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,
     84                            {k: type(v).__name__ for k, v in zip(header, columns)},
     85                            match_depth=False,
     86                        )
     87            elif isinstance(source, Scope) and source.is_udtf:
     88                udtf = source.expression
     89                table_alias = udtf.args.get("alias") or exp.TableAlias(
     90                    this=exp.to_identifier(next_alias_name())
     91                )
     92                udtf.set("alias", table_alias)
     93
     94                if not table_alias.name:
     95                    table_alias.set("this", exp.to_identifier(next_alias_name()))
     96                if isinstance(udtf, exp.Values) and not table_alias.columns:
     97                    for i, e in enumerate(udtf.expressions[0].expressions):
     98                        table_alias.append("columns", exp.to_identifier(f"_col_{i}"))
     99
    100    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,
     85                            {k: type(v).__name__ for k, v in zip(header, columns)},
     86                            match_depth=False,
     87                        )
     88            elif isinstance(source, Scope) and source.is_udtf:
     89                udtf = source.expression
     90                table_alias = udtf.args.get("alias") or exp.TableAlias(
     91                    this=exp.to_identifier(next_alias_name())
     92                )
     93                udtf.set("alias", table_alias)
     94
     95                if not table_alias.name:
     96                    table_alias.set("this", exp.to_identifier(next_alias_name()))
     97                if isinstance(udtf, exp.Values) and not table_alias.columns:
     98                    for i, e in enumerate(udtf.expressions[0].expressions):
     99                        table_alias.append("columns", exp.to_identifier(f"_col_{i}"))
    100
    101    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.