sqlglot.optimizer.qualify_tables

  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
 11from sqlglot.dialects.dialect import Dialect
 12
 13if t.TYPE_CHECKING:
 14    from sqlglot._typing import E
 15
 16
 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    dialect = Dialect.get_or_raise(dialect)
 54
 55    def _qualify(table: exp.Table) -> None:
 56        if isinstance(table.this, exp.Identifier):
 57            if db and not table.args.get("db"):
 58                table.set("db", db.copy())
 59            if catalog and not table.args.get("catalog") and table.args.get("db"):
 60                table.set("catalog", catalog.copy())
 61
 62    if (db or catalog) and not isinstance(expression, exp.Query):
 63        for node in expression.walk(prune=lambda n: isinstance(n, exp.Query)):
 64            if isinstance(node, exp.Table):
 65                _qualify(node)
 66
 67    for scope in traverse_scope(expression):
 68        for derived_table in itertools.chain(scope.ctes, scope.derived_tables):
 69            if isinstance(derived_table, exp.Subquery):
 70                unnested = derived_table.unnest()
 71                if isinstance(unnested, exp.Table):
 72                    joins = unnested.args.pop("joins", None)
 73                    derived_table.this.replace(exp.select("*").from_(unnested.copy(), copy=False))
 74                    derived_table.this.set("joins", joins)
 75
 76            if not derived_table.args.get("alias"):
 77                alias_ = next_alias_name()
 78                derived_table.set("alias", exp.TableAlias(this=exp.to_identifier(alias_)))
 79                scope.rename_source(None, alias_)
 80
 81            pivots = derived_table.args.get("pivots")
 82            if pivots and not pivots[0].alias:
 83                pivots[0].set("alias", exp.TableAlias(this=exp.to_identifier(next_alias_name())))
 84
 85        table_aliases = {}
 86
 87        for name, source in scope.sources.items():
 88            if isinstance(source, exp.Table):
 89                pivots = source.args.get("pivots")
 90                if not source.alias:
 91                    # Don't add the pivot's alias to the pivoted table, use the table's name instead
 92                    if pivots and pivots[0].alias == name:
 93                        name = source.name
 94
 95                    # Mutates the source by attaching an alias to it
 96                    alias(source, name or source.name or next_alias_name(), copy=False, table=True)
 97
 98                table_aliases[".".join(p.name for p in source.parts)] = exp.to_identifier(
 99                    source.alias
100                )
101
102                if pivots:
103                    pivot = pivots[0]
104                    if not pivot.alias:
105                        pivot_alias = source.alias if pivot.unpivot else next_alias_name()
106                        pivot.set("alias", exp.TableAlias(this=exp.to_identifier(pivot_alias)))
107
108                    # This case corresponds to a pivoted CTE, we don't want to qualify that
109                    if isinstance(scope.sources.get(source.alias_or_name), Scope):
110                        continue
111
112                _qualify(source)
113
114                if infer_csv_schemas and schema and isinstance(source.this, exp.ReadCSV):
115                    with csv_reader(source.this) as reader:
116                        header = next(reader)
117                        columns = next(reader)
118                        schema.add_table(
119                            source,
120                            {k: type(v).__name__ for k, v in zip(header, columns)},
121                            match_depth=False,
122                        )
123            elif isinstance(source, Scope) and source.is_udtf:
124                udtf = source.expression
125                table_alias = udtf.args.get("alias") or exp.TableAlias(
126                    this=exp.to_identifier(next_alias_name())
127                )
128                udtf.set("alias", table_alias)
129
130                if not table_alias.name:
131                    table_alias.set("this", exp.to_identifier(next_alias_name()))
132                if isinstance(udtf, exp.Values) and not table_alias.columns:
133                    column_aliases = dialect.generate_values_aliases(udtf)
134                    table_alias.set("columns", column_aliases)
135            else:
136                for node in scope.walk():
137                    if (
138                        isinstance(node, exp.Table)
139                        and not node.alias
140                        and isinstance(node.parent, (exp.From, exp.Join))
141                    ):
142                        # Mutates the table by attaching an alias to it
143                        alias(node, node.name, copy=False, table=True)
144
145        for column in scope.columns:
146            if column.db:
147                table_alias = table_aliases.get(".".join(p.name for p in column.parts[0:-1]))
148
149                if table_alias:
150                    for p in exp.COLUMN_PARTS[1:]:
151                        column.set(p, None)
152
153                    column.set("table", table_alias.copy())
154
155    return expression