# sqlglot.optimizer.qualify_tables API documentation

Edit on GitHub

# sqlglot.optimizer.qualify_tables

View Source

      1from __future__ import annotations
      2
      3import itertools
      4import typing as t
      5
      6from sqlglot import alias, exp
      7from sqlglot.dialects.dialect import DialectType
      8from sqlglot.helper import csv_reader, name_sequence
      9from sqlglot.optimizer.scope import Scope, traverse_scope
     10from sqlglot.schema import Schema
     11
     12if t.TYPE_CHECKING:
     13    from sqlglot._typing import E
     14
     15
     16def qualify_tables(
     17    expression: E,
     18    db: t.Optional[str | exp.Identifier] = None,
     19    catalog: t.Optional[str | exp.Identifier] = None,
     20    schema: t.Optional[Schema] = None,
     21    infer_csv_schemas: bool = False,
     22    dialect: DialectType = None,
     23) -> E:
     24    """
     25    Rewrite sqlglot AST to have fully qualified tables. Join constructs such as
     26    (t1 JOIN t2) AS t will be expanded into (SELECT * FROM t1 AS t1, t2 AS t2) AS t.
     27
     28    Examples:
     29        >>> import sqlglot
     30        >>> expression = sqlglot.parse_one("SELECT 1 FROM tbl")
     31        >>> qualify_tables(expression, db="db").sql()
     32        'SELECT 1 FROM db.tbl AS tbl'
     33        >>>
     34        >>> expression = sqlglot.parse_one("SELECT 1 FROM (t1 JOIN t2) AS t")
     35        >>> qualify_tables(expression).sql()
     36        'SELECT 1 FROM (SELECT * FROM t1 AS t1, t2 AS t2) AS t'
     37
     38    Args:
     39        expression: Expression to qualify
     40        db: Database name
     41        catalog: Catalog name
     42        schema: A schema to populate
     43        infer_csv_schemas: Whether to scan READ_CSV calls in order to infer the CSVs' schemas.
     44        dialect: The dialect to parse catalog and schema into.
     45
     46    Returns:
     47        The qualified expression.
     48    """
     49    next_alias_name = name_sequence("_q_")
     50    db = exp.parse_identifier(db, dialect=dialect) if db else None
     51    catalog = exp.parse_identifier(catalog, dialect=dialect) if catalog else None
     52
     53    def _qualify(table: exp.Table) -> None:
     54        if isinstance(table.this, exp.Identifier):
     55            if not table.args.get("db"):
     56                table.set("db", db)
     57            if not table.args.get("catalog") and table.args.get("db"):
     58                table.set("catalog", catalog)
     59
     60    if (db or catalog) and not isinstance(expression, exp.Query):
     61        for node in expression.walk(prune=lambda n: isinstance(n, exp.Query)):
     62            if isinstance(node, exp.Table):
     63                _qualify(node)
     64
     65    for scope in traverse_scope(expression):
     66        for derived_table in itertools.chain(scope.ctes, scope.derived_tables):
     67            if isinstance(derived_table, exp.Subquery):
     68                unnested = derived_table.unnest()
     69                if isinstance(unnested, exp.Table):
     70                    joins = unnested.args.pop("joins", None)
     71                    derived_table.this.replace(exp.select("*").from_(unnested.copy(), copy=False))
     72                    derived_table.this.set("joins", joins)
     73
     74            if not derived_table.args.get("alias"):
     75                alias_ = next_alias_name()
     76                derived_table.set("alias", exp.TableAlias(this=exp.to_identifier(alias_)))
     77                scope.rename_source(None, alias_)
     78
     79            pivots = derived_table.args.get("pivots")
     80            if pivots and not pivots[0].alias:
     81                pivots[0].set("alias", exp.TableAlias(this=exp.to_identifier(next_alias_name())))
     82
     83        table_aliases = {}
     84
     85        for name, source in scope.sources.items():
     86            if isinstance(source, exp.Table):
     87                pivots = source.args.get("pivots")
     88                if not source.alias:
     89                    # Don't add the pivot's alias to the pivoted table, use the table's name instead
     90                    if pivots and pivots[0].alias == name:
     91                        name = source.name
     92
     93                    # Mutates the source by attaching an alias to it
     94                    alias(source, name or source.name or next_alias_name(), copy=False, table=True)
     95
     96                table_aliases[".".join(p.name for p in source.parts)] = exp.to_identifier(
     97                    source.alias
     98                )
     99
    100                _qualify(source)
    101
    102                if pivots and not pivots[0].alias:
    103                    pivots[0].set(
    104                        "alias", exp.TableAlias(this=exp.to_identifier(next_alias_name()))
    105                    )
    106
    107                if infer_csv_schemas and schema and isinstance(source.this, exp.ReadCSV):
    108                    with csv_reader(source.this) as reader:
    109                        header = next(reader)
    110                        columns = next(reader)
    111                        schema.add_table(
    112                            source,
    113                            {k: type(v).__name__ for k, v in zip(header, columns)},
    114                            match_depth=False,
    115                        )
    116            elif isinstance(source, Scope) and source.is_udtf:
    117                udtf = source.expression
    118                table_alias = udtf.args.get("alias") or exp.TableAlias(
    119                    this=exp.to_identifier(next_alias_name())
    120                )
    121                udtf.set("alias", table_alias)
    122
    123                if not table_alias.name:
    124                    table_alias.set("this", exp.to_identifier(next_alias_name()))
    125                if isinstance(udtf, exp.Values) and not table_alias.columns:
    126                    for i, e in enumerate(udtf.expressions[0].expressions):
    127                        table_alias.append("columns", exp.to_identifier(f"_col_{i}"))
    128            else:
    129                for node in scope.walk():
    130                    if (
    131                        isinstance(node, exp.Table)
    132                        and not node.alias
    133                        and isinstance(node.parent, (exp.From, exp.Join))
    134                    ):
    135                        # Mutates the table by attaching an alias to it
    136                        alias(node, node.name, copy=False, table=True)
    137
    138        for column in scope.columns:
    139            if column.db:
    140                table_alias = table_aliases.get(".".join(p.name for p in column.parts[0:-1]))
    141
    142                if table_alias:
    143                    for p in exp.COLUMN_PARTS[1:]:
    144                        column.set(p, None)
    145                    column.set("table", table_alias)
    146
    147    return expression

