/usr/lib/python2.7/dist-packages/twext/enterprise/dal/syntax.py is in python-twext 0.1.b2.dev15059-1.
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##
# Copyright (c) 2010-2015 Apple Inc. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
##
"""
Syntax wrappers and generators for SQL.
"""
__all__ = [
"DALError",
"QueryPlaceholder",
"FixedPlaceholder",
"NumericPlaceholder",
"defaultPlaceholder",
"QueryGenerator",
"TableMismatch",
"NotEnoughValues",
"Syntax",
"comparison",
"ExpressionSyntax",
"FunctionInvocation",
"Constant",
"NamedValue",
"Function",
"SchemaSyntax",
"SequenceSyntax",
"TableSyntax",
"TableAlias",
"Join",
"ColumnSyntax",
"ResultAliasSyntax",
"AliasReferenceSyntax",
"AliasedColumnSyntax",
"Comparison",
"Not",
"NullComparison",
"CompoundComparison",
"ColumnComparison",
"Column",
"Tuple",
"SetExpression",
"Union",
"Intersect",
"Except",
"Select",
"Insert",
"Update",
"Delete",
"Lock",
"DatabaseLock",
"DatabaseUnlock",
"RollbackToSavepoint",
"ReleaseSavepoint",
"SavepointAction",
"NoOp",
"SQLFragment",
"Parameter",
]
from itertools import count, repeat
from functools import partial
from operator import eq, ne
from zope.interface import implements
from twisted.internet.defer import succeed
from twext.enterprise.dal.model import Schema, Table, Column, Sequence, SQLType
from twext.enterprise.ienterprise import (
POSTGRES_DIALECT, ORACLE_DIALECT, SQLITE_DIALECT, IDerivedParameter
)
from twext.enterprise.util import mapOracleOutputType
from twisted.internet.defer import inlineCallbacks, returnValue
try:
import cx_Oracle
cx_Oracle
except ImportError:
cx_Oracle = None
class DALError(Exception):
"""
Base class for exceptions raised by this module. This can be raised
directly for API violations. This exception represents a serious
programming error and should normally never be caught or ignored.
"""
class QueryPlaceholder(object):
"""
Representation of the placeholders required to generate some SQL, for a
single statement. Contains information necessary to generate place holder
strings based on the database dialect.
"""
def placeholder(self):
raise NotImplementedError("See subclasses.")
class FixedPlaceholder(QueryPlaceholder):
"""
Fixed string used as the place holder.
"""
def __init__(self, placeholder):
self._placeholder = placeholder
def placeholder(self):
return self._placeholder
class NumericPlaceholder(QueryPlaceholder):
"""
Numeric counter used as the place holder.
"""
def __init__(self):
self._next = count(1).next
def placeholder(self):
return ":" + str(self._next())
def defaultPlaceholder():
"""
Generate a default L{QueryPlaceholder}
"""
return FixedPlaceholder("?")
class QueryGenerator(object):
"""
Maintains various pieces of transient information needed when building a
query. This includes the SQL dialect, the format of the place holder and
and automated id generator.
"""
def __init__(self, dialect=None, placeholder=None):
self.dialect = dialect if dialect else POSTGRES_DIALECT
if placeholder is None:
placeholder = defaultPlaceholder()
self.placeholder = placeholder
self.generatedID = count(1).next
def nextGeneratedID(self):
return "genid_%d" % (self.generatedID(),)
def shouldQuote(self, name):
return (self.dialect == ORACLE_DIALECT and name.lower() in _KEYWORDS)
class TableMismatch(Exception):
"""
A table in a statement did not match with a column.
"""
class NotEnoughValues(DALError):
"""
Not enough values were supplied for an L{Insert}.
"""
class _Statement(object):
"""
An SQL statement that may be executed. (An abstract base class, must
implement several methods.)
"""
_paramstyles = {
"pyformat": partial(FixedPlaceholder, "%s"),
"numeric": NumericPlaceholder,
"qmark": defaultPlaceholder,
}
def toSQL(self, queryGenerator=None):
if queryGenerator is None:
queryGenerator = QueryGenerator()
return self._toSQL(queryGenerator)
def _extraVars(self, txn, queryGenerator):
"""
A hook for subclasses to provide additional keyword arguments to the
C{bind} call when L{_Statement.on} is executed. Currently this is used
only for "out" parameters to capture results when executing statements
that do not normally have a result (L{Insert}, L{Delete}, L{Update}).
"""
return {}
def _extraResult(self, result, outvars, queryGenerator):
"""
A hook for subclasses to manipulate the results of "on", after they've
been retrieved by the database but before they've been given to
application code.
@param result: a L{Deferred} that will fire with the rows as returned
by the database.
@type result: C{list} of rows, which are C{list}s or C{tuple}s.
@param outvars: a dictionary of extra variables returned by
C{self._extraVars}.
@param queryGenerator: information about the connection where the
statement was executed.
@type queryGenerator: L{QueryGenerator} (a subclass thereof)
@return: the result to be returned from L{_Statement.on}.
@rtype: L{Deferred} firing result rows
"""
return result
def on(self, txn, raiseOnZeroRowCount=None, **kw):
"""
Execute this statement on a given L{IAsyncTransaction} and return the
resulting L{Deferred}.
@param txn: the L{IAsyncTransaction} to execute this on.
@param raiseOnZeroRowCount: a 0-argument callable which returns an
exception to raise if the executed SQL does not affect any rows.
@param kw: keyword arguments, mapping names of L{Parameter} objects
located somewhere in C{self}
@return: results from the database.
@rtype: a L{Deferred} firing a C{list} of records (C{tuple}s or
C{list}s)
"""
queryGenerator = QueryGenerator(
txn.dialect, self._paramstyles[txn.paramstyle]()
)
outvars = self._extraVars(txn, queryGenerator)
kw.update(outvars)
fragment = self.toSQL(queryGenerator).bind(**kw)
result = txn.execSQL(
fragment.text, fragment.parameters, raiseOnZeroRowCount
)
result = self._extraResult(result, outvars, queryGenerator)
if queryGenerator.dialect == ORACLE_DIALECT and result:
result.addCallback(self._fixOracleNulls)
return result
def _resultColumns(self):
"""
Subclasses must implement this to return a description of the columns
expected to be returned. This is a list of L{ColumnSyntax} objects,
and possibly other expression syntaxes which will be converted to
C{None}.
"""
raise NotImplementedError(
"Each statement subclass must describe its result"
)
def _resultShape(self):
"""
Process the result of the subclass's C{_resultColumns}, as described in
the docstring above.
