sqlglot.optimizer.qualify_columns API documentation

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# sqlglot.optimizer.qualify_columns

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      1import itertools
      2import typing as t
      3
      4from sqlglot import alias, exp
      5from sqlglot.errors import OptimizeError
      6from sqlglot.optimizer.scope import Scope, traverse_scope
      7from sqlglot.schema import ensure_schema
      8
      9
     10def qualify_columns(expression, schema):
     11    """
     12    Rewrite sqlglot AST to have fully qualified columns.
     13
     14    Example:
     15        >>> import sqlglot
     16        >>> schema = {"tbl": {"col": "INT"}}
     17        >>> expression = sqlglot.parse_one("SELECT col FROM tbl")
     18        >>> qualify_columns(expression, schema).sql()
     19        'SELECT tbl.col AS col FROM tbl'
     20
     21    Args:
     22        expression (sqlglot.Expression): expression to qualify
     23        schema (dict|sqlglot.optimizer.Schema): Database schema
     24    Returns:
     25        sqlglot.Expression: qualified expression
     26    """
     27    schema = ensure_schema(schema)
     28
     29    for scope in traverse_scope(expression):
     30        resolver = Resolver(scope, schema)
     31        _pop_table_column_aliases(scope.ctes)
     32        _pop_table_column_aliases(scope.derived_tables)
     33        using_column_tables = _expand_using(scope, resolver)
     34        _qualify_columns(scope, resolver)
     35        if not isinstance(scope.expression, exp.UDTF):
     36            _expand_stars(scope, resolver, using_column_tables)
     37            _qualify_outputs(scope)
     38        _expand_alias_refs(scope, resolver)
     39        _expand_group_by(scope, resolver)
     40        _expand_order_by(scope)
     41
     42    return expression
     43
     44
     45def validate_qualify_columns(expression):
     46    """Raise an `OptimizeError` if any columns aren't qualified"""
     47    unqualified_columns = []
     48    for scope in traverse_scope(expression):
     49        if isinstance(scope.expression, exp.Select):
     50            unqualified_columns.extend(scope.unqualified_columns)
     51            if scope.external_columns and not scope.is_correlated_subquery:
     52                column = scope.external_columns[0]
     53                raise OptimizeError(f"Unknown table: '{column.table}' for column '{column}'")
     54
     55    if unqualified_columns:
     56        raise OptimizeError(f"Ambiguous columns: {unqualified_columns}")
     57    return expression
     58
     59
     60def _pop_table_column_aliases(derived_tables):
     61    """
     62    Remove table column aliases.
     63
     64    (e.g. SELECT ... FROM (SELECT ...) AS foo(col1, col2)
     65    """
     66    for derived_table in derived_tables:
     67        table_alias = derived_table.args.get("alias")
     68        if table_alias:
     69            table_alias.args.pop("columns", None)
     70
     71
     72def _expand_using(scope, resolver):
     73    joins = list(scope.find_all(exp.Join))
     74    names = {join.this.alias for join in joins}
     75    ordered = [key for key in scope.selected_sources if key not in names]
     76
     77    # Mapping of automatically joined column names to an ordered set of source names (dict).
     78    column_tables = {}
     79
     80    for join in joins:
     81        using = join.args.get("using")
     82
     83        if not using:
     84            continue
     85
     86        join_table = join.this.alias_or_name
     87
     88        columns = {}
     89
     90        for k in scope.selected_sources:
     91            if k in ordered:
     92                for column in resolver.get_source_columns(k):
     93                    if column not in columns:
     94                        columns[column] = k
     95
     96        ordered.append(join_table)
     97        join_columns = resolver.get_source_columns(join_table)
     98        conditions = []
     99
    100        for identifier in using:
    101            identifier = identifier.name
    102            table = columns.get(identifier)
    103
    104            if not table or identifier not in join_columns:
    105                raise OptimizeError(f"Cannot automatically join: {identifier}")
    106
    107            conditions.append(
    108                exp.condition(
    109                    exp.EQ(
    110                        this=exp.column(identifier, table=table),
    111                        expression=exp.column(identifier, table=join_table),
    112                    )
    113                )
    114            )
    115
    116            # Set all values in the dict to None, because we only care about the key ordering
    117            tables = column_tables.setdefault(identifier, {})
    118            if table not in tables:
    119                tables[table] = None
    120            if join_table not in tables:
    121                tables[join_table] = None
    122
    123        join.args.pop("using")
    124        join.set("on", exp.and_(*conditions))
    125
    126    if column_tables:
    127        for column in scope.columns:
    128            if not column.table and column.name in column_tables:
    129                tables = column_tables[column.name]
    130                coalesce = [exp.column(column.name, table=table) for table in tables]
    131                replacement = exp.Coalesce(this=coalesce[0], expressions=coalesce[1:])
    132
    133                # Ensure selects keep their output name
    134                if isinstance(column.parent, exp.Select):
    135                    replacement = exp.alias_(replacement, alias=column.name)
    136
    137                scope.replace(column, replacement)
    138
    139    return column_tables
    140
    141
    142def _expand_alias_refs(scope, resolver):
    143    selects = {}
    144
    145    # Replace references to select aliases
    146    def transform(node, *_):
    147        if isinstance(node, exp.Column) and not node.table:
    148            table = resolver.get_table(node.name)
    149
    150            # Source columns get priority over select aliases
    151            if table:
    152                node.set("table", table)
    153                return node
    154
    155            if not selects:
    156                for s in scope.selects:
    157                    selects[s.alias_or_name] = s
    158            select = selects.get(node.name)
    159
    160            if select:
    161                scope.clear_cache()
    162                if isinstance(select, exp.Alias):
    163                    select = select.this
    164                return select.copy()
    165
    166        return node
    167
    168    where = scope.expression.args.get("where")
    169    if where:
    170        where.transform(transform, copy=False)
    171
    172    group = scope.expression.args.get("group")
    173    if group:
    174        group.transform(transform, copy=False)
    175
    176
    177def _expand_group_by(scope, resolver):
    178    group = scope.expression.args.get("group")
    179    if not group:
    180        return
    181
    182    group.set("expressions", _expand_positional_references(scope, group.expressions))
    183    scope.expression.set("group", group)
    184
    185
    186def _expand_order_by(scope):
    187    order = scope.expression.args.get("order")
    188    if not order:
    189        return
    190
    191    ordereds = order.expressions
    192    for ordered, new_expression in zip(
    193        ordereds,
    194        _expand_positional_references(scope, (o.this for o in ordereds)),
    195    ):
    196        ordered.set("this", new_expression)
    197
    198
    199def _expand_positional_references(scope, expressions):
    200    new_nodes = []
    201    for node in expressions:
    202        if node.is_int:
    203            try:
    204                select = scope.selects[int(node.name) - 1]
    205            except IndexError:
    206                raise OptimizeError(f"Unknown output column: {node.name}")
    207            if isinstance(select, exp.Alias):
    208                select = select.this
    209            new_nodes.append(select.copy())
    210            scope.clear_cache()
    211        else:
    212            new_nodes.append(node)
    213
    214    return new_nodes
    215
    216
    217def _qualify_columns(scope, resolver):
    218    """Disambiguate columns, ensuring each column specifies a source"""
    219    for column in scope.columns:
    220        column_table = column.table
    221        column_name = column.name
    222
    223        if column_table and column_table in scope.sources:
    224            source_columns = resolver.get_source_columns(column_table)
    225            if source_columns and column_name not in source_columns and "*" not in source_columns:
    226                raise OptimizeError(f"Unknown column: {column_name}")
    227
    228        if not column_table:
    229            column_table = resolver.get_table(column_name)
    230
    231            # column_table can be a '' because bigquery unnest has no table alias
    232            if column_table:
    233                column.set("table", column_table)
    234        elif column_table not in scope.sources:
    235            # structs are used like tables (e.g. "struct"."field"), so they need to be qualified
    236            # separately and represented as dot(dot(...(<table>.<column>, field1), field2, ...))
    237
    238            root, *parts = column.parts
    239
    240            if root.name in scope.sources:
    241                # struct is already qualified, but we still need to change the AST representation
    242                column_table = root
    243                root, *parts = parts
    244            else:
    245                column_table = resolver.get_table(root.name)
    246
    247            if column_table:
    248                column.replace(exp.Dot.build([exp.column(root, table=column_table), *parts]))
    249
    250    columns_missing_from_scope = []
    251
    252    # Determine whether each reference in the order by clause is to a column or an alias.
    253    order = scope.expression.args.get("order")
    254
    255    if order:
    256        for ordered in order.expressions:
    257            for column in ordered.find_all(exp.Column):
    258                if (
    259                    not column.table
    260                    and column.parent is not ordered
