entries are used otherwise. <br />
Database... is the name of the database to use, if
it is missing then 'Database' may be used instead.
<br /> User... is the name of the database user to
use, if it is missing then 'User' may be used instead.
<br /> Password... is the name of the database user
password, if it is missing then 'Password' may be
used instead. <br /> ServerType... is the name of the
backend server to be used... by convention the name
of a bundle containing the interface to that backend. If
this is missing then 'Postgres' is used. <br /> The
database name may be of the format
'name@host:port' when you wish to connect
to a database on a different host over the network.
</desc>
</method>
<method type="BOOL">
<sel>isEqual:</sel>
<arg type="id">other</arg>
<desc>
Two clients are considered equal if they refer to the
same database and are logged in as the same database
user using the same protocol. These are the general
criteria for transactions to be compatoible so
that an SQLTransaction object generated by one client
can be used by the <var>other</var>.
</desc>
</method>
<method type="BOOL">
<sel>isInTransaction</sel>
<desc>
Return the state of the flag indicating whether the
library thinks a transaction is in progress. This
flag is normally maintained by
<ref type="method" id="-begin">
-begin
</ref>
, <ref type="method" id="-commit">-commit</ref>, and
<ref type="method" id="-rollback">
-rollback
</ref>
.
</desc>
</method>
<method type="NSDate*">
<sel>lastOperation</sel>
<desc>
Returns the date/time stamp of the last database
operation performed by the receiver, or
<code>nil</code> if no operation has ever been done
by it. <br /> Simply connecting to or disconnecting from
the databsse does not count as an operation.
</desc>
</method>
<method type="SQLClient*">
<sel>longestIdle:</sel>
<arg type="SQLClient*">other</arg>
<desc>
Compares the receiver with the <var>other</var>
client to see which one has been inactive but
connected for longest (if they are connected) and
returns that instance. <br /> If neither is idle
but connected, the method returns <code>nil</code>.
<br /> In a tie, the method returns the
<var>other</var> instance.
</desc>
</method>
<method type="NSString*">
<sel>name</sel>
<desc>
Return the database reference name for this instance
(or <code>nil</code>).
</desc>
</method>
<method type="NSString*">
<sel>password</sel>
<desc>
Return the database password for this instance (or
<code>nil</code>).
</desc>
</method>
<method type="NSMutableArray*">
<sel>query:</sel>
<arg type="NSString*">stmt</arg>
<vararg />
<desc>
<p>
Perform arbitrary query
<em>which returns values.</em>
</p>
<p>
This method handles its arguments in the same way as
the
<ref type="method" id="-buildQuery:,...">
-buildQuery:,...
</ref>
method and returns the result of the query.
</p>
<example>
result = [db query: @"SELECT Name FROM ", table, nil];
</example>
<p>
Upon error, an exception is raised.
</p>
<p>
The query returns an array of records (each of which
is represented by an SQLRecord object).
</p>
<p>
Each SQLRecord object contains one or more fields,
in the order in which they occurred in the query.
Fields may also be retrieved by name.
</p>
<p>
NULL field items are returned as NSNull objects.
</p>
<p>
Most other field items are returned as NSString
objects.
</p>
<p>
Date and timestamp field items are returned as
NSDate objects.
</p>
</desc>
</method>
<method type="NSMutableArray*">
<sel>query:</sel>
<arg type="NSString*">stmt</arg>
<sel>with:</sel>
<arg type="NSDictionary*">values</arg>
<desc>
Takes the query statement and substitutes in
<var>values</var> from the dictionary (in the same
manner as the
<ref type="method" id="-buildQuery:with:">
-buildQuery:with:
</ref>
method) then executes the query and returns the
response. <br />
<example>
result = [db query: @"SELECT Name FROM {Table} WHERE ID = {ID}"
with: values];
</example>
Any non-string <var>values</var> in the dictionary will
be replaced by the results of the
<ref type="method" id="-quote:">
-quote:
</ref>
method. <br /> The markup format may also be
{key?default} where <em>default</em> is a
string to be used if there is no value for the
<em>key</em> in the dictionary.
</desc>
</method>
<method type="NSString*">
<sel>quote:</sel>
<arg type="id">obj</arg>
<desc>
Convert an object to a string suitable for use in
an SQL query. <br /> Normally the
<ref type="method" id="-execute:,...">
-execute:,...
</ref>
, and
<ref type="method" id="-query:,...">
-query:,...
</ref>
methods will call this method automatically for
everything apart from string objects. <br />
Strings have to be handled specially, because they
are used both for parts of the SQL command, and as
values (where they need to be quoted). So where you
need to pass a string value which needs quoting, you
must call this method explicitly. <br /> Subclasses
may override this method to provide appropriate quoting
for types of object which need database backend
specific quoting conventions. However, the defalt
implementation should be OK for most cases.
<br /> This method makes use of
<ref type="method" id="-quoteString:">
-quoteString:
</ref>
to quote literal strings. <br /> The base class
implementation formats NSDate objects as
<br /> YYYY-MM-DD hh:mm:ss.mmm ?ZZZZ <br /> NSData
objects are not quoted... they must not appear in
queries, and where used for insert/update
operations, they need to be passed to the
<ref type="method" id="-backendExecute:">
-backendExecute:
</ref>
method unchanged. <br /> For a <code>nil</code>
object, we return NULL. <br /> For a number, we
simply convert directly to a string. <br /> For a
date, we convert to the text format used by the
database, and add leading and trailing quotes.
<br /> For a data object, we don't quote... the
other parts of the code need to know they have an
NSData object and pass it on unchanged to the
<ref type="method" id="-backendExecute:">
-backendExecute:
</ref>
method. <br /> Just in case an NSNull subclass has
been created by someone. The normal NSNull instance
should have been handled earlier. <br /> For an
NSArray or NSSet, we produce a bracketed list of
the (quoted) objects in the array. <br /> For any other
type of data, we just produce a quoted string
representation of the objects description.
</desc>
</method>
<method type="NSString*">
<sel>quoteBigInteger:</sel>
<arg type="int64_t">i</arg>
<desc>
Convert a big (64 bit) integer to a string suitable
for use in an SQL query.
</desc>
</method>
<method type="NSString*">
<sel>quoteCString:</sel>
<arg type="const char*">s</arg>
<desc>
Convert a 'C' string to a string suitable for use
in an SQL query by using
<ref type="method" id="-quoteString:">
-quoteString:
</ref>
to convert it to a literal string format. <br /> NB. a
null pointer is treated as an empty string.
</desc>
</method>
<method type="NSString*">
<sel>quoteChar:</sel>
<arg type="char">c</arg>
<desc>
Convert a single character to a string suitable for
use in an SQL query by using
<ref type="method" id="-quoteString:">
-quoteString:
</ref>
to convert it to a literal string format. <br /> NB. a
nul character is not allowed and will cause an
exception.
</desc>
</method>
<method type="NSString*">
<sel>quoteFloat:</sel>
<arg type="float">f</arg>
<desc>
Convert a <strong>float</strong> to a string
suitable for use in an SQL query.
</desc>
</method>
<method type="NSString*">
<sel>quoteInteger:</sel>
<arg type="int">i</arg>
<desc>
Convert an integer to a string suitable for use in
an SQL query.
</desc>
</method>
<method type="NSString*">
<sel>quoteString:</sel>
<arg type="NSString*">s</arg>
<desc>
Convert a string to a form suitable for use as a
string literal in an SQL query. <br /> Subclasses
may override this for non-standard literal string
quoting conventions.
</desc>
</method>
<method type="NSString*">
<sel>quotef:</sel>
<arg type="NSString*">fmt</arg>
<vararg />
<desc>
Produce a quoted string from the supplied arguments
(printf style).
</desc>
</method>
<method type="void">
<sel>rollback</sel>
<desc>
Revert a transaction for this database client.
<br /> If there is no transaction in progress, this
method does nothing. <br />
<p>
NB. You must <strong>not</strong> execute an SQL
statement which would commit or rollback a
transaction directly... use only this method
or the
<ref type="method" id="-rollback">
-rollback
</ref>
method.
</p>
<p>
Where possible, consider using the
<ref type="class" id="SQLTransaction">SQLTransaction</ref>class rather than calling <ref type="method" id="-begin">-begin</ref> <ref type="method" id="-commit">-commit</ref> or <ref type="method" id="-rollback">-rollback</ref> yourself.</p>
</desc>
</method>
<method type="void">
<sel>setDatabase:</sel>
<arg type="NSString*">s</arg>
<desc>
Set the database host/name for this object. <br /> This
is called automatically to configure the connection...
you normally shouldn't need to call it yourself.
