sqlglot.optimizer.scope API documentation

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# sqlglot.optimizer.scope

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      1from __future__ import annotations
      2
      3import itertools
      4import logging
      5import typing as t
      6from collections import defaultdict
      7from enum import Enum, auto
      8
      9from sqlglot import exp
     10from sqlglot.errors import OptimizeError
     11from sqlglot.helper import ensure_collection, find_new_name, seq_get
     12
     13logger = logging.getLogger("sqlglot")
     14
     15TRAVERSABLES = (exp.Query, exp.DDL, exp.DML)
     16
     17
     18class ScopeType(Enum):
     19    ROOT = auto()
     20    SUBQUERY = auto()
     21    DERIVED_TABLE = auto()
     22    CTE = auto()
     23    UNION = auto()
     24    UDTF = auto()
     25
     26
     27class Scope:
     28    """
     29    Selection scope.
     30
     31    Attributes:
     32        expression (exp.Select|exp.SetOperation): Root expression of this scope
     33        sources (dict[str, exp.Table|Scope]): Mapping of source name to either
     34            a Table expression or another Scope instance. For example:
     35                SELECT * FROM x                     {"x": Table(this="x")}
     36                SELECT * FROM x AS y                {"y": Table(this="x")}
     37                SELECT * FROM (SELECT ...) AS y     {"y": Scope(...)}
     38        lateral_sources (dict[str, exp.Table|Scope]): Sources from laterals
     39            For example:
     40                SELECT c FROM x LATERAL VIEW EXPLODE (a) AS c;
     41            The LATERAL VIEW EXPLODE gets x as a source.
     42        cte_sources (dict[str, Scope]): Sources from CTES
     43        outer_columns (list[str]): If this is a derived table or CTE, and the outer query
     44            defines a column list for the alias of this scope, this is that list of columns.
     45            For example:
     46                SELECT * FROM (SELECT ...) AS y(col1, col2)
     47            The inner query would have `["col1", "col2"]` for its `outer_columns`
     48        parent (Scope): Parent scope
     49        scope_type (ScopeType): Type of this scope, relative to it's parent
     50        subquery_scopes (list[Scope]): List of all child scopes for subqueries
     51        cte_scopes (list[Scope]): List of all child scopes for CTEs
     52        derived_table_scopes (list[Scope]): List of all child scopes for derived_tables
     53        udtf_scopes (list[Scope]): List of all child scopes for user defined tabular functions
     54        table_scopes (list[Scope]): derived_table_scopes + udtf_scopes, in the order that they're defined
     55        union_scopes (list[Scope, Scope]): If this Scope is for a Union expression, this will be
     56            a list of the left and right child scopes.
     57    """
     58
     59    def __init__(
     60        self,
     61        expression,
     62        sources=None,
     63        outer_columns=None,
     64        parent=None,
     65        scope_type=ScopeType.ROOT,
     66        lateral_sources=None,
     67        cte_sources=None,
     68        can_be_correlated=None,
     69    ):
     70        self.expression = expression
     71        self.sources = sources or {}
     72        self.lateral_sources = lateral_sources or {}
     73        self.cte_sources = cte_sources or {}
     74        self.sources.update(self.lateral_sources)
     75        self.sources.update(self.cte_sources)
     76        self.outer_columns = outer_columns or []
     77        self.parent = parent
     78        self.scope_type = scope_type
     79        self.subquery_scopes = []
     80        self.derived_table_scopes = []
     81        self.table_scopes = []
     82        self.cte_scopes = []
     83        self.union_scopes = []
     84        self.udtf_scopes = []
     85        self.can_be_correlated = can_be_correlated
     86        self.clear_cache()
     87
     88    def clear_cache(self):
     89        self._collected = False
     90        self._raw_columns = None
     91        self._stars = None
     92        self._derived_tables = None
     93        self._udtfs = None
     94        self._tables = None
     95        self._ctes = None
     96        self._subqueries = None
     97        self._selected_sources = None
     98        self._columns = None
     99        self._external_columns = None
    100        self._join_hints = None
    101        self._pivots = None
    102        self._references = None
    103        self._semi_anti_join_tables = None
    104
    105    def branch(
    106        self, expression, scope_type, sources=None, cte_sources=None, lateral_sources=None, **kwargs
    107    ):
    108        """Branch from the current scope to a new, inner scope"""
    109        return Scope(
    110            expression=expression.unnest(),
    111            sources=sources.copy() if sources else None,
    112            parent=self,
    113            scope_type=scope_type,
    114            cte_sources={**self.cte_sources, **(cte_sources or {})},
    115            lateral_sources=lateral_sources.copy() if lateral_sources else None,
    116            can_be_correlated=self.can_be_correlated
    117            or scope_type in (ScopeType.SUBQUERY, ScopeType.UDTF),
    118            **kwargs,
    119        )
    120
    121    def _collect(self):
    122        self._tables = []
    123        self._ctes = []
    124        self._subqueries = []
    125        self._derived_tables = []
    126        self._udtfs = []
    127        self._raw_columns = []
    128        self._stars = []
    129        self._join_hints = []
    130        self._semi_anti_join_tables = set()
    131
    132        for node in self.walk(bfs=False):
    133            if node is self.expression:
    134                continue
    135
    136            if isinstance(node, exp.Dot) and node.is_star:
    137                self._stars.append(node)
    138            elif isinstance(node, exp.Column):
    139                if isinstance(node.this, exp.Star):
    140                    self._stars.append(node)
    141                else:
    142                    self._raw_columns.append(node)
    143            elif isinstance(node, exp.Table) and not isinstance(node.parent, exp.JoinHint):
    144                parent = node.parent
    145                if isinstance(parent, exp.Join) and parent.is_semi_or_anti_join:
    146                    self._semi_anti_join_tables.add(node.alias_or_name)
    147
    148                self._tables.append(node)
    149            elif isinstance(node, exp.JoinHint):
    150                self._join_hints.append(node)
    151            elif isinstance(node, exp.UDTF):
    152                self._udtfs.append(node)
    153            elif isinstance(node, exp.CTE):
    154                self._ctes.append(node)
    155            elif _is_derived_table(node) and _is_from_or_join(node):
    156                self._derived_tables.append(node)
    157            elif isinstance(node, exp.UNWRAPPED_QUERIES):
    158                self._subqueries.append(node)
    159
    160        self._collected = True
    161
    162    def _ensure_collected(self):
    163        if not self._collected:
    164            self._collect()
    165
    166    def walk(self, bfs=True, prune=None):
    167        return walk_in_scope(self.expression, bfs=bfs, prune=None)
    168
    169    def find(self, *expression_types, bfs=True):
    170        return find_in_scope(self.expression, expression_types, bfs=bfs)
    171
    172    def find_all(self, *expression_types, bfs=True):
    173        return find_all_in_scope(self.expression, expression_types, bfs=bfs)
    174
    175    def replace(self, old, new):
    176        """
    177        Replace `old` with `new`.
    178
    179        This can be used instead of `exp.Expression.replace` to ensure the `Scope` is kept up-to-date.
    180
    181        Args:
    182            old (exp.Expression): old node
    183            new (exp.Expression): new node
    184        """
    185        old.replace(new)
    186        self.clear_cache()
    187
    188    @property
    189    def tables(self):
    190        """
    191        List of tables in this scope.
    192
    193        Returns:
    194            list[exp.Table]: tables
    195        """
    196        self._ensure_collected()
    197        return self._tables
    198
    199    @property
    200    def ctes(self):
    201        """
    202        List of CTEs in this scope.
    203
    204        Returns:
    205            list[exp.CTE]: ctes
    206        """
    207        self._ensure_collected()
    208        return self._ctes
    209
    210    @property
    211    def derived_tables(self):
    212        """
    213        List of derived tables in this scope.
    214
    215        For example:
    216            SELECT * FROM (SELECT ...) <- that's a derived table
    217
    218        Returns:
    219            list[exp.Subquery]: derived tables
    220        """
    221        self._ensure_collected()
    222        return self._derived_tables
    223
    224    @property
    225    def udtfs(self):
    226        """
    227        List of "User Defined Tabular Functions" in this scope.
    228
    229        Returns:
    230            list[exp.UDTF]: UDTFs
    231        """
    232        self._ensure_collected()
    233        return self._udtfs
    234
    235    @property
    236    def subqueries(self):
    237        """
    238        List of subqueries in this scope.
    239
    240        For example:
    241            SELECT * FROM x WHERE a IN (SELECT ...) <- that's a subquery
    242
    243        Returns:
    244            list[exp.Select | exp.SetOperation]: subqueries
    245        """
    246        self._ensure_collected()
    247        return self._subqueries
    248
    249    @property
    250    def stars(self) -> t.List[exp.Column | exp.Dot]:
    251        """
    252        List of star expressions (columns or dots) in this scope.
    253        """
    254        self._ensure_collected()
    255        return self._stars
    256
    257    @property
    258    def columns(self):
    259        """
    260        List of columns in this scope.
    261
    262        Returns:
    263            list[exp.Column]: Column instances in this scope, plus any
    264                Columns that reference this scope from correlated subqueries.
    265        """
    266        if self._columns is None:
    267            self._ensure_collected()
    268            columns = self._raw_columns
    269
    270            external_columns = [
    271                column
    272                for scope in itertools.chain(
    273                    self.subquery_scopes,
    274                    self.udtf_scopes,
    275                    (dts for dts in self.derived_table_scopes if dts.can_be_correlated),
    276                )
    277                for column in scope.external_columns
    278            ]
    279
    280            named_selects = set(self.expression.named_selects)
    281
    282            self._columns = []
    283            for column in columns + external_columns:
    284                ancestor = column.find_ancestor(
    285                    exp.Select,
    286                    exp.Qualify,
    287                    exp.Order,
    288                    exp.Having,
    289                    exp.Hint,
    290                    exp.Table,
    291                    exp.Star,
    292                    exp.Distinct,
    293                )
    294                if (
    295                    not ancestor
    296                    or column.table
    297                    or isinstance(ancestor, exp.Select)
    298                    or (isinstance(ancestor, exp.Table) and not isinstance(ancestor.this, exp.Func))
    299                    or (
    300                        isinstance(ancestor, (exp.Order, exp.Distinct))
