/usr/lib/python2.7/dist-packages/peak/rules/indexing.py is in python-peak.rules 0.5a1+r2713-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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import sys
from peak.util.addons import AddOn
from peak.rules.core import *
from peak.rules.criteria import *
from peak.rules.core import sorted, set, frozenset
from peak.util.extremes import Min, Max, Extreme
from peak.util.decorators import decorate
from types import InstanceType
__all__ = [
'Ordering', 'BitmapIndex', 'TreeBuilder', 'split_ranges',
'to_bits', 'from_bits', 'RangeIndex', 'TypeIndex', 'TruthIndex',
'PointerIndex', 'bitmap_index_type'
]
def define_ordering(ob, seq):
items = []
for key in seq:
Ordering(ob, key).requires(items)
items.append(key)
class Ordering(AddOn):
"""Track inter-expression ordering constraints"""
def __init__(self, owner, expr):
self.constraints = set()
def requires(self, guards):
c = frozenset(guards)
cs = self.constraints
if c in cs:
return
for oldc in list(cs):
if c >= oldc:
return # already a less-restrictive condition
elif oldc >= c:
cs.remove(oldc)
cs.add(c)
def can_precede(self, exprs):
if not self.constraints:
return True
for c in self.constraints:
for e in c:
if e in exprs:
break
else:
return True
else:
return False
def to_bits(ints):
"""Return a bitset encoding the numbers contained in sequence `ints`"""
b = 0
for i in ints:
b |= 1<<i
return b
if sys.version<"2.4":
def to_bits(ints):
"""Return a bitset encoding the numbers contained in sequence `ints`"""
b = 0
for i in ints:
if i>31:
i = long(i)
b |= 1<<i # under 2.3, this breaks when i>31 unless it's a long
return b
def from_bits(n):
"""Yield the (ascending) numbers contained in bitset n"""
b = 0
while n:
while not n & 15:
n >>= 4
b += 4
if n & 1:
yield b
n >>= 1
b += 1
class TreeBuilder(object):
"""Template methods for the Chambers&Chen dispatch tree algorithm"""
def build(self, cases, exprs, memo):
key = (cases, exprs)
if key in memo:
return memo[key]
if not exprs:
node = self.build_leaf(cases, memo)
else:
best, rest = self.best_expr(cases, exprs)
assert len(rest) < len(exprs)
if best is None:
# No best expression found, recurse
node = self.build(cases, rest, memo)
else:
node = self.build_node(best, cases, rest, memo)
memo[key] = node
return node
def build_node(self, expr, cases, remaining_exprs, memo):
raise NotImplementedError
def build_leaf(self, cases, memo):
raise NotImplementedError
def selectivity(self, expression, cases):
"""Return (seedcount,totalcases) selectivity statistics"""
raise NotImplementedError
def cost(self, expr, remaining_exprs):
return 1
def best_expr(self, cases, exprs):
best_expr = None
best_spread = None
to_do = list(exprs)
remaining = dict.fromkeys(exprs)
active_cases = len(cases)
skipped = []
while to_do:
expr = to_do.pop()
if not Ordering(self, expr).can_precede(remaining):
# Skip criteria that have unchecked prerequisites
skipped.append(expr)
continue
branches, total_cases = self.selectivity(expr, cases)
if total_cases == active_cases * branches:
# None of the branches for this expression eliminate any
# cases, so this expression isn't needed for dispatching
del remaining[expr]
# recheck skipped exprs that might be legal now
to_do.extend(skipped)