    261                    and column.name in resolver.all_columns
    262                ):
    263                    columns_missing_from_scope.append(column)
    264
    265    # Determine whether each reference in the having clause is to a column or an alias.
    266    having = scope.expression.args.get("having")
    267
    268    if having:
    269        for column in having.find_all(exp.Column):
    270            if (
    271                not column.table
    272                and column.find_ancestor(exp.AggFunc)
    273                and column.name in resolver.all_columns
    274            ):
    275                columns_missing_from_scope.append(column)
    276
    277    for column in columns_missing_from_scope:
    278        column_table = resolver.get_table(column.name)
    279
    280        if column_table:
    281            column.set("table", column_table)
    282
    283
    284def _expand_stars(scope, resolver, using_column_tables):
    285    """Expand stars to lists of column selections"""
    286
    287    new_selections = []
    288    except_columns = {}
    289    replace_columns = {}
    290    coalesced_columns = set()
    291
    292    for expression in scope.selects:
    293        if isinstance(expression, exp.Star):
    294            tables = list(scope.selected_sources)
    295            _add_except_columns(expression, tables, except_columns)
    296            _add_replace_columns(expression, tables, replace_columns)
    297        elif expression.is_star:
    298            tables = [expression.table]
    299            _add_except_columns(expression.this, tables, except_columns)
    300            _add_replace_columns(expression.this, tables, replace_columns)
    301        else:
    302            new_selections.append(expression)
    303            continue
    304
    305        for table in tables:
    306            if table not in scope.sources:
    307                raise OptimizeError(f"Unknown table: {table}")
    308            columns = resolver.get_source_columns(table, only_visible=True)
    309
    310            if columns and "*" not in columns:
    311                table_id = id(table)
    312                for name in columns:
    313                    if name in using_column_tables and table in using_column_tables[name]:
    314                        if name in coalesced_columns:
    315                            continue
    316
    317                        coalesced_columns.add(name)
    318                        tables = using_column_tables[name]
    319                        coalesce = [exp.column(name, table=table) for table in tables]
    320
    321                        new_selections.append(
    322                            exp.alias_(
    323                                exp.Coalesce(this=coalesce[0], expressions=coalesce[1:]), alias=name
    324                            )
    325                        )
    326                    elif name not in except_columns.get(table_id, set()):
    327                        alias_ = replace_columns.get(table_id, {}).get(name, name)
    328                        column = exp.column(name, table)
    329                        new_selections.append(alias(column, alias_) if alias_ != name else column)
    330            else:
    331                return
    332    scope.expression.set("expressions", new_selections)
    333
    334
    335def _add_except_columns(expression, tables, except_columns):
    336    except_ = expression.args.get("except")
    337
    338    if not except_:
    339        return
    340
    341    columns = {e.name for e in except_}
    342
    343    for table in tables:
    344        except_columns[id(table)] = columns
    345
    346
    347def _add_replace_columns(expression, tables, replace_columns):
    348    replace = expression.args.get("replace")
    349
    350    if not replace:
    351        return
    352
    353    columns = {e.this.name: e.alias for e in replace}
    354
    355    for table in tables:
    356        replace_columns[id(table)] = columns
    357
    358
    359def _qualify_outputs(scope):
    360    """Ensure all output columns are aliased"""
    361    new_selections = []
    362
    363    for i, (selection, aliased_column) in enumerate(
    364        itertools.zip_longest(scope.selects, scope.outer_column_list)
    365    ):
    366        if isinstance(selection, exp.Subquery):
    367            if not selection.output_name:
    368                selection.set("alias", exp.TableAlias(this=exp.to_identifier(f"_col_{i}")))
    369        elif not isinstance(selection, exp.Alias) and not selection.is_star:
    370            alias_ = alias(exp.column(""), alias=selection.output_name or f"_col_{i}")
    371            alias_.set("this", selection)
    372            selection = alias_
    373
    374        if aliased_column:
    375            selection.set("alias", exp.to_identifier(aliased_column))
    376
    377        new_selections.append(selection)
    378
    379    scope.expression.set("expressions", new_selections)
    380
    381
    382class Resolver:
    383    """
    384    Helper for resolving columns.
    385
    386    This is a class so we can lazily load some things and easily share them across functions.
    387    """
    388
    389    def __init__(self, scope, schema):