    301                        and (
    302                            isinstance(ancestor.parent, (exp.Window, exp.WithinGroup))
    303                            or column.name not in named_selects
    304                        )
    305                    )
    306                    or (isinstance(ancestor, exp.Star) and not column.arg_key == "except")
    307                ):
    308                    self._columns.append(column)
    309
    310        return self._columns
    311
    312    @property
    313    def selected_sources(self):
    314        """
    315        Mapping of nodes and sources that are actually selected from in this scope.
    316
    317        That is, all tables in a schema are selectable at any point. But a
    318        table only becomes a selected source if it's included in a FROM or JOIN clause.
    319
    320        Returns:
    321            dict[str, (exp.Table|exp.Select, exp.Table|Scope)]: selected sources and nodes
    322        """
    323        if self._selected_sources is None:
    324            result = {}
    325
    326            for name, node in self.references:
    327                if name in self._semi_anti_join_tables:
    328                    # The RHS table of SEMI/ANTI joins shouldn't be collected as a
    329                    # selected source
    330                    continue
    331
    332                if name in result:
    333                    raise OptimizeError(f"Alias already used: {name}")
    334                if name in self.sources:
    335                    result[name] = (node, self.sources[name])
    336
    337            self._selected_sources = result
    338        return self._selected_sources
    339
    340    @property
    341    def references(self) -> t.List[t.Tuple[str, exp.Expression]]:
    342        if self._references is None:
    343            self._references = []
    344
    345            for table in self.tables:
    346                self._references.append((table.alias_or_name, table))
    347            for expression in itertools.chain(self.derived_tables, self.udtfs):
    348                self._references.append(
    349                    (
    350                        expression.alias,
    351                        expression if expression.args.get("pivots") else expression.unnest(),
    352                    )
    353                )
    354
    355        return self._references
    356
    357    @property
    358    def external_columns(self):
    359        """
    360        Columns that appear to reference sources in outer scopes.
    361
    362        Returns:
    363            list[exp.Column]: Column instances that don't reference
    364                sources in the current scope.
    365        """
    366        if self._external_columns is None:
    367            if isinstance(self.expression, exp.SetOperation):
    368                left, right = self.union_scopes
    369                self._external_columns = left.external_columns + right.external_columns
    370            else:
    371                self._external_columns = [
    372                    c
    373                    for c in self.columns
    374                    if c.table not in self.selected_sources
    375                    and c.table not in self.semi_or_anti_join_tables
    376                ]
    377
    378        return self._external_columns
    379
    380    @property
    381    def unqualified_columns(self):
    382        """
    383        Unqualified columns in the current scope.
    384
    385        Returns:
    386             list[exp.Column]: Unqualified columns
    387        """
    388        return [c for c in self.columns if not c.table]
    389
    390    @property
    391    def join_hints(self):
    392        """
    393        Hints that exist in the scope that reference tables
    394
    395        Returns:
    396            list[exp.JoinHint]: Join hints that are referenced within the scope
    397        """
    398        if self._join_hints is None:
    399            return []
    400        return self._join_hints
    401
    402    @property
    403    def pivots(self):
    404        if not self._pivots:
    405            self._pivots = [
    406                pivot for _, node in self.references for pivot in node.args.get("pivots") or []
    407            ]
    408
    409        return self._pivots
    410
    411    @property
    412    def semi_or_anti_join_tables(self):
    413        return self._semi_anti_join_tables or set()
    414
    415    def source_columns(self, source_name):
    416        """
    417        Get all columns in the current scope for a particular source.
    418
    419        Args:
    420            source_name (str): Name of the source
    421        Returns:
    422            list[exp.Column]: Column instances that reference `source_name`
    423        """
    424        return [column for column in self.columns if column.table == source_name]
    425
    426    @property
    427    def is_subquery(self):
    428        """Determine if this scope is a subquery"""
    429        return self.scope_type == ScopeType.SUBQUERY
    430
    431    @property
    432    def is_derived_table(self):
    433        """Determine if this scope is a derived table"""
    434        return self.scope_type == ScopeType.DERIVED_TABLE
    435
    436    @property
    437    def is_union(self):
    438        """Determine if this scope is a union"""
    439        return self.scope_type == ScopeType.UNION
    440
    441    @property
    442    def is_cte(self):
    443        """Determine if this scope is a common table expression"""
    444        return self.scope_type == ScopeType.CTE
    445
    446    @property
    447    def is_root(self):
    448        """Determine if this is the root scope"""
    449        return self.scope_type == ScopeType.ROOT
    450
    451    @property
    452    def is_udtf(self):
    453        """Determine if this scope is a UDTF (User Defined Table Function)"""
    454        return self.scope_type == ScopeType.UDTF
    455
    456    @property
    457    def is_correlated_subquery(self):
    458        """Determine if this scope is a correlated subquery"""
    459        return bool(self.can_be_correlated and self.external_columns)
    460
    461    def rename_source(self, old_name, new_name):
    462        """Rename a source in this scope"""
    463        columns = self.sources.pop(old_name or "", [])
    464        self.sources[new_name] = columns
    465
    466    def add_source(self, name, source):
    467        """Add a source to this scope"""
    468        self.sources[name] = source
    469        self.clear_cache()
    470
    471    def remove_source(self, name):
    472        """Remove a source from this scope"""
    473        self.sources.pop(name, None)
    474        self.clear_cache()
    475
    476    def __repr__(self):
    477        return f"Scope<{self.expression.sql()}>"
    478
    479    def traverse(self):
    480        """
    481        Traverse the scope tree from this node.
    482
    483        Yields:
    484            Scope: scope instances in depth-first-search post-order
    485        """
    486        stack = [self]
    487        result = []
    488        while stack:
    489            scope = stack.pop()
    490            result.append(scope)
    491            stack.extend(
    492                itertools.chain(
    493                    scope.cte_scopes,
    494                    scope.union_scopes,
    495                    scope.table_scopes,
    496                    scope.subquery_scopes,
    497                )
    498            )
    499
    500        yield from reversed(result)
    501
    502    def ref_count(self):
    503        """
    504        Count the number of times each scope in this tree is referenced.
    505
    506        Returns:
    507            dict[int, int]: Mapping of Scope instance ID to reference count
    508        """
    509        scope_ref_count = defaultdict(lambda: 0)
    510
    511        for scope in self.traverse():
    512            for _, source in scope.selected_sources.values():
    513                scope_ref_count[id(source)] += 1
    514
    515        return scope_ref_count
    516
    517
    518def traverse_scope(expression: exp.Expression) -> t.List[Scope]:
    519    """
    520    Traverse an expression by its "scopes".
    521
    522    "Scope" represents the current context of a Select statement.
    523
    524    This is helpful for optimizing queries, where we need more information than
    525    the expression tree itself. For example, we might care about the source
    526    names within a subquery. Returns a list because a generator could result in
    527    incomplete properties which is confusing.
    528
    529    Examples:
    530        >>> import sqlglot
    531        >>> expression = sqlglot.parse_one("SELECT a FROM (SELECT a FROM x) AS y")
    532        >>> scopes = traverse_scope(expression)
    533        >>> scopes[0].expression.sql(), list(scopes[0].sources)
    534        ('SELECT a FROM x', ['x'])
    535        >>> scopes[1].expression.sql(), list(scopes[1].sources)
    536        ('SELECT a FROM (SELECT a FROM x) AS y', ['y'])
    537
    538    Args:
    539        expression: Expression to traverse
    540
    541    Returns:
    542        A list of the created scope instances
    543    """
    544    if isinstance(expression, TRAVERSABLES):
    545        return list(_traverse_scope(Scope(expression)))
    546    return []
    547
    548
    549def build_scope(expression: exp.Expression) -> t.Optional[Scope]:
    550    """
    551    Build a scope tree.
    552
    553    Args:
    554        expression: Expression to build the scope tree for.
    555
    556    Returns:
    557        The root scope
    558    """
    559    return seq_get(traverse_scope(expression), -1)
    560
    561
    562def _traverse_scope(scope):
    563    expression = scope.expression
    564
    565    if isinstance(expression, exp.Select):
    566        yield from _traverse_select(scope)
    567    elif isinstance(expression, exp.SetOperation):
    568        yield from _traverse_ctes(scope)
    569        yield from _traverse_union(scope)
    570        return
    571    elif isinstance(expression, exp.Subquery):
    572        if scope.is_root:
    573            yield from _traverse_select(scope)
    574        else:
    575            yield from _traverse_subqueries(scope)
    576    elif isinstance(expression, exp.Table):
    577        yield from _traverse_tables(scope)
    578    elif isinstance(expression, exp.UDTF):
    579        yield from _traverse_udtfs(scope)
    580    elif isinstance(expression, exp.DDL):
    581        if isinstance(expression.expression, exp.Query):
    582            yield from _traverse_ctes(scope)
    583            yield from _traverse_scope(Scope(expression.expression, cte_sources=scope.cte_sources))
    584        return
    585    elif isinstance(expression, exp.DML):
    586        yield from _traverse_ctes(scope)
    587        for query in find_all_in_scope(expression, exp.Query):
    588            # This check ensures we don't yield the CTE/nested queries twice
    589            if not isinstance(query.parent, (exp.CTE, exp.Subquery)):
    590                yield from _traverse_scope(Scope(query, cte_sources=scope.cte_sources))
    591        return
    592    else:
    593        logger.warning("Cannot traverse scope %s with type '%s'", expression, type(expression))
    594        return
    595
    596    yield scope
    597
    598
    599def _traverse_select(scope):
    600    yield from _traverse_ctes(scope)
    601    yield from _traverse_tables(scope)
    602    yield from _traverse_subqueries(scope)
    603
    604
    605def _traverse_union(scope):
    606    prev_scope = None
    607    union_scope_stack = [scope]
    608    expression_stack = [scope.expression.right, scope.expression.left]
    609