def qualify_tables( expression: ~E, db: Union[ sqlglot.expressions.Identifier , str, NoneType] = None, catalog: Union[ sqlglot.expressions.Identifier , str, NoneType] = None, schema: Optional[ sqlglot.schema.Schema ] = None, infer_csv_schemas: bool = False, dialect: Union[str, sqlglot.dialects.dialect.Dialect , Type[ sqlglot.dialects.dialect.Dialect ], NoneType] = None) -> ~E: View Source

     17def qualify_tables(
     18    expression: E,
     19    db: t.Optional[str | exp.Identifier] = None,
     20    catalog: t.Optional[str | exp.Identifier] = None,
     21    schema: t.Optional[Schema] = None,
     22    infer_csv_schemas: bool = False,
     23    dialect: DialectType = None,
     24) -> E:
     25    """
     26    Rewrite sqlglot AST to have fully qualified tables. Join constructs such as
     27    (t1 JOIN t2) AS t will be expanded into (SELECT * FROM t1 AS t1, t2 AS t2) AS t.
     28
     29    Examples:
     30        >>> import sqlglot
     31        >>> expression = sqlglot.parse_one("SELECT 1 FROM tbl")
     32        >>> qualify_tables(expression, db="db").sql()
     33        'SELECT 1 FROM db.tbl AS tbl'
     34        >>>
     35        >>> expression = sqlglot.parse_one("SELECT 1 FROM (t1 JOIN t2) AS t")
     36        >>> qualify_tables(expression).sql()
     37        'SELECT 1 FROM (SELECT * FROM t1 AS t1, t2 AS t2) AS t'
     38
     39    Args:
     40        expression: Expression to qualify
     41        db: Database name
     42        catalog: Catalog name
     43        schema: A schema to populate
     44        infer_csv_schemas: Whether to scan READ_CSV calls in order to infer the CSVs' schemas.
     45        dialect: The dialect to parse catalog and schema into.
     46
     47    Returns:
     48        The qualified expression.
     49    """
     50    next_alias_name = name_sequence("_q_")
     51    db = exp.parse_identifier(db, dialect=dialect) if db else None
     52    catalog = exp.parse_identifier(catalog, dialect=dialect) if catalog else None
     53
     54    def _qualify(table: exp.Table) -> None:
     55        if isinstance(table.this, exp.Identifier):
     56            if not table.args.get("db"):
     57                table.set("db", db)
     58            if not table.args.get("catalog") and table.args.get("db"):
     59                table.set("catalog", catalog)
     60
     61    if (db or catalog) and not isinstance(expression, exp.Query):
     62        for node in expression.walk(prune=lambda n: isinstance(n, exp.Query)):
     63            if isinstance(node, exp.Table):
     64                _qualify(node)
     65
     66    for scope in traverse_scope(expression):
     67        for derived_table in itertools.chain(scope.ctes, scope.derived_tables):
     68            if isinstance(derived_table, exp.Subquery):
     69                unnested = derived_table.unnest()
     70                if isinstance(unnested, exp.Table):
     71                    joins = unnested.args.pop("joins", None)
     72                    derived_table.this.replace(exp.select("*").from_(unnested.copy(), copy=False))
     73                    derived_table.this.set("joins", joins)
     74
     75            if not derived_table.args.get("alias"):
     76                alias_ = next_alias_name()
     77                derived_table.set("alias", exp.TableAlias(this=exp.to_identifier(alias_)))
     78                scope.rename_source(None, alias_)
     79
     80            pivots = derived_table.args.get("pivots")
     81            if pivots and not pivots[0].alias:
     82                pivots[0].set("alias", exp.TableAlias(this=exp.to_identifier(next_alias_name())))
     83
     84        table_aliases = {}
     85
     86        for name, source in scope.sources.items():
     87            if isinstance(source, exp.Table):
     88                pivots = source.args.get("pivots")
     89                if not source.alias:
     90                    # Don't add the pivot's alias to the pivoted table, use the table's name instead
     91                    if pivots and pivots[0].alias == name:
     92                        name = source.name
     93
     94                    # Mutates the source by attaching an alias to it
     95                    alias(source, name or source.name or next_alias_name(), copy=False, table=True)
     96
     97                table_aliases[".".join(p.name for p in source.parts)] = exp.to_identifier(
     98                    source.alias
     99                )
    100
    101                _qualify(source)
    102
    103                if pivots and not pivots[0].alias:
    104                    pivots[0].set(
    105                        "alias", exp.TableAlias(this=exp.to_identifier(next_alias_name()))
    106                    )
    107
    108                if infer_csv_schemas and schema and isinstance(source.this, exp.ReadCSV):
    109                    with csv_reader(source.this) as reader:
    110                        header = next(reader)
    111                        columns = next(reader)
    112                        schema.add_table(
    113                            source,
    114                            {k: type(v).__name__ for k, v in zip(header, columns)},
    115                            match_depth=False,
    116                        )
    117            elif isinstance(source, Scope) and source.is_udtf:
    118                udtf = source.expression
    119                table_alias = udtf.args.get("alias") or exp.TableAlias(
    120                    this=exp.to_identifier(next_alias_name())
    121                )
    122                udtf.set("alias", table_alias)
    123
    124                if not table_alias.name:
    125                    table_alias.set("this", exp.to_identifier(next_alias_name()))
    126                if isinstance(udtf, exp.Values) and not table_alias.columns:
    127                    for i, e in enumerate(udtf.expressions[0].expressions):
    128                        table_alias.append("columns", exp.to_identifier(f"_col_{i}"))
    129            else:
    130                for node in scope.walk():
    131                    if (
    132                        isinstance(node, exp.Table)
    133                        and not node.alias
    134                        and isinstance(node.parent, (exp.From, exp.Join))
    135                    ):
    136                        # Mutates the table by attaching an alias to it
    137                        alias(node, node.name, copy=False, table=True)
    138
    139        for column in scope.columns:
    140            if column.db:
    141                table_alias = table_aliases.get(".".join(p.name for p in column.parts[0:-1]))
    142
    143                if table_alias:
    144                    for p in exp.COLUMN_PARTS[1:]:
    145                        column.set(p, None)
    146                    column.set("table", table_alias)
    147
    148    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
- infer_csv_schemas: Whether to scan READ_CSV calls in order to infer the CSVs' schemas.
- dialect: The dialect to parse catalog and schema into.

###### Returns:

> The qualified expression.