sqlglot.optimizer.qualify_tables API documentation

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# sqlglot.optimizer.qualify_tables

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     1import itertools
     2import typing as t
     3
     4from sqlglot import alias, exp
     5from sqlglot._typing import E
     6from sqlglot.helper import csv_reader, name_sequence
     7from sqlglot.optimizer.scope import Scope, traverse_scope
     8from sqlglot.schema import Schema
     9
    10
    11def qualify_tables(
    12    expression: E,
    13    db: t.Optional[str] = None,
    14    catalog: t.Optional[str] = None,
    15    schema: t.Optional[Schema] = None,
    16) -> E:
    17    """
    18    Rewrite sqlglot AST to have fully qualified tables. Join constructs such as
    19    (t1 JOIN t2) AS t will be expanded into (SELECT * FROM t1 AS t1, t2 AS t2) AS t.
    20
    21    Examples:
    22        >>> import sqlglot
    23        >>> expression = sqlglot.parse_one("SELECT 1 FROM tbl")
    24        >>> qualify_tables(expression, db="db").sql()
    25        'SELECT 1 FROM db.tbl AS tbl'
    26        >>>
    27        >>> expression = sqlglot.parse_one("SELECT 1 FROM (t1 JOIN t2) AS t")
    28        >>> qualify_tables(expression).sql()
    29        'SELECT 1 FROM (SELECT * FROM t1 AS t1, t2 AS t2) AS t'
    30
    31    Args:
    32        expression: Expression to qualify
    33        db: Database name
    34        catalog: Catalog name
    35        schema: A schema to populate
    36
    37    Returns:
    38        The qualified expression.
    39    """
    40    next_alias_name = name_sequence("_q_")
    41
    42    for scope in traverse_scope(expression):
    43        for derived_table in itertools.chain(scope.ctes, scope.derived_tables):
    44            if isinstance(derived_table, exp.Subquery):
    45                unnested = derived_table.unnest()
    46                if isinstance(unnested, exp.Table):
    47                    joins = unnested.args.pop("joins", None)
    48                    derived_table.this.replace(exp.select("*").from_(unnested.copy(), copy=False))
    49                    derived_table.this.set("joins", joins)
    50
    51            if not derived_table.args.get("alias"):
    52                alias_ = next_alias_name()
    53                derived_table.set("alias", exp.TableAlias(this=exp.to_identifier(alias_)))
    54                scope.rename_source(None, alias_)
    55
    56            pivots = derived_table.args.get("pivots")
    57            if pivots and not pivots[0].alias:
    58                pivots[0].set("alias", exp.TableAlias(this=exp.to_identifier(next_alias_name())))
    59
    60        for name, source in scope.sources.items():
    61            if isinstance(source, exp.Table):
    62                if isinstance(source.this, exp.Identifier):
    63                    if not source.args.get("db"):
    64                        source.set("db", exp.to_identifier(db))
    65                    if not source.args.get("catalog"):
    66                        source.set("catalog", exp.to_identifier(catalog))
    67
    68                if not source.alias:
    69                    # Mutates the source by attaching an alias to it
    70                    alias(source, name or source.name or next_alias_name(), copy=False, table=True)
    71
    72                pivots = source.args.get("pivots")
    73                if pivots and not pivots[0].alias:
    74                    pivots[0].set(
    75                        "alias", exp.TableAlias(this=exp.to_identifier(next_alias_name()))
    76                    )
    77
    78                if schema and isinstance(source.this, exp.ReadCSV):
    79                    with csv_reader(source.this) as reader:
    80                        header = next(reader)
    81                        columns = next(reader)
    82                        schema.add_table(
    83                            source, {k: type(v).__name__ for k, v in zip(header, columns)}
    84                        )
    85            elif isinstance(source, Scope) and source.is_udtf:
    86                udtf = source.expression
    87                table_alias = udtf.args.get("alias") or exp.TableAlias(
    88                    this=exp.to_identifier(next_alias_name())
    89                )
    90                udtf.set("alias", table_alias)
    91
    92                if not table_alias.name:
    93                    table_alias.set("this", exp.to_identifier(next_alias_name()))
    94                if isinstance(udtf, exp.Values) and not table_alias.columns:
    95                    for i, e in enumerate(udtf.expressions[0].expressions):
    96                        table_alias.append("columns", exp.to_identifier(f"_col_{i}"))
    97
    98    return expression

def qualify_tables( expression: ~E, db: Optional[str] = None, catalog: Optional[str] = None, schema: Optional[sqlglot.schema.Schema] = None) -> ~E: View Source