</desc>
</method>
<method type="void">
<sel>setName:</sel>
<arg type="NSString*">s</arg>
<desc>
Set the database reference name for this object. This
is used to differentiate between multiple connections to
the database. <br /> This is called automatically to
configure the connection... you normally
shouldn't need to call it yourself. <br /> NB.
attempts to change the name of an instance to that
of an existing instance are ignored.
</desc>
</method>
<method type="void">
<sel>setPassword:</sel>
<arg type="NSString*">s</arg>
<desc>
Set the database password for this object. <br /> This
is called automatically to configure the connection...
you normally shouldn't need to call it yourself.
</desc>
</method>
<method type="void">
<sel>setShouldTrim:</sel>
<arg type="BOOL">aFlag</arg>
<desc>
Sets an internal flag to indicate whether leading and
trailing white space characters should be removed
from values retrieved from the database by the
receiver.
</desc>
</method>
<method type="void">
<sel>setUser:</sel>
<arg type="NSString*">s</arg>
<desc>
Set the database user for this object. <br /> This is
called automatically to configure the connection...
you normally shouldn't need to call it yourself.
</desc>
</method>
<method type="NSInteger">
<sel>simpleExecute:</sel>
<arg type="NSArray*">info</arg>
<desc>
Calls
<ref type="method" id="-backendExecute:">
-backendExecute:
</ref>
in a safe manner. <br /> Handles locking. <br />
Maintains
<ref type="method" id="-lastOperation">
-lastOperation
</ref>
date. <br /> Returns the result of
<ref type="method" id="-backendExecute:">
-backendExecute:
</ref>
</desc>
</method>
<method type="NSMutableArray*">
<sel>simpleQuery:</sel>
<arg type="NSString*">stmt</arg>
<desc>
Calls
<ref type="method" id="-simpleQuery:recordType:listType:">
-simpleQuery:recordType:listType:
</ref>
with the default record class and default array class.
</desc>
</method>
<method type="NSMutableArray*">
<sel>simpleQuery:</sel>
<arg type="NSString*">stmt</arg>
<sel>recordType:</sel>
<arg type="id">rtype</arg>
<sel>listType:</sel>
<arg type="id">ltype</arg>
<desc>
Calls
<ref type="method" id="-backendQuery:recordType:listType:">-backendQuery:recordType:listType:</ref> in a safe manner. <br /> Handles locking. <br /> Maintains <ref type="method" id="-lastOperation">-lastOperation</ref> date. <br /> The value of <var>rtype</var> must respond to the <ref type="method" id="+newWithValues:keys:count:" class="SQLRecord">[SQLRecord +newWithValues:keys:count:]</ref> method. <br /> If <var>rtype</var> is <code>nil</code> then the
<ref type="class" id="SQLRecord">SQLRecord</ref>
class is used. <br /> The value of <var>ltype</var>
must respond to the
<ref type="method" id="+alloc" class="NSObject">
[NSObject +alloc]
</ref>
method to produce a container which must repond to
the
<ref type="method" id="-initWithCapacity:" class="NSMutableArray">[NSMutableArray -initWithCapacity:]</ref> method to initialise itsself and the <ref type="method" id="-addObject:" class="NSMutableArray">[NSMutableArray -addObject:]</ref> method to add records to the list. <br /> If <var>ltype</var> is <code>nil</code> then the
<ref type="class" id="NSMutableArray">NSMutableArray</ref>
class is used. <br /> This library provides a few
helper classes to provide alternative values for
<var>rtype</var> and <var>ltype</var>.
</desc>
</method>
<method type="NSString*">
<sel>user</sel>
<desc>
Return the database user for this instance (or
<code>nil</code>).
</desc>
</method>
</class>
</chapter>
<chapter>
<heading>
Software documentation for the SQLClientPool class
</heading>
<class name="SQLClientPool" super="NSObject">
<declared>SQLClient.h</declared>
<desc>
<p>
An SQLClientPool instance may be used to create/control
a pool of client objects. Code may obtain autoreleased
proxies to the clients from the pool and use them
safe in the knowledge that they won't be used anywhere
else... as soon as the client would be deallocated, it
is returned to the pool.
</p>
<p>
All clients in the pool share the same cache object, so
query results cached by one client will be available
to other clients in the pool.
</p>
</desc>
<ivariable type="NSDictionary*" name="_config" validity="protected">
<desc>
The pool configuration object <br /> <em>Warning</em>
the underscore at the start of the name of this
instance variable indicates that, even though it
is not technically <em>private</em>, it is intended for
internal use within the package, and you should
not use the variable in other code.
</desc>
</ivariable>
<ivariable type="unsigned int" name="_debugging" validity="protected">
<desc>
The current debugging level <br /> <em>Warning</em> the
underscore at the start of the name of this
instance variable indicates that, even though it
is not technically <em>private</em>, it is intended for
internal use within the package, and you should
not use the variable in other code.
</desc>
</ivariable>
<ivariable type="NSTimeInterval" name="_delayWaits" validity="protected">
<desc>
Time waiting for provisions <br /> <em>Warning</em>
the underscore at the start of the name of this
instance variable indicates that, even though it
is not technically <em>private</em>, it is intended for
internal use within the package, and you should
not use the variable in other code.
</desc>
</ivariable>
<ivariable type="uint64_t" name="_delayed" validity="protected">
<desc>
Count of delayed provisions <br /> <em>Warning</em>
the underscore at the start of the name of this
instance variable indicates that, even though it
is not technically <em>private</em>, it is intended for
internal use within the package, and you should
not use the variable in other code.
</desc>
</ivariable>
<ivariable type="NSTimeInterval" name="_duration" validity="protected">
<desc>
Duration logging threshold <br /> <em>Warning</em>
the underscore at the start of the name of this
instance variable indicates that, even though it
is not technically <em>private</em>, it is intended for
internal use within the package, and you should
not use the variable in other code.
</desc>
</ivariable>
<ivariable type="NSTimeInterval" name="_failWaits" validity="protected">
<desc>
Time waiting for timewouts <br /> <em>Warning</em> the
underscore at the start of the name of this
instance variable indicates that, even though it
is not technically <em>private</em>, it is intended for
internal use within the package, and you should
not use the variable in other code.
</desc>
</ivariable>
<ivariable type="uint64_t" name="_failed" validity="protected">
<desc>
Count of timed out provisions <br /> <em>Warning</em>
the underscore at the start of the name of this
instance variable indicates that, even though it
is not technically <em>private</em>, it is intended for
internal use within the package, and you should
not use the variable in other code.
</desc>
</ivariable>
<ivariable type="uint64_t" name="_immediate" validity="protected">
<desc>
Immediate client provisions <br />
<em>Warning</em> the underscore at the start of the
name of this instance variable indicates that, even
though it is not technically <em>private</em>, it is
intended for internal use within the package, and
you should not use the variable in other code.
</desc>
</ivariable>
<ivariable type="NSTimeInterval" name="_longest" validity="protected">
<desc>
Count of longest delay <br /> <em>Warning</em> the
underscore at the start of the name of this
instance variable indicates that, even though it
is not technically <em>private</em>, it is intended for
internal use within the package, and you should
not use the variable in other code.
</desc>
</ivariable>
<ivariable type="NSString*" name="_name" validity="protected">
<desc>
The pool configuration name <br /> <em>Warning</em> the
underscore at the start of the name of this
instance variable indicates that, even though it
is not technically <em>private</em>, it is intended for
internal use within the package, and you should
not use the variable in other code.
</desc>
</ivariable>
<ivariable type="SQLClient**" name="c" validity="protected">
<desc>
The clients of the pool.
</desc>
</ivariable>
<ivariable type="NSConditionLock*" name="lock" validity="protected">
<desc>
Controls access to the pool contents
</desc>
</ivariable>
<ivariable type="int" name="max" validity="protected">
<desc>
Maximum connection count
</desc>
</ivariable>
<ivariable type="int" name="min" validity="protected">
<desc>
Minimum connection count
</desc>
</ivariable>
<ivariable type="BOOL*" name="u" validity="protected">
<desc>
Whether the client is in use.
</desc>
</ivariable>
<method type="int">
<sel>availableConnections</sel>
<desc>
Returns the count of currently available
connections in the pool.
</desc>
</method>
<method type="id">
<sel>initWithConfiguration:</sel>
<arg type="NSDictionary*">config</arg>
<sel>name:</sel>
<arg type="NSString*">reference</arg>
<sel>max:</sel>
<arg type="int">maxConnections</arg>
<sel>min:</sel>
<arg type="int">minConnections</arg>
<desc>
Creates a pool of clients using a single client
configuration. <br /> Calls
<ref type="method" id="-initWithConfiguration:name:pool:">
-initWithConfiguration:name:pool:
</ref>
(passing <code>NO</code> to say the client is not
in a pool) to create each client. <br /> The value of
<var>maxConnections</var> is the size of the pool (ie
the number of clients created) and thus the maximum
number of concurrent connections to the database
server. <br /> The value of
<var>minConnections</var> is the minimum number of
connected clients normally expected to be in the
pool. The pool tries to ensure that it doesn't
contain more than this number of idle connected
clients.
