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import datetime
import functools
import itertools
from collections import deque
from decimal import Decimal
from sqlglot import exp
from sqlglot.expressions import FALSE, NULL, TRUE
from sqlglot.generator import Generator
from sqlglot.helper import while_changing
GENERATOR = Generator(normalize=True, identify=True)
def simplify(expression):
"""
Rewrite sqlglot AST to simplify expressions.
Example:
>>> import sqlglot
>>> expression = sqlglot.parse_one("TRUE AND TRUE")
>>> simplify(expression).sql()
'TRUE'
Args:
expression (sqlglot.Expression): expression to simplify
Returns:
sqlglot.Expression: simplified expression
"""
def _simplify(expression, root=True):
node = expression
node = uniq_sort(node)
node = absorb_and_eliminate(node)
exp.replace_children(node, lambda e: _simplify(e, False))
node = simplify_not(node)
node = flatten(node)
node = simplify_connectors(node)
node = remove_compliments(node)
node.parent = expression.parent
node = simplify_literals(node)
node = simplify_parens(node)
if root:
expression.replace(node)
return node
expression = while_changing(expression, _simplify)
remove_where_true(expression)
return expression
def simplify_not(expression):
"""
Demorgan's Law
NOT (x OR y) -> NOT x AND NOT y
NOT (x AND y) -> NOT x OR NOT y
"""
if isinstance(expression, exp.Not):
if isinstance(expression.this, exp.Null):
return NULL
if isinstance(expression.this, exp.Paren):
condition = expression.this.unnest()
if isinstance(condition, exp.And):
return exp.or_(exp.not_(condition.left), exp.not_(condition.right))
if isinstance(condition, exp.Or):
return exp.and_(exp.not_(condition.left), exp.not_(condition.right))
if isinstance(condition, exp.Null):
return NULL
if always_true(expression.this):
return FALSE
if expression.this == FALSE:
return TRUE
if isinstance(expression.this, exp.Not):
# double negation
# NOT NOT x -> x
return expression.this.this
return expression
def flatten(expression):
"""
A AND (B AND C) -> A AND B AND C
A OR (B OR C) -> A OR B OR C
"""
if isinstance(expression, exp.Connector):
for node in expression.args.values():
child = node.unnest()
if isinstance(child, expression.__class__):
node.replace(child)
return expression
def simplify_connectors(expression):
if isinstance(expression, exp.Connector):
left = expression.left
right = expression.right
if left == right:
return left
if isinstance(expression, exp.And):
if FALSE in (left, right):
return FALSE
if NULL in (left, right):
return NULL
if always_true(left) and always_true(right):
return TRUE
if always_true(left):
return right
if always_true(right):
return left
elif isinstance(expression, exp.Or):
if always_true(left) or always_true(right):
return TRUE
if left == FALSE and right == FALSE:
return FALSE
if (
(left == NULL and right == NULL)
or (left == NULL and right == FALSE)
or (left == FALSE and right == NULL)
):
return NULL
if left == FALSE:
return right
if right == FALSE:
return left
return expression
def remove_compliments(expression):
"""
Removing compliments.
A AND NOT A -> FALSE
A OR NOT A -> TRUE
"""
if isinstance(expression, exp.Connector):
compliment = FALSE if isinstance(expression, exp.And) else TRUE
for a, b in itertools.permutations(expression.flatten(), 2):
if is_complement(a, b):
return compliment
return expression
def uniq_sort(expression):
"""
Uniq and sort a connector.
C AND A AND B AND B -> A AND B AND C
"""
if isinstance(expression, exp.Connector):
result_func = exp.and_ if isinstance(expression, exp.And) else exp.or_
flattened = tuple(expression.flatten())
deduped = {GENERATOR.generate(e): e for e in flattened}
arr = tuple(deduped.items())
# check if the operands are already sorted, if not sort them
# A AND C AND B -> A AND B AND C
for i, (sql, e) in enumerate(arr[1:]):
if sql < arr[i][0]:
expression = result_func(*(deduped[sql] for sql in sorted(deduped)))
break
else:
# we didn't have to sort but maybe we need to dedup
if len(deduped) < len(flattened):
expression = result_func(*deduped.values())
return expression
def absorb_and_eliminate(expression):
"""
absorption:
A AND (A OR B) -> A
A OR (A AND B) -> A
A AND (NOT A OR B) -> A AND B
A OR (NOT A AND B) -> A OR B
elimination:
(A AND B) OR (A AND NOT B) -> A
(A OR B) AND (A OR NOT B) -> A
"""
if isinstance(expression, exp.Connector):
kind = exp.Or if isinstance(expression, exp.And) else exp.And
for a, b in itertools.permutations(expression.flatten(), 2):
if isinstance(a, kind):
aa, ab = a.unnest_operands()
# absorb
if is_complement(b, aa):
aa.replace(exp.true() if kind == exp.And else exp.false())
elif is_complement(b, ab):
ab.replace(exp.true() if kind == exp.And else exp.false())