    610    while expression_stack:
    611        expression = expression_stack.pop()
    612        union_scope = union_scope_stack[-1]
    613
    614        new_scope = union_scope.branch(
    615            expression,
    616            outer_columns=union_scope.outer_columns,
    617            scope_type=ScopeType.UNION,
    618        )
    619
    620        if isinstance(expression, exp.SetOperation):
    621            yield from _traverse_ctes(new_scope)
    622
    623            union_scope_stack.append(new_scope)
    624            expression_stack.extend([expression.right, expression.left])
    625            continue
    626
    627        for scope in _traverse_scope(new_scope):
    628            yield scope
    629
    630        if prev_scope:
    631            union_scope_stack.pop()
    632            union_scope.union_scopes = [prev_scope, scope]
    633            prev_scope = union_scope
    634
    635            yield union_scope
    636        else:
    637            prev_scope = scope
    638
    639
    640def _traverse_ctes(scope):
    641    sources = {}
    642
    643    for cte in scope.ctes:
    644        cte_name = cte.alias
    645
    646        # if the scope is a recursive cte, it must be in the form of base_case UNION recursive.
    647        # thus the recursive scope is the first section of the union.
    648        with_ = scope.expression.args.get("with")
    649        if with_ and with_.recursive:
    650            union = cte.this
    651
    652            if isinstance(union, exp.SetOperation):
    653                sources[cte_name] = scope.branch(union.this, scope_type=ScopeType.CTE)
    654
    655        child_scope = None
    656
    657        for child_scope in _traverse_scope(
    658            scope.branch(
    659                cte.this,
    660                cte_sources=sources,
    661                outer_columns=cte.alias_column_names,
    662                scope_type=ScopeType.CTE,
    663            )
    664        ):
    665            yield child_scope
    666
    667        # append the final child_scope yielded
    668        if child_scope:
    669            sources[cte_name] = child_scope
    670            scope.cte_scopes.append(child_scope)
    671
    672    scope.sources.update(sources)
    673    scope.cte_sources.update(sources)
    674
    675
    676def _is_derived_table(expression: exp.Subquery) -> bool:
    677    """
    678    We represent (tbl1 JOIN tbl2) as a Subquery, but it's not really a "derived table",
    679    as it doesn't introduce a new scope. If an alias is present, it shadows all names
    680    under the Subquery, so that's one exception to this rule.
    681    """
    682    return isinstance(expression, exp.Subquery) and bool(
    683        expression.alias or isinstance(expression.this, exp.UNWRAPPED_QUERIES)
    684    )
    685
    686
    687def _is_from_or_join(expression: exp.Expression) -> bool:
    688    """
    689    Determine if `expression` is the FROM or JOIN clause of a SELECT statement.
    690    """
    691    parent = expression.parent
    692
    693    # Subqueries can be arbitrarily nested
    694    while isinstance(parent, exp.Subquery):
    695        parent = parent.parent
    696
    697    return isinstance(parent, (exp.From, exp.Join))
    698
    699
    700def _traverse_tables(scope):
    701    sources = {}
    702
    703    # Traverse FROMs, JOINs, and LATERALs in the order they are defined
    704    expressions = []
    705    from_ = scope.expression.args.get("from")
    706    if from_:
    707        expressions.append(from_.this)
    708
    709    for join in scope.expression.args.get("joins") or []:
    710        expressions.append(join.this)
    711
    712    if isinstance(scope.expression, exp.Table):
    713        expressions.append(scope.expression)
    714
    715    expressions.extend(scope.expression.args.get("laterals") or [])
    716
    717    for expression in expressions:
    718        if isinstance(expression, exp.Final):
    719            expression = expression.this
    720        if isinstance(expression, exp.Table):
    721            table_name = expression.name
    722            source_name = expression.alias_or_name
    723
    724            if table_name in scope.sources and not expression.db:
    725                # This is a reference to a parent source (e.g. a CTE), not an actual table, unless
    726                # it is pivoted, because then we get back a new table and hence a new source.
    727                pivots = expression.args.get("pivots")
    728                if pivots:
    729                    sources[pivots[0].alias] = expression
    730                else:
    731                    sources[source_name] = scope.sources[table_name]
    732            elif source_name in sources:
    733                sources[find_new_name(sources, table_name)] = expression
    734            else:
    735                sources[source_name] = expression
    736
    737            # Make sure to not include the joins twice
    738            if expression is not scope.expression:
    739                expressions.extend(join.this for join in expression.args.get("joins") or [])
    740
    741            continue
    742
    743        if not isinstance(expression, exp.DerivedTable):
    744            continue
    745
    746        if isinstance(expression, exp.UDTF):
    747            lateral_sources = sources
    748            scope_type = ScopeType.UDTF
    749            scopes = scope.udtf_scopes
    750        elif _is_derived_table(expression):
    751            lateral_sources = None
    752            scope_type = ScopeType.DERIVED_TABLE
    753            scopes = scope.derived_table_scopes
    754            expressions.extend(join.this for join in expression.args.get("joins") or [])
    755        else:
    756            # Makes sure we check for possible sources in nested table constructs
    757            expressions.append(expression.this)
    758            expressions.extend(join.this for join in expression.args.get("joins") or [])
    759            continue
    760
    761        for child_scope in _traverse_scope(
    762            scope.branch(
    763                expression,
    764                lateral_sources=lateral_sources,
    765                outer_columns=expression.alias_column_names,
    766                scope_type=scope_type,
    767            )
    768        ):
    769            yield child_scope
    770
    771            # Tables without aliases will be set as ""
    772            # This shouldn't be a problem once qualify_columns runs, as it adds aliases on everything.
    773            # Until then, this means that only a single, unaliased derived table is allowed (rather,
    774            # the latest one wins.
    775            sources[expression.alias] = child_scope
    776
    777        # append the final child_scope yielded
    778        scopes.append(child_scope)
    779        scope.table_scopes.append(child_scope)
    780
    781    scope.sources.update(sources)
    782
    783
    784def _traverse_subqueries(scope):
    785    for subquery in scope.subqueries:
    786        top = None
    787        for child_scope in _traverse_scope(scope.branch(subquery, scope_type=ScopeType.SUBQUERY)):
    788            yield child_scope
    789            top = child_scope
    790        scope.subquery_scopes.append(top)
    791
    792
    793def _traverse_udtfs(scope):
    794    if isinstance(scope.expression, exp.Unnest):
    795        expressions = scope.expression.expressions
    796    elif isinstance(scope.expression, exp.Lateral):
    797        expressions = [scope.expression.this]
    798    else:
    799        expressions = []
    800
    801    sources = {}
    802    for expression in expressions:
    803        if _is_derived_table(expression):
    804            top = None
    805            for child_scope in _traverse_scope(
    806                scope.branch(
    807                    expression,
    808                    scope_type=ScopeType.SUBQUERY,
    809                    outer_columns=expression.alias_column_names,
    810                )
    811            ):
    812                yield child_scope
    813                top = child_scope
    814                sources[expression.alias] = child_scope
    815
    816            scope.subquery_scopes.append(top)
    817
    818    scope.sources.update(sources)
    819
    820
    821def walk_in_scope(expression, bfs=True, prune=None):
    822    """
    823    Returns a generator object which visits all nodes in the syntrax tree, stopping at
    824    nodes that start child scopes.
    825
    826    Args:
    827        expression (exp.Expression):
    828        bfs (bool): if set to True the BFS traversal order will be applied,
    829            otherwise the DFS traversal will be used instead.
    830        prune ((node, parent, arg_key) -> bool): callable that returns True if
    831            the generator should stop traversing this branch of the tree.
    832
    833    Yields:
    834        tuple[exp.Expression, Optional[exp.Expression], str]: node, parent, arg key
    835    """
    836    # We'll use this variable to pass state into the dfs generator.
    837    # Whenever we set it to True, we exclude a subtree from traversal.
    838    crossed_scope_boundary = False
    839
    840    for node in expression.walk(
    841        bfs=bfs, prune=lambda n: crossed_scope_boundary or (prune and prune(n))
    842    ):
    843        crossed_scope_boundary = False
    844
    845        yield node
    846
    847        if node is expression:
    848            continue
    849        if (
    850            isinstance(node, exp.CTE)
    851            or (
    852                isinstance(node.parent, (exp.From, exp.Join, exp.Subquery))
    853                and (_is_derived_table(node) or isinstance(node, exp.UDTF))
    854            )
    855            or isinstance(node, exp.UNWRAPPED_QUERIES)
    856        ):
    857            crossed_scope_boundary = True
    858
    859            if isinstance(node, (exp.Subquery, exp.UDTF)):
    860                # The following args are not actually in the inner scope, so we should visit them
    861                for key in ("joins", "laterals", "pivots"):
    862                    for arg in node.args.get(key) or []:
    863                        yield from walk_in_scope(arg, bfs=bfs)
    864
    865
    866def find_all_in_scope(expression, expression_types, bfs=True):
    867    """
    868    Returns a generator object which visits all nodes in this scope and only yields those that
    869    match at least one of the specified expression types.
    870
    871    This does NOT traverse into subscopes.
    872
    873    Args:
    874        expression (exp.Expression):
    875        expression_types (tuple[type]|type): the expression type(s) to match.
    876        bfs (bool): True to use breadth-first search, False to use depth-first.
    877
    878    Yields:
    879        exp.Expression: nodes
    880    """
    881    for expression in walk_in_scope(expression, bfs=bfs):
    882        if isinstance(expression, tuple(ensure_collection(expression_types))):
    883            yield expression
    884
    885
    886def find_in_scope(expression, expression_types, bfs=True):
    887    """
    888    Returns the first node in this scope which matches at least one of the specified types.
    889
    890    This does NOT traverse into subscopes.
    891
    892    Args:
    893        expression (exp.Expression):
    894        expression_types (tuple[type]|type): the expression type(s) to match.
    895        bfs (bool): True to use breadth-first search, False to use depth-first.
    896
    897    Returns:
    898        exp.Expression: the node which matches the criteria or None if no node matching
    899        the criteria was found.
    900    """
    901    return next(find_all_in_scope(expression, expression_types, bfs=bfs), None)