"""
for expectation in self._resultColumns():
if isinstance(expectation, ColumnSyntax):
yield expectation.model
else:
yield None
def _fixOracleNulls(self, rows):
"""
Oracle treats empty strings as C{NULL}. Fix this by looking at the
columns we expect to have returned, and replacing any C{None}s with
empty strings in the appropriate position.
"""
if rows is None:
return None
newRows = []
for row in rows:
newRow = []
for column, description in zip(row, self._resultShape()):
if (
description is not None and
# FIXME: "is the python type str" is what I mean; this list
# should be more centrally maintained
description.type.name in ("varchar", "text", "char") and
column is None
):
column = ""
newRow.append(column)
newRows.append(newRow)
return newRows
class Syntax(object):
"""
Base class for syntactic convenience.
This class will define dynamic attribute access to represent its underlying
model as a Python namespace.
You can access the underlying model as ".model".
"""
modelType = None
model = None
def __init__(self, model):
if not isinstance(model, self.modelType):
# make sure we don't get a misleading repr()
raise DALError("type mismatch: %r %r", type(self), model)
self.model = model
def __repr__(self):
if self.model is not None:
return "<Syntax for: %r>" % (self.model,)
return super(Syntax, self).__repr__()
def comparison(comparator):
def __(self, other):
if other is None:
return NullComparison(self, comparator)
if isinstance(other, Select):
return NotImplemented
if isinstance(other, ColumnSyntax):
return ColumnComparison(self, comparator, other)
if isinstance(other, ExpressionSyntax):
return CompoundComparison(self, comparator, other)
else:
return CompoundComparison(self, comparator, Constant(other))
return __
class ExpressionSyntax(Syntax):
__eq__ = comparison("=")
__ne__ = comparison("!=")
# NB: these operators "cannot be used with lists" (see ORA-01796)
__gt__ = comparison(">")
__ge__ = comparison(">=")
__lt__ = comparison("<")
__le__ = comparison("<=")
# TODO: operators aren't really comparisons; these should behave slightly
# differently. (For example; in Oracle, C{select 3 = 4 from dual} doesn't
# work, but C{select 3 + 4 from dual} does; similarly, you can't do
# C{select * from foo where 3 + 4}, but you can do C{select * from foo
# where 3 + 4 > 0}.)
__add__ = comparison("+")
__sub__ = comparison("-")
__div__ = comparison("/")
__mul__ = comparison("*")
def __nonzero__(self):
raise DALError(
"SQL expressions should not be tested for truth value in Python.")
def In(self, other):
"""
We support two forms of the SQL "IN" syntax: one where a list of values
is supplied, the other where a sub-select is used to provide a set of
values.
@param other: a constant parameter or sub-select
@type other: L{Parameter} or L{Select}
"""
return self._commonIn('in', other)
def NotIn(self, other):
"""
We support two forms of the SQL "NOT IN" syntax: one where a list of values
is supplied, the other where a sub-select is used to provide a set of
values.
@param other: a constant parameter or sub-select
@type other: L{Parameter} or L{Select}
"""
return self._commonIn('not in', other)
def _commonIn(self, op, other):
"""
We support two forms of the SQL "IN" and "NOT IN" syntax: one where a list
of values is supplied, the other where a sub-select is used to provide a set
of values.
@param other: a constant parameter or sub-select
@type other: L{Parameter} or L{Select}
"""
if isinstance(other, Parameter):
if other.count is None:
raise DALError(
"{} expression needs an explicit count of parameters".format(op.upper())
)
return CompoundComparison(self, op, Constant(other))
elif isinstance(other, set) or isinstance(other, frozenset) or isinstance(other, list) or isinstance(other, tuple):
return CompoundComparison(self, op, Constant(other))
else:
# Can't be Select.__contains__ because __contains__ gets
# __nonzero__ called on its result by the "in" syntax.
return CompoundComparison(self, op, other)
def StartsWith(self, other):
return CompoundComparison(
self, "like",
CompoundComparison(Constant(other), "||", Constant("%"))
)
def NotStartsWith(self, other):
return CompoundComparison(
self, "not like",
CompoundComparison(Constant(other), "||", Constant("%"))
)
def EndsWith(self, other):
return CompoundComparison(
self, "like",
CompoundComparison(Constant("%"), "||", Constant(other))
)
def NotEndsWith(self, other):
return CompoundComparison(
self, "not like",
CompoundComparison(Constant("%"), "||", Constant(other))
)
def Contains(self, other):
return CompoundComparison(
self, "like",
CompoundComparison(
Constant("%"), "||",
CompoundComparison(Constant(other), "||", Constant("%"))
)
)
def NotContains(self, other):
return CompoundComparison(
self, "not like",
CompoundComparison(
Constant("%"), "||",
CompoundComparison(Constant(other), "||", Constant("%"))
)
)
class FunctionInvocation(ExpressionSyntax):
def __init__(self, function, *args):
self.function = function
self.args = args
def allColumns(self):
"""
All of the columns in all of the arguments' columns.
"""
def ac():
for arg in self.args:
for column in arg.allColumns():
yield column
return list(ac())
def subSQL(self, queryGenerator, allTables):
result = SQLFragment(self.function.nameFor(queryGenerator))
result.append(_inParens(
_commaJoined(
_convert(arg).subSQL(queryGenerator, allTables)
for arg in self.args
)
))
return result
class Constant(ExpressionSyntax):
"""
Generates an expression for a place holder where a value will be bound to
the query. If the constant is a Parameter with count > 1 then a
parenthesized, comma-separated list of place holders will be generated.
"""
def __init__(self, value):
self.value = value
def allColumns(self):
return []
def subSQL(self, queryGenerator, allTables):
if isinstance(self.value, Parameter) and self.value.count is not None:
return _inParens(
_CommaList([
SQLFragment(
queryGenerator.placeholder.placeholder(),
[self.value] if counter == 0 else []
)
for counter in range(self.value.count)
]).subSQL(queryGenerator, allTables)
)
elif isinstance(self.value, set) or isinstance(self.value, frozenset) or isinstance(self.value, list) or isinstance(self.value, tuple):
return _inParens(
_CommaList([
SQLFragment(queryGenerator.placeholder.placeholder(), [value])
for value in self.value
]).subSQL(queryGenerator, allTables)
)
else:
return SQLFragment(
queryGenerator.placeholder.placeholder(), [self.value]
)
class NamedValue(ExpressionSyntax):
"""
A constant within the database; something predefined, such as
CURRENT_TIMESTAMP.
