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select_union_intersect_subtract

master
Salvo 'LtWorf' Tomaselli 2020-06-09 19:27:47 +07:00
parent ff2f890b98
commit a2111a90c1
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1 changed files with 9 additions and 15 deletions
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relational/optimizations.py
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@ -394,21 +394,19 @@ def swap_rename_select(n: parser.Node) -> int:
def select_union_intersect_subtract(n: parser.Node) -> int: def select_union_intersect_subtract(n: parser.Node) -> int:
'''This function locates things like σ i(a) ∪ σ q(a) '''This function locates things like
and replaces them with σ (i OR q) (a) σ i(a) ∪ σ q(a)
and replaces them with
σ (i OR q) (a)
Removing a O(n²) operation like the union''' Removing a O(n²) operation like the union'''
changes = 0
if n.name in {UNION, INTERSECTION, DIFFERENCE} and \ if n.name in {UNION, INTERSECTION, DIFFERENCE} and \
n.left.name == SELECTION and \ n.left.name == SELECTION and \
n.right.name == SELECTION and \ n.right.name == SELECTION and \
n.left.child == n.right.child: n.left.child == n.right.child:
changes = 1
d = {UNION: 'or', INTERSECTION: 'and', DIFFERENCE: 'and not'} d = {UNION: 'or', INTERSECTION: 'and', DIFFERENCE: 'and not'}
op = d[n.name] op = d[n.name]
newnode = parser.Node()
if n.left.prop.startswith('(') or n.right.prop.startswith('('): if n.left.prop.startswith('(') or n.right.prop.startswith('('):
t_str = '(' t_str = '('
if n.left.prop.startswith('('): if n.left.prop.startswith('('):
@ -422,15 +420,11 @@ def select_union_intersect_subtract(n: parser.Node) -> int:
t_str += '%s' t_str += '%s'
t_str += ')' t_str += ')'
newnode.prop = t_str % (n.left.prop, op, n.right.prop) prop = t_str % (n.left.prop, op, n.right.prop)
else: else:
newnode.prop = '%s %s %s' % (n.left.prop, op, n.right.prop) prop = '%s %s %s' % (n.left.prop, op, n.right.prop)
newnode.name = SELECTION return parser.Unary(SELECTION, prop, n.left.child), 1
newnode.child = n.left.child return n, 0
newnode.kind = parser.UNARY
replace_node(n, newnode)
return changes + recoursive_scan(select_union_intersect_subtract, n)
def union_and_product(n: parser.Node) -> Tuple[parser.Node, int]: def union_and_product(n: parser.Node) -> Tuple[parser.Node, int]:
@ -606,7 +600,7 @@ general_optimizations = [
futile_union_intersection_subtraction, futile_union_intersection_subtraction,
swap_union_renames, swap_union_renames,
swap_rename_projection, swap_rename_projection,
#select_union_intersect_subtract, select_union_intersect_subtract,
union_and_product, union_and_product,
] ]
specific_optimizations = [ specific_optimizations = [