logger = <Logger sqlglot (WARNING)>
TRAVERSABLES = (<class 'sqlglot.expressions.Query'>, <class 'sqlglot.expressions.DDL'>, <class 'sqlglot.expressions.DML'>)
class ScopeType(enum.Enum): View Source

    19class ScopeType(Enum):
    20    ROOT = auto()
    21    SUBQUERY = auto()
    22    DERIVED_TABLE = auto()
    23    CTE = auto()
    24    UNION = auto()
    25    UDTF = auto()

An enumeration.

ROOT = <ScopeType.ROOT: 1>
SUBQUERY = <ScopeType.SUBQUERY: 2>
DERIVED_TABLE = <ScopeType.DERIVED_TABLE: 3>
CTE = <ScopeType.CTE: 4>
UNION = <ScopeType.UNION: 5>
UDTF = <ScopeType.UDTF: 6>
class Scope: View Source

     28class Scope:
     29    """
     30    Selection scope.
     31
     32    Attributes:
     33        expression (exp.Select|exp.SetOperation): Root expression of this scope
     34        sources (dict[str, exp.Table|Scope]): Mapping of source name to either
     35            a Table expression or another Scope instance. For example:
     36                SELECT * FROM x                     {"x": Table(this="x")}
     37                SELECT * FROM x AS y                {"y": Table(this="x")}
     38                SELECT * FROM (SELECT ...) AS y     {"y": Scope(...)}
     39        lateral_sources (dict[str, exp.Table|Scope]): Sources from laterals
     40            For example:
     41                SELECT c FROM x LATERAL VIEW EXPLODE (a) AS c;
     42            The LATERAL VIEW EXPLODE gets x as a source.
     43        cte_sources (dict[str, Scope]): Sources from CTES
     44        outer_columns (list[str]): If this is a derived table or CTE, and the outer query
     45            defines a column list for the alias of this scope, this is that list of columns.
     46            For example:
     47                SELECT * FROM (SELECT ...) AS y(col1, col2)
     48            The inner query would have `["col1", "col2"]` for its `outer_columns`
     49        parent (Scope): Parent scope
     50        scope_type (ScopeType): Type of this scope, relative to it's parent
     51        subquery_scopes (list[Scope]): List of all child scopes for subqueries
     52        cte_scopes (list[Scope]): List of all child scopes for CTEs
     53        derived_table_scopes (list[Scope]): List of all child scopes for derived_tables
     54        udtf_scopes (list[Scope]): List of all child scopes for user defined tabular functions
     55        table_scopes (list[Scope]): derived_table_scopes + udtf_scopes, in the order that they're defined
     56        union_scopes (list[Scope, Scope]): If this Scope is for a Union expression, this will be
     57            a list of the left and right child scopes.
     58    """
     59
     60    def __init__(
     61        self,
     62        expression,
     63        sources=None,
     64        outer_columns=None,
     65        parent=None,
     66        scope_type=ScopeType.ROOT,
     67        lateral_sources=None,
     68        cte_sources=None,
     69        can_be_correlated=None,
     70    ):
     71        self.expression = expression
     72        self.sources = sources or {}
     73        self.lateral_sources = lateral_sources or {}
     74        self.cte_sources = cte_sources or {}
     75        self.sources.update(self.lateral_sources)
     76        self.sources.update(self.cte_sources)
     77        self.outer_columns = outer_columns or []
     78        self.parent = parent
     79        self.scope_type = scope_type
     80        self.subquery_scopes = []
     81        self.derived_table_scopes = []
     82        self.table_scopes = []
     83        self.cte_scopes = []
     84        self.union_scopes = []
     85        self.udtf_scopes = []
     86        self.can_be_correlated = can_be_correlated
     87        self.clear_cache()
     88
     89    def clear_cache(self):
     90        self._collected = False
     91        self._raw_columns = None
     92        self._stars = None
     93        self._derived_tables = None
     94        self._udtfs = None
     95        self._tables = None
     96        self._ctes = None
     97        self._subqueries = None
     98        self._selected_sources = None
     99        self._columns = None
    100        self._external_columns = None
    101        self._join_hints = None
    102        self._pivots = None
    103        self._references = None
    104        self._semi_anti_join_tables = None
    105
    106    def branch(
    107        self, expression, scope_type, sources=None, cte_sources=None, lateral_sources=None, **kwargs
    108    ):
    109        """Branch from the current scope to a new, inner scope"""
    110        return Scope(
    111            expression=expression.unnest(),
    112            sources=sources.copy() if sources else None,
    113            parent=self,
    114            scope_type=scope_type,
    115            cte_sources={**self.cte_sources, **(cte_sources or {})},
    116            lateral_sources=lateral_sources.copy() if lateral_sources else None,
    117            can_be_correlated=self.can_be_correlated
    118            or scope_type in (ScopeType.SUBQUERY, ScopeType.UDTF),
    119            **kwargs,
    120        )
    121
    122    def _collect(self):
    123        self._tables = []
    124        self._ctes = []
    125        self._subqueries = []
    126        self._derived_tables = []
    127        self._udtfs = []
    128        self._raw_columns = []
    129        self._stars = []
    130        self._join_hints = []
    131        self._semi_anti_join_tables = set()
    132
    133        for node in self.walk(bfs=False):
    134            if node is self.expression:
    135                continue
    136
    137            if isinstance(node, exp.Dot) and node.is_star:
    138                self._stars.append(node)
    139            elif isinstance(node, exp.Column):
    140                if isinstance(node.this, exp.Star):
    141                    self._stars.append(node)
    142                else:
    143                    self._raw_columns.append(node)
    144            elif isinstance(node, exp.Table) and not isinstance(node.parent, exp.JoinHint):
    145                parent = node.parent
    146                if isinstance(parent, exp.Join) and parent.is_semi_or_anti_join:
    147                    self._semi_anti_join_tables.add(node.alias_or_name)
    148
    149                self._tables.append(node)
    150            elif isinstance(node, exp.JoinHint):
    151                self._join_hints.append(node)
    152            elif isinstance(node, exp.UDTF):
    153                self._udtfs.append(node)
    154            elif isinstance(node, exp.CTE):
    155                self._ctes.append(node)
    156            elif _is_derived_table(node) and _is_from_or_join(node):
    157                self._derived_tables.append(node)
    158            elif isinstance(node, exp.UNWRAPPED_QUERIES):
    159                self._subqueries.append(node)
    160
    161        self._collected = True
    162
    163    def _ensure_collected(self):
    164        if not self._collected:
    165            self._collect()
    166
    167    def walk(self, bfs=True, prune=None):
    168        return walk_in_scope(self.expression, bfs=bfs, prune=None)
    169
    170    def find(self, *expression_types, bfs=True):
    171        return find_in_scope(self.expression, expression_types, bfs=bfs)
    172
    173    def find_all(self, *expression_types, bfs=True):
    174        return find_all_in_scope(self.expression, expression_types, bfs=bfs)
    175
    176    def replace(self, old, new):
    177        """
    178        Replace `old` with `new`.
    179
    180        This can be used instead of `exp.Expression.replace` to ensure the `Scope` is kept up-to-date.
    181
    182        Args:
    183            old (exp.Expression): old node
    184            new (exp.Expression): new node
    185        """
    186        old.replace(new)
    187        self.clear_cache()
    188
    189    @property
    190    def tables(self):
    191        """
    192        List of tables in this scope.
    193
    194        Returns:
    195            list[exp.Table]: tables
    196        """
    197        self._ensure_collected()
    198        return self._tables
    199
    200    @property
    201    def ctes(self):
    202        """
    203        List of CTEs in this scope.
    204
    205        Returns:
    206            list[exp.CTE]: ctes
    207        """
    208        self._ensure_collected()
    209        return self._ctes
    210
    211    @property
    212    def derived_tables(self):
    213        """
    214        List of derived tables in this scope.
    215
    216        For example:
    217            SELECT * FROM (SELECT ...) <- that's a derived table
    218
    219        Returns:
    220            list[exp.Subquery]: derived tables
    221        """
    222        self._ensure_collected()
    223        return self._derived_tables
    224
    225    @property
    226    def udtfs(self):
    227        """
    228        List of "User Defined Tabular Functions" in this scope.
    229
    230        Returns:
    231            list[exp.UDTF]: UDTFs
    232        """
    233        self._ensure_collected()
    234        return self._udtfs
    235
    236    @property
    237    def subqueries(self):
    238        """
    239        List of subqueries in this scope.
    240
    241        For example:
    242            SELECT * FROM x WHERE a IN (SELECT ...) <- that's a subquery
    243
    244        Returns:
    245            list[exp.Select | exp.SetOperation]: subqueries
    246        """
    247        self._ensure_collected()
    248        return self._subqueries
    249
    250    @property
    251    def stars(self) -> t.List[exp.Column | exp.Dot]:
    252        """
    253        List of star expressions (columns or dots) in this scope.
    254        """
    255        self._ensure_collected()
    256        return self._stars
    257
    258    @property
    259    def columns(self):
    260        """
