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, source_first=True):
    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 source_first and 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            node.set("table", table)
    167        elif isinstance(node, exp.Expression) and not isinstance(node, exp.Subqueryable):
    168            exp.replace_children(node, transform, source_first)
    169
    170        return node
    171
    172    for select in scope.expression.selects:
    173        transform(select)
    174
    175    for modifier, source_first in (
    176        ("where", True),
    177        ("group", True),
    178        ("having", False),
    179    ):
    180        transform(scope.expression.args.get(modifier), source_first=source_first)
    181
    182
    183def _expand_group_by(scope, resolver):
    184    group = scope.expression.args.get("group")
    185    if not group:
    186        return
    187
    188    group.set("expressions", _expand_positional_references(scope, group.expressions))
    189    scope.expression.set("group", group)
    190
    191
    192def _expand_order_by(scope):
    193    order = scope.expression.args.get("order")
    194    if not order:
    195        return
    196
    197    ordereds = order.expressions
    198    for ordered, new_expression in zip(
    199        ordereds,
    200        _expand_positional_references(scope, (o.this for o in ordereds)),
    201    ):
    202        ordered.set("this", new_expression)
    203
    204
    205def _expand_positional_references(scope, expressions):
    206    new_nodes = []
    207    for node in expressions:
    208        if node.is_int:
    209            try:
    210                select = scope.selects[int(node.name) - 1]
    211            except IndexError:
    212                raise OptimizeError(f"Unknown output column: {node.name}")
    213            if isinstance(select, exp.Alias):
    214                select = select.this
    215            new_nodes.append(select.copy())
    216            scope.clear_cache()
    217        else:
    218            new_nodes.append(node)
    219
    220    return new_nodes
    221
    222
    223def _qualify_columns(scope, resolver):
    224    """Disambiguate columns, ensuring each column specifies a source"""
    225    for column in scope.columns:
    226        column_table = column.table
    227        column_name = column.name
    228
    229        if column_table and column_table in scope.sources:
    230            source_columns = resolver.get_source_columns(column_table)
    231            if source_columns and column_name not in source_columns and "*" not in source_columns:
    232                raise OptimizeError(f"Unknown column: {column_name}")
    233
    234        if not column_table:
    235            column_table = resolver.get_table(column_name)
    236
    237            # column_table can be a '' because bigquery unnest has no table alias
    238            if column_table:
    239                column.set("table", column_table)
    240        elif column_table not in scope.sources:
    241            # structs are used like tables (e.g. "struct"."field"), so they need to be qualified
    242            # separately and represented as dot(dot(...(<table>.<column>, field1), field2, ...))
    243
    244            root, *parts = column.parts
    245
    246            if root.name in scope.sources:
    247                # struct is already qualified, but we still need to change the AST representation
    248                column_table = root
    249                root, *parts = parts
    250            else:
    251                column_table = resolver.get_table(root.name)
    252
    253            if column_table:
    254                column.replace(exp.Dot.build([exp.column(root, table=column_table), *parts]))
    255
    256    columns_missing_from_scope = []
    257
    258    # Determine whether each reference in the order by clause is to a column or an alias.
    259    order = scope.expression.args.get("order")
    260
    261    if order:
    262        for ordered in order.expressions:
    263            for column in ordered.find_all(exp.Column):
    264                if (
    265                    not column.table
    266                    and column.parent is not ordered
    267                    and column.name in resolver.all_columns
    268                ):
    269                    columns_missing_from_scope.append(column)
    270
    271    # Determine whether each reference in the having clause is to a column or an alias.
    272    having = scope.expression.args.get("having")
    273
    274    if having:
    275        for column in having.find_all(exp.Column):
    276            if (
    277                not column.table
    278                and column.find_ancestor(exp.AggFunc)
    279                and column.name in resolver.all_columns
    280            ):
    281                columns_missing_from_scope.append(column)
    282
    283    for column in columns_missing_from_scope:
    284        column_table = resolver.get_table(column.name)
    285
    286        if column_table:
    287            column.set("table", column_table)
    288
    289
    290def _expand_stars(scope, resolver, using_column_tables):
    291    """Expand stars to lists of column selections"""
    292
    293    new_selections = []
    294    except_columns = {}
    295    replace_columns = {}
    296    coalesced_columns = set()
    297
    298    for expression in scope.selects:
    299        if isinstance(expression, exp.Star):
    300            tables = list(scope.selected_sources)
    301            _add_except_columns(expression, tables, except_columns)
    302            _add_replace_columns(expression, tables, replace_columns)
    303        elif expression.is_star:
    304            tables = [expression.table]
    305            _add_except_columns(expression.this, tables, except_columns)
    306            _add_replace_columns(expression.this, tables, replace_columns)
    307        else:
    308            new_selections.append(expression)
    309            continue
    310
    311        for table in tables:
    312            if table not in scope.sources:
    313                raise OptimizeError(f"Unknown table: {table}")
    314            columns = resolver.get_source_columns(table, only_visible=True)
    315
    316            if columns and "*" not in columns:
    317                table_id = id(table)
    318                for name in columns:
    319                    if name in using_column_tables and table in using_column_tables[name]:
    320                        if name in coalesced_columns:
    321                            continue
    322
    323                        coalesced_columns.add(name)
    324                        tables = using_column_tables[name]
    325                        coalesce = [exp.column(name, table=table) for table in tables]
    326
    327                        new_selections.append(
    328                            exp.alias_(
    329                                exp.Coalesce(this=coalesce[0], expressions=coalesce[1:]), alias=name
    330                            )
    331                        )
    332                    elif name not in except_columns.get(table_id, set()):
    333                        alias_ = replace_columns.get(table_id, {}).get(name, name)
    334                        column = exp.column(name, table)
