802 lines
26 KiB
Python
802 lines
26 KiB
Python
import itertools
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import logging
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import typing as t
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from collections import defaultdict
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from enum import Enum, auto
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from sqlglot import exp
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from sqlglot.errors import OptimizeError
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from sqlglot.helper import find_new_name
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logger = logging.getLogger("sqlglot")
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class ScopeType(Enum):
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ROOT = auto()
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SUBQUERY = auto()
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DERIVED_TABLE = auto()
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CTE = auto()
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UNION = auto()
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UDTF = auto()
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class Scope:
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"""
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Selection scope.
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Attributes:
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expression (exp.Select|exp.Union): Root expression of this scope
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sources (dict[str, exp.Table|Scope]): Mapping of source name to either
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a Table expression or another Scope instance. For example:
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SELECT * FROM x {"x": Table(this="x")}
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SELECT * FROM x AS y {"y": Table(this="x")}
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SELECT * FROM (SELECT ...) AS y {"y": Scope(...)}
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lateral_sources (dict[str, exp.Table|Scope]): Sources from laterals
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For example:
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SELECT c FROM x LATERAL VIEW EXPLODE (a) AS c;
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The LATERAL VIEW EXPLODE gets x as a source.
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outer_column_list (list[str]): If this is a derived table or CTE, and the outer query
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defines a column list of it's alias of this scope, this is that list of columns.
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For example:
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SELECT * FROM (SELECT ...) AS y(col1, col2)
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The inner query would have `["col1", "col2"]` for its `outer_column_list`
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parent (Scope): Parent scope
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scope_type (ScopeType): Type of this scope, relative to it's parent
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subquery_scopes (list[Scope]): List of all child scopes for subqueries
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cte_scopes (list[Scope]): List of all child scopes for CTEs
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derived_table_scopes (list[Scope]): List of all child scopes for derived_tables
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udtf_scopes (list[Scope]): List of all child scopes for user defined tabular functions
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table_scopes (list[Scope]): derived_table_scopes + udtf_scopes, in the order that they're defined
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union_scopes (list[Scope, Scope]): If this Scope is for a Union expression, this will be
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a list of the left and right child scopes.
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"""
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def __init__(
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self,
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expression,
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sources=None,
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outer_column_list=None,
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parent=None,
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scope_type=ScopeType.ROOT,
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lateral_sources=None,
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):
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self.expression = expression
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self.sources = sources or {}
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self.lateral_sources = lateral_sources.copy() if lateral_sources else {}
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self.sources.update(self.lateral_sources)
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self.outer_column_list = outer_column_list or []
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self.parent = parent
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self.scope_type = scope_type
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self.subquery_scopes = []
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self.derived_table_scopes = []
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self.table_scopes = []
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self.cte_scopes = []
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self.union_scopes = []
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self.udtf_scopes = []
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self.clear_cache()
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def clear_cache(self):
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self._collected = False
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self._raw_columns = None
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self._derived_tables = None
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self._udtfs = None
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self._tables = None
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self._ctes = None
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self._subqueries = None
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self._selected_sources = None
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self._columns = None
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self._external_columns = None
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self._join_hints = None
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self._pivots = None
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self._references = None
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def branch(self, expression, scope_type, chain_sources=None, **kwargs):
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"""Branch from the current scope to a new, inner scope"""
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return Scope(
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expression=expression.unnest(),
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sources={**self.cte_sources, **(chain_sources or {})},
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parent=self,
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scope_type=scope_type,
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**kwargs,
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)
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def _collect(self):
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self._tables = []
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self._ctes = []
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self._subqueries = []
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self._derived_tables = []
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self._udtfs = []
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self._raw_columns = []
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self._join_hints = []
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for node, parent, _ in self.walk(bfs=False):
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if node is self.expression:
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continue
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elif isinstance(node, exp.Column) and not isinstance(node.this, exp.Star):
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self._raw_columns.append(node)
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elif isinstance(node, exp.Table) and not isinstance(node.parent, exp.JoinHint):
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self._tables.append(node)
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elif isinstance(node, exp.JoinHint):
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self._join_hints.append(node)
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elif isinstance(node, exp.UDTF):
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self._udtfs.append(node)
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elif isinstance(node, exp.CTE):
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self._ctes.append(node)
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elif (
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isinstance(node, exp.Subquery)
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and isinstance(parent, (exp.From, exp.Join, exp.Subquery))
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and _is_derived_table(node)
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):
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self._derived_tables.append(node)
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elif isinstance(node, exp.Subqueryable):
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self._subqueries.append(node)
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self._collected = True
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def _ensure_collected(self):
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if not self._collected:
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self._collect()
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def walk(self, bfs=True):
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return walk_in_scope(self.expression, bfs=bfs)
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def find(self, *expression_types, bfs=True):
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"""
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Returns the first node in this scope which matches at least one of the specified types.