</desc>
</method>
<method type="int">
<sel>maxConnections</sel>
<desc>
Return the maximum number of database connections in
the pool.
</desc>
</method>
<method type="int">
<sel>minConnections</sel>
<desc>
Return the minimum number of database connections in
the pool.
</desc>
</method>
<method type="SQLClient*">
<sel>provideClient</sel>
<desc>
Fetches an (autoreleased) client from the pool.
<br /> This method blocks indefinitely waiting for a
client to become available in the pool.
</desc>
</method>
<method type="SQLClient*">
<sel>provideClientBeforeDate:</sel>
<arg type="NSDate*">when</arg>
<desc>
Fetches an (autoreleased) client from the pool.
<br /> If no client is or becomes available before
the specified date then the method returns
<code>nil</code>. <br /> If <var>when</var> is
<code>nil</code> then a date in the distant future
is used so that the method will effectively wait forever
to get a client.
</desc>
</method>
<method type="void">
<sel>setCache:</sel>
<arg type="GSCache*">aCache</arg>
<desc>
Sets the cache for all the clients in the pool.
</desc>
</method>
<method type="void">
<sel>setCacheThread:</sel>
<arg type="NSThread*">aThread</arg>
<desc>
Sets the cache thread for all the clients in the pool.
</desc>
</method>
<method type="void">
<sel>setDebugging:</sel>
<arg type="unsigned int">level</arg>
<desc>
Set the debugging <var>level</var> for all clients in
the pool.
</desc>
</method>
<method type="void">
<sel>setDurationLogging:</sel>
<arg type="NSTimeInterval">threshold</arg>
<desc>
Set the duration logging <var>threshold</var> for all
clients in the pool.
</desc>
</method>
<method type="void">
<sel>setMax:</sel>
<arg type="int">maxConnections</arg>
<sel>min:</sel>
<arg type="int">minConnections</arg>
<desc>
Sets the pool size limits (number of connections we
try to maintain). <br /> The value of
<var>maxConnections</var> is the size of the pool (ie
the number of clients created) and thus the maximum
number of concurrent connections to the database
server. <br /> The value of
<var>minConnections</var> is the minimum number of
connected clients normally expected to be in the
pool. The pool tries to ensure that it doesn't
contain more than this number of idle connected
clients. <br /> The value of
<var>maxConnections</var> must be greater than or
equal to that of <var>minConnections</var> and may
not be greater than 100. The value of
<var>minConnections</var> must be less than or equal
to that of <var>maxConnections</var> and may not be less
than 1.
</desc>
</method>
<method type="NSString*">
<sel>statistics</sel>
<desc>
Returns a string describing the usage of the pool.
</desc>
</method>
<method type="BOOL">
<sel>swallowClient:</sel>
<arg type="SQLClient*">client</arg>
<desc>
Puts the <var>client</var> back in the pool. This
happens automatically when a <var>client</var> from
a pool would normally be deallocated so you don't
generally need to do it. <br /> Returns
<code>YES</code> if the supplied <var>client</var>
was from the pool, <code>NO</code> otherwise. <br /> If
the swallowed <var>client</var> would take the count of
idle <var>client</var> connections in the pool above
the configured minimum, the oldest (ie longest idle)
<var>client</var> in the pool is disconnected.
</desc>
</method>
</class>
</chapter>
<chapter>
<heading>
Software documentation for the SQLDictionaryBuilder
class
</heading>
<class name="SQLDictionaryBuilder" super="NSObject">
<declared>SQLClient.h</declared>
<desc>
<em>Description forthcoming.</em>
</desc>
<ivariable type="NSMutableDictionary*" name="content" validity="protected">
<desc>
<em>Description forthcoming.</em>
</desc>
</ivariable>
<method type="void">
<sel>addObject:</sel>
<arg type="id">anObject</arg>
<desc>
No need to do anything... the object will already have
been added by the
<ref type="method" id="-newWithValues:keys:count:">
-newWithValues:keys:count:
</ref>
method.
</desc>
</method>
<method type="id">
<sel>alloc</sel>
<desc>
When a container is supposed to be allocated, we just
return the receiver (which will then quietly ignore
<ref type="method" id="-addObject:">
-addObject:
</ref>
messages).
</desc>
</method>
<method type="NSMutableDictionary*">
<sel>content</sel>
<desc>
Returns the content dictionary for the receiver.
</desc>
</method>
<method type="id">
<sel>initWithCapacity:</sel>
<arg type="NSUInteger">capacity</arg>
<desc>
Creates a new content dictionary... this method
will be called automatically by the SQLClient object
when it performs a query, so there is no need to call
it at any other time.
</desc>
</method>
<method type="id">
<sel>mutableCopyWithZone:</sel>
<arg type="NSZone*">aZone</arg>
<desc>
Makes a mutable copy of the content dictionary
(called when a caching query uses this helper to
produce the cached collection).
</desc>
</method>
<method type="id">
<sel>newWithValues:</sel>
<arg type="id*">values</arg>
<sel>keys:</sel>
<arg type="NSString**">keys</arg>
<sel>count:</sel>
<arg type="unsigned int">count</arg>
<desc>
This is the main workhorse of the class... it is
called once for every record read from the database,
and is responsible for adding that record to the
content dictionary. The default implementation,
instead of creating an object to hold the supplied
record data, uses the two fields from the record as
a key-value pair to add to the content dictionary, and
returns <code>nil</code> as the record object. It's
OK to return a <code>nil</code> object since we ignore
the
<ref type="method" id="-addObject:">
-addObject:
</ref>
argument.
</desc>
</method>
</class>
</chapter>
<chapter>
<heading>
Software documentation for the SQLRecord class
</heading>
<class name="SQLRecord" super="NSArray">
<declared>SQLClient.h</declared>
<desc>
<p>
An enhanced array to represent a record returned from a
query. You should <em>NOT</em> try to create
instances of this class except via the
<ref type="method" id="+newWithValues:keys:count:">
+newWithValues:keys:count:
</ref>
method.
</p>
<p>
SQLRecord is the abstract base class of a class
cluster. If you wish to subclass it you must
implement the primitive methods
<ref type="method" id="+newWithValues:keys:count:">
+newWithValues:keys:count:
</ref>
<ref type="method" id="-count">
-count
</ref>
<ref type="method" id="-keyAtIndex:">
-keyAtIndex:
</ref>
<ref type="method" id="-objectAtIndex:">
-objectAtIndex:
</ref>
and
<ref type="method" id="-replaceObjectAtIndex:withObject:">
-replaceObjectAtIndex:withObject:
</ref>
</p>
<p>
NB. You do not need to use SQLRecord (or a subclass of
it), all you actually need to supply is a class which
responds to the
<ref type="method" id="+newWithValues:keys:count:">
+newWithValues:keys:count:
</ref>
method that the system uses to create new records...
none of the other methods of the SQLRecord class are
used internally by the SQLClient system.
</p>
</desc>
<method type="id" factory="yes">
<sel>newWithValues:</sel>
<arg type="id*">v</arg>
<sel>keys:</sel>
<arg type="NSString**">k</arg>
<sel>count:</sel>
<arg type="unsigned int">c</arg>
<desc>
Create a new SQLRecord containing the specified
fields. <br /> NB. The values and keys are
<em>retained</em> by the record rather than being
copied. <br /> A <code>nil</code> value is
represented by [NSNull null]. <br /> Keys must
be unique string values (case insensitive comparison).
</desc>
</method>
<method type="NSArray*">
<sel>allKeys</sel>
<desc>
Returns an array containing the names of all the
fields in the record.
</desc>
</method>
<method type="NSUInteger">
<sel>count</sel>
<desc>
Returns the number of items in the record. <br />
Subclasses must implement this method.
</desc>
</method>
<method type="NSMutableDictionary*">
<sel>dictionary</sel>
<desc>
Return the record as a mutable dictionary with the
keys as the record field names standardised to be
lowercase strings.
</desc>
</method>
<method type="void">
<sel>getKeys:</sel>
<arg type="id*">buf</arg>
<desc>
Optimised mechanism for retrieving all keys in
order.
</desc>
</method>
<method type="void">
<sel>getObjects:</sel>
<arg type="id*">buf</arg>
<desc>
Optimised mechanism for retrieving all objects.
