Do not raise ERROR if all the TOASTed columns have been dropped.

In that case (but possibly also in other cases) it's o.k. for the new relation
to have no TOAST relation.

Author: Antonin Houska

pg_squeeze.c

@@ -3197,49 +3197,44 @@ swap_toast_names(Oid relid1, Oid toastrelid1, Oid relid2, Oid toastrelid2)
 	Oid			toastidxid;
 
 	/*
-	 * As we haven't changed tuple descriptor, both relation do or both do not
-	 * have TOAST - see toasting.c:needs_toast_table().
+	 * If relid1 no longer needs TOAST, we don't even rename that of relid2.
 	 */
 	if (!OidIsValid(toastrelid1))
-	{
-		if (OidIsValid(toastrelid2))
-			elog(ERROR, "Unexpected TOAST relation exists");
 		return;
-	}
-	if (!OidIsValid(toastrelid2))
-		elog(ERROR, "Missing TOAST relation");
 
-	/*
-	 * Added underscore should be enough to keep names unique (at least within
-	 * the pg_toast namespace). This assumption makes name retrieval
-	 * unnecessary.
-	 */
-	snprintf(name, NAMEDATALEN, "pg_toast_%u_", relid1);
-	RenameRelationInternal(toastrelid2, name, true, false);
+	if (OidIsValid(toastrelid2))
+	{
+		/*
+		 * Added underscore should be enough to keep names unique (at least
+		 * within the pg_toast namespace). This assumption makes name
+		 * retrieval unnecessary.
+		 */
+		snprintf(name, NAMEDATALEN, "pg_toast_%u_", relid1);
+		RenameRelationInternal(toastrelid2, name, true, false);
 
-	snprintf(name, NAMEDATALEN, "pg_toast_%u_index_", relid1);
+		snprintf(name, NAMEDATALEN, "pg_toast_%u_index_", relid1);
 #if PG_VERSION_NUM < 130000
-	/* NoLock as RenameRelationInternal() did not release its lock. */
-	toastidxid = get_toast_index(toastrelid2);
+		/* NoLock as RenameRelationInternal() did not release its lock. */
+		toastidxid = get_toast_index(toastrelid2);
 #else
-	/* TOAST relation is locked, but not its indexes. */
-	toastidxid = toast_get_valid_index(toastrelid2, AccessExclusiveLock);
+		/* TOAST relation is locked, but not its indexes. */
+		toastidxid = toast_get_valid_index(toastrelid2, AccessExclusiveLock);
 #endif
-	/*
-	 * Pass is_index=false so that even the index is locked in
-	 * AccessExclusiveLock mode. ShareUpdateExclusiveLock mode (allowing
-	 * concurrent read / write access to the index or even its renaming)
-	 * should not be a problem at this stage of table squeezing, but it'd also
-	 * bring little benefit (the table is locked exclusively, so no one should
-	 * need read / write access to the TOAST indexes).
-	 */
-	RenameRelationInternal(toastidxid, name, true, false);
-	CommandCounterIncrement();
+		/*
+		 * Pass is_index=false so that even the index is locked in
+		 * AccessExclusiveLock mode. ShareUpdateExclusiveLock mode (allowing
+		 * concurrent read / write access to the index or even its renaming)
+		 * should not be a problem at this stage of table squeezing, but it'd
+		 * also bring little benefit (the table is locked exclusively, so no
+		 * one should need read / write access to the TOAST indexes).
+		 */
+		RenameRelationInternal(toastidxid, name, true, false);
+		CommandCounterIncrement();
+	}
 
 	/* Now set the desired names on the TOAST stuff of relid1. */
 	snprintf(name, NAMEDATALEN, "pg_toast_%u", relid1);
 	RenameRelationInternal(toastrelid1, name, true, false);
-	/* NoLock as RenameRelationInternal() did not release its lock. */
 #if PG_VERSION_NUM < 130000
 	/* NoLock as RenameRelationInternal() did not release its lock. */
 	toastidxid = get_toast_index(toastrelid1);