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This does NOT traverse into subscopes.
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Args:
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expression_types (type): the expression type(s) to match.
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bfs (bool): True to use breadth-first search, False to use depth-first.
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Returns:
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exp.Expression: the node which matches the criteria or None if no node matching
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the criteria was found.
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"""
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return next(self.find_all(*expression_types, bfs=bfs), None)
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def find_all(self, *expression_types, bfs=True):
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"""
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Returns a generator object which visits all nodes in this scope and only yields those that
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match at least one of the specified expression types.
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This does NOT traverse into subscopes.
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Args:
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expression_types (type): the expression type(s) to match.
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bfs (bool): True to use breadth-first search, False to use depth-first.
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Yields:
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exp.Expression: nodes
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"""
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for expression, *_ in self.walk(bfs=bfs):
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if isinstance(expression, expression_types):
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yield expression
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def replace(self, old, new):
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"""
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Replace `old` with `new`.
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This can be used instead of `exp.Expression.replace` to ensure the `Scope` is kept up-to-date.
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Args:
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old (exp.Expression): old node
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new (exp.Expression): new node
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"""
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old.replace(new)
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self.clear_cache()
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@property
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def tables(self):
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"""
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List of tables in this scope.
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Returns:
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list[exp.Table]: tables
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"""
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self._ensure_collected()
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return self._tables
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@property
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def ctes(self):
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"""
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List of CTEs in this scope.
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Returns:
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list[exp.CTE]: ctes
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"""
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self._ensure_collected()
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return self._ctes
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@property
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def derived_tables(self):
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"""
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List of derived tables in this scope.
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For example:
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SELECT * FROM (SELECT ...) <- that's a derived table
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Returns:
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list[exp.Subquery]: derived tables
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"""
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self._ensure_collected()
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return self._derived_tables
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@property
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def udtfs(self):
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"""
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List of "User Defined Tabular Functions" in this scope.
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Returns:
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list[exp.UDTF]: UDTFs
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"""
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self._ensure_collected()
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return self._udtfs
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@property
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def subqueries(self):
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"""
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List of subqueries in this scope.
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For example:
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SELECT * FROM x WHERE a IN (SELECT ...) <- that's a subquery
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Returns:
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list[exp.Subqueryable]: subqueries
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"""
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self._ensure_collected()
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return self._subqueries
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@property
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def columns(self):
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"""
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List of columns in this scope.
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Returns:
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list[exp.Column]: Column instances in this scope, plus any
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Columns that reference this scope from correlated subqueries.
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"""
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if self._columns is None:
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self._ensure_collected()
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columns = self._raw_columns
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external_columns = [
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column
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for scope in itertools.chain(self.subquery_scopes, self.udtf_scopes)
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for column in scope.external_columns
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]
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named_selects = set(self.expression.named_selects)
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self._columns = []
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for column in columns + external_columns:
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ancestor = column.find_ancestor(
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exp.Select, exp.Qualify, exp.Order, exp.Having, exp.Hint, exp.Table
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)
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if (
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not ancestor
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or column.table
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or isinstance(ancestor, exp.Select)
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or (isinstance(ancestor, exp.Table) and not isinstance(ancestor.this, exp.Func))
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or (
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isinstance(ancestor, exp.Order)
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and (
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isinstance(ancestor.parent, exp.Window)
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or column.name not in named_selects
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)
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)
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):
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self._columns.append(column)
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return self._columns
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@property
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def selected_sources(self):
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"""
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Mapping of nodes and sources that are actually selected from in this scope.