    390        self.scope = scope
    391        self.schema = schema
    392        self._source_columns = None
    393        self._unambiguous_columns = None
    394        self._all_columns = None
    395
    396    def get_table(self, column_name: str) -> t.Optional[exp.Identifier]:
    397        """
    398        Get the table for a column name.
    399
    400        Args:
    401            column_name: The column name to find the table for.
    402        Returns:
    403            The table name if it can be found/inferred.
    404        """
    405        if self._unambiguous_columns is None:
    406            self._unambiguous_columns = self._get_unambiguous_columns(
    407                self._get_all_source_columns()
    408            )
    409
    410        table_name = self._unambiguous_columns.get(column_name)
    411
    412        if not table_name:
    413            sources_without_schema = tuple(
    414                source
    415                for source, columns in self._get_all_source_columns().items()
    416                if not columns or "*" in columns
    417            )
    418            if len(sources_without_schema) == 1:
    419                table_name = sources_without_schema[0]
    420
    421        if table_name not in self.scope.selected_sources:
    422            return exp.to_identifier(table_name)
    423
    424        node, _ = self.scope.selected_sources.get(table_name)
    425
    426        if isinstance(node, exp.Subqueryable):
    427            while node and node.alias != table_name:
    428                node = node.parent
    429
    430        node_alias = node.args.get("alias")
    431        if node_alias:
    432            return node_alias.this
    433
    434        return exp.to_identifier(
    435            table_name, quoted=node.this.quoted if isinstance(node, exp.Table) else None
    436        )
    437
    438    @property
    439    def all_columns(self):
    440        """All available columns of all sources in this scope"""
    441        if self._all_columns is None:
    442            self._all_columns = {
    443                column for columns in self._get_all_source_columns().values() for column in columns
    444            }
    445        return self._all_columns
    446
    447    def get_source_columns(self, name, only_visible=False):
    448        """Resolve the source columns for a given source `name`"""
    449        if name not in self.scope.sources:
    450            raise OptimizeError(f"Unknown table: {name}")
    451
    452        source = self.scope.sources[name]
    453
    454        # If referencing a table, return the columns from the schema
    455        if isinstance(source, exp.Table):
    456            return self.schema.column_names(source, only_visible)
    457
    458        if isinstance(source, Scope) and isinstance(source.expression, exp.Values):
    459            return source.expression.alias_column_names
    460
    461        # Otherwise, if referencing another scope, return that scope's named selects
    462        return source.expression.named_selects
    463
    464    def _get_all_source_columns(self):
    465        if self._source_columns is None:
    466            self._source_columns = {
    467                k: self.get_source_columns(k)
    468                for k in itertools.chain(self.scope.selected_sources, self.scope.lateral_sources)
    469            }
    470        return self._source_columns
    471
    472    def _get_unambiguous_columns(self, source_columns):
    473        """
    474        Find all the unambiguous columns in sources.
    475
    476        Args:
    477            source_columns (dict): Mapping of names to source columns
    478        Returns:
    479            dict: Mapping of column name to source name
    480        """
    481        if not source_columns:
    482            return {}
    483
    484        source_columns = list(source_columns.items())
    485
    486        first_table, first_columns = source_columns[0]
    487        unambiguous_columns = {col: first_table for col in self._find_unique_columns(first_columns)}
    488        all_columns = set(unambiguous_columns)
    489
    490        for table, columns in source_columns[1:]:
    491            unique = self._find_unique_columns(columns)
    492            ambiguous = set(all_columns).intersection(unique)
    493            all_columns.update(columns)
    494            for column in ambiguous:
    495                unambiguous_columns.pop(column, None)
    496            for column in unique.difference(ambiguous):
    497                unambiguous_columns[column] = table
    498
    499        return unambiguous_columns
    500
    501    @staticmethod
    502    def _find_unique_columns(columns):
    503        """
    504        Find the unique columns in a list of columns.
    505
    506        Example:
    507            >>> sorted(Resolver._find_unique_columns(["a", "b", "b", "c"]))
    508            ['a', 'c']
    509
    510        This is necessary because duplicate column names are ambiguous.
    511        """
    512        counts = {}
    513        for column in columns:
    514            counts[column] = counts.get(column, 0) + 1
    515        return {column for column, count in counts.items() if count == 1}

