sqlglot.optimizer.canonicalize

  1from __future__ import annotations
  2
  3import itertools
  4import typing as t
  5
  6from sqlglot import exp
  7from sqlglot.helper import is_date_unit, is_iso_date, is_iso_datetime
  8
  9
 10def canonicalize(expression: exp.Expression) -> exp.Expression:
 11    """Converts a sql expression into a standard form.
 12
 13    This method relies on annotate_types because many of the
 14    conversions rely on type inference.
 15
 16    Args:
 17        expression: The expression to canonicalize.
 18    """
 19    exp.replace_children(expression, canonicalize)
 20
 21    expression = add_text_to_concat(expression)
 22    expression = replace_date_funcs(expression)
 23    expression = coerce_type(expression)
 24    expression = remove_redundant_casts(expression)
 25    expression = ensure_bools(expression, _replace_int_predicate)
 26    expression = remove_ascending_order(expression)
 27
 28    return expression
 29
 30
 31def add_text_to_concat(node: exp.Expression) -> exp.Expression:
 32    if isinstance(node, exp.Add) and node.type and node.type.this in exp.DataType.TEXT_TYPES:
 33        node = exp.Concat(expressions=[node.left, node.right])
 34    return node
 35
 36
 37def replace_date_funcs(node: exp.Expression) -> exp.Expression:
 38    if isinstance(node, exp.Date) and not node.expressions and not node.args.get("zone"):
 39        return exp.cast(node.this, to=exp.DataType.Type.DATE)
 40    if isinstance(node, exp.Timestamp) and not node.expression:
 41        return exp.cast(node.this, to=exp.DataType.Type.TIMESTAMP)
 42    return node
 43
 44
 45COERCIBLE_DATE_OPS = (
 46    exp.Add,
 47    exp.Sub,
 48    exp.EQ,
 49    exp.NEQ,
 50    exp.GT,
 51    exp.GTE,
 52    exp.LT,
 53    exp.LTE,
 54    exp.NullSafeEQ,
 55    exp.NullSafeNEQ,
 56)
 57
 58
 59def coerce_type(node: exp.Expression) -> exp.Expression:
 60    if isinstance(node, COERCIBLE_DATE_OPS):
 61        _coerce_date(node.left, node.right)
 62    elif isinstance(node, exp.Between):
 63        _coerce_date(node.this, node.args["low"])
 64    elif isinstance(node, exp.Extract) and not node.expression.type.is_type(
 65        *exp.DataType.TEMPORAL_TYPES
 66    ):
 67        _replace_cast(node.expression, exp.DataType.Type.DATETIME)
 68    elif isinstance(node, (exp.DateAdd, exp.DateSub, exp.DateTrunc)):
 69        _coerce_timeunit_arg(node.this, node.unit)
 70    elif isinstance(node, exp.DateDiff):
 71        _coerce_datediff_args(node)
 72
 73    return node
 74
 75
 76def remove_redundant_casts(expression: exp.Expression) -> exp.Expression:
 77    if (
 78        isinstance(expression, exp.Cast)
 79        and expression.to.type
 80        and expression.this.type
 81        and expression.to.type.this == expression.this.type.this
 82    ):
 83        return expression.this
 84    return expression
 85
 86
 87def ensure_bools(
 88    expression: exp.Expression, replace_func: t.Callable[[exp.Expression], None]
 89) -> exp.Expression:
 90    if isinstance(expression, exp.Connector):
 91        replace_func(expression.left)
 92        replace_func(expression.right)
 93    elif isinstance(expression, exp.Not):
 94        replace_func(expression.this)
 95        # We can't replace num in CASE x WHEN num ..., because it's not the full predicate
 96    elif isinstance(expression, exp.If) and not (
 97        isinstance(expression.parent, exp.Case) and expression.parent.this
 98    ):
 99        replace_func(expression.this)
100    elif isinstance(expression, (exp.Where, exp.Having)):
101        replace_func(expression.this)
102
103    return expression
104
105
106def remove_ascending_order(expression: exp.Expression) -> exp.Expression:
107    if isinstance(expression, exp.Ordered) and expression.args.get("desc") is False:
108        # Convert ORDER BY a ASC to ORDER BY a
109        expression.set("desc", None)
110
111    return expression
112
113
114def _coerce_date(a: exp.Expression, b: exp.Expression) -> None:
115    for a, b in itertools.permutations([a, b]):
116        if isinstance(b, exp.Interval):
117            a = _coerce_timeunit_arg(a, b.unit)
118        if (
119            a.type
120            and a.type.this == exp.DataType.Type.DATE
121            and b.type
122            and b.type.this
123            not in (
124                exp.DataType.Type.DATE,
125                exp.DataType.Type.INTERVAL,
126            )
127        ):
128            _replace_cast(b, exp.DataType.Type.DATE)
129
130
131def _coerce_timeunit_arg(arg: exp.Expression, unit: t.Optional[exp.Expression]) -> exp.Expression:
132    if not arg.type:
133        return arg
134
135    if arg.type.this in exp.DataType.TEXT_TYPES:
136        date_text = arg.name
137        is_iso_date_ = is_iso_date(date_text)
138
139        if is_iso_date_ and is_date_unit(unit):
140            return arg.replace(exp.cast(arg.copy(), to=exp.DataType.Type.DATE))
141
142        # An ISO date is also an ISO datetime, but not vice versa
143        if is_iso_date_ or is_iso_datetime(date_text):
144            return arg.replace(exp.cast(arg.copy(), to=exp.DataType.Type.DATETIME))
145
146    elif arg.type.this == exp.DataType.Type.DATE and not is_date_unit(unit):
147        return arg.replace(exp.cast(arg.copy(), to=exp.DataType.Type.DATETIME))
148
149    return arg
150
151
152def _coerce_datediff_args(node: exp.DateDiff) -> None:
153    for e in (node.this, node.expression):
154        if e.type.this not in exp.DataType.TEMPORAL_TYPES:
155            e.replace(exp.cast(e.copy(), to=exp.DataType.Type.DATETIME))
156
157
158def _replace_cast(node: exp.Expression, to: exp.DataType.Type) -> None:
159    node.replace(exp.cast(node.copy(), to=to))
160
161
162# this was originally designed for presto, there is a similar transform for tsql
163# this is different in that it only operates on int types, this is because
164# presto has a boolean type whereas tsql doesn't (people use bits)
165# with y as (select true as x) select x = 0 FROM y -- illegal presto query
166def _replace_int_predicate(expression: exp.Expression) -> None:
167    if isinstance(expression, exp.Coalesce):
168        for _, child in expression.iter_expressions():
169            _replace_int_predicate(child)
170    elif expression.type and expression.type.this in exp.DataType.INTEGER_TYPES:
171        expression.replace(expression.neq(0))