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That is, all tables in a schema are selectable at any point. But a
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table only becomes a selected source if it's included in a FROM or JOIN clause.
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Returns:
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dict[str, (exp.Table|exp.Select, exp.Table|Scope)]: selected sources and nodes
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"""
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if self._selected_sources is None:
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result = {}
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for name, node in self.references:
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if name in result:
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raise OptimizeError(f"Alias already used: {name}")
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if name in self.sources:
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result[name] = (node, self.sources[name])
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self._selected_sources = result
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return self._selected_sources
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@property
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def references(self) -> t.List[t.Tuple[str, exp.Expression]]:
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if self._references is None:
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self._references = []
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for table in self.tables:
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self._references.append((table.alias_or_name, table))
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for expression in itertools.chain(self.derived_tables, self.udtfs):
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self._references.append(
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(
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expression.alias,
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expression if expression.args.get("pivots") else expression.unnest(),
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)
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)
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return self._references
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@property
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def cte_sources(self):
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"""
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Sources that are CTEs.
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Returns:
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dict[str, Scope]: Mapping of source alias to Scope
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"""
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return {
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alias: scope
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for alias, scope in self.sources.items()
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if isinstance(scope, Scope) and scope.is_cte
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}
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@property
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def external_columns(self):
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"""
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Columns that appear to reference sources in outer scopes.
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Returns:
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list[exp.Column]: Column instances that don't reference
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sources in the current scope.
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"""
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if self._external_columns is None:
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self._external_columns = [
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c for c in self.columns if c.table not in self.selected_sources
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]
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return self._external_columns
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@property
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def unqualified_columns(self):
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"""
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Unqualified columns in the current scope.
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Returns:
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list[exp.Column]: Unqualified columns
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"""
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return [c for c in self.columns if not c.table]
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@property
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def join_hints(self):
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"""
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Hints that exist in the scope that reference tables
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Returns:
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list[exp.JoinHint]: Join hints that are referenced within the scope
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"""
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if self._join_hints is None:
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return []
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return self._join_hints
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@property
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def pivots(self):
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if not self._pivots:
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self._pivots = [
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pivot for _, node in self.references for pivot in node.args.get("pivots") or []
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]
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return self._pivots
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def source_columns(self, source_name):
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"""
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Get all columns in the current scope for a particular source.
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Args:
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source_name (str): Name of the source
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Returns:
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list[exp.Column]: Column instances that reference `source_name`
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"""
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return [column for column in self.columns if column.table == source_name]
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@property
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def is_subquery(self):
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"""Determine if this scope is a subquery"""
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return self.scope_type == ScopeType.SUBQUERY
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@property
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def is_derived_table(self):
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"""Determine if this scope is a derived table"""
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return self.scope_type == ScopeType.DERIVED_TABLE
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@property
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def is_union(self):
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"""Determine if this scope is a union"""
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return self.scope_type == ScopeType.UNION
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@property
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def is_cte(self):
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"""Determine if this scope is a common table expression"""
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return self.scope_type == ScopeType.CTE
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@property
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def is_root(self):
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"""Determine if this is the root scope"""
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return self.scope_type == ScopeType.ROOT
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@property
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def is_udtf(self):
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"""Determine if this scope is a UDTF (User Defined Table Function)"""
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return self.scope_type == ScopeType.UDTF
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@property
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def is_correlated_subquery(self):
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"""Determine if this scope is a correlated subquery"""
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return bool(
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(self.is_subquery or (self.parent and isinstance(self.parent.expression, exp.Lateral)))
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and self.external_columns
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)
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def rename_source(self, old_name, new_name):
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"""Rename a source in this scope"""
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columns = self.sources.pop(old_name or "", [])
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self.sources[new_name] = columns
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def add_source(self, name, source):
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"""Add a source to this scope"""
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self.sources[name] = source
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self.clear_cache()
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def remove_source(self, name):
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"""Remove a source from this scope"""
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self.sources.pop(name, None)
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self.clear_cache()
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def __repr__(self):
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return f"Scope<{self.expression.sql()}>"
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def traverse(self):
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"""
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Traverse the scope tree from this node.