    335                        new_selections.append(alias(column, alias_) if alias_ != name else column)
    336            else:
    337                return
    338    scope.expression.set("expressions", new_selections)
    339
    340
    341def _add_except_columns(expression, tables, except_columns):
    342    except_ = expression.args.get("except")
    343
    344    if not except_:
    345        return
    346
    347    columns = {e.name for e in except_}
    348
    349    for table in tables:
    350        except_columns[id(table)] = columns
    351
    352
    353def _add_replace_columns(expression, tables, replace_columns):
    354    replace = expression.args.get("replace")
    355
    356    if not replace:
    357        return
    358
    359    columns = {e.this.name: e.alias for e in replace}
    360
    361    for table in tables:
    362        replace_columns[id(table)] = columns
    363
    364
    365def _qualify_outputs(scope):
    366    """Ensure all output columns are aliased"""
    367    new_selections = []
    368
    369    for i, (selection, aliased_column) in enumerate(
    370        itertools.zip_longest(scope.selects, scope.outer_column_list)
    371    ):
    372        if isinstance(selection, exp.Subquery):
    373            if not selection.output_name:
    374                selection.set("alias", exp.TableAlias(this=exp.to_identifier(f"_col_{i}")))
    375        elif not isinstance(selection, exp.Alias) and not selection.is_star:
    376            alias_ = alias(exp.column(""), alias=selection.output_name or f"_col_{i}")
    377            alias_.set("this", selection)
    378            selection = alias_
    379
    380        if aliased_column:
    381            selection.set("alias", exp.to_identifier(aliased_column))
    382
    383        new_selections.append(selection)
    384
    385    scope.expression.set("expressions", new_selections)
    386
    387
    388class Resolver:
    389    """
    390    Helper for resolving columns.
    391
    392    This is a class so we can lazily load some things and easily share them across functions.
    393    """
    394
    395    def __init__(self, scope, schema):
    396        self.scope = scope
    397        self.schema = schema
    398        self._source_columns = None
    399        self._unambiguous_columns = None
    400        self._all_columns = None
    401
    402    def get_table(self, column_name: str) -> t.Optional[exp.Identifier]:
    403        """
    404        Get the table for a column name.
    405
    406        Args:
    407            column_name: The column name to find the table for.
    408        Returns:
    409            The table name if it can be found/inferred.
    410        """
    411        if self._unambiguous_columns is None:
    412            self._unambiguous_columns = self._get_unambiguous_columns(
    413                self._get_all_source_columns()
    414            )
    415
    416        table_name = self._unambiguous_columns.get(column_name)
    417
    418        if not table_name:
    419            sources_without_schema = tuple(
    420                source
    421                for source, columns in self._get_all_source_columns().items()
    422                if not columns or "*" in columns
    423            )
    424            if len(sources_without_schema) == 1:
    425                table_name = sources_without_schema[0]
    426
    427        if table_name not in self.scope.selected_sources:
    428            return exp.to_identifier(table_name)
    429
    430        node, _ = self.scope.selected_sources.get(table_name)
    431
    432        if isinstance(node, exp.Subqueryable):
    433            while node and node.alias != table_name:
    434                node = node.parent
    435
    436        node_alias = node.args.get("alias")
    437        if node_alias:
    438            return node_alias.this
    439
    440        return exp.to_identifier(
    441            table_name, quoted=node.this.quoted if isinstance(node, exp.Table) else None
    442        )
    443
    444    @property
    445    def all_columns(self):
    446        """All available columns of all sources in this scope"""
    447        if self._all_columns is None:
    448            self._all_columns = {
    449                column for columns in self._get_all_source_columns().values() for column in columns
    450            }
    451        return self._all_columns
    452
    453    def get_source_columns(self, name, only_visible=False):
    454        """Resolve the source columns for a given source `name`"""
    455        if name not in self.scope.sources:
    456            raise OptimizeError(f"Unknown table: {name}")
    457
    458        source = self.scope.sources[name]
    459
    460        # If referencing a table, return the columns from the schema
    461        if isinstance(source, exp.Table):
    462            return self.schema.column_names(source, only_visible)
    463
    464        if isinstance(source, Scope) and isinstance(source.expression, exp.Values):
    465            return source.expression.alias_column_names
    466
    467        # Otherwise, if referencing another scope, return that scope's named selects
    468        return source.expression.named_selects
    469
    470    def _get_all_source_columns(self):
    471        if self._source_columns is None:
    472            self._source_columns = {
    473                k: self.get_source_columns(k)
    474                for k in itertools.chain(self.scope.selected_sources, self.scope.lateral_sources)
    475            }
    476        return self._source_columns
    477
    478    def _get_unambiguous_columns(self, source_columns):
    479        """
    480        Find all the unambiguous columns in sources.
    481
    482        Args:
    483            source_columns (dict): Mapping of names to source columns
    484        Returns:
    485            dict: Mapping of column name to source name
    486        """
    487        if not source_columns:
    488            return {}
    489
    490        source_columns = list(source_columns.items())
    491
    492        first_table, first_columns = source_columns[0]
    493        unambiguous_columns = {col: first_table for col in self._find_unique_columns(first_columns)}
    494        all_columns = set(unambiguous_columns)
    495
    496        for table, columns in source_columns[1:]:
    497            unique = self._find_unique_columns(columns)
    498            ambiguous = set(all_columns).intersection(unique)
    499            all_columns.update(columns)
    500            for column in ambiguous:
    501                unambiguous_columns.pop(column, None)
    502            for column in unique.difference(ambiguous):
    503                unambiguous_columns[column] = table
    504
    505        return unambiguous_columns
    506
    507    @staticmethod
    508    def _find_unique_columns(columns):
    509        """
    510        Find the unique columns in a list of columns.
    511
    512        Example:
    513            >>> sorted(Resolver._find_unique_columns(["a", "b", "b", "c"]))
    514            ['a', 'c']
    515
    516        This is necessary because duplicate column names are ambiguous.
    517        """
    518        counts = {}
    519        for column in columns:
    520            counts[column] = counts.get(column, 0) + 1
    521        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

