64 lines
2 KiB
Python
64 lines
2 KiB
Python
from __future__ import annotations
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import typing as t
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from sqlglot import exp
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from sqlglot.dialects.dialect import Dialect, DialectType
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if t.TYPE_CHECKING:
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from sqlglot._typing import E
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@t.overload
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def normalize_identifiers(expression: E, dialect: DialectType = None) -> E: ...
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@t.overload
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def normalize_identifiers(expression: str, dialect: DialectType = None) -> exp.Identifier: ...
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def normalize_identifiers(expression, dialect=None):
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"""
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Normalize identifiers by converting them to either lower or upper case,
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ensuring the semantics are preserved in each case (e.g. by respecting
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case-sensitivity).
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This transformation reflects how identifiers would be resolved by the engine corresponding
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to each SQL dialect, and plays a very important role in the standardization of the AST.
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It's possible to make this a no-op by adding a special comment next to the
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identifier of interest:
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SELECT a /* sqlglot.meta case_sensitive */ FROM table
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In this example, the identifier `a` will not be normalized.
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Note:
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Some dialects (e.g. DuckDB) treat all identifiers as case-insensitive even
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when they're quoted, so in these cases all identifiers are normalized.
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Example:
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>>> import sqlglot
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>>> expression = sqlglot.parse_one('SELECT Bar.A AS A FROM "Foo".Bar')
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>>> normalize_identifiers(expression).sql()
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'SELECT bar.a AS a FROM "Foo".bar'
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>>> normalize_identifiers("foo", dialect="snowflake").sql(dialect="snowflake")
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'FOO'
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Args:
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expression: The expression to transform.
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dialect: The dialect to use in order to decide how to normalize identifiers.
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Returns:
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The transformed expression.
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"""
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dialect = Dialect.get_or_raise(dialect)
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if isinstance(expression, str):
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expression = exp.parse_identifier(expression, dialect=dialect)
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for node in expression.walk(prune=lambda n: n.meta.get("case_sensitive")):
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if not node.meta.get("case_sensitive"):
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dialect.normalize_identifier(node)
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return expression
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