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More of the same

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Salvo 'LtWorf' Tomaselli 2020-06-17 23:05:27 +07:00
parent e35fc0f4bd
commit 95a4287e68
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GPG Key ID: B3A7CF0C801886CF
1 changed files with 28 additions and 17 deletions
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relational/optimizations.py
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@ -91,29 +91,34 @@ def futile_union_intersection_subtraction(n: parser.Node) -> Tuple[parser.Node,
σ k (R) ∩ R --> σ k (R)
'''
changes = 0
if not isinstance(n, Binary):
return n, 0
# Union and intersection of the same thing
if n.name in (UNION, INTERSECTION, JOIN, JOIN_LEFT, JOIN_RIGHT, JOIN_FULL) and n.left == n.right:
return n.left, 1
# selection and union of the same thing
elif (n.name == UNION):
if n.left.name == SELECTION and n.left.child == n.right:
elif n.name == UNION:
if n.left.name == SELECTION and isinstance(n.left, Unary) and n.left.child == n.right:
return n.right, 1
elif n.right.name == SELECTION and n.right.child == n.left:
elif n.right.name == SELECTION and isinstance(n.right, Unary) and n.right.child == n.left:
return n.left, 1
# selection and intersection of the same thing
elif n.name == INTERSECTION:
if n.left.name == SELECTION and n.left.child == n.right:
return n.left, 1
elif n.right.name == SELECTION and n.right.child == n.left:
elif n.right.name == SELECTION and \
isinstance(n.right, Unary) and \
n.right.child == n.left:
return n.right, 1
# Subtraction and selection of the same thing
elif n.name == DIFFERENCE and \
isinstance(n, Binary) and \
n.right.name == SELECTION and \
isinstance(n.right, Unary) and \
n.right.child == n.left:
return Unary(
SELECTION,
@ -178,7 +183,12 @@ def swap_union_renames(n: parser.Node) -> Tuple[parser.Node, int]:
and replaces them with
ρ a➡b(R ∪ Q).
Does the same with subtraction and intersection'''
if n.name in (DIFFERENCE, UNION, INTERSECTION) and n.left.name == RENAME and n.right.name == RENAME:
if n.name in (DIFFERENCE, UNION, INTERSECTION) and \
isinstance(n, Binary) and \
n.left.name == RENAME and \
isinstance(n.left, Unary) and\
n.right.name == RENAME and \
isinstance(n.right, Unary):
l_vars = n.left.get_rename_prop()
r_vars = n.right.get_rename_prop()
if r_vars == l_vars:
@ -327,7 +337,7 @@ def swap_rename_projection(n: parser.Node) -> Tuple[parser.Node, int]:
return n, 0
def swap_rename_select(n: parser.Node) -> int:
def swap_rename_select(n: parser.Node) -> Tuple[parser.Node, int]:
'''This function locates things like
σ k(ρ j(R))
and replaces them with
@ -358,20 +368,19 @@ def swap_rename_select(n: parser.Node) -> int:
return n, 0
def select_union_intersect_subtract(n: parser.Node) -> int:
def select_union_intersect_subtract(n: parser.Node) -> Tuple[parser.Node, int]:
'''This function locates things like
σ i(a) ∪ σ q(a)
and replaces them with
σ (i OR q) (a)
Removing a O(n²) operation like the union'''
if isinstance(n, Binary) and \
n.name in {UNION, INTERSECTION, DIFFERENCE} and \
isinstance(n.left, Unary) and \
n.left.name == SELECTION and \
isinstance(n.right, Unary) and \
n.right.name == SELECTION and \
n.left.child == n.right.child:
n.name in {UNION, INTERSECTION, DIFFERENCE} and \
isinstance(n.left, Unary) and \
n.left.name == SELECTION and \
isinstance(n.right, Unary) and \
n.right.name == SELECTION and \
n.left.child == n.right.child:
d = {UNION: 'or', INTERSECTION: 'and', DIFFERENCE: 'and not'}
op = d[n.name]
@ -432,16 +441,18 @@ def projection_and_union(n: parser.Node, rels: Dict[str, Relation]) -> Tuple[par
'''
changes = 0
if n.name == UNION and \
isinstance(n, Binary) and \
n.left.name == PROJECTION and \
isinstance(n.left, Unary) and \
n.right.name == PROJECTION and \
isinstance(n.right, Unary) and \
set(n.left.child.result_format(rels)) == set(n.right.child.result_format(rels)):
child = Binary(UNION, n.left.child, n.right.child)
return Unary(PROJECTION, n.right.prop, child), 0
return n, 0
def selection_and_product(n: parser.Node, rels: Dict[str, Relation]) -> parser.Node:
def selection_and_product(n: parser.Node, rels: Dict[str, Relation]) -> Tuple[parser.Node, int]:
'''This function locates things like σ k (R*Q) and converts them into
σ l (σ j (R) * σ i (Q)). Where j contains only attributes belonging to R,
i contains attributes belonging to Q and l contains attributes belonging to both'''