</desc>
</method>
<method type="NSString*" override="subclass">
<sel>keyAtIndex:</sel>
<arg type="NSUInteger">index</arg>
<desc>
Returns the key at the specified indes. <br />
</desc>
</method>
<method type="id" override="subclass">
<sel>objectAtIndex:</sel>
<arg type="NSUInteger">index</arg>
<desc>
Returns the object at the specified indes. <br />
</desc>
</method>
<method type="id">
<sel>objectForKey:</sel>
<arg type="NSString*">key</arg>
<desc>
Returns the value of the named field. <br /> The
field name is case insensitive.
</desc>
</method>
<method type="void">
<sel>replaceObjectAtIndex:</sel>
<arg type="NSUInteger">index</arg>
<sel>withObject:</sel>
<arg type="id">anObject</arg>
<desc>
Replaces the value at the specified
<var>index</var>. <br /> Subclasses must implement
this method.
</desc>
</method>
<method type="void">
<sel>setObject:</sel>
<arg type="id">anObject</arg>
<sel>forKey:</sel>
<arg type="NSString*">aKey</arg>
<desc>
Replaces the value of the named field. <br /> The
field name is case insensitive. <br /> NB. You must
be careful not to change the contents of a record which
has been cached (unless you are sure you really want
to), as you will be changing the contents of the
cache, not just a private copy.
</desc>
</method>
<method type="NSUInteger">
<sel>sizeInBytes:</sel>
<arg type="NSMutableSet*">exclude</arg>
<desc>
Return approximate size of this record in bytes.
<br /> The <var>exclude</var> set is used to specify
objects to <var>exclude</var> from the calculation
(to prevent recursion etc).
</desc>
</method>
</class>
</chapter>
<chapter>
<heading>
Software documentation for the SQLSetBuilder class
</heading>
<class name="SQLSetBuilder" super="NSObject">
<declared>SQLClient.h</declared>
<desc>
<em>Description forthcoming.</em>
</desc>
<ivariable type="NSUInteger" name="added" validity="protected">
<desc>
<em>Description forthcoming.</em>
</desc>
</ivariable>
<ivariable type="NSCountedSet*" name="content" validity="protected">
<desc>
<em>Description forthcoming.</em>
</desc>
</ivariable>
<method type="void">
<sel>addObject:</sel>
<arg type="id">anObject</arg>
<desc>
No need to do anything... the object will already have
been added by the
<ref type="method" id="-newWithValues:keys:count:">
-newWithValues:keys:count:
</ref>
method.
</desc>
</method>
<method type="NSUInteger">
<sel>added</sel>
<desc>
Returns the number of objects actually added to the
counted set.
</desc>
</method>
<method type="id">
<sel>alloc</sel>
<desc>
When a container is supposed to be allocated, we just
return the receiver (which will then quietly ignore
<ref type="method" id="-addObject:">
-addObject:
</ref>
messages).
</desc>
</method>
<method type="NSCountedSet*">
<sel>content</sel>
<desc>
Returns the counted set for the receiver.
</desc>
</method>
<method type="id">
<sel>initWithCapacity:</sel>
<arg type="NSUInteger">capacity</arg>
<desc>
Creates a new content set... this method will be
called automatically by the SQLClient object when it
performs a query, so there is no need to call it
at any other time.
</desc>
</method>
<method type="id">
<sel>mutableCopyWithZone:</sel>
<arg type="NSZone*">aZone</arg>
<desc>
Makes a mutable copy of the content dictionary
(called when a caching query uses this helper to
produce the cached collection).
</desc>
</method>
<method type="id">
<sel>newWithValues:</sel>
<arg type="id*">values</arg>
<sel>keys:</sel>
<arg type="NSString**">keys</arg>
<sel>count:</sel>
<arg type="unsigned int">count</arg>
<desc>
This is the main workhorse of the class... it is
called once for every record read from the database,
and is responsible for adding that record to the
content set. The default implementation, instead of
creating an object to hold the supplied record
data, uses the singe field from the record to add to
the content set, and returns <code>nil</code> as the
record object. It's OK to return a <code>nil</code>
object since we ignore the
<ref type="method" id="-addObject:">
-addObject:
</ref>
argument.
</desc>
</method>
</class>
</chapter>
<chapter>
<heading>
Software documentation for the SQLSingletonBuilder
class
</heading>
<class name="SQLSingletonBuilder" super="NSObject">
<declared>SQLClient.h</declared>
<desc>
<em>Description forthcoming.</em>
</desc>
<method type="id">
<sel>newWithValues:</sel>
<arg type="id*">values</arg>
<sel>keys:</sel>
<arg type="NSString**">keys</arg>
<sel>count:</sel>
<arg type="unsigned int">count</arg>
<desc>
<em>Description forthcoming.</em>
</desc>
</method>
</class>
</chapter>
<chapter>
<heading>
Software documentation for the SQLTransaction class
</heading>
<class name="SQLTransaction" super="NSObject">
<declared>SQLClient.h</declared>
<conform>NSCopying</conform>
<desc>
The SQLTransaction transaction class provides a
convenient mechanism for grouping together a
series of SQL statements to be executed as a single
transaction. It avoids the need for handling
begin/commit, and should be as efficient as
reasonably possible. <br /> You obtain an instance
by calling
<ref type="method" id="-transaction" class="SQLClient">
[SQLClient -transaction]
</ref>
, add SQL statements to it using the
<ref type="method" id="-add:,...">
-add:,...
</ref>
and/or
<ref type="method" id="-add:with:">
-add:with:
</ref>
methods, and then use the
<ref type="method" id="-execute">
-execute
</ref>
method to perform all the statements as a single
operation. <br /> Any exception is caught and
re-raised in the
<ref type="method" id="-execute">
-execute
</ref>
method after any tidying up to leave the database in a
consistent state. <br /> NB. This class is not in
itsself thread-safe, though the underlying database
operations should be. If you have multiple
threads, you should create multiple SQLTransaction
instances, at least one per thread.
</desc>
<ivariable type="BOOL" name="_batch" validity="protected">
<desc>
<em>Warning</em> the underscore at the start of the
name of this instance variable indicates that, even
though it is not technically <em>private</em>, it is
intended for internal use within the package, and
you should not use the variable in other code.
</desc>
</ivariable>
<ivariable type="unsigned int" name="_count" validity="protected">
<desc>
<em>Warning</em> the underscore at the start of the
name of this instance variable indicates that, even
though it is not technically <em>private</em>, it is
intended for internal use within the package, and
you should not use the variable in other code.
</desc>
</ivariable>
<ivariable type="SQLClient*" name="_db" validity="protected">
<desc>
<em>Warning</em> the underscore at the start of the
name of this instance variable indicates that, even
though it is not technically <em>private</em>, it is
intended for internal use within the package, and
you should not use the variable in other code.
</desc>
</ivariable>
<ivariable type="NSMutableArray*" name="_info" validity="protected">
<desc>
<em>Warning</em> the underscore at the start of the
name of this instance variable indicates that, even
though it is not technically <em>private</em>, it is
intended for internal use within the package, and
you should not use the variable in other code.
</desc>
</ivariable>
<ivariable type="uint8_t" name="_merge" validity="protected">
<desc>
<em>Warning</em> the underscore at the start of the
name of this instance variable indicates that, even
though it is not technically <em>private</em>, it is
intended for internal use within the package, and
you should not use the variable in other code.
</desc>
</ivariable>
<ivariable type="BOOL" name="_stop" validity="protected">
<desc>
<em>Warning</em> the underscore at the start of the
name of this instance variable indicates that, even
though it is not technically <em>private</em>, it is
intended for internal use within the package, and
you should not use the variable in other code.
</desc>
</ivariable>
<method type="void">
<sel>add:</sel>
<arg type="NSString*">stmt</arg>
<vararg />
<desc>
Adds an SQL statement to the transaction. This is
similar to
<ref type="method" id="-execute:,..." class="SQLClient">
[SQLClient -execute:,...]
</ref>
but does not cause any database operation until
<ref type="method" id="-execute">
-execute
</ref>
is called, so it will not raise a database exception.
</desc>
</method>
<method type="void">
<sel>add:</sel>
<arg type="NSString*">stmt</arg>
<sel>with:</sel>
<arg type="NSDictionary*">values</arg>
<desc>
Adds an SQL statement to the transaction. This is
similar to
<ref type="method" id="-execute:with:" class="SQLClient">
[SQLClient -execute:with:]
</ref>
but does not cause any database operation until
<ref type="method" id="-execute">
-execute
</ref>
is called, so it will not raise a database exception.