elif (set(b.flatten()) if isinstance(b, kind) else {b}) < set(a.flatten()):
a.replace(exp.false() if kind == exp.And else exp.true())
elif isinstance(b, kind):
# eliminate
rhs = b.unnest_operands()
ba, bb = rhs
if aa in rhs and (is_complement(ab, ba) or is_complement(ab, bb)):
a.replace(aa)
b.replace(aa)
elif ab in rhs and (is_complement(aa, ba) or is_complement(aa, bb)):
a.replace(ab)
b.replace(ab)
return expression
def simplify_literals(expression):
if isinstance(expression, exp.Binary):
operands = []
queue = deque(expression.flatten(unnest=False))
size = len(queue)
while queue:
a = queue.popleft()
for b in queue:
result = _simplify_binary(expression, a, b)
if result:
queue.remove(b)
queue.append(result)
break
else:
operands.append(a)
if len(operands) < size:
return functools.reduce(
lambda a, b: expression.__class__(this=a, expression=b), operands
)
elif isinstance(expression, exp.Neg):
this = expression.this
if this.is_number:
value = this.name
if value[0] == "-":
return exp.Literal.number(value[1:])
return exp.Literal.number(f"-{value}")
return expression
def _simplify_binary(expression, a, b):
if isinstance(expression, exp.Is):
if isinstance(b, exp.Not):
c = b.this
not_ = True
else:
c = b
not_ = False
if c == NULL:
if isinstance(a, exp.Literal):
return TRUE if not_ else FALSE
if a == NULL:
return FALSE if not_ else TRUE
elif isinstance(expression, exp.NullSafeEQ):
if a == b:
return TRUE
elif isinstance(expression, exp.NullSafeNEQ):
if a == b:
return FALSE
elif NULL in (a, b):
return NULL
if isinstance(expression, exp.EQ) and a == b:
return TRUE
if a.is_number and b.is_number:
a = int(a.name) if a.is_int else Decimal(a.name)
b = int(b.name) if b.is_int else Decimal(b.name)
if isinstance(expression, exp.Add):
return exp.Literal.number(a + b)
if isinstance(expression, exp.Sub):
return exp.Literal.number(a - b)
if isinstance(expression, exp.Mul):
return exp.Literal.number(a * b)
if isinstance(expression, exp.Div):
if isinstance(a, int) and isinstance(b, int):
return exp.Literal.number(a // b)
return exp.Literal.number(a / b)
boolean = eval_boolean(expression, a, b)
if boolean:
return boolean
elif a.is_string and b.is_string:
boolean = eval_boolean(expression, a, b)
if boolean:
return boolean
elif isinstance(a, exp.Cast) and isinstance(b, exp.Interval):
a, b = extract_date(a), extract_interval(b)
if b:
if isinstance(expression, exp.Add):
return date_literal(a + b)
if isinstance(expression, exp.Sub):
return date_literal(a - b)
elif isinstance(a, exp.Interval) and isinstance(b, exp.Cast):
a, b = extract_interval(a), extract_date(b)
# you cannot subtract a date from an interval
if a and isinstance(expression, exp.Add):
return date_literal(a + b)
return None
def simplify_parens(expression):
if (
isinstance(expression, exp.Paren)
and not isinstance(expression.this, exp.Select)
and (
not isinstance(expression.parent, (exp.Condition, exp.Binary))
or isinstance(expression.this, (exp.Is, exp.Like))
or not isinstance(expression.this, exp.Binary)
)
):
return expression.this
return expression
def remove_where_true(expression):
for where in expression.find_all(exp.Where):
if always_true(where.this):
where.parent.set("where", None)
for join in expression.find_all(exp.Join):
if always_true(join.args.get("on")):
join.set("kind", "CROSS")
join.set("on", None)
def always_true(expression):
return expression == TRUE or isinstance(expression, exp.Literal)
def is_complement(a, b):
return isinstance(b, exp.Not) and b.this == a
def eval_boolean(expression, a, b):
if isinstance(expression, (exp.EQ, exp.Is)):
return boolean_literal(a == b)
if isinstance(expression, exp.NEQ):
return boolean_literal(a != b)
if isinstance(expression, exp.GT):
return boolean_literal(a > b)
if isinstance(expression, exp.GTE):
return boolean_literal(a >= b)
if isinstance(expression, exp.LT):
return boolean_literal(a < b)
if isinstance(expression, exp.LTE):
return boolean_literal(a <= b)
return None
def extract_date(cast):
if cast.args["to"].this == exp.DataType.Type.DATE:
return datetime.date.fromisoformat(cast.name)
return None
def extract_interval(interval):
try:
from dateutil.relativedelta import relativedelta # type: ignore
except ModuleNotFoundError:
return None
n = int(interval.name)
unit = interval.text("unit").lower()
if unit == "year":
return relativedelta(years=n)
if unit == "month":
return relativedelta(months=n)
if unit == "week":
return relativedelta(weeks=n)
if unit == "day":
return relativedelta(days=n)
return None
def date_literal(date):
return exp.Cast(this=exp.Literal.string(date), to=exp.DataType.build("DATE"))
def boolean_literal(condition):
return TRUE if condition else FALSE
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