sqlglot.optimizer.expand_laterals

 1from __future__ import annotations
 2
 3import typing as t
 4
 5from sqlglot import exp
 6
 7
 8def expand_laterals(expression: exp.Expression) -> exp.Expression:
 9    """
10    Expand lateral column alias references.
11
12    This assumes `qualify_columns` as already run.
13
14    Example:
15        >>> import sqlglot
16        >>> sql = "SELECT x.a + 1 AS b, b + 1 AS c FROM x"
17        >>> expression = sqlglot.parse_one(sql)
18        >>> expand_laterals(expression).sql()
19        'SELECT x.a + 1 AS b, x.a + 1 + 1 AS c FROM x'
20
21    Args:
22        expression: expression to optimize
23    Returns:
24        optimized expression
25    """
26    for select in expression.find_all(exp.Select):
27        alias_to_expression: t.Dict[str, exp.Expression] = {}
28        for projection in select.expressions:
29            for column in projection.find_all(exp.Column):
30                if not column.table and column.name in alias_to_expression:
31                    column.replace(alias_to_expression[column.name].copy())
32                if isinstance(projection, exp.Alias):
33                    alias_to_expression[projection.alias] = projection.this
34    return expression