sql: fix "descriptor not found" error when dropping a database with t…

pkg/sql/logictest/testdata/logic_test/temp_table

@@ -285,3 +285,54 @@ grant testuser to root
 
 statement ok
 ALTER TABLE second_db.pg_temp.a OWNER TO testuser
+
+# Regression test for dropping a database which contains schemas from other
+# sessions.
+
+subtest drop_database_with_temp_schemas_from_other_sessions
+
+statement ok
+CREATE DATABASE to_drop;
+ALTER DATABASE to_drop OWNER TO testuser;
+
+user testuser
+
+statement ok
+USE to_drop;
+SET experimental_enable_temp_tables=true;
+CREATE TABLE not_temp (i INT PRIMARY KEY);
+CREATE TEMPORARY TABLE testuser_tmp (i INT PRIMARY KEY);
+CREATE TEMPORARY VIEW tempuser_view AS SELECT i FROM testuser_tmp;
+USE test
+
+user root
+
+statement ok
+USE to_drop;
+CREATE TEMPORARY TABLE root_temp (i INT PRIMARY KEY);
+
+let $before_drop
+SELECT now()
+
+statement ok
+USE test;
+DROP DATABASE to_drop CASCADE
+
+query T
+  SELECT regexp_replace(
+            json_array_elements_text(
+                (info::JSONB)->'DroppedSchemaObjects'
+            ),
+            'pg_temp_[^.]+.',
+            'pg_temp.'
+         ) AS name
+    FROM system.eventlog
+   WHERE "timestamp" > '$before_drop'
+ORDER BY name DESC;
+----
+to_drop.public.not_temp
+to_drop.pg_temp.testuser_tmp
+to_drop.pg_temp.tempuser_view
+to_drop.pg_temp.root_temp
+
+user testuser

pkg/sql/resolver.go

@@ -662,22 +662,47 @@ func (p *planner) getQualifiedTableName(
 			Required:       true,
 			IncludeOffline: true,
 			IncludeDropped: true,
+			AvoidCached:    true,
 		})
 	if err != nil {
 		return nil, err
 	}
+	// Get the schema name. Use some specialized logic to deal with descriptors
+	// from other temporary schemas.
+	//
+	// TODO(ajwerner): We shouldn't need this temporary logic if we properly
+	// tracked all descriptors as we read them and made them available in the
+	// collection. We should only be hitting this edge case when dropping a
+	// database, in which case we've already read all of the temporary schema
+	// information from the namespace table.
+	var schemaName tree.Name
 	schemaID := desc.GetParentSchemaID()
 	scDesc, err := p.Descriptors().GetImmutableSchemaByID(ctx, p.txn, schemaID,
 		tree.SchemaLookupFlags{
 			IncludeOffline: true,
 			IncludeDropped: true,
+			AvoidCached:    true,
 		})
-	if err != nil {
-		return nil, err
+	switch {
+	case err == nil:
+		schemaName = tree.Name(scDesc.GetName())
+	case desc.IsTemporary() && errors.Is(err, catalog.ErrDescriptorNotFound):
+		// We've lost track of the session which owned this schema, but we
+		// can come up with a name that is also going to be unique and
+		// informative and looks like a pg_temp_<session_id> name.
+		schemaName = tree.Name(fmt.Sprintf("pg_temp_%d", schemaID))
+	default:
+		return nil, errors.Wrapf(err,
+			"resolving schema name for %s.[%d].%s",
+			tree.Name(dbDesc.GetName()),
+			schemaID,
+			tree.Name(desc.GetName()),
+		)
 	}
+
 	tbName := tree.MakeTableNameWithSchema(
 		tree.Name(dbDesc.GetName()),
-		tree.Name(scDesc.GetName()),
+		schemaName,
 		tree.Name(desc.GetName()),
 	)
 	return &tbName, nil