    389class Resolver:
    390    """
    391    Helper for resolving columns.
    392
    393    This is a class so we can lazily load some things and easily share them across functions.
    394    """
    395
    396    def __init__(self, scope, schema):
    397        self.scope = scope
    398        self.schema = schema
    399        self._source_columns = None
    400        self._unambiguous_columns = None
    401        self._all_columns = None
    402
    403    def get_table(self, column_name: str) -> t.Optional[exp.Identifier]:
    404        """
    405        Get the table for a column name.
    406
    407        Args:
    408            column_name: The column name to find the table for.
    409        Returns:
    410            The table name if it can be found/inferred.
    411        """
    412        if self._unambiguous_columns is None:
    413            self._unambiguous_columns = self._get_unambiguous_columns(
    414                self._get_all_source_columns()
    415            )
    416
    417        table_name = self._unambiguous_columns.get(column_name)
    418
    419        if not table_name:
    420            sources_without_schema = tuple(
    421                source
    422                for source, columns in self._get_all_source_columns().items()
    423                if not columns or "*" in columns
    424            )
    425            if len(sources_without_schema) == 1:
    426                table_name = sources_without_schema[0]
    427
    428        if table_name not in self.scope.selected_sources:
    429            return exp.to_identifier(table_name)
    430
    431        node, _ = self.scope.selected_sources.get(table_name)
    432
    433        if isinstance(node, exp.Subqueryable):
    434            while node and node.alias != table_name:
    435                node = node.parent
    436
    437        node_alias = node.args.get("alias")
    438        if node_alias:
    439            return node_alias.this
    440
    441        return exp.to_identifier(
    442            table_name, quoted=node.this.quoted if isinstance(node, exp.Table) else None
    443        )
    444
    445    @property
    446    def all_columns(self):
    447        """All available columns of all sources in this scope"""
    448        if self._all_columns is None:
    449            self._all_columns = {
    450                column for columns in self._get_all_source_columns().values() for column in columns
    451            }
    452        return self._all_columns
    453
    454    def get_source_columns(self, name, only_visible=False):
    455        """Resolve the source columns for a given source `name`"""
    456        if name not in self.scope.sources:
    457            raise OptimizeError(f"Unknown table: {name}")
    458
    459        source = self.scope.sources[name]
    460
    461        # If referencing a table, return the columns from the schema
    462        if isinstance(source, exp.Table):
    463            return self.schema.column_names(source, only_visible)
    464
    465        if isinstance(source, Scope) and isinstance(source.expression, exp.Values):
    466            return source.expression.alias_column_names
    467
    468        # Otherwise, if referencing another scope, return that scope's named selects
    469        return source.expression.named_selects
    470
    471    def _get_all_source_columns(self):
    472        if self._source_columns is None:
    473            self._source_columns = {
    474                k: self.get_source_columns(k)
    475                for k in itertools.chain(self.scope.selected_sources, self.scope.lateral_sources)
    476            }
    477        return self._source_columns
    478
    479    def _get_unambiguous_columns(self, source_columns):
    480        """
    481        Find all the unambiguous columns in sources.
    482
    483        Args:
    484            source_columns (dict): Mapping of names to source columns
    485        Returns:
    486            dict: Mapping of column name to source name
    487        """
    488        if not source_columns:
    489            return {}
    490
    491        source_columns = list(source_columns.items())
    492
    493        first_table, first_columns = source_columns[0]
    494        unambiguous_columns = {col: first_table for col in self._find_unique_columns(first_columns)}
    495        all_columns = set(unambiguous_columns)
    496
    497        for table, columns in source_columns[1:]:
    498            unique = self._find_unique_columns(columns)
    499            ambiguous = set(all_columns).intersection(unique)
    500            all_columns.update(columns)
    501            for column in ambiguous:
    502                unambiguous_columns.pop(column, None)
    503            for column in unique.difference(ambiguous):
    504                unambiguous_columns[column] = table
    505
    506        return unambiguous_columns
    507
    508    @staticmethod
    509    def _find_unique_columns(columns):
    510        """
    511        Find the unique columns in a list of columns.
    512
    513        Example:
    514            >>> sorted(Resolver._find_unique_columns(["a", "b", "b", "c"]))
    515            ['a', 'c']
    516
    517        This is necessary because duplicate column names are ambiguous.
    518        """
    519        counts = {}
    520        for column in columns:
    521            counts[column] = counts.get(column, 0) + 1
    522        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