def qualify_columns(expression, schema): View Source

    11def qualify_columns(expression, schema):
    12    """
    13    Rewrite sqlglot AST to have fully qualified columns.
    14
    15    Example:
    16        >>> import sqlglot
    17        >>> schema = {"tbl": {"col": "INT"}}
    18        >>> expression = sqlglot.parse_one("SELECT col FROM tbl")
    19        >>> qualify_columns(expression, schema).sql()
    20        'SELECT tbl.col AS col FROM tbl'
    21
    22    Args:
    23        expression (sqlglot.Expression): expression to qualify
    24        schema (dict|sqlglot.optimizer.Schema): Database schema
    25    Returns:
    26        sqlglot.Expression: qualified expression
    27    """
    28    schema = ensure_schema(schema)
    29
    30    for scope in traverse_scope(expression):
    31        resolver = Resolver(scope, schema)
    32        _pop_table_column_aliases(scope.ctes)
    33        _pop_table_column_aliases(scope.derived_tables)
    34        using_column_tables = _expand_using(scope, resolver)
    35        _qualify_columns(scope, resolver)
    36        if not isinstance(scope.expression, exp.UDTF):
    37            _expand_stars(scope, resolver, using_column_tables)
    38            _qualify_outputs(scope)
    39        _expand_alias_refs(scope, resolver)
    40        _expand_group_by(scope, resolver)
    41        _expand_order_by(scope)
    42
    43    return expression

Rewrite sqlglot AST to have fully qualified columns.

###### Example:

>     >>> import sqlglot
>     >>> schema = {"tbl": {"col": "INT"}}
>     >>> expression = sqlglot.parse_one("SELECT col FROM tbl")
>     >>> qualify_columns(expression, schema).sql()
>     'SELECT tbl.col AS col FROM tbl'

###### Arguments:

- expression (sqlglot.Expression): expression to qualify
- schema (dict|sqlglot.optimizer.Schema): Database schema