</desc>
</method>
<method type="void">
<sel>append:</sel>
<arg type="SQLTransaction*">other</arg>
<desc>
Appends a copy of the <var>other</var> transaction
to the receiver. <br /> This provides a convenient way
of merging transactions which have been built by
different code modules, in order to have them all
executed together in a single operation (for
efficiency etc). <br /> This does not alter the
<var>other</var> transaction, so if the execution of
a group of merged transactions fails, it is then possible
to attempt to commit the individual transactions
separately. <br /> NB. All transactions
appended must be using the same database
connection (SQLClient instance).
</desc>
</method>
<method type="id">
<sel>copyWithZone:</sel>
<arg type="NSZone*">z</arg>
<desc>
Make a copy of the receiver.
</desc>
</method>
<method type="NSUInteger">
<sel>count</sel>
<desc>
Returns the number of individual statements and/or
subsidiary transactions which have been added to
the receiver. For a count of the total number of
statements, use the
<ref type="method" id="-totalCount">
-totalCount
</ref>
method.
</desc>
</method>
<method type="SQLClient*">
<sel>db</sel>
<desc>
Returns the database client with which this
instance operates. <br /> This client is retained
by the transaction.
</desc>
</method>
<method type="void">
<sel>execute</sel>
<desc>
<p>
Performs any statements added to the transaction
as a single operation. If any problem occurs, an
NSException is raised, but the database
connection is left in a consistent state and a
partially completed operation is rolled back.
</p>
<p>
NB. If the database is not already in a transaction,
this implicitly calls the
<ref type="method" id="-begin">
-begin
</ref>
method to start the transaction before executing
the statements. <br /> The method always commits the
transaction, even if the transaction was
begun earlier rather than in
<ref type="method" id="-execute">
-execute
</ref>
. <br /> This behavior allows you to call
<ref type="method" id="-begin" class="SQLClient">
[SQLClient -begin]
</ref>
, then run one or more queries, build up a transaction
based upon the query results, and then
<ref type="method" id="-execute">
-execute
</ref>
that transaction, causing the entire process to be
commited as a single transaction.
</p>
</desc>
</method>
<method type="unsigned">
<sel>executeBatch</sel>
<desc>
Convenience method which calls
<ref type="method" id="-executeBatchReturningFailures:logExceptions:">-executeBatchReturningFailures:logExceptions:</ref> with a <code>nil</code> failures argument and exception logging off.
</desc>
</method>
<method type="unsigned">
<sel>executeBatchReturningFailures:</sel>
<arg type="SQLTransaction*">failures</arg>
<sel>logExceptions:</sel>
<arg type="BOOL">log</arg>
<desc>
<p>
This is similar to the
<ref type="method" id="-execute">
-execute
</ref>
method, but may allow partial execution of the
transaction if appropriate:
</p>
<p>
If the transaction was created using the
<ref type="method" id="-batch:" class="SQLClient">
[SQLClient -batch:]
</ref>
method and the transaction as a whole fails,
individual statements are retried. <br /> The
stopOnFailure flag for the batch creation
indicates whether the retries are stopped at
the first statement to fail, or continue (skipping
any failed statements).
</p>
<p>
If the transaction has had transactions appended to
it, those subsidiary transactions may succeed or fail
atomically depending on their individual
attributes.
</p>
<p>
If the transaction was not created using
<ref type="method" id="-batch:" class="SQLClient">
[SQLClient -batch:]
</ref>
, then calling this method is equivalent to calling the
<ref type="method" id="-execute">
-execute
</ref>
method.
</p>
<p>
If any statements/transactions in the batch fail, they
are added to the transaction supplied in the
<var>failures</var> parameter (if it's not
<code>nil</code>) so that you can retry them
later. <br /> NB. statements/transactions which
are not executed at all (because the batch is set to
stop on the first failure) are <em>also</em> added
to the <var>failures</var> transaction.
</p>
<p>
If the <var>log</var> argument is <code>YES</code>,
then any exceptions encountered when executing the
batch are logged using the
<ref type="method" id="-debug:,..." class="SQLClient">
[SQLClient -debug:,...]
</ref>
method, even if debug logging is not enabled with
<ref type="method" id="-setDebugging:" class="SQLClient">[SQLClient -setDebugging:]</ref>.
</p>
The method returns the number of statements which
actually succeeded.
</desc>
</method>
<method type="void">
<sel>insertTransaction:</sel>
<arg type="SQLTransaction*">trn</arg>
<sel>atIndex:</sel>
<arg type="unsigned">index</arg>
<desc>
Insert <var>trn</var> at the index'th position in
the receiver. <br /> The transaction <var>trn</var>
must be non-empty and must use the same database
client as the receiver.
</desc>
</method>
<method type="void">
<sel>removeTransactionAtIndex:</sel>
<arg type="unsigned">index</arg>
<desc>
Remove the index'th transaction or statement from
the receiver.
</desc>
</method>
<method type="void">
<sel>reset</sel>
<desc>
Resets the transaction, removing all previously
added statements. This allows the transaction object
to be re-used for multiple transactions.
</desc>
</method>
<method type="uint8_t">
<sel>setMerge:</sel>
<arg type="uint8_t">history</arg>
<desc>
<p>
Use this method to enable merging of statemements
subsequently added or appended to the
receiver. The <var>history</var> argument
specifies how many of the most recent
statements in the transaction should be
checked for merging in a new statement, with a
value of zero meaning that no merging is done.
<br /> Returns the previous setting for the
transaction.
</p>
<p>
You may use this feature with an insert statement of
the form: <br /> INSERT INTO table (fieldnames)
VALUES (values); <br /> For databases which
support multiline inserts such that they can be
merged into something of the form: INSERT INTO
table (fieldnames) VALUES (values1),(values2),...;
</p>
<p>
Or may use this with an update or delete statement of
the form: <br /> command table SET settings WHERE
condition; <br /> So that statements may be
merged into: <br /> command table SET settings
WHERE (condition1) OR (condition2) OR...;
</p>
If no opportunity for merging is found, the new
statement is simply added to the transaction.
<br /> Caveats: <br /> 1. databases may not actually
support multiline insert. <br /> 2. Merging is done
only if the statement up to the string 'VALUES' (for
insert) or 'WHERE' (for update) matches. <br /> 3.
Merging into any of the last N statements (where N
is greater than 1) may of course change the order of
statements in the transaction, so care must be
taken not to use this feature where that might
matter. <br /> 4. This is a simple text match
rather than sql syntactic analysis, so it's possible
to confuse the process with complex statements.
</desc>
</method>
<method type="unsigned">
<sel>totalCount</sel>
<desc>
Returns the total count of statements in this
transaction including those in any subsidiary
transactions. For a count of the statements
and/or transactions directly added to the receiver,
use the <ref type="method" id="-count">-count</ref>
method.
</desc>
</method>
<method type="SQLTransaction*">
<sel>transactionAtIndex:</sel>
<arg type="unsigned">index</arg>
<desc>
Return an autoreleased copy of the index'th
transaction or statement added to the receiver.
<br /> Since the returned transaction contains a
copy of the statement/transaction in the receiver, you
can modify it without effecting the original.
</desc>
</method>
</class>
</chapter>
<chapter>
<heading>
Software documentation for the SQLClient(Caching)
category
</heading>
<category name="Caching" class="SQLClient">
<declared>SQLClient.h</declared>
<desc>
This category provides methods for caching the results
of queries in order to reduce the number of client-server
trips and the database load produced by an application
which needs update its information from the database
frequently.
</desc>
<method type="GSCache*">
<sel>cache</sel>
<desc>
Returns the cache used by the receiver for storing
the results of requests made through it. Creates a new
cache if necessary.
</desc>
</method>
<method type="NSMutableArray*">
<sel>cache:</sel>
<arg type="int">seconds</arg>
<sel>query:</sel>
<arg type="NSString*">stmt</arg>
<vararg />
<desc>
Calls
<ref type="method" id="-cache:simpleQuery:recordType:listType:">-cache:simpleQuery:recordType:listType:</ref> with the default record class, array class, and with a query string formed from <var>stmt</var> and the following values (if any).
</desc>
</method>
<method type="NSMutableArray*">
<sel>cache:</sel>
<arg type="int">seconds</arg>
<sel>query:</sel>
<arg type="NSString*">stmt</arg>
<sel>with:</sel>
<arg type="NSDictionary*">values</arg>
<desc>
Calls
<ref type="method" id="-cache:simpleQuery:recordType:listType:">-cache:simpleQuery:recordType:listType:</ref> with the default record class array class and with a query string formed from <var>stmt</var> and <var>values</var>.