"""
def __init__(self, name):
self.name = name
def subSQL(self, queryGenerator, allTables):
return SQLFragment(self.name)
class Function(object):
"""
An L{Function} is a representation of an SQL Function function.
"""
def __init__(self, name, oracleName=None):
self.name = name
self.oracleName = oracleName
def nameFor(self, queryGenerator):
if (
queryGenerator.dialect == ORACLE_DIALECT and
self.oracleName is not None
):
return self.oracleName
return self.name
def __call__(self, *args):
"""
Produce an L{FunctionInvocation}
"""
return FunctionInvocation(self, *args)
Count = Function("count")
Sum = Function("sum")
Max = Function("max")
Min = Function("min")
Len = Function("character_length", "length")
Upper = Function("upper")
Lower = Function("lower")
Coalesce = Function("coalesce")
_sqliteLastInsertRowID = Function("last_insert_rowid")
# Use a specific value here for "the convention for case-insensitive values in
# the database" so we don't need to keep remembering whether it's upper or
# lowercase.
CaseFold = Lower
class SchemaSyntax(Syntax):
"""
Syntactic convenience for L{Schema}.
"""
modelType = Schema
def __getattr__(self, attr):
try:
tableModel = self.model.tableNamed(attr)
except KeyError:
try:
seqModel = self.model.sequenceNamed(attr)
except KeyError:
raise AttributeError(
"schema has no table or sequence %r" % (attr,)
)
else:
return SequenceSyntax(seqModel)
else:
syntax = TableSyntax(tableModel)
# Needs to be preserved here so that aliasing will work.
setattr(self, attr, syntax)
return syntax
def __iter__(self):
for table in self.model.tables:
yield TableSyntax(table)
class SequenceSyntax(ExpressionSyntax):
"""
Syntactic convenience for L{Sequence}.
"""
modelType = Sequence
def subSQL(self, queryGenerator, allTables):
"""
Convert to an SQL fragment.
"""
if queryGenerator.dialect == ORACLE_DIALECT:
fmt = "%s.nextval"
else:
fmt = "nextval('%s')"
return SQLFragment(fmt % (self.model.name,))
def _nameForDialect(name, dialect):
"""
If the given name is being computed in the oracle dialect, truncate it to
30 characters.
"""
if dialect == ORACLE_DIALECT:
name = name[:30]
return name
class TableSyntax(Syntax):
"""
Syntactic convenience for L{Table}.
"""
modelType = Table
def alias(self):
"""
Return an alias for this L{TableSyntax} so that it might be joined
against itself.
As in SQL, C{someTable.join(someTable)} is an error; you can't join a
table against itself. However, C{t = someTable.alias();
someTable.join(t)} is usable as a C{from} clause.
"""
return TableAlias(self.model)
def join(self, otherTableSyntax, on=None, type=""):
"""
Create a L{Join}, representing a join between two tables.
"""
if on is None and not type:
type = "cross"
return Join(self, type, otherTableSyntax, on)
def subSQL(self, queryGenerator, allTables):
"""
Generate the L{SQLFragment} for this table's identification; this is
for use in a C{from} clause.
"""
# XXX maybe there should be a specific method which is only invoked
# from the FROM clause, that only tables and joins would implement?
return SQLFragment(
_nameForDialect(self.model.name, queryGenerator.dialect)
)
def __getattr__(self, attr):
"""
Attributes named after columns on a L{TableSyntax} are returned by
accessing their names as attributes. For example, if there is a schema
syntax object created from SQL equivalent to C{create table foo (bar
integer, baz integer)}, C{schemaSyntax.foo.bar} and
C{schemaSyntax.foo.baz}
"""
try:
column = self.model.columnNamed(attr)
except KeyError:
raise AttributeError(
"table {0} has no column {1}".format(self.model.name, attr)
)
else:
return ColumnSyntax(column)
def __iter__(self):
"""
Yield a L{ColumnSyntax} for each L{Column} in this L{TableSyntax}'s
model's table.
"""
for column in self.model.columns:
yield ColumnSyntax(column)
def tables(self):
"""
Return a C{list} of tables involved in the query by this table. (This
method is expected by anything that can act as the C{From} clause: see
L{Join.tables})
"""
return [self]
def columnAliases(self):
"""
Inspect the Python aliases for this table in the given schema. Python
aliases for a table are created by setting an attribute on the schema.
For example, in a schema which had "schema.MYTABLE.ID =
schema.MYTABLE.MYTABLE_ID" applied to it,
schema.MYTABLE.columnAliases() would return C{[("ID",
schema.MYTABLE.MYTABLE_ID)]}.
@return: a list of 2-tuples of (alias (C{str}), column
(C{ColumnSyntax})), enumerating all of the Python aliases provided.
"""
result = {}
for k, v in self.__dict__.items():
if isinstance(v, ColumnSyntax):
result[k] = v
return result
def __contains__(self, columnSyntax):
if isinstance(columnSyntax, FunctionInvocation):
columnSyntax = columnSyntax.arg
return (columnSyntax.model.table is self.model)
class TableAlias(TableSyntax):
"""
An alias for a table, under a different name, for the purpose of doing a
self-join.
"""
def subSQL(self, queryGenerator, allTables):
"""
Return an L{SQLFragment} with a string of the form C{"mytable myalias"}
suitable for use in a FROM clause.
"""
result = super(TableAlias, self).subSQL(queryGenerator, allTables)
result.append(SQLFragment(" " + self._aliasName(allTables)))
return result
def _aliasName(self, allTables):
"""
The alias under which this table will be known in the query.
@param allTables: a C{list}, as passed to a C{subSQL} method during SQL
generation.
@return: a string naming this alias, a unique identifier, albeit one
which is only stable within the query which populated C{allTables}.
@rtype: C{str}
"""
anum = [
t for t in allTables
if isinstance(t, TableAlias)
].index(self) + 1
return "alias%d" % (anum,)
def __getattr__(self, attr):
return AliasedColumnSyntax(self, self.model.columnNamed(attr))
class Join(object):
"""
A DAL object representing an SQL C{join} statement.
@ivar leftSide: a L{Join} or L{TableSyntax} representing the left side of
this join.
@ivar rightSide: a L{TableSyntax} representing the right side of this join.
@ivar type: the type of join this is. For example, for a left outer join,
this would be C{"left outer"}.
@type type: C{str}
@ivar on: the "on" clause of this table.