###### Returns:

> sqlglot.Expression: qualified expression

def validate_qualify_columns(expression): View Source

    46def validate_qualify_columns(expression):
    47    """Raise an `OptimizeError` if any columns aren't qualified"""
    48    unqualified_columns = []
    49    for scope in traverse_scope(expression):
    50        if isinstance(scope.expression, exp.Select):
    51            unqualified_columns.extend(scope.unqualified_columns)
    52            if scope.external_columns and not scope.is_correlated_subquery:
    53                column = scope.external_columns[0]
    54                raise OptimizeError(f"Unknown table: '{column.table}' for column '{column}'")
    55
    56    if unqualified_columns:
    57        raise OptimizeError(f"Ambiguous columns: {unqualified_columns}")
    58    return expression

Raise an `OptimizeError` if any columns aren't qualified

class Resolver: View Source

    383class Resolver:
    384    """
    385    Helper for resolving columns.
    386
    387    This is a class so we can lazily load some things and easily share them across functions.
    388    """
    389
    390    def __init__(self, scope, schema):
    391        self.scope = scope
    392        self.schema = schema
    393        self._source_columns = None
    394        self._unambiguous_columns = None
    395        self._all_columns = None
    396
    397    def get_table(self, column_name: str) -> t.Optional[exp.Identifier]:
    398        """
    399        Get the table for a column name.
    400
    401        Args:
    402            column_name: The column name to find the table for.
    403        Returns:
    404            The table name if it can be found/inferred.
    405        """
    406        if self._unambiguous_columns is None:
    407            self._unambiguous_columns = self._get_unambiguous_columns(
    408                self._get_all_source_columns()
    409            )
    410
    411        table_name = self._unambiguous_columns.get(column_name)
    412
    413        if not table_name:
    414            sources_without_schema = tuple(
    415                source
    416                for source, columns in self._get_all_source_columns().items()
    417                if not columns or "*" in columns
    418            )
    419            if len(sources_without_schema) == 1:
    420                table_name = sources_without_schema[0]
    421
    422        if table_name not in self.scope.selected_sources:
    423            return exp.to_identifier(table_name)
    424
    425        node, _ = self.scope.selected_sources.get(table_name)
    426
    427        if isinstance(node, exp.Subqueryable):
    428            while node and node.alias != table_name:
    429                node = node.parent
    430
    431        node_alias = node.args.get("alias")
    432        if node_alias:
    433            return node_alias.this
    434
    435        return exp.to_identifier(
    436            table_name, quoted=node.this.quoted if isinstance(node, exp.Table) else None
    437        )
    438
    439    @property
    440    def all_columns(self):
    441        """All available columns of all sources in this scope"""
    442        if self._all_columns is None:
    443            self._all_columns = {
    444                column for columns in self._get_all_source_columns().values() for column in columns
    445            }
    446        return self._all_columns
    447
    448    def get_source_columns(self, name, only_visible=False):
    449        """Resolve the source columns for a given source `name`"""
    450        if name not in self.scope.sources:
    451            raise OptimizeError(f"Unknown table: {name}")
    452
    453        source = self.scope.sources[name]
    454
    455        # If referencing a table, return the columns from the schema
    456        if isinstance(source, exp.Table):
    457            return self.schema.column_names(source, only_visible)
    458
    459        if isinstance(source, Scope) and isinstance(source.expression, exp.Values):
    460            return source.expression.alias_column_names
    461
    462        # Otherwise, if referencing another scope, return that scope's named selects
    463        return source.expression.named_selects
    464
    465    def _get_all_source_columns(self):
    466        if self._source_columns is None:
    467            self._source_columns = {
    468                k: self.get_source_columns(k)
    469                for k in itertools.chain(self.scope.selected_sources, self.scope.lateral_sources)
    470            }
    471        return self._source_columns
    472
    473    def _get_unambiguous_columns(self, source_columns):
    474        """
    475        Find all the unambiguous columns in sources.
    476
    477        Args:
    478            source_columns (dict): Mapping of names to source columns
    479        Returns:
    480            dict: Mapping of column name to source name
    481        """
    482        if not source_columns:
    483            return {}
    484
    485        source_columns = list(source_columns.items())
    486
    487        first_table, first_columns = source_columns[0]
    488        unambiguous_columns = {col: first_table for col in self._find_unique_columns(first_columns)}
    489        all_columns = set(unambiguous_columns)
    490
    491        for table, columns in source_columns[1:]:
    492            unique = self._find_unique_columns(columns)
    493            ambiguous = set(all_columns).intersection(unique)
    494            all_columns.update(columns)
    495            for column in ambiguous:
    496                unambiguous_columns.pop(column, None)
    497            for column in unique.difference(ambiguous):
    498                unambiguous_columns[column] = table
    499
    500        return unambiguous_columns
    501
    502    @staticmethod
    503    def _find_unique_columns(columns):
    504        """
    505        Find the unique columns in a list of columns.
    506
    507        Example:
    508            >>> sorted(Resolver._find_unique_columns(["a", "b", "b", "c"]))
    509            ['a', 'c']
    510
    511        This is necessary because duplicate column names are ambiguous.
    512        """
    513        counts = {}
    514        for column in columns:
    515            counts[column] = counts.get(column, 0) + 1
    516        return {column for column, count in counts.items() if count == 1}

