Merging upstream version 25.26.0.

Signed-off-by: Daniel Baumann <daniel@debian.org>

sqlglot/optimizer/eliminate_subqueries.py

@@ -1,11 +1,18 @@
+from __future__ import annotations
+
 import itertools
+import typing as t
 
 from sqlglot import expressions as exp
 from sqlglot.helper import find_new_name
-from sqlglot.optimizer.scope import build_scope
+from sqlglot.optimizer.scope import Scope, build_scope
+
+if t.TYPE_CHECKING:
+    ExistingCTEsMapping = t.Dict[exp.Expression, str]
+    TakenNameMapping = t.Dict[str, t.Union[Scope, exp.Expression]]
 
 
-def eliminate_subqueries(expression):
+def eliminate_subqueries(expression: exp.Expression) -> exp.Expression:
     """
     Rewrite derived tables as CTES, deduplicating if possible.
 
@@ -38,7 +45,7 @@ def eliminate_subqueries(expression):
     # Map of alias->Scope|Table
     # These are all aliases that are already used in the expression.
     # We don't want to create new CTEs that conflict with these names.
-    taken = {}
+    taken: TakenNameMapping = {}
 
     # All CTE aliases in the root scope are taken
     for scope in root.cte_scopes:
@@ -56,7 +63,7 @@ def eliminate_subqueries(expression):
 
     # Map of Expression->alias
     # Existing CTES in the root expression. We'll use this for deduplication.
-    existing_ctes = {}
+    existing_ctes: ExistingCTEsMapping = {}
 
     with_ = root.expression.args.get("with")
     recursive = False
@@ -95,15 +102,21 @@ def eliminate_subqueries(expression):
     return expression
 
 
-def _eliminate(scope, existing_ctes, taken):
+def _eliminate(
+    scope: Scope, existing_ctes: ExistingCTEsMapping, taken: TakenNameMapping
+) -> t.Optional[exp.Expression]:
     if scope.is_derived_table:
         return _eliminate_derived_table(scope, existing_ctes, taken)
 
     if scope.is_cte:
         return _eliminate_cte(scope, existing_ctes, taken)
 
+    return None
 
-def _eliminate_derived_table(scope, existing_ctes, taken):
+
+def _eliminate_derived_table(
+    scope: Scope, existing_ctes: ExistingCTEsMapping, taken: TakenNameMapping
+) -> t.Optional[exp.Expression]:
     # This makes sure that we don't:
     # - drop the "pivot" arg from a pivoted subquery
     # - eliminate a lateral correlated subquery
@@ -121,7 +134,9 @@ def _eliminate_derived_table(scope, existing_ctes, taken):
     return cte
 
 
-def _eliminate_cte(scope, existing_ctes, taken):
+def _eliminate_cte(
+    scope: Scope, existing_ctes: ExistingCTEsMapping, taken: TakenNameMapping
+) -> t.Optional[exp.Expression]:
     parent = scope.expression.parent
     name, cte = _new_cte(scope, existing_ctes, taken)
 
@@ -140,7 +155,9 @@ def _eliminate_cte(scope, existing_ctes, taken):
     return cte
 
 
-def _new_cte(scope, existing_ctes, taken):
+def _new_cte(
+    scope: Scope, existing_ctes: ExistingCTEsMapping, taken: TakenNameMapping
+) -> t.Tuple[str, t.Optional[exp.Expression]]:
     """
     Returns:
         tuple of (name, cte)