@type on: L{ExpressionSyntax}
"""
def __init__(self, leftSide, type, rightSide, on):
self.leftSide = leftSide
self.type = type
self.rightSide = rightSide
self.on = on
def subSQL(self, queryGenerator, allTables):
stmt = SQLFragment()
stmt.append(self.leftSide.subSQL(queryGenerator, allTables))
if self.type == ",":
stmt.text += ", "
else:
stmt.text += " "
if self.type:
stmt.text += self.type
stmt.text += " "
stmt.text += "join "
stmt.append(self.rightSide.subSQL(queryGenerator, allTables))
if self.type not in ("cross", ","):
stmt.text += " on "
stmt.append(self.on.subSQL(queryGenerator, allTables))
return stmt
def tables(self):
"""
Return a C{list} of tables which this L{Join} will involve in a query:
all those present on the left side, as well as all those present on the
right side.
"""
return self.leftSide.tables() + self.rightSide.tables()
def join(self, otherTable, on=None, type=None):
if on is None:
type = "cross"
return Join(self, type, otherTable, on)
_KEYWORDS = [
# SQL keyword, but we have a column with this name
"access",
# Not actually a standard keyword, but a function in oracle, and we have a
# column with this name.
"path",
# not actually sure what this is; only experimentally determined that not
# quoting it causes an issue.
"size",
]
class ColumnSyntax(ExpressionSyntax):
"""
Syntactic convenience for L{Column}.
@ivar _alwaysQualified: a boolean indicating whether to always qualify the
column name in generated SQL, regardless of whether the column name is
specific enough even when unqualified.
@type _alwaysQualified: C{bool}
"""
modelType = Column
_alwaysQualified = False
def allColumns(self):
return [self]
def subSQL(self, queryGenerator, allTables):
# XXX This, and "model", could in principle conflict with column names.
# Maybe do something about that.
name = self.model.name
if queryGenerator.shouldQuote(name):
name = '"%s"' % (name,)
if self._alwaysQualified:
qualified = True
else:
qualified = False
for tableSyntax in allTables:
if self.model.table is not tableSyntax.model:
if (
self.model.name in (
c.name for c in
tableSyntax.model.columns
)
):
qualified = True
break
if qualified:
return SQLFragment(self._qualify(name, allTables))
else:
return SQLFragment(name)
def __hash__(self):
return hash(self.model) + 10
def _qualify(self, name, allTables):
return self.model.table.name + "." + name
class ResultAliasSyntax(ExpressionSyntax):
def __init__(self, expression, alias=None):
self.expression = expression
self.alias = alias
def aliasName(self, queryGenerator):
if self.alias is None:
self.alias = queryGenerator.nextGeneratedID()
return self.alias
def columnReference(self):
return AliasReferenceSyntax(self)
def allColumns(self):
return self.expression.allColumns()
def subSQL(self, queryGenerator, allTables):
result = SQLFragment()
result.append(self.expression.subSQL(queryGenerator, allTables))
result.append(SQLFragment(" %s" % (self.aliasName(queryGenerator),)))
return result
class AliasReferenceSyntax(ExpressionSyntax):
def __init__(self, resultAlias):
self.resultAlias = resultAlias
def allColumns(self):
return self.resultAlias.allColumns()
def subSQL(self, queryGenerator, allTables):
return SQLFragment(self.resultAlias.aliasName(queryGenerator))
class AliasedColumnSyntax(ColumnSyntax):
"""
An L{AliasedColumnSyntax} is like a L{ColumnSyntax}, but it generates SQL
for a column of a table under an alias, rather than directly. i.e. this is
used for C{"something.col"} in C{"select something.col from tablename
something"} rather than the "col" in C{"select col from tablename"}.
@see: L{TableSyntax.alias}
"""
_alwaysQualified = True
def __init__(self, tableAlias, model):
super(AliasedColumnSyntax, self).__init__(model)
self._tableAlias = tableAlias
def _qualify(self, name, allTables):
return self._tableAlias._aliasName(allTables) + "." + name
class Comparison(ExpressionSyntax):
def __init__(self, a, op, b):
self.a = a
self.op = op
self.b = b
def _subexpression(self, expr, queryGenerator, allTables):
result = expr.subSQL(queryGenerator, allTables)
if self.op not in ("and", "or") and isinstance(expr, Comparison):
result = _inParens(result)
return result
def booleanOp(self, operand, other):
return CompoundComparison(self, operand, other)
def And(self, other):
return self.booleanOp("and", other)
def Or(self, other):
return self.booleanOp("or", other)
class Not(Comparison):
"""
A L{NotColumn} is a logical NOT of an expression.
"""
def __init__(self, a):
# "op" and "b" are always None for this comparison type
super(Not, self).__init__(a, None, None)
def subSQL(self, queryGenerator, allTables):
sqls = SQLFragment()
sqls.text += "not "
result = self.a.subSQL(queryGenerator, allTables)
if isinstance(self.a, CompoundComparison) and self.a.op in ("or", "and"):
result = _inParens(result)
sqls.append(result)
return sqls
class NullComparison(Comparison):
"""
A L{NullComparison} is a comparison of a column or expression with None.
"""
def __init__(self, a, op):
# "b" is always None for this comparison type
super(NullComparison, self).__init__(a, op, None)
def subSQL(self, queryGenerator, allTables):
sqls = SQLFragment()
sqls.append(self.a.subSQL(queryGenerator, allTables))
sqls.text += " is "
if self.op != "=":
sqls.text += "not "
sqls.text += "null"
return sqls
class CompoundComparison(Comparison):
"""
A compound comparison; two or more constraints, joined by an operation
(currently only AND or OR).
"""
def allColumns(self):
return self.a.allColumns() + self.b.allColumns()
def subSQL(self, queryGenerator, allTables):
if (
queryGenerator.dialect == ORACLE_DIALECT and
isinstance(self.b, Constant) and
self.b.value == "" and self.op in ("=", "!=")
):
return NullComparison(self.a, self.op).subSQL(
queryGenerator, allTables
)
stmt = SQLFragment()
result = self._subexpression(self.a, queryGenerator, allTables)
if (
isinstance(self.a, CompoundComparison) and
self.a.op == "or" and self.op == "and"
):
result = _inParens(result)
stmt.append(result)
stmt.text += " %s " % (self.op,)
result = self._subexpression(self.b, queryGenerator, allTables)
if (
isinstance(self.b, CompoundComparison) and
self.b.op == "or" and self.op == "and"
):
result = _inParens(result)
if isinstance(self.b, Tuple):
# If the right-hand side of the comparison is a Tuple, it needs to
# be double-parenthesized in Oracle, as per
# http://docs.oracle.com/cd/B28359_01/server.111/b28286/expressions015.htm#i1033664
# because it is an expression list.
result = _inParens(result)
stmt.append(result)
return stmt
_operators = {"=": eq, "!=": ne}
class ColumnComparison(CompoundComparison):
"""
Comparing two columns is the same as comparing any other two expressions,
except that Python can retrieve a truth value, so that columns may be
compared for value equality in scripts that want to interrogate schemas.