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Yields:
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Scope: scope instances in depth-first-search post-order
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"""
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for child_scope in itertools.chain(
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self.cte_scopes, self.union_scopes, self.table_scopes, self.subquery_scopes
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):
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yield from child_scope.traverse()
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yield self
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def ref_count(self):
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"""
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Count the number of times each scope in this tree is referenced.
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Returns:
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dict[int, int]: Mapping of Scope instance ID to reference count
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"""
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scope_ref_count = defaultdict(lambda: 0)
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for scope in self.traverse():
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for _, source in scope.selected_sources.values():
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scope_ref_count[id(source)] += 1
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return scope_ref_count
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def traverse_scope(expression: exp.Expression) -> t.List[Scope]:
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"""
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Traverse an expression by its "scopes".
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"Scope" represents the current context of a Select statement.
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This is helpful for optimizing queries, where we need more information than
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the expression tree itself. For example, we might care about the source
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names within a subquery. Returns a list because a generator could result in
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incomplete properties which is confusing.
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Examples:
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>>> import sqlglot
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>>> expression = sqlglot.parse_one("SELECT a FROM (SELECT a FROM x) AS y")
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>>> scopes = traverse_scope(expression)
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>>> scopes[0].expression.sql(), list(scopes[0].sources)
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('SELECT a FROM x', ['x'])
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>>> scopes[1].expression.sql(), list(scopes[1].sources)
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('SELECT a FROM (SELECT a FROM x) AS y', ['y'])
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Args:
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expression (exp.Expression): expression to traverse
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Returns:
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list[Scope]: scope instances
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"""
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if isinstance(expression, exp.Unionable) or (
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isinstance(expression, exp.DDL) and isinstance(expression.expression, exp.Subqueryable)
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):
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return list(_traverse_scope(Scope(expression)))
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return []
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def build_scope(expression: exp.Expression) -> t.Optional[Scope]:
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"""
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Build a scope tree.
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Args:
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expression (exp.Expression): expression to build the scope tree for
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Returns:
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Scope: root scope
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"""
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scopes = traverse_scope(expression)
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if scopes:
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return scopes[-1]
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return None
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def _traverse_scope(scope):
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if isinstance(scope.expression, exp.Select):
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yield from _traverse_select(scope)
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elif isinstance(scope.expression, exp.Union):
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yield from _traverse_union(scope)
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elif isinstance(scope.expression, exp.Subquery):
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yield from _traverse_subqueries(scope)
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elif isinstance(scope.expression, exp.Table):
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yield from _traverse_tables(scope)
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elif isinstance(scope.expression, exp.UDTF):
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yield from _traverse_udtfs(scope)
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elif isinstance(scope.expression, exp.DDL):
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yield from _traverse_ddl(scope)
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else:
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logger.warning(
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"Cannot traverse scope %s with type '%s'", scope.expression, type(scope.expression)
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)
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return
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yield scope
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def _traverse_select(scope):
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yield from _traverse_ctes(scope)
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yield from _traverse_tables(scope)
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yield from _traverse_subqueries(scope)
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def _traverse_union(scope):
|
|
yield from _traverse_ctes(scope)
|
|
|
|
# The last scope to be yield should be the top most scope
|
|
left = None
|
|
for left in _traverse_scope(scope.branch(scope.expression.left, scope_type=ScopeType.UNION)):
|
|
yield left
|
|
|
|
right = None
|
|
for right in _traverse_scope(scope.branch(scope.expression.right, scope_type=ScopeType.UNION)):
|
|
yield right
|
|
|
|
scope.union_scopes = [left, right]
|
|
|
|
|
|
def _traverse_ctes(scope):
|
|
sources = {}
|
|
|
|
for cte in scope.ctes:
|
|
recursive_scope = None
|
|
|
|
# if the scope is a recursive cte, it must be in the form of base_case UNION recursive.
|
|
# thus the recursive scope is the first section of the union.
|
|
with_ = scope.expression.args.get("with")
|
|
if with_ and with_.recursive:
|
|
union = cte.this
|
|
|
|
if isinstance(union, exp.Union):
|
|
recursive_scope = scope.branch(union.this, scope_type=ScopeType.CTE)
|
|
|
|
child_scope = None
|
|
|
|
for child_scope in _traverse_scope(
|
|
scope.branch(
|
|
cte.this,
|
|
chain_sources=sources,
|
|
outer_column_list=cte.alias_column_names,
|
|
scope_type=ScopeType.CTE,
|
|
)
|
|
):
|
|
yield child_scope
|
|
|
|
alias = cte.alias
|
|
sources[alias] = child_scope
|
|
|
|
if recursive_scope:
|
|
child_scope.add_source(alias, recursive_scope)
|
|
|
|
# append the final child_scope yielded
|
|
if child_scope:
|
|
scope.cte_scopes.append(child_scope)
|
|
|
|
scope.sources.update(sources)
|
|
|
|
|
|
def _is_derived_table(expression: exp.Subquery) -> bool:
|
|
"""
|
|
We represent (tbl1 JOIN tbl2) as a Subquery, but it's not really a "derived table",
|
|
as it doesn't introduce a new scope. If an alias is present, it shadows all names
|
|
under the Subquery, so that's one exception to this rule.
|
|
"""
|
|
return bool(expression.alias or isinstance(expression.this, exp.Subqueryable))
|
|
|
|
|
|
def _traverse_tables(scope):
|
|
sources = {}
|
|
|
|
# Traverse FROMs, JOINs, and LATERALs in the order they are defined
|
|
expressions = []
|
|
from_ = scope.expression.args.get("from")
|
|
if from_:
|
|
expressions.append(from_.this)
|
|
|
|
for join in scope.expression.args.get("joins") or []:
|
|
expressions.append(join.this)
|
|
|
|
if isinstance(scope.expression, exp.Table):
|
|
expressions.append(scope.expression)
|
|
|
|
expressions.extend(scope.expression.args.get("laterals") or [])
|
|
|
|
for expression in expressions:
|
|
if isinstance(expression, exp.Table):
|
|
table_name = expression.name
|
|
source_name = expression.alias_or_name
|
|
|
|
if table_name in scope.sources and not expression.db:
|
|
# This is a reference to a parent source (e.g. a CTE), not an actual table, unless
|
|
# it is pivoted, because then we get back a new table and hence a new source.
|
|
pivots = expression.args.get("pivots")
|
|
if pivots:
|
|
sources[pivots[0].alias] = expression
|
|
else:
|
|
sources[source_name] = scope.sources[table_name]
|
|
elif source_name in sources:
|
|
sources[find_new_name(sources, table_name)] = expression
|
|
else:
|
|
sources[source_name] = expression
|
|
|
|
# Make sure to not include the joins twice
|
|
if expression is not scope.expression:
|
|
expressions.extend(join.this for join in expression.args.get("joins") or [])
|
|
|
|
continue
|
|
|
|
if not isinstance(expression, exp.DerivedTable):
|
|
continue
|
|
|
|
if isinstance(expression, exp.UDTF):
|
|
lateral_sources = sources
|
|
scope_type = ScopeType.UDTF
|
|
scopes = scope.udtf_scopes
|
|
elif _is_derived_table(expression):
|
|
lateral_sources = None
|
|
scope_type = ScopeType.DERIVED_TABLE
|
|
scopes = scope.derived_table_scopes
|
|
expressions.extend(join.this for join in expression.args.get("joins") or [])
|
|
else:
|
|
# Makes sure we check for possible sources in nested table constructs
|
|
expressions.append(expression.this)
|
|
expressions.extend(join.this for join in expression.args.get("joins") or [])
|
|
continue
|
|
|
|
for child_scope in _traverse_scope(
|
|
scope.branch(
|
|
expression,
|
|
lateral_sources=lateral_sources,
|
|
outer_column_list=expression.alias_column_names,
|
|
scope_type=scope_type,
|
|
)
|
|
):