</desc>
</method>
<method type="NSMutableArray*">
<sel>cache:</sel>
<arg type="int">seconds</arg>
<sel>simpleQuery:</sel>
<arg type="NSString*">stmt</arg>
<desc>
Calls
<ref type="method" id="-cache:simpleQuery:recordType:listType:">-cache:simpleQuery:recordType:listType:</ref> with the default record class and array class.
</desc>
</method>
<method type="NSMutableArray*">
<sel>cache:</sel>
<arg type="int">seconds</arg>
<sel>simpleQuery:</sel>
<arg type="NSString*">stmt</arg>
<sel>recordType:</sel>
<arg type="id">rtype</arg>
<sel>listType:</sel>
<arg type="id">ltype</arg>
<desc>
If the result of the query is already cached and has not
expired, return it. Otherwise, perform the query
and cache the result giving it the specified lifetime
in <var>seconds</var>. <br /> If <var>seconds</var> is
negative, the query is performed irrespective of
whether it is already cached, and its absolute
value is used to set the lifetime of the results.
<br /> If <var>seconds</var> is zero, the cache for
this query is emptied. <br /> Handles locking. <br />
Maintains
<ref type="method" id="-lastOperation">
-lastOperation
</ref>
date. <br /> The value of <var>rtype</var> must
respond to the
<ref type="method" id="+newWithValues:keys:count:" class="SQLRecord">[SQLRecord +newWithValues:keys:count:]</ref> method. <br /> If <var>rtype</var> is <code>nil</code> then the
<ref type="class" id="SQLRecord">SQLRecord</ref>
class is used. <br /> The value of <var>ltype</var>
must respond to the
<ref type="method" id="+alloc" class="NSObject">
[NSObject +alloc]
</ref>
method to produce a container which must repond to
the
<ref type="method" id="-initWithCapacity:" class="NSMutableArray">[NSMutableArray -initWithCapacity:]</ref> method to initialise itsself and the <ref type="method" id="-addObject:" class="NSMutableArray">[NSMutableArray -addObject:]</ref> method to add records to the list. <br /> If <var>ltype</var> is <code>nil</code> then the
<ref type="class" id="NSMutableArray">NSMutableArray</ref>
class is used. <br /> The list produced by this
argument is used as the return value of this
method. <br /> If a cache thread has been set
using the
<ref type="method" id="-setCacheThread:">
-setCacheThread:
</ref>
method, and the
<ref type="method" id="-cache:simpleQuery:recordType:listType:">-cache:simpleQuery:recordType:listType:</ref> method is called from a thread other than the cache thread, then any query to retrieve uncached data will be performed in the cache thread, and for cached (but expired) data, the old (expired) results may be returned... in which case an asynchronous query to update the cache will be executed as soon as possible in the cache thread.
</desc>
</method>
<method type="void">
<sel>setCache:</sel>
<arg type="GSCache*">aCache</arg>
<desc>
Sets the cache to be used by the receiver for storing
the results of requests made through it. <br /> If
<var>aCache</var> is <code>nil</code>, the current
cache is released, and a new cache will be
automatically created as soon as there is a
need to cache anything.
</desc>
</method>
<method type="void">
<sel>setCacheThread:</sel>
<arg type="NSThread*">aThread</arg>
<desc>
Sets the thread to be used to retrieve data to
populate the cache. <br /> All cached queries will
be performed in this thread (if non-nil). <br /> The
setting of a thread for the cache also implies that
expired items in the cache may not be removed when
they are queried from another thread, rather they can
be kept (if they are not <em>too</em> old) and an
asynchronous query to update them will be run
on the cache thread. <br /> The rule is that, if the
item's age is more than twice its nominal lifetime,
it will be retrieved immediately, otherwise it will be
retrieved asynchronously. <br /> Currently this
may only be the main thread or <code>nil</code>. Any
attempt to set another thread will use the main
thread instead.
</desc>
</method>
</category>
</chapter>
<chapter>
<heading>
Software documentation for the SQLClient(Convenience)
category
</heading>
<category name="Convenience" class="SQLClient">
<declared>SQLClient.h</declared>
<desc>
This category contains convenience methods including
those for frequently performed database operations...
message logging etc.
</desc>
<method type="SQLTransaction*">
<sel>batch:</sel>
<arg type="BOOL">stopOnFailure</arg>
<desc>
Returns a transaction object configured to handle
batching and execute part of a batch of statements
if execution of the whole using the
<ref type="method" id="-executeBatch" class="SQLTransaction">[SQLTransaction -executeBatch]</ref> method fails. <br /> If <var>stopOnFailure</var> is <code>YES</code> than execution of the transaction will stop with the first statement to fail, otherwise it will execute all the statements it can, skipping any failed statements.
</desc>
</method>
<method type="NSMutableArray*">
<sel>columns:</sel>
<arg type="NSMutableArray*">records</arg>
<desc>
Convenience method to deal with the results of
a query converting the normal array of <var>records</var>
into an array of record columns. Each column in the
array is an array containing all the values from that
column.
</desc>
</method>
<method type="SQLRecord*">
<sel>queryRecord:</sel>
<arg type="NSString*">stmt</arg>
<vararg />
<desc>
Executes a query (like the
<ref type="method" id="-query:,...">
-query:,...
</ref>
method) and checks the result (raising an exception
if the query did not contain a single record) and
returns the resulting record.
</desc>
</method>
<method type="NSString*">
<sel>queryString:</sel>
<arg type="NSString*">stmt</arg>
<vararg />
<desc>
Executes a query (like the
<ref type="method" id="-query:,...">
-query:,...
</ref>
method) and checks the result. <br /> Raises an
exception if the query did not contain a single
record, or if the record did not contain a single
field. <br /> Returns the resulting field as a
<em>string</em>.
</desc>
</method>
<method type="void">
<sel>singletons:</sel>
<arg type="NSMutableArray*">records</arg>
<desc>
Convenience method to deal with the results of
a query where each record contains a single field... it
converts the array of <var>records</var> returned
by the query to an array containing the fields. <br />
NB. This does not check that the contents of the
<var>records</var> array are actually instances of
<ref type="class" id="SQLRecord">SQLRecord</ref>
, so you must ensure you don't call it more than once
on the same array (something that may happen if you
retrieve the array using a cache based query).
</desc>
</method>
<method type="SQLTransaction*">
<sel>transaction</sel>
<desc>
Creates and returns an autoreleased SQLTransaction
instance which will use the receiver as the
database connection to perform transactions.
</desc>
</method>
</category>
</chapter>
<chapter>
<heading>
Software documentation for the SQLClient(Logging)
category
</heading>
<category name="Logging" class="SQLClient">
<declared>SQLClient.h</declared>
<desc>
This category porovides basic methods for logging debug
information.
</desc>
<method type="unsigned int" factory="yes">
<sel>debugging</sel>
<desc>
Return the class-wide debugging level, which is
inherited by all newly created instances.
</desc>
</method>
<method type="NSTimeInterval" factory="yes">
<sel>durationLogging</sel>
<desc>
Return the class-wide duration logging threshold,
which is inherited by all newly created instances.
</desc>
</method>
<method type="void" factory="yes">
<sel>setDebugging:</sel>
<arg type="unsigned int">level</arg>
<desc>
Set the debugging <var>level</var> to be inherited by
all new instances. <br /> See
<ref type="method" id="-setDebugging:" class="SQLClient(Logging)">[SQLClient(Logging) -setDebugging:]</ref> for controlling an individual instance of the class.
</desc>
</method>
<method type="void" factory="yes">
<sel>setDurationLogging:</sel>
<arg type="NSTimeInterval">threshold</arg>
<desc>
Set the duration logging <var>threshold</var> to be
inherited by new instances. <br /> See
<ref type="method" id="-setDurationLogging:" class="SQLClient(Logging)">[SQLClient(Logging) -setDurationLogging:]</ref> for controlling an individual instance of the class.
</desc>
</method>
<method type="void">
<sel>debug:</sel>
<arg type="NSString*">fmt</arg>
<vararg />
<desc>
The default implementation calls NSLogv to log a debug
message. <br /> Override this in a category to
provide more sophisticated logging. <br /> Do NOT
override with code which can be slow or which
calls (directly or indirectly) any SQLCLient methods,
since this method will be used inside locked regions
of the SQLClient code and you could cause deadlocks or
<strong>long</strong> delays to other threads
using the class.
</desc>
</method>
<method type="unsigned int">
<sel>debugging</sel>
<desc>
Return the current debugging level. <br /> A level
of zero (default) means that no debug output is
produced, except for that concerned with logging
the database transactions taking over a certain amount
of time (see the
<ref type="method" id="-setDurationLogging:">
-setDurationLogging:
</ref>
method).