"""
def __nonzero__(self):
thunk = _operators.get(self.op)
if thunk is None:
return super(ColumnComparison, self).__nonzero__()
return thunk(self.a.model, self.b.model)
class _AllColumns(NamedValue):
def __init__(self):
self.name = "*"
def allColumns(self):
return []
ALL_COLUMNS = _AllColumns()
class _SomeColumns(object):
def __init__(self, columns):
self.columns = columns
def subSQL(self, queryGenerator, allTables):
first = True
cstatement = SQLFragment()
for column in self.columns:
if first:
first = False
else:
cstatement.append(SQLFragment(", "))
cstatement.append(column.subSQL(queryGenerator, allTables))
return cstatement
def _checkColumnsMatchTables(columns, tables):
"""
Verify that the given C{columns} match the given C{tables}; that is, that
every L{TableSyntax} referenced by every L{ColumnSyntax} referenced by
every L{ExpressionSyntax} in the given C{columns} list is present in the
given C{tables} list.
@param columns: a L{list} of L{ExpressionSyntax}, each of which references
some set of L{ColumnSyntax}es via its C{allColumns} method.
@param tables: a L{list} of L{TableSyntax}
@return: L{None}
@rtype: L{NoneType}
@raise TableMismatch: if any table referenced by a column is I{not} found
in C{tables}
"""
for expression in columns:
for column in expression.allColumns():
for table in tables:
if column in table:
break
else:
raise TableMismatch(
"{} not found in {}".format(column, tables)
)
return None
class Tuple(ExpressionSyntax):
def __init__(self, columns):
self.columns = columns
def __iter__(self):
return iter(self.columns)
def subSQL(self, queryGenerator, allTables):
return _inParens(_commaJoined(
c.subSQL(queryGenerator, allTables)
for c in self.columns
))
def allColumns(self):
return self.columns
class SetExpression(object):
"""
A UNION, INTERSECT, or EXCEPT construct used inside a SELECT.
"""
OPTYPE_ALL = "all"
OPTYPE_DISTINCT = "distinct"
def __init__(self, selects, optype=None):
"""
@param selects: a single Select or a list of Selects
@type selects: C{list} or L{Select}
@param optype: whether to use the ALL, DISTINCT constructs: C{None} use
neither, OPTYPE_ALL, or OPTYPE_DISTINCT
@type optype: C{str}
"""
if isinstance(selects, Select):
selects = (selects,)
self.selects = selects
self.optype = optype
for select in self.selects:
if not isinstance(select, Select):
raise DALError(
"Must have SELECT statements in a set expression"
)
if self.optype not in (
None, SetExpression.OPTYPE_ALL, SetExpression.OPTYPE_DISTINCT,
):
raise DALError(
"Must have either 'all' or 'distinct' in a set expression"
)
def subSQL(self, queryGenerator, allTables):
result = SQLFragment()
for select in self.selects:
result.append(self.setOpSQL(queryGenerator))
if self.optype == SetExpression.OPTYPE_ALL:
result.append(SQLFragment("ALL "))
elif self.optype == SetExpression.OPTYPE_DISTINCT:
result.append(SQLFragment("DISTINCT "))
result.append(select.subSQL(queryGenerator, allTables))
return result
def allColumns(self):
return []
class Union(SetExpression):
"""
A UNION construct used inside a SELECT.
"""
def setOpSQL(self, queryGenerator):
return SQLFragment(" UNION ")
class Intersect(SetExpression):
"""
An INTERSECT construct used inside a SELECT.
"""
def setOpSQL(self, queryGenerator):
return SQLFragment(" INTERSECT ")
class Except(SetExpression):
"""
An EXCEPT construct used inside a SELECT.
"""
def setOpSQL(self, queryGenerator):
if queryGenerator.dialect == POSTGRES_DIALECT:
return SQLFragment(" EXCEPT ")
elif queryGenerator.dialect == ORACLE_DIALECT:
return SQLFragment(" MINUS ")
else:
raise NotImplementedError("Unsupported dialect")
class Select(_Statement):
"""
C{select} statement.
"""
def __init__(
self,
columns=None, Where=None, From=None,
OrderBy=None, GroupBy=None,
Limit=None, ForUpdate=False, NoWait=False, Ascending=None,
Having=None, Distinct=False, As=None, SetExpression=None
):
self.From = From
self.Where = Where
self.Distinct = Distinct
if not isinstance(OrderBy, (Tuple, list, tuple, type(None))):
OrderBy = [OrderBy]
self.OrderBy = OrderBy
if not isinstance(GroupBy, (list, tuple, type(None))):
GroupBy = [GroupBy]
self.GroupBy = GroupBy
self.Limit = Limit
self.Having = Having
self.SetExpression = SetExpression
if columns is None:
columns = ALL_COLUMNS
else:
_checkColumnsMatchTables(columns, From.tables())
columns = _SomeColumns(columns)
self.columns = columns
self.ForUpdate = ForUpdate
self.NoWait = NoWait
self.Ascending = Ascending
self.As = As
# A FROM that uses a sub-select will need the AS alias name
if isinstance(self.From, Select):
if self.From.As is None:
self.From.As = ""
def __eq__(self, other):
"""
Create a comparison.