|
|
yield child_scope
|
|
|
|
# Tables without aliases will be set as ""
|
|
# This shouldn't be a problem once qualify_columns runs, as it adds aliases on everything.
|
|
# Until then, this means that only a single, unaliased derived table is allowed (rather,
|
|
# the latest one wins.
|
|
sources[expression.alias] = child_scope
|
|
|
|
# append the final child_scope yielded
|
|
scopes.append(child_scope)
|
|
scope.table_scopes.append(child_scope)
|
|
|
|
scope.sources.update(sources)
|
|
|
|
|
|
def _traverse_subqueries(scope):
|
|
for subquery in scope.subqueries:
|
|
top = None
|
|
for child_scope in _traverse_scope(scope.branch(subquery, scope_type=ScopeType.SUBQUERY)):
|
|
yield child_scope
|
|
top = child_scope
|
|
scope.subquery_scopes.append(top)
|
|
|
|
|
|
def _traverse_udtfs(scope):
|
|
if isinstance(scope.expression, exp.Unnest):
|
|
expressions = scope.expression.expressions
|
|
elif isinstance(scope.expression, exp.Lateral):
|
|
expressions = [scope.expression.this]
|
|
else:
|
|
expressions = []
|
|
|
|
sources = {}
|
|
for expression in expressions:
|
|
if isinstance(expression, exp.Subquery) and _is_derived_table(expression):
|
|
top = None
|
|
for child_scope in _traverse_scope(
|
|
scope.branch(
|
|
expression,
|
|
scope_type=ScopeType.DERIVED_TABLE,
|
|
outer_column_list=expression.alias_column_names,
|
|
)
|
|
):
|
|
yield child_scope
|
|
top = child_scope
|
|
sources[expression.alias] = child_scope
|
|
|
|
scope.derived_table_scopes.append(top)
|
|
scope.table_scopes.append(top)
|
|
|
|
scope.sources.update(sources)
|
|
|
|
|
|
def _traverse_ddl(scope):
|
|
yield from _traverse_ctes(scope)
|
|
|
|
query_scope = scope.branch(
|
|
scope.expression.expression, scope_type=ScopeType.DERIVED_TABLE, chain_sources=scope.sources
|
|
)
|
|
query_scope._collect()
|
|
query_scope._ctes = scope.ctes + query_scope._ctes
|
|
|
|
yield from _traverse_scope(query_scope)
|
|
|
|
|
|
def walk_in_scope(expression, bfs=True):
|
|
"""
|
|
Returns a generator object which visits all nodes in the syntrax tree, stopping at
|
|
nodes that start child scopes.
|
|
|
|
Args:
|
|
expression (exp.Expression):
|
|
bfs (bool): if set to True the BFS traversal order will be applied,
|
|
otherwise the DFS traversal will be used instead.
|
|
|
|
Yields:
|
|
tuple[exp.Expression, Optional[exp.Expression], str]: node, parent, arg key
|
|
"""
|
|
# We'll use this variable to pass state into the dfs generator.
|
|
# Whenever we set it to True, we exclude a subtree from traversal.
|
|
prune = False
|
|
|
|
for node, parent, key in expression.walk(bfs=bfs, prune=lambda *_: prune):
|
|
prune = False
|
|
|
|
yield node, parent, key
|
|
|
|
if node is expression:
|
|
continue
|
|
if (
|
|
isinstance(node, exp.CTE)
|
|
or (
|
|
isinstance(node, exp.Subquery)
|
|
and isinstance(parent, (exp.From, exp.Join, exp.Subquery))
|
|
and _is_derived_table(node)
|
|
)
|
|
or isinstance(node, exp.UDTF)
|
|
or isinstance(node, exp.Subqueryable)
|
|
):
|
|
prune = True
|
|
|
|
if isinstance(node, (exp.Subquery, exp.UDTF)):
|
|
# The following args are not actually in the inner scope, so we should visit them
|
|
for key in ("joins", "laterals", "pivots"):
|
|
for arg in node.args.get(key) or []:
|
|
yield from walk_in_scope(arg, bfs=bfs)
|