Fix: dont expand bq pseudocolumns in optimizer star expansion (#1826)

* fix: dont expand bq pseudocolumns in star if present in schema

* test: add test for correct expansion with pseudocols in schema

* ci: more typing for mypy and explicit guards

sqlglot/optimizer/qualify_columns.py

@@ -62,7 +62,7 @@ def qualify_columns(
     return expression
 
 
-def validate_qualify_columns(expression):
+def validate_qualify_columns(expression: E) -> E:
     """Raise an `OptimizeError` if any columns aren't qualified"""
     unqualified_columns = []
     for scope in traverse_scope(expression):
@@ -79,7 +79,7 @@ def validate_qualify_columns(expression):
     return expression
 
 
-def _pop_table_column_aliases(derived_tables):
+def _pop_table_column_aliases(derived_tables: t.List[exp.CTE]) -> None:
     """
     Remove table column aliases.
 
@@ -91,13 +91,13 @@ def _pop_table_column_aliases(derived_tables):
             table_alias.args.pop("columns", None)
 
 
-def _expand_using(scope, resolver):
+def _expand_using(scope: Scope, resolver: Resolver) -> t.Dict[str, t.Any]:
     joins = list(scope.find_all(exp.Join))
     names = {join.alias_or_name for join in joins}
     ordered = [key for key in scope.selected_sources if key not in names]
 
     # Mapping of automatically joined column names to an ordered set of source names (dict).
-    column_tables = {}
+    column_tables: t.Dict[str, t.Dict[str, t.Any]] = {}
 
     for join in joins:
         using = join.args.get("using")
@@ -174,7 +174,7 @@ def _expand_alias_refs(scope: Scope, resolver: Resolver) -> None:
 
     def replace_columns(
         node: t.Optional[exp.Expression], expand: bool = True, resolve_agg: bool = False
-    ):
+    ) -> None:
         if not node:
             return
 
@@ -201,7 +201,7 @@ def replace_columns(
     scope.clear_cache()
 
 
-def _expand_group_by(scope, resolver):
+def _expand_group_by(scope: Scope, resolver: Resolver):
     group = scope.expression.args.get("group")
     if not group:
         return
@@ -210,7 +210,7 @@ def _expand_group_by(scope, resolver):
     scope.expression.set("group", group)
 
 
-def _expand_order_by(scope):
+def _expand_order_by(scope: Scope):
     order = scope.expression.args.get("order")
     if not order:
         return
@@ -229,7 +229,7 @@ def _expand_order_by(scope):
             ordered.set("this", selects.get(ordered.this, ordered.this))
 
 
-def _expand_positional_references(scope, expressions):
+def _expand_positional_references(scope: Scope, expressions: t.Iterable[E]) -> t.List[E]:
     new_nodes = []
     for node in expressions:
         if node.is_int:
@@ -247,7 +247,7 @@ def _expand_positional_references(scope, expressions):
     return new_nodes
 
 
-def _qualify_columns(scope, resolver):
+def _qualify_columns(scope: Scope, resolver: Resolver) -> None:
     """Disambiguate columns, ensuring each column specifies a source"""
     for column in scope.columns:
         column_table = column.table
@@ -296,21 +296,23 @@ def _qualify_columns(scope, resolver):
                     column.set("table", column_table)
 
 
-def _expand_stars(scope, resolver, using_column_tables):
+def _expand_stars(
+    scope: Scope, resolver: Resolver, using_column_tables: t.Dict[str, t.Any]
+) -> None:
     """Expand stars to lists of column selections"""
 
     new_selections = []
-    except_columns = {}
-    replace_columns = {}
+    except_columns: t.Dict[int, t.Set[str]] = {}
+    replace_columns: t.Dict[int, t.Dict[str, str]] = {}
     coalesced_columns = set()
 