</desc>
</method>
<method type="NSTimeInterval">
<sel>durationLogging</sel>
<desc>
Returns the threshold above which queries and
statements taking a <strong>long</strong> time
to execute are logged. A negative value (default)
indicates that this logging is disabled. A value
of zero means that all statements are logged.
</desc>
</method>
<method type="void">
<sel>setDebugging:</sel>
<arg type="unsigned int">level</arg>
<desc>
Set the debugging <var>level</var> of this instance...
overrides the default <var>level</var> inherited
from the class.
</desc>
</method>
<method type="void">
<sel>setDurationLogging:</sel>
<arg type="NSTimeInterval">threshold</arg>
<desc>
Set a <var>threshold</var> above which queries and
statements taking a <strong>long</strong> time
to execute are logged. A negative value (default)
disables this logging. A value of zero logs all
statements.
</desc>
</method>
</category>
</chapter>
<chapter>
<heading>
Software documentation for the
SQLClient(Notifications) category
</heading>
<category name="Notifications" class="SQLClient">
<declared>SQLClient.h</declared>
<desc>
This category contains methods for asynchronous
notification of events via the database (for
those database backends which support it: currently
only PostgreSQL).
</desc>
<method type="void">
<sel>addObserver:</sel>
<arg type="id">anObserver</arg>
<sel>selector:</sel>
<arg type="SEL">aSelector</arg>
<sel>name:</sel>
<arg type="NSString*">name</arg>
<desc>
Adds <var>anObserver</var> to receive notifications
when the backend database server sends an asynchronous
event identified by the specified <var>name</var>
(which must be a valid database identifier). <br />
When a notification (NSNotification instance) is
received by the method specified by
<var>aSelector</var>, its <em>object</em> will be the
SQLClient instance to which <var>anObserver</var>
was added and its userInfo dictionary will contain the
key 'Local' and possibly the key 'Payload'. <br /> If
the 'Local' value is the boolean <code>YES</code>, the
notification originated as an action by this
SQLClient instance. <br /> If the 'Payload' value
is not <code>nil</code>, then it is a string providing
extra information about the notification. <br /> NB.
At the point when the observer is notified about an
event the database client object will be locked and
may not be used to query or modify the database
(typically a database query will already be in
progress). The method handling the notification
must therefore handle any database operations in a
later timeout.
</desc>
</method>
<method type="void">
<sel>postNotificationName:</sel>
<arg type="NSString*">name</arg>
<sel>payload:</sel>
<arg type="NSString*">more</arg>
<desc>
Posts a notification via the database. The
<var>name</var> is an SQL identifier (for which
observers may have registered) and the extra
payload information may be <code>nil</code> if not
required.
</desc>
</method>
<method type="void">
<sel>removeObserver:</sel>
<arg type="id">anObserver</arg>
<sel>name:</sel>
<arg type="NSString*">name</arg>
<desc>
Removes <var>anObserver</var> as an observer for
asynchronous notifications from the database
server. If <var>name</var> is omitted, the observer
will be removed for all names.
</desc>
</method>
</category>
</chapter>
<chapter>
<heading>
Software documentation for the SQLClient(Subclass)
category
</heading>
<category name="Subclass" class="SQLClient">
<declared>SQLClient.h</declared>
<desc>
This category contains the methods which a subclass
<em>must</em> override to provide a working instance,
and helper methods for the backend implementations.
<br /> Application programmers should <em>not</em>
call the backend methods directly. <br />
<p>
When subclassing to produce a backend driver bundle,
please be aware that the subclass must <em>NOT</em>
introduce additional instance variables. Instead
the <em>extra</em> instance variable is provided for
use as a pointer to subclass specific data.
</p>
</desc>
<method type="BOOL" override="subclass">
<sel>backendConnect</sel>
<desc>
Attempts to establish a connection to the database
server. <br /> Returns a flag to indicate whether
the connection has been established. <br /> If a
connection was already established, returns
<code>YES</code> and does nothing. <br /> You should
not need to use this method normally, as it is called
for you automatically when necessary. <br />
<p>
Subclasses <strong>must</strong> implement
this method to establish a connection to the
database server process (and initialise the
<em>extra</em> instance variable if necessary),
setting the <em>connected</em> instance variable
to indicate the state of the object.
</p>
<p>
This method must call
<ref type="method" id="+purgeConnections:">
+purgeConnections:
</ref>
to ensure that there is a free slot for the new
connection.
</p>
<p>
Application code must <em>not</em> call this
method directly, it is for internal use only. The
<ref type="method" id="-connect">
-connect
</ref>
method calls this method if the <em>connected</em>
instance variable is <code>NO</code>.
</p>
</desc>
</method>
<method type="void" override="subclass">
<sel>backendDisconnect</sel>
<desc>
Disconnect from the database unless already
disconnected. <br />
<p>
This method is called automatically when the
receiver is deallocated or reconfigured, and may
also be called automatically when there are too many
database connections active.
</p>
<p>
If the receiver is an instance of a subclass which
uses the <em>extra</em> instance variable, it
<strong>must</strong> clear that variable in the
<ref type="method" id="-backendDisconnect">
-backendDisconnect
</ref>
method, because a reconfiguration may cause the
class of the receiver to change.
</p>
<p>
This method must set the <em>connected</em> instance
variable to <code>NO</code>.
</p>
<p>
Application code must <em>not</em> call this
method directly, it is for internal use only. The
<ref type="method" id="-disconnect">
-disconnect
</ref>
method calls this method if the <em>connected</em>
instance variable is <code>YES</code>.
</p>
</desc>
</method>
<method type="NSInteger" override="subclass">
<sel>backendExecute:</sel>
<arg type="NSArray*">info</arg>
<desc>
Perform arbitrary operation
<em>which does not return any value.</em> <br /> This
method has a single argument, an array containing
the string representing the statement to be executed as
its first object, and an optional sequence of data
objects following it. <br />
<example>
[db backendExecute: [NSArray arrayWithObject:
@"UPDATE MyTable SET Name = 'The name' WHERE ID = 123"]];
</example>
<p>
The backend implementation is required to perform the
SQL statement using the supplied NSData objects at
the points in the statement marked by the
<code>'?'''?'</code> sequence. The marker
saequences are inserted into the statement at
an earlier stage by the
<ref type="method" id="-execute:,...">
-execute:,...
</ref>
and
<ref type="method" id="-execute:with:">
-execute:with:
</ref>
methods.
</p>
<p>
Callers should lock the instance using the
<em>lock</em> instance variable for the duration of
the operation, and unlock it afterwards.
</p>
<p>
NB. callers (other than the
<ref type="method" id="-begin">
-begin
</ref>
, <ref type="method" id="-commit">-commit</ref>, and
<ref type="method" id="-rollback">
-rollback
</ref>
methods) should not pass any statement to this
method which would cause a transaction to begin or
end.
</p>
<p>
Application code must <em>not</em> call this
method directly, it is for internal use only.
</p>
<p>
Where the database backend support it, this method
returns the count of the number of rows to which
the operation applied. Otherwise this returns -1.
</p>
</desc>
</method>
<method type="void" override="subclass">
<sel>backendListen:</sel>
<arg type="NSString*">name</arg>
<desc>
Called to enable asynchronous notification of
database events using the specified
<var>name</var> (which must be a valid identifier
consisting of ascii letters, digits, and
underscore characters, starting with a letter).
Names are not case sensitive (so AAA is the same as
aaa). <br /> Repeated calls to list on the same
<var>name</var> should be treated as a single call.
<br /> The backend is responsible for implicitly
unlistening when a connection is closed. <br />
There is a default implementation which does nothing
... for backends which don't support asynchronous
notifications. <br /> If a backend
<em>does</em> support asynchronous notifications, it
should do so by posting NSNotification instances to
[NSNotificationCenter defaultCenter]
using the SQLClient instance as the notification
object and supplying any payload as a string using
the 'Payload' key in the NSNotification userInfo
dictionary. The userInfo dictionary should also
contain a boolean (NSNumber) value, using the
'Local' key, to indicate whether the notification
was sent by the current SQLClient instance or by some
other client/
</desc>
</method>
<method type="void" override="subclass">
<sel>backendNotify:</sel>
<arg type="NSString*">name</arg>
<sel>payload:</sel>
<arg type="NSString*">more</arg>
<desc>
The backend should implement this to send asynchronous
notifications to anything listening for them.
The <var>name</var> of the notification is an SQL
identifier used for listening for the
asynchronous data. <br /> The payload string
may be <code>nil</code> if no additional information is
needed in the notification.
</desc>
</method>
<method type="NSMutableArray*">
<sel>backendQuery:</sel>
<arg type="NSString*">stmt</arg>
<desc>
Calls
<ref type="method" id="-backendQuery:recordType:listType:">-backendQuery:recordType:listType:</ref> with the default record class and array class.