skipped = []
continue
spread = total_cases / branches
if best_expr is None or spread < best_spread:
best_expr, best_spread = expr, spread
best_cost = self.cost(expr, remaining)
elif spread==best_spread:
cost = self.cost(expr, remaining)
if cost < best_cost:
best_expr, best_cost = expr, cost
if best_expr is not None:
del remaining[best_expr]
return best_expr, frozenset(remaining)
class BitmapIndex(AddOn):
"""Index that computes selectivity and handles basic caching w/bitmaps"""
known_cases = 0
match = True,
decorate(staticmethod)
def addon_key(*args):
# Always use BitmapIndex as the add-on key
return (BitmapIndex,)+args
def __new__(cls, engine, expr):
if cls is BitmapIndex:
cls = bitmap_index_type(engine, expr)
return super(BitmapIndex, cls).__new__(cls)
def __init__(self, engine, expr):
self.extra = {}
self.null = self.all_seeds = {} # seed -> inc_cri, exc_cri
self.criteria_bits = {} # cri -> case bits
self.case_seeds = [] # case -> seed set
self.criteria_seeds = {} # cri -> seeds
def add_case(self, case_id, criterion):
if criterion in self.criteria_seeds:
seeds = self.criteria_seeds[criterion]
else:
self.criteria_bits.setdefault(criterion, 0)
seeds = self.criteria_seeds[criterion] = self.add_criterion(criterion)
case_seeds = self.case_seeds
if case_id==len(case_seeds):
case_seeds.append(seeds)
else:
self._extend_cases(case_id)
case_seeds[case_id] = seeds
bit = to_bits([case_id])
self.known_cases |= bit
self.criteria_bits[criterion] |= bit
def add_criterion(self, criterion):
"""Ensure `criterion` is indexed, return its "applicable seeds" set
As a side effect, ``self.all_seeds`` must be updated to include any
new seeds required by `criterion`.
"""
raise NotImplementedError
def _extend_cases(self, case_id):
if case_id >= len(self.case_seeds):
self.case_seeds.extend(
[self.null]*(case_id+1-len(self.case_seeds))
)
def selectivity(self, cases):
if cases and cases[-1] >= len(self.case_seeds):
self._extend_cases(cases[-1])
cases = map(self.case_seeds.__getitem__, cases)
return (len(self.all_seeds), sum(map(len, cases)))
def seed_bits(self, cases):
bits = self.criteria_bits
return cases ^ (self.known_cases & cases), dict([
(seed,
(sum([bits[i] for i in inc]) & cases,
sum([bits[e] for e in exc]) & cases))
for seed, (inc, exc) in self.all_seeds.items()
])
def expanded_sets(self):
return [
(seed, [list(from_bits(inc)), list(from_bits(exc))])
for seed, (inc, exc) in self.seed_bits(self.known_cases)[1].items()
]
def reseed(self, criterion):
self.add_criterion(criterion)
def include(self, seed, criterion, exclude=False):
try:
s = self.all_seeds[seed]
except KeyError:
s = self.all_seeds[seed] = set(), set()
s[exclude].add(criterion)
self.criteria_bits.setdefault(criterion, 0)
def exclude(self, seed, criterion):
self.include(seed, criterion, True)
def split_ranges(dont_cares, bitmap, node=lambda b:b):
"""Return (exact, ranges) where `exact` is a dict[value]->node and `ranges`
is a sorted list of ``((lo,hi),node)`` tuples expressing non-inclusive
ranges. `dont_cares` and `bitmap` should be the return values from
a bitmap index's ``seed_bits()`` method. `node(bits)` should return
the value to be used as a node in the output; the default is to just return
a bitmap of cases.
