Fix tablespace inheritance for partitioned rels

Commit ca4103025dfe left a few loose ends.  The most important one
(broken pg_dump output) is already fixed by virtue of commit
3b23552ad8bb, but some things remained:

* When ALTER TABLE rewrites tables, the indexes must remain in the
  tablespace they were originally in.  This didn't work because
  index recreation during ALTER TABLE runs manufactured SQL (yuck),
  which runs afoul of default_tablespace in competition with the parent
  relation tablespace.  To fix, reset default_tablespace to the empty
  string temporarily, and add the TABLESPACE clause as appropriate.

* Setting a partitioned rel's tablespace to the database default is
  confusing; if it worked, it would direct the partitions to that
  tablespace regardless of default_tablespace.  But in reality it does
  not work, and making it work is a larger project.  Therefore, throw
  an error when this condition is detected, to alert the unwary.

Add some docs and tests, too.

Author: Álvaro Herrera
Discussion: https://postgr.es/m/CAKJS1f_1c260nOt_vBJ067AZ3JXptXVRohDVMLEBmudX1YEx-A@mail.gmail.com

1 files changed, 13 insertions, 3 deletions

diff --git a/src/backend/commands/tablespace.c b/src/backend/commands/tablespace.c
index 3784ea4b4fa..8ec963f1cfb 100644
--- a/src/backend/commands/tablespace.c
+++ b/src/backend/commands/tablespace.c
@@ -1104,7 +1104,9 @@ check_default_tablespace(char **newval, void **extra, GucSource source)
  * GetDefaultTablespace -- get the OID of the current default tablespace
  *
  * Temporary objects have different default tablespaces, hence the
- * relpersistence parameter must be specified.
+ * relpersistence parameter must be specified.  Also, for partitioned tables,
+ * we disallow specifying the database default, so that needs to be specified
+ * too.
  *
  * May return InvalidOid to indicate "use the database's default tablespace".
  *
@@ -1115,7 +1117,7 @@ check_default_tablespace(char **newval, void **extra, GucSource source)
  * default_tablespace GUC variable.
  */
 Oid
-GetDefaultTablespace(char relpersistence)
+GetDefaultTablespace(char relpersistence, bool partitioned)
 {
 	Oid			result;
 
@@ -1141,10 +1143,18 @@ GetDefaultTablespace(char relpersistence)
 
 	/*
 	 * Allow explicit specification of database's default tablespace in
-	 * default_tablespace without triggering permissions checks.
+	 * default_tablespace without triggering permissions checks.  Don't
+	 * allow specifying that when creating a partitioned table, however,
+	 * since the result is confusing.
 	 */
 	if (result == MyDatabaseTableSpace)
+	{
+		if (partitioned)
+			ereport(ERROR,
+					(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+					 errmsg("cannot specify default tablespace for partitioned relations")));
 		result = InvalidOid;
+	}
 	return result;
 }