    396    def __init__(self, scope, schema):
    397        self.scope = scope
    398        self.schema = schema
    399        self._source_columns = None
    400        self._unambiguous_columns = None
    401        self._all_columns = None

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

    403    def get_table(self, column_name: str) -> t.Optional[exp.Identifier]:
    404        """
    405        Get the table for a column name.
    406
    407        Args:
    408            column_name: The column name to find the table for.
    409        Returns:
    410            The table name if it can be found/inferred.
    411        """
    412        if self._unambiguous_columns is None:
    413            self._unambiguous_columns = self._get_unambiguous_columns(
    414                self._get_all_source_columns()
    415            )
    416
    417        table_name = self._unambiguous_columns.get(column_name)
    418
    419        if not table_name:
    420            sources_without_schema = tuple(
    421                source
    422                for source, columns in self._get_all_source_columns().items()
    423                if not columns or "*" in columns
    424            )
    425            if len(sources_without_schema) == 1:
    426                table_name = sources_without_schema[0]
    427
    428        if table_name not in self.scope.selected_sources:
    429            return exp.to_identifier(table_name)
    430
    431        node, _ = self.scope.selected_sources.get(table_name)
    432
    433        if isinstance(node, exp.Subqueryable):
    434            while node and node.alias != table_name:
    435                node = node.parent
    436
    437        node_alias = node.args.get("alias")
    438        if node_alias:
    439            return node_alias.this
    440
    441        return exp.to_identifier(
    442            table_name, quoted=node.this.quoted if isinstance(node, exp.Table) else None
    443        )

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

    454    def get_source_columns(self, name, only_visible=False):
    455        """Resolve the source columns for a given source `name`"""
    456        if name not in self.scope.sources:
    457            raise OptimizeError(f"Unknown table: {name}")
    458
    459        source = self.scope.sources[name]
    460
    461        # If referencing a table, return the columns from the schema
    462        if isinstance(source, exp.Table):
    463            return self.schema.column_names(source, only_visible)
    464
    465        if isinstance(source, Scope) and isinstance(source.expression, exp.Values):
    466            return source.expression.alias_column_names
    467
    468        # Otherwise, if referencing another scope, return that scope's named selects
    469        return source.expression.named_selects

Resolve the source columns for a given source `name`