    12def qualify_tables(
    13    expression: E,
    14    db: t.Optional[str] = None,
    15    catalog: t.Optional[str] = None,
    16    schema: t.Optional[Schema] = None,
    17) -> E:
    18    """
    19    Rewrite sqlglot AST to have fully qualified tables. Join constructs such as
    20    (t1 JOIN t2) AS t will be expanded into (SELECT * FROM t1 AS t1, t2 AS t2) AS t.
    21
    22    Examples:
    23        >>> import sqlglot
    24        >>> expression = sqlglot.parse_one("SELECT 1 FROM tbl")
    25        >>> qualify_tables(expression, db="db").sql()
    26        'SELECT 1 FROM db.tbl AS tbl'
    27        >>>
    28        >>> expression = sqlglot.parse_one("SELECT 1 FROM (t1 JOIN t2) AS t")
    29        >>> qualify_tables(expression).sql()
    30        'SELECT 1 FROM (SELECT * FROM t1 AS t1, t2 AS t2) AS t'
    31
    32    Args:
    33        expression: Expression to qualify
    34        db: Database name
    35        catalog: Catalog name
    36        schema: A schema to populate
    37
    38    Returns:
    39        The qualified expression.
    40    """
    41    next_alias_name = name_sequence("_q_")
    42
    43    for scope in traverse_scope(expression):
    44        for derived_table in itertools.chain(scope.ctes, scope.derived_tables):
    45            if isinstance(derived_table, exp.Subquery):
    46                unnested = derived_table.unnest()
    47                if isinstance(unnested, exp.Table):
    48                    joins = unnested.args.pop("joins", None)
    49                    derived_table.this.replace(exp.select("*").from_(unnested.copy(), copy=False))
    50                    derived_table.this.set("joins", joins)
    51
    52            if not derived_table.args.get("alias"):
    53                alias_ = next_alias_name()
    54                derived_table.set("alias", exp.TableAlias(this=exp.to_identifier(alias_)))
    55                scope.rename_source(None, alias_)
    56
    57            pivots = derived_table.args.get("pivots")
    58            if pivots and not pivots[0].alias:
    59                pivots[0].set("alias", exp.TableAlias(this=exp.to_identifier(next_alias_name())))
    60
    61        for name, source in scope.sources.items():
    62            if isinstance(source, exp.Table):
    63                if isinstance(source.this, exp.Identifier):
    64                    if not source.args.get("db"):
    65                        source.set("db", exp.to_identifier(db))
    66                    if not source.args.get("catalog"):
    67                        source.set("catalog", exp.to_identifier(catalog))
    68
    69                if not source.alias:
    70                    # Mutates the source by attaching an alias to it
    71                    alias(source, name or source.name or next_alias_name(), copy=False, table=True)
    72
    73                pivots = source.args.get("pivots")
    74                if pivots and not pivots[0].alias:
    75                    pivots[0].set(
    76                        "alias", exp.TableAlias(this=exp.to_identifier(next_alias_name()))
    77                    )
    78
    79                if schema and isinstance(source.this, exp.ReadCSV):
    80                    with csv_reader(source.this) as reader:
    81                        header = next(reader)
    82                        columns = next(reader)
    83                        schema.add_table(
    84                            source, {k: type(v).__name__ for k, v in zip(header, columns)}
    85                        )
    86            elif isinstance(source, Scope) and source.is_udtf:
    87                udtf = source.expression
    88                table_alias = udtf.args.get("alias") or exp.TableAlias(
    89                    this=exp.to_identifier(next_alias_name())
    90                )
    91                udtf.set("alias", table_alias)
    92
    93                if not table_alias.name:
    94                    table_alias.set("this", exp.to_identifier(next_alias_name()))
    95                if isinstance(udtf, exp.Values) and not table_alias.columns:
    96                    for i, e in enumerate(udtf.expressions[0].expressions):
    97                        table_alias.append("columns", exp.to_identifier(f"_col_{i}"))
    98
    99    return expression

Rewrite sqlglot AST to have fully qualified tables. Join constructs such as (t1 JOIN t2) AS t will be expanded into (SELECT * FROM t1 AS t1, t2 AS t2) AS t.

###### Examples:

>     >>> import sqlglot
>     >>> expression = sqlglot.parse_one("SELECT 1 FROM tbl")
>     >>> qualify_tables(expression, db="db").sql()
>     'SELECT 1 FROM db.tbl AS tbl'
>     >>>
>     >>> expression = sqlglot.parse_one("SELECT 1 FROM (t1 JOIN t2) AS t")
>     >>> qualify_tables(expression).sql()
>     'SELECT 1 FROM (SELECT * FROM t1 AS t1, t2 AS t2) AS t'

###### Arguments:

- expression: Expression to qualify
- db: Database name
- catalog: Catalog name
- schema: A schema to populate

###### Returns:

> The qualified expression.