"""
if isinstance(other, (list, tuple)):
other = Tuple(other)
return CompoundComparison(other, "=", self)
def _toSQL(self, queryGenerator):
"""
@return: a C{select} statement with placeholders and arguments
@rtype: L{SQLFragment}
"""
if self.SetExpression is not None:
stmt = SQLFragment("(")
else:
stmt = SQLFragment()
stmt.append(SQLFragment("select "))
if self.Distinct:
stmt.text += "distinct "
allTables = self.From.tables()
stmt.append(self.columns.subSQL(queryGenerator, allTables))
stmt.text += " from "
stmt.append(self.From.subSQL(queryGenerator, allTables))
if self.Where is not None:
wherestmt = self.Where.subSQL(queryGenerator, allTables)
stmt.text += " where "
stmt.append(wherestmt)
if self.GroupBy is not None:
stmt.text += " group by "
fst = True
for subthing in self.GroupBy:
if fst:
fst = False
else:
stmt.text += ", "
stmt.append(subthing.subSQL(queryGenerator, allTables))
if self.Having is not None:
havingstmt = self.Having.subSQL(queryGenerator, allTables)
stmt.text += " having "
stmt.append(havingstmt)
if self.SetExpression is not None:
stmt.append(SQLFragment(")"))
stmt.append(self.SetExpression.subSQL(queryGenerator, allTables))
if self.OrderBy is not None:
stmt.text += " order by "
fst = True
for subthing in self.OrderBy:
if fst:
fst = False
else:
stmt.text += ", "
stmt.append(subthing.subSQL(queryGenerator, allTables))
if self.Ascending is not None:
if self.Ascending:
kw = " asc"
else:
kw = " desc"
stmt.append(SQLFragment(kw))
if self.ForUpdate:
# FOR UPDATE not supported with sqlite - but that is probably not relevant
# given that sqlite does file level locking of the DB
if queryGenerator.dialect != SQLITE_DIALECT:
# Oracle turns this statement into a sub-select if Limit is non-zero, but we can't have
# the "for update" in the sub-select. So suppress it here and add it in the outer limit
# select later.
if self.Limit is None or queryGenerator.dialect != ORACLE_DIALECT:
stmt.text += " for update"
if self.NoWait:
stmt.text += " nowait"
if self.Limit is not None:
limitConst = Constant(self.Limit).subSQL(queryGenerator, allTables)
if queryGenerator.dialect == ORACLE_DIALECT:
wrapper = SQLFragment("select * from (")
wrapper.append(stmt)
wrapper.append(SQLFragment(") where ROWNUM <= "))
stmt = wrapper
else:
stmt.text += " limit "
stmt.append(limitConst)
# Add in any Oracle "for update"
if self.ForUpdate and queryGenerator.dialect == ORACLE_DIALECT:
stmt.text += " for update"
if self.NoWait:
stmt.text += " nowait"
return stmt
def subSQL(self, queryGenerator, allTables):
result = SQLFragment("(")
result.append(self.toSQL(queryGenerator))
result.append(SQLFragment(")"))
if self.As is not None:
if self.As == "":
self.As = queryGenerator.nextGeneratedID()
result.append(SQLFragment(" %s" % (self.As,)))
return result
def _resultColumns(self):
"""
Determine the list of L{ColumnSyntax} objects that will represent the
result. Normally just the list of selected columns; if wildcard syntax
is used though, determine the ordering from the database.
"""
if self.columns is ALL_COLUMNS:
# TODO: Possibly this rewriting should always be done, before even
# executing the query, so that if we develop a schema mismatch with
# the database (additional columns), the application will still see
# the right rows.
for table in self.From.tables():
for column in table:
yield column
else:
for column in self.columns.columns:
yield column
def tables(self):
"""
Determine the tables used by the result columns.
"""
if self.columns is ALL_COLUMNS:
# TODO: Possibly this rewriting should always be done, before even
# executing the query, so that if we develop a schema mismatch with
# the database (additional columns), the application will still see
# the right rows.
return self.From.tables()
else:
tables = set([
column.model.table for column in self.columns.columns
if isinstance(column, ColumnSyntax)
])
for table in self.From.tables():
tables.add(table.model)
return [TableSyntax(table) for table in tables]
def _commaJoined(stmts):
first = True
cstatement = SQLFragment()
for stmt in stmts:
if first:
first = False
else:
cstatement.append(SQLFragment(", "))
cstatement.append(stmt)
return cstatement
def _inParens(stmt):
result = SQLFragment("(")
result.append(stmt)
result.append(SQLFragment(")"))
return result
def _fromSameTable(columns):
"""
Extract the common table used by a list of L{Column} objects, raising
L{TableMismatch}.
"""
table = columns[0].table
for column in columns:
if table is not column.table:
raise TableMismatch("Columns must all be from the same table.")
return table
def _modelsFromMap(columnMap):
"""
Get the L{Column} objects from a mapping of L{ColumnSyntax} to values.
"""
return [c.model for c in columnMap.keys()]
class _CommaList(object):
def __init__(self, subfragments):
self.subfragments = subfragments
def subSQL(self, queryGenerator, allTables):
return _commaJoined(
f.subSQL(queryGenerator, allTables)
for f in self.subfragments
)
class _DMLStatement(_Statement):
"""
Common functionality of Insert/Update/Delete statements.
"""
def _returningClause(self, queryGenerator, stmt, allTables):
"""
Add a dialect-appropriate C{returning} clause to the end of the given
SQL statement.
@param queryGenerator: describes the database we are generating the
statement for.
@type queryGenerator: L{QueryGenerator}
@param stmt: the SQL fragment generated without the C{returning} clause
@type stmt: L{SQLFragment}
@param allTables: all tables involved in the query; see any C{subSQL}
method.
@return: the C{stmt} parameter.
"""
retclause = self.Return
if retclause is None:
return stmt
if isinstance(retclause, (tuple, list)):
retclause = _CommaList(retclause)
if queryGenerator.dialect == SQLITE_DIALECT:
# sqlite does this another way.
return stmt
if retclause is not None:
stmt.text += " returning "
stmt.append(retclause.subSQL(queryGenerator, allTables))
if queryGenerator.dialect == ORACLE_DIALECT:
stmt.text += " into "
params = []
retvals = self._returnAsList()
for n, _ignore_v in enumerate(retvals):
params.append(
Constant(Parameter("oracle_out_" + str(n)))
.subSQL(queryGenerator, allTables)
)
stmt.append(_commaJoined(params))
return stmt
def _returnAsList(self):
if not isinstance(self.Return, (tuple, list)):
return [self.Return]
else:
return self.Return
def _extraVars(self, txn, queryGenerator):
if self.Return is None:
return []
result = []
rvars = self._returnAsList()
if queryGenerator.dialect == ORACLE_DIALECT:
for n, v in enumerate(rvars):
result.append(("oracle_out_" + str(n), _OracleOutParam(v)))
return result
def _extraResult(self, result, outvars, queryGenerator):
if (
queryGenerator.dialect == ORACLE_DIALECT and
self.Return is not None
):
def processIt(emptyListResult):
# See comment in L{adbapi2._ConnectedTxn._reallyExecSQL}. If the
# result is L{None} then also return L{None}. If the result is a
# L{list} of empty L{list} then there are return into rows to return.
if emptyListResult:
emptyListResult = [[v.value for _ignore_k, v in outvars]]
return emptyListResult
return result.addCallback(processIt)
else:
return result
def _resultColumns(self):
return self._returnAsList()
class _OracleOutParam(object):
"""
A parameter that will be populated using the cx_Oracle API for host
variables.