    261        List of columns in this scope.
    262
    263        Returns:
    264            list[exp.Column]: Column instances in this scope, plus any
    265                Columns that reference this scope from correlated subqueries.
    266        """
    267        if self._columns is None:
    268            self._ensure_collected()
    269            columns = self._raw_columns
    270
    271            external_columns = [
    272                column
    273                for scope in itertools.chain(
    274                    self.subquery_scopes,
    275                    self.udtf_scopes,
    276                    (dts for dts in self.derived_table_scopes if dts.can_be_correlated),
    277                )
    278                for column in scope.external_columns
    279            ]
    280
    281            named_selects = set(self.expression.named_selects)
    282
    283            self._columns = []
    284            for column in columns + external_columns:
    285                ancestor = column.find_ancestor(
    286                    exp.Select,
    287                    exp.Qualify,
    288                    exp.Order,
    289                    exp.Having,
    290                    exp.Hint,
    291                    exp.Table,
    292                    exp.Star,
    293                    exp.Distinct,
    294                )
    295                if (
    296                    not ancestor
    297                    or column.table
    298                    or isinstance(ancestor, exp.Select)
    299                    or (isinstance(ancestor, exp.Table) and not isinstance(ancestor.this, exp.Func))
    300                    or (
    301                        isinstance(ancestor, (exp.Order, exp.Distinct))
    302                        and (
    303                            isinstance(ancestor.parent, (exp.Window, exp.WithinGroup))
    304                            or column.name not in named_selects
    305                        )
    306                    )
    307                    or (isinstance(ancestor, exp.Star) and not column.arg_key == "except")
    308                ):
    309                    self._columns.append(column)
    310
    311        return self._columns
    312
    313    @property
    314    def selected_sources(self):
    315        """
    316        Mapping of nodes and sources that are actually selected from in this scope.
    317
    318        That is, all tables in a schema are selectable at any point. But a
    319        table only becomes a selected source if it's included in a FROM or JOIN clause.
    320
    321        Returns:
    322            dict[str, (exp.Table|exp.Select, exp.Table|Scope)]: selected sources and nodes
    323        """
    324        if self._selected_sources is None:
    325            result = {}
    326
    327            for name, node in self.references:
    328                if name in self._semi_anti_join_tables:
    329                    # The RHS table of SEMI/ANTI joins shouldn't be collected as a
    330                    # selected source
    331                    continue
    332
    333                if name in result:
    334                    raise OptimizeError(f"Alias already used: {name}")
    335                if name in self.sources:
    336                    result[name] = (node, self.sources[name])
    337
    338            self._selected_sources = result
    339        return self._selected_sources
    340
    341    @property
    342    def references(self) -> t.List[t.Tuple[str, exp.Expression]]:
    343        if self._references is None:
    344            self._references = []
    345
    346            for table in self.tables:
    347                self._references.append((table.alias_or_name, table))
    348            for expression in itertools.chain(self.derived_tables, self.udtfs):
    349                self._references.append(
    350                    (
    351                        expression.alias,
    352                        expression if expression.args.get("pivots") else expression.unnest(),
    353                    )
    354                )
    355
    356        return self._references
    357
    358    @property
    359    def external_columns(self):
    360        """
    361        Columns that appear to reference sources in outer scopes.
    362
    363        Returns:
    364            list[exp.Column]: Column instances that don't reference
    365                sources in the current scope.
    366        """
    367        if self._external_columns is None:
    368            if isinstance(self.expression, exp.SetOperation):
    369                left, right = self.union_scopes
    370                self._external_columns = left.external_columns + right.external_columns
    371            else:
    372                self._external_columns = [
    373                    c
    374                    for c in self.columns
    375                    if c.table not in self.selected_sources
    376                    and c.table not in self.semi_or_anti_join_tables
    377                ]
    378
    379        return self._external_columns
    380
    381    @property
    382    def unqualified_columns(self):
    383        """
    384        Unqualified columns in the current scope.
    385
    386        Returns:
    387             list[exp.Column]: Unqualified columns
    388        """
    389        return [c for c in self.columns if not c.table]
    390
    391    @property
    392    def join_hints(self):
    393        """
    394        Hints that exist in the scope that reference tables
    395
    396        Returns:
    397            list[exp.JoinHint]: Join hints that are referenced within the scope
    398        """
    399        if self._join_hints is None:
    400            return []
    401        return self._join_hints
    402
    403    @property
    404    def pivots(self):
    405        if not self._pivots:
    406            self._pivots = [
    407                pivot for _, node in self.references for pivot in node.args.get("pivots") or []
    408            ]
    409
    410        return self._pivots
    411
    412    @property
    413    def semi_or_anti_join_tables(self):
    414        return self._semi_anti_join_tables or set()
    415
    416    def source_columns(self, source_name):
    417        """
    418        Get all columns in the current scope for a particular source.
    419
    420        Args:
    421            source_name (str): Name of the source
    422        Returns:
    423            list[exp.Column]: Column instances that reference `source_name`
    424        """
    425        return [column for column in self.columns if column.table == source_name]
    426
    427    @property
    428    def is_subquery(self):
    429        """Determine if this scope is a subquery"""
    430        return self.scope_type == ScopeType.SUBQUERY
    431
    432    @property
    433    def is_derived_table(self):
    434        """Determine if this scope is a derived table"""
    435        return self.scope_type == ScopeType.DERIVED_TABLE
    436
    437    @property
    438    def is_union(self):
    439        """Determine if this scope is a union"""
    440        return self.scope_type == ScopeType.UNION
    441
    442    @property
    443    def is_cte(self):
    444        """Determine if this scope is a common table expression"""
    445        return self.scope_type == ScopeType.CTE
    446
    447    @property
    448    def is_root(self):
    449        """Determine if this is the root scope"""
    450        return self.scope_type == ScopeType.ROOT
    451
    452    @property
    453    def is_udtf(self):
    454        """Determine if this scope is a UDTF (User Defined Table Function)"""
    455        return self.scope_type == ScopeType.UDTF
    456
    457    @property
    458    def is_correlated_subquery(self):
    459        """Determine if this scope is a correlated subquery"""
    460        return bool(self.can_be_correlated and self.external_columns)
    461
    462    def rename_source(self, old_name, new_name):
    463        """Rename a source in this scope"""
    464        columns = self.sources.pop(old_name or "", [])
    465        self.sources[new_name] = columns
    466
    467    def add_source(self, name, source):
    468        """Add a source to this scope"""
    469        self.sources[name] = source
    470        self.clear_cache()
    471
    472    def remove_source(self, name):
    473        """Remove a source from this scope"""
    474        self.sources.pop(name, None)
    475        self.clear_cache()
    476
    477    def __repr__(self):
    478        return f"Scope<{self.expression.sql()}>"
    479
    480    def traverse(self):
    481        """
    482        Traverse the scope tree from this node.
    483
    484        Yields:
    485            Scope: scope instances in depth-first-search post-order
    486        """
    487        stack = [self]
    488        result = []
    489        while stack:
    490            scope = stack.pop()
    491            result.append(scope)
    492            stack.extend(
    493                itertools.chain(
    494                    scope.cte_scopes,
    495                    scope.union_scopes,
    496                    scope.table_scopes,
    497                    scope.subquery_scopes,
    498                )
    499            )
    500
    501        yield from reversed(result)
    502
    503    def ref_count(self):
    504        """
    505        Count the number of times each scope in this tree is referenced.
    506
    507        Returns:
    508            dict[int, int]: Mapping of Scope instance ID to reference count
    509        """
    510        scope_ref_count = defaultdict(lambda: 0)
    511
    512        for scope in self.traverse():
    513            for _, source in scope.selected_sources.values():
    514                scope_ref_count[id(source)] += 1
    515
    516        return scope_ref_count

