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