"""
ranges = []
exact = {}
current = dont_cares
for (val,d), (inc, exc) in bitmap.iteritems():
if d and not (val is Min and d==-1 and not inc):
break # something other than == was used; use full algorithm
exact[val] = node(current | inc)
else:
return exact, [((Min, Max), node(dont_cares))]
low = Min
for (val,d), (inc, exc) in sorted(bitmap.iteritems()):
if val != low:
if ranges and ranges[-1][-1]==current:
low = ranges.pop()[0][0]
ranges.append(((low, val), node(current)))
low = val
new = current | inc
new ^= (new & exc)
if not isinstance(val, Extreme):
if d==0 or d<0:
exact[val] = node(new)
elif val not in exact:
exact[val] = node(current)
if d:
current = new
if low != Max:
if ranges and ranges[-1][-1]==current:
low = ranges.pop()[0][0]
ranges.append(((low, Max), node(current)))
return exact, ranges
class PointerIndex(BitmapIndex):
"""Index for pointer equality"""
def add_criterion(self, criterion):
if isinstance(criterion, Intersection):
match = False
items = criterion
else:
match = criterion.match
items = [criterion]
for cri in items:
seed = id(cri.ref)
self.extra[seed] = 1
if match:
self.include(seed, criterion)
self.exclude(None, criterion)
else:
self.include(None, criterion)
self.exclude(seed, criterion)
if match:
return self.match
return self.extra
def seed_bits(self, cases):
dontcares, seedmap = BitmapIndex.seed_bits(self, cases)
defaults = seedmap[None][0] # default inclusions
for seed, (inc, exc) in seedmap.items():
if seed is not None:
inc |= defaults ^ (defaults & exc)
seedmap[seed] = inc, exc
return dontcares, seedmap
class TruthIndex(BitmapIndex):
"""Index for simple boolean expression tests"""
def add_criterion(self, criterion):
assert isinstance(criterion, Value) and criterion.value is True
self.include(criterion.match, criterion)
self.include(not criterion.match, not criterion)
return self.match
abstract()
def bitmap_index_type(engine, expr):
"""Get the BitmapIndex subclass to use for the given engine and `expr`"""
raise NotImplementedError(engine, expr)
def class_seeds_for(criterion):
"""Yield class objects that 'criterion' thinks are relevant"""
if isinstance(criterion, istype):
yield criterion.type
elif isinstance(criterion, Class):
yield criterion.cls
elif isinstance(criterion, Intersection):
for c in criterion:
for seed in class_seeds_for(c):
yield seed
class TypeIndex(BitmapIndex):
"""Index for istype(), Class(), and Classes() criteria"""
def add_class(self, cls):
t = istype(cls)
for criterion, seeds in self.criteria_seeds.iteritems():
if implies(t, criterion):
self.include(cls, criterion)
seeds.add(cls)
self.include(cls, t) # ensure it's in all_seeds
def reseed(self, criterion):
map(self.add_class, class_seeds_for(criterion))
if object not in self.all_seeds:
self.include(object, istype(object))
def add_criterion(self, criterion):
my_seeds = self.criteria_seeds.setdefault(criterion, set())
self.reseed(criterion)
for seed in self.all_seeds:
if implies(istype(seed), criterion):
self.include(seed, criterion)
my_seeds.add(seed)
return my_seeds
class RangeIndex(BitmapIndex):
def __init__(self, engine, expr):
BitmapIndex.__init__(self, engine, expr)
self.null = None
def add_criterion(self, criterion):
if isinstance(criterion, Range):
lo = i = criterion.lo
hi = e = criterion.hi
match = True
elif isinstance(criterion, Value):
lo = hi = val = (criterion.value, 0)
if criterion.match:
e = (Min, -1)
i = val
else:
i = (Min, -1)
e = val
match = criterion.match
else:
raise TypeError(criterion)
if (i not in self.all_seeds or e not in self.all_seeds
or (lo,hi,match) not in self.extra
):
# oops, there's a seed we haven't seen before:
# make sure the offsets are rebuilt on the next selectivity() call
self.extra.clear()
self.include(i, criterion)
self.exclude(e, criterion)
return lo, hi, match
def selectivity(self, cases):
case_seeds = self.case_seeds
if cases and cases[-1] >= len(case_seeds):
self._extend_cases(cases[-1])
extras = self.extra
if not extras:
all_seeds = self.all_seeds
offsets = dict([(k,n) for n,k in enumerate(sorted(all_seeds))])
all = extras[None] = len(all_seeds)
all_but_one = all - 1
for lo,hi,inc in self.criteria_seeds.values():
if lo==hi:
extras[lo,hi,inc] = [all_but_one, 1][inc]
else:
extras[lo,hi,inc] = offsets[hi] - offsets[lo]
cases = map(case_seeds.__getitem__, cases)
return (len(self.all_seeds), sum(map(extras.__getitem__, cases)))
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