Selection scope.

###### Attributes:

- expression (exp.Select|exp.SetOperation): Root expression of this scope
- sources (dict[str, exp.Table|Scope]): Mapping of source name to either a Table expression or another Scope instance. For example: SELECT * FROM x {"x": Table(this="x")} SELECT * FROM x AS y {"y": Table(this="x")} SELECT * FROM (SELECT ...) AS y {"y": Scope(...)}
- lateral_sources (dict[str, exp.Table|Scope]): Sources from laterals For example: SELECT c FROM x LATERAL VIEW EXPLODE (a) AS c; The LATERAL VIEW EXPLODE gets x as a source.
- cte_sources (dict[str, Scope]): Sources from CTES
- outer_columns (list[str]): If this is a derived table or CTE, and the outer query defines a column list for the alias of this scope, this is that list of columns. For example: SELECT * FROM (SELECT ...) AS y(col1, col2) The inner query would have `["col1", "col2"]` for its `outer_columns`
- parent (Scope): Parent scope
- scope_type (ScopeType): Type of this scope, relative to it's parent
- subquery_scopes (list[Scope]): List of all child scopes for subqueries
- cte_scopes (list[Scope]): List of all child scopes for CTEs
- derived_table_scopes (list[Scope]): List of all child scopes for derived_tables
- udtf_scopes (list[Scope]): List of all child scopes for user defined tabular functions
- table_scopes (list[Scope]): derived_table_scopes + udtf_scopes, in the order that they're defined
- union_scopes (list[Scope, Scope]): If this Scope is for a Union expression, this will be a list of the left and right child scopes.

Scope( expression, sources=None, outer_columns=None, parent=None, scope_type=<ScopeType.ROOT: 1>, lateral_sources=None, cte_sources=None, can_be_correlated=None) View Source

    60    def __init__(
    61        self,
    62        expression,
    63        sources=None,
    64        outer_columns=None,
    65        parent=None,
    66        scope_type=ScopeType.ROOT,
    67        lateral_sources=None,
    68        cte_sources=None,
    69        can_be_correlated=None,
    70    ):
    71        self.expression = expression
    72        self.sources = sources or {}
    73        self.lateral_sources = lateral_sources or {}
    74        self.cte_sources = cte_sources or {}
    75        self.sources.update(self.lateral_sources)
    76        self.sources.update(self.cte_sources)
    77        self.outer_columns = outer_columns or []
    78        self.parent = parent
    79        self.scope_type = scope_type
    80        self.subquery_scopes = []
    81        self.derived_table_scopes = []
    82        self.table_scopes = []
    83        self.cte_scopes = []
    84        self.union_scopes = []
    85        self.udtf_scopes = []
    86        self.can_be_correlated = can_be_correlated
    87        self.clear_cache()

expression
sources
lateral_sources
cte_sources
outer_columns
parent
scope_type
subquery_scopes
derived_table_scopes
table_scopes
cte_scopes
union_scopes
udtf_scopes
can_be_correlated
def clear_cache(self): View Source

     89    def clear_cache(self):
     90        self._collected = False
     91        self._raw_columns = None
     92        self._stars = None
     93        self._derived_tables = None
     94        self._udtfs = None
     95        self._tables = None
     96        self._ctes = None
     97        self._subqueries = None
     98        self._selected_sources = None
     99        self._columns = None
    100        self._external_columns = None
    101        self._join_hints = None
    102        self._pivots = None
    103        self._references = None
    104        self._semi_anti_join_tables = None

def branch( self, expression, scope_type, sources=None, cte_sources=None, lateral_sources=None, **kwargs): View Source

    106    def branch(
    107        self, expression, scope_type, sources=None, cte_sources=None, lateral_sources=None, **kwargs
    108    ):
    109        """Branch from the current scope to a new, inner scope"""
    110        return Scope(
    111            expression=expression.unnest(),
    112            sources=sources.copy() if sources else None,
    113            parent=self,
    114            scope_type=scope_type,
    115            cte_sources={**self.cte_sources, **(cte_sources or {})},
    116            lateral_sources=lateral_sources.copy() if lateral_sources else None,
    117            can_be_correlated=self.can_be_correlated
    118            or scope_type in (ScopeType.SUBQUERY, ScopeType.UDTF),
    119            **kwargs,
    120        )

Branch from the current scope to a new, inner scope

def walk(self, bfs=True, prune=None): View Source

    167    def walk(self, bfs=True, prune=None):
    168        return walk_in_scope(self.expression, bfs=bfs, prune=None)

def find(self, *expression_types, bfs=True): View Source

    170    def find(self, *expression_types, bfs=True):
    171        return find_in_scope(self.expression, expression_types, bfs=bfs)

def find_all(self, *expression_types, bfs=True): View Source

    173    def find_all(self, *expression_types, bfs=True):
    174        return find_all_in_scope(self.expression, expression_types, bfs=bfs)

def replace(self, old, new): View Source

    176    def replace(self, old, new):
    177        """
    178        Replace `old` with `new`.
    179
    180        This can be used instead of `exp.Expression.replace` to ensure the `Scope` is kept up-to-date.
    181
    182        Args:
    183            old (exp.Expression): old node
    184            new (exp.Expression): new node
    185        """
    186        old.replace(new)
    187        self.clear_cache()

Replace `old` with `new`.

This can be used instead of `exp.Expression.replace` to ensure the `Scope` is kept up-to-date.

###### Arguments:

- old (exp.Expression): old node
- new (exp.Expression): new node

tables View Source

    189    @property
    190    def tables(self):
    191        """
    192        List of tables in this scope.
    193
    194        Returns:
    195            list[exp.Table]: tables
    196        """
    197        self._ensure_collected()
    198        return self._tables

List of tables in this scope.

###### Returns:

> list[exp.Table]: tables

ctes View Source

    200    @property
    201    def ctes(self):
    202        """
    203        List of CTEs in this scope.
    204
    205        Returns:
    206            list[exp.CTE]: ctes
    207        """
    208        self._ensure_collected()
    209        return self._ctes

List of CTEs in this scope.

###### Returns:

> list[exp.CTE]: ctes

derived_tables View Source

    211    @property
    212    def derived_tables(self):
    213        """
    214        List of derived tables in this scope.
    215
    216        For example:
    217            SELECT * FROM (SELECT ...) <- that's a derived table
    218
    219        Returns:
    220            list[exp.Subquery]: derived tables
    221        """
    222        self._ensure_collected()
    223        return self._derived_tables

List of derived tables in this scope.

###### For example:

> SELECT * FROM (SELECT ...) <- that's a derived table

###### Returns:

> list[exp.Subquery]: derived tables

udtfs View Source

    225    @property
    226    def udtfs(self):
    227        """
    228        List of "User Defined Tabular Functions" in this scope.
    229
    230        Returns:
    231            list[exp.UDTF]: UDTFs
    232        """
    233        self._ensure_collected()
    234        return self._udtfs

List of "User Defined Tabular Functions" in this scope.

