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selection_and_product partial

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Salvo 'LtWorf' Tomaselli 2020-06-09 22:47:54 +02:00
parent f4a8344f3e
commit f4a4b847af
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1 changed files with 30 additions and 32 deletions
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relational/optimizations.py
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@ -468,11 +468,10 @@ def projection_and_union(n: parser.Node, rels: Dict[str, Relation]) -> Tuple[par
return n, 0
def selection_and_product(n, rels):
def selection_and_product(n: parser.Node, rels: Dict[str, Relation]) -> parser.Node:
'''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'''
changes = 0
if n.name == SELECTION and n.child.name in (PRODUCT, JOIN):
l_attr = n.child.left.result_format(rels)
@ -518,52 +517,51 @@ def selection_and_product(n, rels):
# Preparing left selection
if len(left) > 0:
changes = 1
l_node = parser.Node()
l_node.name = SELECTION
l_node.kind = parser.UNARY
l_node.child = n.child.left
l_node.prop = ''
n.child.left = l_node
l_prop = ''
while len(left) > 0:
c = left.pop(0)
for i in c:
l_node.prop += i + ' '
l_prop += i + ' '
if len(left) > 0:
l_node.prop += ' and '
if '(' in l_node.prop:
l_node.prop = '(%s)' % l_node.prop
l_prop += ' and '
if '(' in l_prop:
l_prop = '(%s)' % l_prop
l_node = parser.Unary(SELECTION, l_prop, n.child.left)
else:
l_node = n.child.left
# Preparing right selection
if len(right) > 0:
changes = 1
r_node = parser.Node()
r_node.name = SELECTION
r_node.prop = ''
r_node.kind = parser.UNARY
r_node.child = n.child.right
n.child.right = r_node
r_prop = ''
while len(right) > 0:
c = right.pop(0)
r_node.prop += ' '.join(c)
r_prop += ' '.join(c)
if len(right) > 0:
r_node.prop += ' and '
if '(' in r_node.prop:
r_node.prop = '(%s)' % r_node.prop
r_prop += ' and '
if '(' in r_prop:
r_prop = '(%s)' % r_prop
r_node = parser.Unary(SELECTION, r_prop, n.child.right)
else:
r_node = n.child.right
b_node = parser.Binary(n.child.name, l_node, r_node)
# Changing main selection
n.prop = ''
both_prop = ''
if len(both) != 0:
while len(both) > 0:
c = both.pop(0)
n.prop += ' '.join(c)
both_prop += ' '.join(c)
if len(both) > 0:
n.prop += ' and '
if '(' in n.prop:
n.prop = '(%s)' % n.prop
both_prop += ' and '
if '(' in both_prop:
both_prop = '(%s)' % both_prop
return parser.Unary(SELECTION, both_prop, b_node), 1
else: # No need for general select
replace_node(n, n.child)
return b_node, 1
return changes + recoursive_scan(selection_and_product, n, rels)
return n, 0
def useless_projection(n: parser.Node, rels: Dict[str, Relation]) -> Tuple[parser.Node, int]:
@ -591,7 +589,7 @@ general_optimizations = [
union_and_product,
]
specific_optimizations = [
#selection_and_product,
selection_and_product,
projection_and_union,
useless_projection,
]