     # TODO: handle optimization of multiple PIVOTs (and possibly UNPIVOTs) in the future
     pivot_columns = None
     pivot_output_columns = None
-    pivot = seq_get(scope.pivots, 0)
+    pivot = t.cast(t.Optional[exp.Pivot], seq_get(scope.pivots, 0))
 
     has_pivoted_source = pivot and not pivot.args.get("unpivot")
-    if has_pivoted_source:
+    if pivot and has_pivoted_source:
         pivot_columns = set(col.output_name for col in pivot.find_all(exp.Column))
 
         pivot_output_columns = [col.output_name for col in pivot.args.get("columns", [])]
@@ -336,8 +338,17 @@ def _expand_stars(scope, resolver, using_column_tables):
 
             columns = resolver.get_source_columns(table, only_visible=True)
 
+            # The _PARTITIONTIME and _PARTITIONDATE pseudo-columns are not returned by a SELECT * statement
+            # https://cloud.google.com/bigquery/docs/querying-partitioned-tables#query_an_ingestion-time_partitioned_table
+            if resolver.schema.dialect == "bigquery":
+                columns = [
+                    name
+                    for name in columns
+                    if name.upper() not in ("_PARTITIONTIME", "_PARTITIONDATE")
+                ]
+
             if columns and "*" not in columns:
-                if has_pivoted_source:
+                if pivot and has_pivoted_source and pivot_columns and pivot_output_columns:
                     implicit_columns = [col for col in columns if col not in pivot_columns]
                     new_selections.extend(
                         exp.alias_(exp.column(name, table=pivot.alias), name, copy=False)
@@ -374,7 +385,9 @@ def _expand_stars(scope, resolver, using_column_tables):
     scope.expression.set("expressions", new_selections)
 
 
-def _add_except_columns(expression, tables, except_columns):
+def _add_except_columns(
+    expression: exp.Expression, tables, except_columns: t.Dict[int, t.Set[str]]
+) -> None:
     except_ = expression.args.get("except")
 
     if not except_:
@@ -386,7 +399,9 @@ def _add_except_columns(expression, tables, except_columns):
         except_columns[id(table)] = columns
 
 
-def _add_replace_columns(expression, tables, replace_columns):
+def _add_replace_columns(
+    expression: exp.Expression, tables, replace_columns: t.Dict[int, t.Dict[str, str]]
+) -> None:
     replace = expression.args.get("replace")
 
     if not replace:
@@ -398,7 +413,7 @@ def _add_replace_columns(expression, tables, replace_columns):
         replace_columns[id(table)] = columns
 
 
-def _qualify_outputs(scope):
+def _qualify_outputs(scope: Scope):
     """Ensure all output columns are aliased"""
     new_selections = []
 
@@ -435,7 +450,7 @@ class Resolver:
     This is a class so we can lazily load some things and easily share them across functions.
     """
 
-    def __init__(self, scope, schema, infer_schema: bool = True):
+    def __init__(self, scope: Scope, schema: Schema, infer_schema: bool = True):
         self.scope = scope
         self.schema = schema
         self._source_columns = None

tests/test_optimizer.py

@@ -727,3 +727,20 @@ def test_quotes(self):
             source_query = parse_one('SELECT * FROM example."source"', read="snowflake")
             transformed = func(source_query, dialect="snowflake", schema=schema)
             self.assertEqual(transformed.sql(pretty=True, dialect="snowflake"), expected)
+
+    def test_no_pseudocolumn_expansion(self):
+        schema = {
+            "a": {
+                "a": "text",
+                "b": "text",
+                "_PARTITIONDATE": "date",
+                "_PARTITIONTIME": "timestamp",
+            }
+        }
+
+        self.assertEqual(
+            optimizer.optimize(
+                parse_one("SELECT * FROM a"), schema=MappingSchema(schema, dialect="bigquery")
+            ),
+            parse_one('SELECT "a"."a" AS "a", "a"."b" AS "b" FROM "a" AS "a"'),
+        )