###### Returns:

> list[exp.UDTF]: UDTFs

subqueries View Source

    236    @property
    237    def subqueries(self):
    238        """
    239        List of subqueries in this scope.
    240
    241        For example:
    242            SELECT * FROM x WHERE a IN (SELECT ...) <- that's a subquery
    243
    244        Returns:
    245            list[exp.Select | exp.SetOperation]: subqueries
    246        """
    247        self._ensure_collected()
    248        return self._subqueries

List of subqueries in this scope.

###### For example:

> SELECT * FROM x WHERE a IN (SELECT ...) <- that's a subquery

###### Returns:

> list[exp.Select | exp.SetOperation]: subqueries

stars: List[sqlglot.expressions.Column | sqlglot.expressions.Dot] View Source

    250    @property
    251    def stars(self) -> t.List[exp.Column | exp.Dot]:
    252        """
    253        List of star expressions (columns or dots) in this scope.
    254        """
    255        self._ensure_collected()
    256        return self._stars

List of star expressions (columns or dots) in this scope.

columns View Source

    258    @property
    259    def columns(self):
    260        """
    261        List of columns in this scope.
    262
    263        Returns:
    264            list[exp.Column]: Column instances in this scope, plus any
    265                Columns that reference this scope from correlated subqueries.
    266        """
    267        if self._columns is None:
    268            self._ensure_collected()
    269            columns = self._raw_columns
    270
    271            external_columns = [
    272                column
    273                for scope in itertools.chain(
    274                    self.subquery_scopes,
    275                    self.udtf_scopes,
    276                    (dts for dts in self.derived_table_scopes if dts.can_be_correlated),
    277                )
    278                for column in scope.external_columns
    279            ]
    280
    281            named_selects = set(self.expression.named_selects)
    282
    283            self._columns = []
    284            for column in columns + external_columns:
    285                ancestor = column.find_ancestor(
    286                    exp.Select,
    287                    exp.Qualify,
    288                    exp.Order,
    289                    exp.Having,
    290                    exp.Hint,
    291                    exp.Table,
    292                    exp.Star,
    293                    exp.Distinct,
    294                )
    295                if (
    296                    not ancestor
    297                    or column.table
    298                    or isinstance(ancestor, exp.Select)
    299                    or (isinstance(ancestor, exp.Table) and not isinstance(ancestor.this, exp.Func))
    300                    or (
    301                        isinstance(ancestor, (exp.Order, exp.Distinct))
    302                        and (
    303                            isinstance(ancestor.parent, (exp.Window, exp.WithinGroup))
    304                            or column.name not in named_selects
    305                        )
    306                    )
    307                    or (isinstance(ancestor, exp.Star) and not column.arg_key == "except")
    308                ):
    309                    self._columns.append(column)
    310
    311        return self._columns

List of columns in this scope.

###### Returns:

> list[exp.Column]: Column instances in this scope, plus any Columns that reference this scope from correlated subqueries.

selected_sources View Source

    313    @property
    314    def selected_sources(self):
    315        """
    316        Mapping of nodes and sources that are actually selected from in this scope.
    317
    318        That is, all tables in a schema are selectable at any point. But a
    319        table only becomes a selected source if it's included in a FROM or JOIN clause.
    320
    321        Returns:
    322            dict[str, (exp.Table|exp.Select, exp.Table|Scope)]: selected sources and nodes
    323        """
    324        if self._selected_sources is None:
    325            result = {}
    326
    327            for name, node in self.references:
    328                if name in self._semi_anti_join_tables:
    329                    # The RHS table of SEMI/ANTI joins shouldn't be collected as a
    330                    # selected source
    331                    continue
    332
    333                if name in result:
    334                    raise OptimizeError(f"Alias already used: {name}")
    335                if name in self.sources:
    336                    result[name] = (node, self.sources[name])
    337
    338            self._selected_sources = result
    339        return self._selected_sources

Mapping of nodes and sources that are actually selected from in this scope.

That is, all tables in a schema are selectable at any point. But a table only becomes a selected source if it's included in a FROM or JOIN clause.

###### Returns:

> dict[str, (exp.Table|exp.Select, exp.Table|Scope)]: selected sources and nodes

references: List[Tuple[str, sqlglot.expressions.Expression]] View Source

    341    @property
    342    def references(self) -> t.List[t.Tuple[str, exp.Expression]]:
    343        if self._references is None:
    344            self._references = []
    345
    346            for table in self.tables:
    347                self._references.append((table.alias_or_name, table))
    348            for expression in itertools.chain(self.derived_tables, self.udtfs):
    349                self._references.append(
    350                    (
    351                        expression.alias,
    352                        expression if expression.args.get("pivots") else expression.unnest(),
    353                    )
    354                )
    355
    356        return self._references

external_columns View Source

    358    @property
    359    def external_columns(self):
    360        """
    361        Columns that appear to reference sources in outer scopes.
    362
    363        Returns:
    364            list[exp.Column]: Column instances that don't reference
    365                sources in the current scope.
    366        """
    367        if self._external_columns is None:
    368            if isinstance(self.expression, exp.SetOperation):
    369                left, right = self.union_scopes
    370                self._external_columns = left.external_columns + right.external_columns
    371            else:
    372                self._external_columns = [
    373                    c
    374                    for c in self.columns
    375                    if c.table not in self.selected_sources
    376                    and c.table not in self.semi_or_anti_join_tables
    377                ]
    378
    379        return self._external_columns

Columns that appear to reference sources in outer scopes.

###### Returns:

> list[exp.Column]: Column instances that don't reference sources in the current scope.

unqualified_columns View Source

    381    @property
    382    def unqualified_columns(self):
    383        """
    384        Unqualified columns in the current scope.
    385
    386        Returns:
    387             list[exp.Column]: Unqualified columns
    388        """
    389        return [c for c in self.columns if not c.table]

Unqualified columns in the current scope.

###### Returns:

> list[exp.Column]: Unqualified columns

join_hints View Source

    391    @property
    392    def join_hints(self):
    393        """
    394        Hints that exist in the scope that reference tables
    395
    396        Returns:
    397            list[exp.JoinHint]: Join hints that are referenced within the scope
    398        """
    399        if self._join_hints is None:
    400            return []
    401        return self._join_hints

Hints that exist in the scope that reference tables

###### Returns:

> list[exp.JoinHint]: Join hints that are referenced within the scope

pivots View Source

    403    @property
    404    def pivots(self):
    405        if not self._pivots:
    406            self._pivots = [
    407                pivot for _, node in self.references for pivot in node.args.get("pivots") or []
    408            ]
    409
    410        return self._pivots

semi_or_anti_join_tables View Source

    412    @property
    413    def semi_or_anti_join_tables(self):
    414        return self._semi_anti_join_tables or set()

def source_columns(self, source_name): View Source

    416    def source_columns(self, source_name):
    417        """
    418        Get all columns in the current scope for a particular source.
    419
    420        Args:
    421            source_name (str): Name of the source
    422        Returns:
    423            list[exp.Column]: Column instances that reference `source_name`
    424        """
    425        return [column for column in self.columns if column.table == source_name]

Get all columns in the current scope for a particular source.

###### Arguments:

- source_name (str): Name of the source

###### Returns:

> list[exp.Column]: Column instances that reference `source_name`

is_subquery View Source

    427    @property
    428    def is_subquery(self):
    429        """Determine if this scope is a subquery"""
    430        return self.scope_type == ScopeType.SUBQUERY

Determine if this scope is a subquery

is_derived_table View Source

    432    @property
    433    def is_derived_table(self):
    434        """Determine if this scope is a derived table"""
    435        return self.scope_type == ScopeType.DERIVED_TABLE

Determine if this scope is a derived table

is_union View Source

    437    @property
    438    def is_union(self):
    439        """Determine if this scope is a union"""
    440        return self.scope_type == ScopeType.UNION

Determine if this scope is a union

is_cte View Source

    442    @property
    443    def is_cte(self):
    444        """Determine if this scope is a common table expression"""
    445        return self.scope_type == ScopeType.CTE

Determine if this scope is a common table expression

is_root View Source

    447    @property
    448    def is_root(self):
    449        """Determine if this is the root scope"""
    450        return self.scope_type == ScopeType.ROOT

Determine if this is the root scope

is_udtf View Source

    452    @property
    453    def is_udtf(self):
    454        """Determine if this scope is a UDTF (User Defined Table Function)"""
    455        return self.scope_type == ScopeType.UDTF

Determine if this scope is a UDTF (User Defined Table Function)

is_correlated_subquery View Source

    457    @property
    458    def is_correlated_subquery(self):
    459        """Determine if this scope is a correlated subquery"""
    460        return bool(self.can_be_correlated and self.external_columns)

Determine if this scope is a correlated subquery

def rename_source(self, old_name, new_name): View Source

    462    def rename_source(self, old_name, new_name):
    463        """Rename a source in this scope"""
    464        columns = self.sources.pop(old_name or "", [])
    465        self.sources[new_name] = columns

Rename a source in this scope

def add_source(self, name, source): View Source

    467    def add_source(self, name, source):
    468        """Add a source to this scope"""
    469        self.sources[name] = source
    470        self.clear_cache()

Add a source to this scope

def remove_source(self, name): View Source

    472    def remove_source(self, name):
    473        """Remove a source from this scope"""
    474        self.sources.pop(name, None)
    475        self.clear_cache()

Remove a source from this scope

def traverse(self): View Source

    480    def traverse(self):
    481        """
    482        Traverse the scope tree from this node.
    483
    484        Yields:
    485            Scope: scope instances in depth-first-search post-order
    486        """
    487        stack = [self]
    488        result = []
    489        while stack:
    490            scope = stack.pop()
    491            result.append(scope)
    492            stack.extend(
    493                itertools.chain(
    494                    scope.cte_scopes,
    495                    scope.union_scopes,
    496                    scope.table_scopes,
    497                    scope.subquery_scopes,
    498                )
    499            )
    500
    501        yield from reversed(result)

Traverse the scope tree from this node.