Helper for resolving columns.

This is a class so we can lazily load some things and easily share them across functions.

Resolver(scope, schema) View Source

    390    def __init__(self, scope, schema):
    391        self.scope = scope
    392        self.schema = schema
    393        self._source_columns = None
    394        self._unambiguous_columns = None
    395        self._all_columns = None

def get_table(self, column_name: str) -> Optional[sqlglot.expressions.Identifier]: View Source

    397    def get_table(self, column_name: str) -> t.Optional[exp.Identifier]:
    398        """
    399        Get the table for a column name.
    400
    401        Args:
    402            column_name: The column name to find the table for.
    403        Returns:
    404            The table name if it can be found/inferred.
    405        """
    406        if self._unambiguous_columns is None:
    407            self._unambiguous_columns = self._get_unambiguous_columns(
    408                self._get_all_source_columns()
    409            )
    410
    411        table_name = self._unambiguous_columns.get(column_name)
    412
    413        if not table_name:
    414            sources_without_schema = tuple(
    415                source
    416                for source, columns in self._get_all_source_columns().items()
    417                if not columns or "*" in columns
    418            )
    419            if len(sources_without_schema) == 1:
    420                table_name = sources_without_schema[0]
    421
    422        if table_name not in self.scope.selected_sources:
    423            return exp.to_identifier(table_name)
    424
    425        node, _ = self.scope.selected_sources.get(table_name)
    426
    427        if isinstance(node, exp.Subqueryable):
    428            while node and node.alias != table_name:
    429                node = node.parent
    430
    431        node_alias = node.args.get("alias")
    432        if node_alias:
    433            return node_alias.this
    434
    435        return exp.to_identifier(
    436            table_name, quoted=node.this.quoted if isinstance(node, exp.Table) else None
    437        )

Get the table for a column name.

###### Arguments:

- column_name: The column name to find the table for.

###### Returns:

> The table name if it can be found/inferred.

all_columns

All available columns of all sources in this scope

def get_source_columns(self, name, only_visible=False): View Source

    448    def get_source_columns(self, name, only_visible=False):
    449        """Resolve the source columns for a given source `name`"""
    450        if name not in self.scope.sources:
    451            raise OptimizeError(f"Unknown table: {name}")
    452
    453        source = self.scope.sources[name]
    454
    455        # If referencing a table, return the columns from the schema
    456        if isinstance(source, exp.Table):
    457            return self.schema.column_names(source, only_visible)
    458
    459        if isinstance(source, Scope) and isinstance(source.expression, exp.Values):
    460            return source.expression.alias_column_names
    461
    462        # Otherwise, if referencing another scope, return that scope's named selects
    463        return source.expression.named_selects

Resolve the source columns for a given source `name`