Switch function current_schema[s]() to be parallel-unsafe

michaelpq · michaelpq · commit 5bde1651bbba · 2019-03-27T11:35:12.000+09:00
When invoked for the first time in a session, current_schema() and current_schemas() can finish by creating a temporary schema. Currently those functions are parallel-safe, however if for a reason or another they get launched across multiple parallel workers, they would fail when attempting to create a temporary schema as temporary contexts are not supported in this case. The original issue has been spotted by buildfarm members crake and lapwing, after commit c5660e0 has introduced the first regression tests based on current_schema() in the tree. After that, 396676b has introduced a workaround to avoid parallel plans but that was not completely right either. Catversion is bumped. Author: Michael Paquier Reviewed-by: Daniel Gustafsson Discussion: https://postgr.es/m/20190118024618.GF1883@paquier.xyz
diff --git a/src/include/catalog/catversion.h b/src/include/catalog/catversion.h
@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201903251
+#define CATALOG_VERSION_NO	201903271
 
 #endif
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
@@ -2787,11 +2787,11 @@
   prosrc => 'name_text' },
 
 { oid => '1402', descr => 'current schema name',
-  proname => 'current_schema', provolatile => 's', prorettype => 'name',
-  proargtypes => '', prosrc => 'current_schema' },
+  proname => 'current_schema', provolatile => 's', proparallel => 'u',
+  prorettype => 'name', proargtypes => '', prosrc => 'current_schema' },
 { oid => '1403', descr => 'current schema search list',
-  proname => 'current_schemas', provolatile => 's', prorettype => '_name',
-  proargtypes => 'bool', prosrc => 'current_schemas' },
+  proname => 'current_schemas', provolatile => 's', proparallel => 'u',
+  prorettype => '_name', proargtypes => 'bool', prosrc => 'current_schemas' },
 
 { oid => '1404', descr => 'substitute portion of string',
   proname => 'overlay', prorettype => 'text',
diff --git a/src/test/regress/expected/temp.out b/src/test/regress/expected/temp.out
@@ -360,11 +360,8 @@ prepare transaction 'twophase_tab';
 ERROR:  cannot PREPARE a transaction that has operated on temporary objects
 -- Corner case: current_schema may create a temporary schema if namespace
 -- creation is pending, so check after that.  First reset the connection
--- to remove the temporary namespace, and make sure that non-parallel plans
--- are used.
+-- to remove the temporary namespace.
 \c -
-SET max_parallel_workers = 0;
-SET max_parallel_workers_per_gather = 0;
 SET search_path TO 'pg_temp';
 BEGIN;
 SELECT current_schema() ~ 'pg_temp' AS is_temp_schema;
diff --git a/src/test/regress/sql/temp.sql b/src/test/regress/sql/temp.sql
@@ -274,11 +274,8 @@ prepare transaction 'twophase_tab';
 
 -- Corner case: current_schema may create a temporary schema if namespace
 -- creation is pending, so check after that.  First reset the connection
--- to remove the temporary namespace, and make sure that non-parallel plans
--- are used.
+-- to remove the temporary namespace.
 \c -
-SET max_parallel_workers = 0;
-SET max_parallel_workers_per_gather = 0;
 SET search_path TO 'pg_temp';
 BEGIN;
 SELECT current_schema() ~ 'pg_temp' AS is_temp_schema;