</desc>
</method>
<method type="NSMutableArray*" override="subclass">
<sel>backendQuery:</sel>
<arg type="NSString*">stmt</arg>
<sel>recordType:</sel>
<arg type="id">rtype</arg>
<sel>listType:</sel>
<arg type="id">ltype</arg>
<desc>
<p>
Perform arbitrary query
<em>which returns values.</em>
</p>
<example>
result = [db backendQuery: @"SELECT Name FROM Table"
recordType: [SQLRecord class]]
listType: [NSMutableArray class]];
</example>
<p>
Upon error, an exception is raised.
</p>
<p>
The query returns an array of records (each of which
is represented by an SQLRecord object).
</p>
<p>
Each SQLRecord object contains one or more fields,
in the order in which they occurred in the query.
Fields may also be retrieved by name.
</p>
<p>
NULL field items are returned as NSNull objects.
</p>
<p>
Callers should lock the instance using the
<em>lock</em> instance variable for the duration of
the operation, and unlock it afterwards.
</p>
<p>
Application code must <em>not</em> call this
method directly, it is for internal use only.
</p>
<p>
The <var>rtype</var> argument specifies an object to
be used to create the records produced by the query.
<br /> This is provided as a performance
optimisation when you want to store data
directly into a special class of your own.
<br /> The object must respond to the [SQLRecord
+newWithValues:keys:count:]
method to produce a new record initialised with
the supplied data.
</p>
<p>
The <var>ltype</var> argument specifies an object to
be used to create objects to store the records
produced by the query. <br /> The should be a
subclass of NSMutableArray. It must at least
implement the
<ref type="method" id="+alloc" class="NSObject">
[NSObject +alloc]
</ref>
method to create an instnce to store records. The
instance must implement
<ref type="method" id="-initWithCapacity:" class="NSMutableArray">[NSMutableArray -initWithCapacity:]</ref> to initialise itsself and <ref type="method" id="-addObject:" class="NSMutableArray">[NSMutableArray -addObject:]</ref> to allow the backend to add records to it. <br /> For caching to work, it must be possible to make a mutable copy of the instance using the mutableCopy method.
</p>
</desc>
</method>
<method type="void" override="subclass">
<sel>backendUnlisten:</sel>
<arg type="NSString*">name</arg>
<desc>
Called to disable asynchronous notification of
database events using the specified
<var>name</var>. This has no effect if the
<var>name</var> has not been used in an earlier call
to
<ref type="method" id="-backendListen:">
-backendListen:
</ref>
, or if the <var>name</var> has already been unlistened
since the last call to listen. on it. <br /> There is
a default implementation which does nothing... for
backends which don't support asynchronous
notifications.
</desc>
</method>
<method type="unsigned" override="subclass">
<sel>copyEscapedBLOB:</sel>
<arg type="NSData*">blob</arg>
<sel>into:</sel>
<arg type="void*">buf</arg>
<desc>
This method is <em>only</em> for the use of the
<ref type="method" id="-insertBLOBs:intoStatement:length:withMarker:length:giving:">-insertBLOBs:intoStatement:length:withMarker:length:giving:</ref> method. <br /> Subclasses which need to insert binary data into a statement must implement this method to copy the escaped data into place and return the number of bytes actually copied.
</desc>
</method>
<method type="const void*">
<sel>insertBLOBs:</sel>
<arg type="NSArray*">blobs</arg>
<sel>intoStatement:</sel>
<arg type="const void*">statement</arg>
<sel>length:</sel>
<arg type="unsigned">sLength</arg>
<sel>withMarker:</sel>
<arg type="const void*">marker</arg>
<sel>length:</sel>
<arg type="unsigned">mLength</arg>
<sel>giving:</sel>
<arg type="unsigned*">result</arg>
<desc>
<p>
This method is a convenience method provided for
subclasses which need to insert escaped binary
data into an SQL <var>statement</var> before sending
the <var>statement</var> to a backend server process.
This method makes use of the
<ref type="method" id="-copyEscapedBLOB:into:">
-copyEscapedBLOB:into:
</ref>
and
<ref type="method" id="-lengthOfEscapedBLOB:">
-lengthOfEscapedBLOB:
</ref>
methods, which <em>must</em> be implemented by
the subclass.
</p>
<p>
The <var>blobs</var> array is an array containing the
original SQL <var>statement</var> string (unused
by this method) followed by the data items to be
inserted.
</p>
<p>
The <var>statement</var> and <var>sLength</var>
arguments specify the datastream to be copied
and into which the BLOBs are to be inserted.
</p>
<p>
The <var>marker</var> and <var>mLength</var>
arguments specify the sequence of
<var>marker</var> bytes in the <var>statement</var>
which indicate a position for insertion of an
escaped BLOB.
</p>
<p>
The method returns either the original
<var>statement</var> or a copy containing the
escaped BLOBs. The length of the returned data is
stored in <var>result</var>.
</p>
</desc>
</method>
<method type="unsigned" override="subclass">
<sel>lengthOfEscapedBLOB:</sel>
<arg type="NSData*">blob</arg>
<desc>
This method is <em>only</em> for the use of the
<ref type="method" id="-insertBLOBs:intoStatement:length:withMarker:length:giving:">-insertBLOBs:intoStatement:length:withMarker:length:giving:</ref> method. <br /> Subclasses which need to insert binary data into a statement must implement this method to return the length of the escaped bytestream which will be inserted.
</desc>
</method>
</category>
</chapter>
<chapter>
<heading>SQLClient constants</heading>
<p></p>
<constant type="NSString* const" name="SQLClientDidConnectNotification">
<desc>
Notification sent when an instance becomes
connected to the database server. The notification
object is the instance connected.
</desc>
</constant>
<constant type="NSString* const" name="SQLClientDidDisconnectNotification">
<desc>
Notification sent when an instance becomes
disconnected from the database server. The
notification object is the instance
disconnected.
</desc>
</constant>
</chapter>
<chapter>
<heading>SQLClient variables</heading>
<p></p>
<variable type="NSString*" name="SQLConnectionException">
<desc>
Exception for when a connection to the server is
lost.
</desc>
</variable>
<variable type="NSString*" name="SQLEmptyException">
<desc>
Exception for when a query is supposed to return
data and doesn't.
</desc>
</variable>
<variable type="NSString*" name="SQLException">
<desc>
Exception raised when an error with the remote
database server occurs.
</desc>
</variable>
<variable type="NSString*" name="SQLUniqueException">
<desc>
Exception for when an insert/update would break the
uniqueness of a field or index.
</desc>
</variable>
</chapter>
<chapter>
<heading>SQLClient functions</heading>
<p></p>
<function type="NSTimeInterval" name="SQLClientTimeLast">
<desc>
Returns the timestamp of the most recent call to
<ref type="function" id="SQLClientTimeNow">
SQLClientTimeNow()
</ref>
.
</desc>
</function>
<function type="NSTimeInterval" name="SQLClientTimeNow">
<desc>
Convenience function to provide timing
information quickly. <br /> This returns the
current date/time, and stores the value for use by
the
<ref type="function" id="SQLClientTimeLast">
SQLClientTimeLast()
</ref>
function.
</desc>
</function>
<function type="NSTimeInterval" name="SQLClientTimeStart">
<desc>
This returns the timestamp from which any of the
SQLClient classes was first used or
<ref type="function" id="SQLClientTimeNow">
SQLClientTimeNow()
</ref>
was first called (whichever came first).
</desc>
</function>
<function type="unsigned int" name="SQLClientTimeTick">
<desc>
A convenience method to return the current clock 'tick'...
which is the current second based on the time we
started. This does <em>not</em> check the current
time, but relies on
<ref type="function" id="SQLClientTimeLast">
SQLClientTimeLast()
</ref>
returning an up to date value (so if you need an
accurate tick, you should ensure that
<ref type="function" id="SQLClientTimeNow">
SQLClientTimeNow()
</ref>
is called at least once a second). <br /> The returned
value is always greater than zero, and is basically
calculated as (SQLClientTimeLast() -
<ref type="function" id="SQLClientTimeStart">
SQLClientTimeStart()
</ref>
+ 1). <br /> In the event that the system clock is reset
into the past, the value of
<ref type="function" id="SQLClientTimeStart">
SQLClientTimeStart()
</ref>
is automatically adjusted to ensure that the result of a
call to
<ref type="function" id="SQLClientTimeTick">
SQLClientTimeTick()
</ref>
is never less than the result of any earlier call to the
function.
</desc>
</function>
</chapter>
</body>
</gsdoc>
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