"""
implements(IDerivedParameter)
def __init__(self, columnSyntax):
self.typeID = columnSyntax.model.type.name.lower()
def preQuery(self, cursor):
typeMap = {"integer": cx_Oracle.NUMBER,
"text": cx_Oracle.NCLOB,
"varchar": cx_Oracle.STRING,
"timestamp": cx_Oracle.TIMESTAMP}
self.var = cursor.var(typeMap[self.typeID])
return self.var
def postQuery(self, cursor):
self.value = mapOracleOutputType(self.var.getvalue())
self.var = None
class Insert(_DMLStatement):
"""
C{insert} statement.
"""
def __init__(self, columnMap, Return=None):
self.columnMap = columnMap
self.Return = Return
columns = _modelsFromMap(columnMap)
table = _fromSameTable(columns)
required = [column for column in table.columns if column.needsValue()]
unspecified = [column for column in required
if column not in columns]
if unspecified:
raise NotEnoughValues(
"Columns [%s] required."
% (", ".join([c.name for c in unspecified]))
)
def _toSQL(self, queryGenerator):
"""
@return: a C{insert} statement with placeholders and arguments
@rtype: L{SQLFragment}
"""
columnsAndValues = self.columnMap.items()
tableModel = columnsAndValues[0][0].model.table
specifiedColumnModels = [x.model for x in self.columnMap.keys()]
if queryGenerator.dialect == ORACLE_DIALECT:
# See test_nextSequenceDefaultImplicitExplicitOracle.
for column in tableModel.columns:
if isinstance(column.default, Sequence):
columnSyntax = ColumnSyntax(column)
if column not in specifiedColumnModels:
columnsAndValues.append(
(columnSyntax, SequenceSyntax(column.default))
)
sortedColumns = sorted(
columnsAndValues,
key=lambda (c, v): c.model.name
)
allTables = []
stmt = SQLFragment("insert into ")
stmt.append(TableSyntax(tableModel).subSQL(queryGenerator, allTables))
stmt.append(SQLFragment(" "))
stmt.append(_inParens(_commaJoined([
c.subSQL(queryGenerator, allTables)
for (c, _ignore_v) in sortedColumns
])))
stmt.append(SQLFragment(" values "))
stmt.append(_inParens(_commaJoined([
_convert(v).subSQL(queryGenerator, allTables)
for (c, v) in sortedColumns
])))
return self._returningClause(queryGenerator, stmt, allTables)
@inlineCallbacks
def on(self, txn, *a, **kw):
"""
Override to provide extra logic for L{Insert}s that return values on
databases that don't provide return values as part of their C{INSERT}
behavior.
"""
result = yield super(_DMLStatement, self).on(txn, *a, **kw)
if self.Return is not None and txn.dialect == SQLITE_DIALECT:
table = self._returnAsList()[0].model.table
result = yield Select(
self._returnAsList(),
# TODO: error reporting when "return" includes columns
# foreign to the primary table.
From=TableSyntax(table),
Where=(
ColumnSyntax(
Column(table, "rowid", SQLType("integer", None))
) == _sqliteLastInsertRowID()
)
).on(txn, *a, **kw)
returnValue(result)
def _convert(x):
"""
Convert a value to an appropriate SQL AST node. (Currently a simple
isinstance, could be promoted to use adaptation if we want to get fancy.)
"""
if isinstance(x, ExpressionSyntax):
return x
else:
return Constant(x)
class Update(_DMLStatement):
"""
C{update} statement
@ivar columnMap: A L{dict} mapping L{ColumnSyntax} objects to values to
change; values may be simple database values (such as L{str},
L{unicode}, L{datetime.datetime}, L{float}, L{int} etc) or L{Parameter}
instances.
@type columnMap: L{dict}
"""
def __init__(self, columnMap, Where, Return=None):
super(Update, self).__init__()
_fromSameTable(_modelsFromMap(columnMap))
self.columnMap = columnMap
self.Where = Where
self.Return = Return
@inlineCallbacks
def on(self, txn, *a, **kw):
"""
Override to provide extra logic for L{Update}s that return values on
databases that don't provide return values as part of their C{UPDATE}
behavior.
"""
doExtra = self.Return is not None and txn.dialect == SQLITE_DIALECT
upcall = lambda: super(_DMLStatement, self).on(txn, *a, **kw)
if doExtra:
table = self._returnAsList()[0].model.table
rowidcol = ColumnSyntax(Column(table, "rowid",
SQLType("integer", None)))
prequery = Select([rowidcol], From=TableSyntax(table),
Where=self.Where)
preresult = prequery.on(txn, *a, **kw)
before = yield preresult
yield upcall()
result = yield Select(
self._returnAsList(),
# TODO: error reporting when "return" includes
# columns foreign to the primary table.
From=TableSyntax(table),
Where=reduce(
lambda left, right: left.Or(right),
((rowidcol == x) for [x] in before)
)
).on(txn, *a, **kw)
returnValue(result)
else:
returnValue((yield upcall()))
def _toSQL(self, queryGenerator):
"""
@return: an C{insert} statement with placeholders and arguments
@rtype: L{SQLFragment}
"""
sortedColumns = sorted(
self.columnMap.items(), key=lambda (c, v): c.model.name
)
allTables = []
result = SQLFragment("update ")
result.append(
TableSyntax(sortedColumns[0][0].model.table).subSQL(
queryGenerator, allTables
)
)
result.text += " set "
result.append(_commaJoined([
c.subSQL(queryGenerator, allTables).append(
SQLFragment(" = ").subSQL(queryGenerator, allTables)
).append(
_convert(v).subSQL(queryGenerator, allTables)
)
for (c, v) in sortedColumns
]))
if self.Where is not None:
result.append(SQLFragment(" where "))
result.append(self.Where.subSQL(queryGenerator, allTables))
return self._returningClause(queryGenerator, result, allTables)
class Delete(_DMLStatement):
"""
C{delete} statement.
"""
def __init__(self, From, Where, Return=None):
"""
If Where is None then all rows will be deleted.