###### Yields:

> Scope: scope instances in depth-first-search post-order

def ref_count(self): View Source

    503    def ref_count(self):
    504        """
    505        Count the number of times each scope in this tree is referenced.
    506
    507        Returns:
    508            dict[int, int]: Mapping of Scope instance ID to reference count
    509        """
    510        scope_ref_count = defaultdict(lambda: 0)
    511
    512        for scope in self.traverse():
    513            for _, source in scope.selected_sources.values():
    514                scope_ref_count[id(source)] += 1
    515
    516        return scope_ref_count

Count the number of times each scope in this tree is referenced.

###### Returns:

> dict[int, int]: Mapping of Scope instance ID to reference count

def traverse_scope( expression: sqlglot.expressions.Expression) -> List[Scope]: View Source

    519def traverse_scope(expression: exp.Expression) -> t.List[Scope]:
    520    """
    521    Traverse an expression by its "scopes".
    522
    523    "Scope" represents the current context of a Select statement.
    524
    525    This is helpful for optimizing queries, where we need more information than
    526    the expression tree itself. For example, we might care about the source
    527    names within a subquery. Returns a list because a generator could result in
    528    incomplete properties which is confusing.
    529
    530    Examples:
    531        >>> import sqlglot
    532        >>> expression = sqlglot.parse_one("SELECT a FROM (SELECT a FROM x) AS y")
    533        >>> scopes = traverse_scope(expression)
    534        >>> scopes[0].expression.sql(), list(scopes[0].sources)
    535        ('SELECT a FROM x', ['x'])
    536        >>> scopes[1].expression.sql(), list(scopes[1].sources)
    537        ('SELECT a FROM (SELECT a FROM x) AS y', ['y'])
    538
    539    Args:
    540        expression: Expression to traverse
    541
    542    Returns:
    543        A list of the created scope instances
    544    """
    545    if isinstance(expression, TRAVERSABLES):
    546        return list(_traverse_scope(Scope(expression)))
    547    return []

Traverse an expression by its "scopes".

"Scope" represents the current context of a Select statement.

This is helpful for optimizing queries, where we need more information than the expression tree itself. For example, we might care about the source names within a subquery. Returns a list because a generator could result in incomplete properties which is confusing.

###### Examples:

>     >>> import sqlglot
>     >>> expression = sqlglot.parse_one("SELECT a FROM (SELECT a FROM x) AS y")
>     >>> scopes = traverse_scope(expression)
>     >>> scopes[0].expression.sql(), list(scopes[0].sources)
>     ('SELECT a FROM x', ['x'])
>     >>> scopes[1].expression.sql(), list(scopes[1].sources)
>     ('SELECT a FROM (SELECT a FROM x) AS y', ['y'])

###### Arguments:

- expression: Expression to traverse

###### Returns:

> A list of the created scope instances

def build_scope( expression: sqlglot.expressions.Expression) -> Optional[Scope]: View Source

    550def build_scope(expression: exp.Expression) -> t.Optional[Scope]:
    551    """
    552    Build a scope tree.
    553
    554    Args:
    555        expression: Expression to build the scope tree for.
    556
    557    Returns:
    558        The root scope
    559    """
    560    return seq_get(traverse_scope(expression), -1)

Build a scope tree.

###### Arguments:

- expression: Expression to build the scope tree for.

###### Returns:

> The root scope

def walk_in_scope(expression, bfs=True, prune=None): View Source

    822def walk_in_scope(expression, bfs=True, prune=None):
    823    """
    824    Returns a generator object which visits all nodes in the syntrax tree, stopping at
    825    nodes that start child scopes.
    826
    827    Args:
    828        expression (exp.Expression):
    829        bfs (bool): if set to True the BFS traversal order will be applied,
    830            otherwise the DFS traversal will be used instead.
    831        prune ((node, parent, arg_key) -> bool): callable that returns True if
    832            the generator should stop traversing this branch of the tree.
    833
    834    Yields:
    835        tuple[exp.Expression, Optional[exp.Expression], str]: node, parent, arg key
    836    """
    837    # We'll use this variable to pass state into the dfs generator.
    838    # Whenever we set it to True, we exclude a subtree from traversal.
    839    crossed_scope_boundary = False
    840
    841    for node in expression.walk(
    842        bfs=bfs, prune=lambda n: crossed_scope_boundary or (prune and prune(n))
    843    ):
    844        crossed_scope_boundary = False
    845
    846        yield node
    847
    848        if node is expression:
    849            continue
    850        if (
    851            isinstance(node, exp.CTE)
    852            or (
    853                isinstance(node.parent, (exp.From, exp.Join, exp.Subquery))
    854                and (_is_derived_table(node) or isinstance(node, exp.UDTF))
    855            )
    856            or isinstance(node, exp.UNWRAPPED_QUERIES)
    857        ):
    858            crossed_scope_boundary = True
    859
    860            if isinstance(node, (exp.Subquery, exp.UDTF)):
    861                # The following args are not actually in the inner scope, so we should visit them
    862                for key in ("joins", "laterals", "pivots"):
    863                    for arg in node.args.get(key) or []:
    864                        yield from walk_in_scope(arg, bfs=bfs)

Returns a generator object which visits all nodes in the syntrax tree, stopping at nodes that start child scopes.

###### Arguments:

- expression (exp.Expression):
- bfs (bool): if set to True the BFS traversal order will be applied, otherwise the DFS traversal will be used instead.
- prune ((node, parent, arg_key) -> bool): callable that returns True if the generator should stop traversing this branch of the tree.

###### Yields:

> tuple[exp.Expression, Optional[exp.Expression], str]: node, parent, arg key

def find_all_in_scope(expression, expression_types, bfs=True): View Source

    867def find_all_in_scope(expression, expression_types, bfs=True):
    868    """
    869    Returns a generator object which visits all nodes in this scope and only yields those that
    870    match at least one of the specified expression types.
    871
    872    This does NOT traverse into subscopes.
    873
    874    Args:
    875        expression (exp.Expression):
    876        expression_types (tuple[type]|type): the expression type(s) to match.
    877        bfs (bool): True to use breadth-first search, False to use depth-first.
    878
    879    Yields:
    880        exp.Expression: nodes
    881    """
    882    for expression in walk_in_scope(expression, bfs=bfs):
    883        if isinstance(expression, tuple(ensure_collection(expression_types))):
    884            yield expression

Returns a generator object which visits all nodes in this scope and only yields those that match at least one of the specified expression types.

This does NOT traverse into subscopes.

###### Arguments:

- expression (exp.Expression):
- expression_types (tuple[type]|type): the expression type(s) to match.
- bfs (bool): True to use breadth-first search, False to use depth-first.

###### Yields:

> exp.Expression: nodes

def find_in_scope(expression, expression_types, bfs=True): View Source

    887def find_in_scope(expression, expression_types, bfs=True):
    888    """
    889    Returns the first node in this scope which matches at least one of the specified types.
    890
    891    This does NOT traverse into subscopes.
    892
    893    Args:
    894        expression (exp.Expression):
    895        expression_types (tuple[type]|type): the expression type(s) to match.
    896        bfs (bool): True to use breadth-first search, False to use depth-first.
    897
    898    Returns:
    899        exp.Expression: the node which matches the criteria or None if no node matching
    900        the criteria was found.
    901    """
    902    return next(find_all_in_scope(expression, expression_types, bfs=bfs), None)

Returns the first node in this scope which matches at least one of the specified types.

This does NOT traverse into subscopes.

###### Arguments:

- expression (exp.Expression):
- expression_types (tuple[type]|type): the expression type(s) to match.
- bfs (bool): True to use breadth-first search, False to use depth-first.

###### Returns:

> exp.Expression: the node which matches the criteria or None if no node matching the criteria was found.