"""
self.From = From
self.Where = Where
self.Return = Return
def _toSQL(self, queryGenerator):
result = SQLFragment()
allTables = self.From.tables()
result.text += "delete from "
result.append(self.From.subSQL(queryGenerator, allTables))
if self.Where is not None:
result.text += " where "
result.append(self.Where.subSQL(queryGenerator, allTables))
return self._returningClause(queryGenerator, result, allTables)
@inlineCallbacks
def on(self, txn, *a, **kw):
upcall = lambda: super(Delete, self).on(txn, *a, **kw)
if txn.dialect == SQLITE_DIALECT and self.Return is not None:
result = yield Select(
self._returnAsList(),
From=self.From, Where=self.Where
).on(txn, *a, **kw)
yield upcall()
else:
result = yield upcall()
returnValue(result)
class _LockingStatement(_Statement):
"""
A statement related to lock management, which implicitly has no results.
"""
def _resultColumns(self):
"""
No columns should be expected, so return an infinite iterator of None.
"""
return repeat(None)
class Lock(_LockingStatement):
"""
An SQL "lock" statement.
"""
def __init__(self, table, mode):
self.table = table
self.mode = mode
@classmethod
def exclusive(cls, table):
return cls(table, "exclusive")
def _toSQL(self, queryGenerator):
if queryGenerator.dialect == SQLITE_DIALECT:
# FIXME - this is only stubbed out for testing right now, actual
# concurrency would require some kind of locking statement here.
# BEGIN IMMEDIATE maybe, if that's okay in the middle of a
# transaction or repeatedly?
return SQLFragment("select null")
return SQLFragment("lock table ").append(
self.table.subSQL(queryGenerator, [self.table])
).append(
SQLFragment(" in %s mode" % (self.mode,))
)
class DatabaseLock(_LockingStatement):
"""
An SQL exclusive session level advisory lock
"""
def _toSQL(self, queryGenerator):
assert(queryGenerator.dialect == POSTGRES_DIALECT)
return SQLFragment("select pg_advisory_lock(1)")
def on(self, txn, *a, **kw):
"""
Override on() to only execute on Postgres
"""
if txn.dialect == POSTGRES_DIALECT:
return super(DatabaseLock, self).on(txn, *a, **kw)
return succeed(None)
class DatabaseUnlock(_LockingStatement):
"""
An SQL exclusive session level advisory lock
"""
def _toSQL(self, queryGenerator):
assert(queryGenerator.dialect == POSTGRES_DIALECT)
return SQLFragment("select pg_advisory_unlock(1)")
def on(self, txn, *a, **kw):
"""
Override on() to only execute on Postgres
"""
if txn.dialect == POSTGRES_DIALECT:
return super(DatabaseUnlock, self).on(txn, *a, **kw)
return succeed(None)
class Savepoint(_LockingStatement):
"""
An SQL C{savepoint} statement.
"""
def __init__(self, name):
self.name = name
def _toSQL(self, queryGenerator):
return SQLFragment("savepoint %s" % (self.name,))
class RollbackToSavepoint(_LockingStatement):
"""
An SQL C{rollback to savepoint} statement.
"""
def __init__(self, name):
self.name = name
def _toSQL(self, queryGenerator):
return SQLFragment("rollback to savepoint %s" % (self.name,))
class ReleaseSavepoint(_LockingStatement):
"""
An SQL C{release savepoint} statement.
"""
def __init__(self, name):
self.name = name
def _toSQL(self, queryGenerator):
return SQLFragment("release savepoint %s" % (self.name,))
class SavepointAction(object):
def __init__(self, name):
self._name = name
def _safeName(self, txn):
if txn.dialect == ORACLE_DIALECT:
# Oracle limits the length of identifiers
return self._name[:30]
else:
return self._name
def acquire(self, txn):
return Savepoint(self._safeName(txn)).on(txn)
def rollback(self, txn):
return RollbackToSavepoint(self._safeName(txn)).on(txn)
def release(self, txn):
if txn.dialect == ORACLE_DIALECT:
# There is no "release savepoint" statement in oracle, but then, we
# don't need it because there's no resource to manage. Just don't
# do anything.
return NoOp()
else:
return ReleaseSavepoint(self._safeName(txn)).on(txn)
class NoOp(object):
def on(self, *a, **kw):
return succeed(None)
class SQLFragment(object):
"""
Combination of SQL text and arguments; a statement which may be executed
against a database.
"""
def __init__(self, text="", parameters=None):
self.text = text
if parameters is None:
parameters = []
self.parameters = parameters
def bind(self, **kw):
params = []
for parameter in self.parameters:
if isinstance(parameter, Parameter):
if parameter.count is not None:
if parameter.count != len(kw[parameter.name]):
raise DALError(
"Number of place holders does not match "
"number of items to bind"
)
for item in kw[parameter.name]:
params.append(item)
else:
params.append(kw[parameter.name])
else:
params.append(parameter)
return SQLFragment(self.text, params)
def append(self, anotherStatement):
self.text += anotherStatement.text
self.parameters += anotherStatement.parameters
return self
def __eq__(self, stmt):
if not isinstance(stmt, SQLFragment):
return NotImplemented
return (self.text, self.parameters) == (stmt.text, stmt.parameters)
def __ne__(self, stmt):
if not isinstance(stmt, SQLFragment):
return NotImplemented
return not self.__eq__(stmt)
def __repr__(self):
return self.__class__.__name__ + repr((self.text, self.parameters))
def subSQL(self, queryGenerator, allTables):
return self
class Parameter(object):
"""
Used to represent a place holder for a value to be bound to the query
at a later date. If count > 1, then a "set" of parenthesized,
comma separate place holders will be generated.
"""
def __init__(self, name, count=None):
self.name = name
self.count = count
if self.count is not None and self.count < 1:
raise DALError("Must have Parameter.count > 0")
def __eq__(self, param):
if not isinstance(param, Parameter):
return NotImplemented
return self.name == param.name and self.count == param.count
def __ne__(self, param):
if not isinstance(param, Parameter):
return NotImplemented
return not self.__eq__(param)
def __repr__(self):
return "Parameter(%r)" % (self.name,)
# Common helpers:
# current timestamp in UTC format. Hack to support standard syntax for this,
# rather than the compatibility procedure found in various databases.
utcNowSQL = NamedValue("CURRENT_TIMESTAMP at time zone 'UTC'")
# You can't insert a column with no rows. In SQL that just isn't valid syntax,
# and in this DAL you need at least one key or we can't tell what table you're
# talking about. Luckily there's the C{default} keyword to the rescue, which,
# in the context of an INSERT statement means "use the default value
# explicitly".
# (Although this is a special keyword in a CREATE statement, in an INSERT it
# behaves like an expression to the best of my knowledge.)
default = NamedValue("default")
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