Adjust the order of the prechecks in pgrowlocks()

4b8266415 added a precheck to pgrowlocks() to ensure the given object's
pg_class.relam is HEAP_TABLE_AM_OID, however, that check was put before
another check which was checking if the given object was a partitioned
table.  Since the pg_class.relam is always InvalidOid for partitioned
tables, if pgrowlocks() was called passing a partitioned table, then the
"only heap AM is supported" error would be raised instead of the intended
error about the given object being a partitioned table.

Here we simply move the pg_class.relam check to after the check that
verifies that we are in fact working with a normal (non-partitioned)
table.

Reported-by: jian he
Discussion: https://postgr.es/m/CACJufxFaSp_WguFCf0X98951zFVX+dXFnF1mxAb-G3g1HiHOow@mail.gmail.com
Backpatch-through: 12, where 4b8266415 was introduced.

diff --git a/contrib/pgrowlocks/pgrowlocks.c b/contrib/pgrowlocks/pgrowlocks.c
index c543277b7c550b772803f51721796be965884889..fd104e30e720f6e0e86c3cf56f232108c2ee384a 100644 (file)
--- a/contrib/pgrowlocks/pgrowlocks.c
+++ b/contrib/pgrowlocks/pgrowlocks.c
@@ -81,10 +81,6 @@ pgrowlocks(PG_FUNCTION_ARGS)
    relrv = makeRangeVarFromNameList(textToQualifiedNameList(relname));
    rel = relation_openrv(relrv, AccessShareLock);
 
-   if (rel->rd_rel->relam != HEAP_TABLE_AM_OID)
-       ereport(ERROR, (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-                       errmsg("only heap AM is supported")));
-
    if (rel->rd_rel->relkind == RELKIND_PARTITIONED_TABLE)
        ereport(ERROR,
                (errcode(ERRCODE_WRONG_OBJECT_TYPE),
@@ -96,6 +92,10 @@ pgrowlocks(PG_FUNCTION_ARGS)
                (errcode(ERRCODE_WRONG_OBJECT_TYPE),
                 errmsg("\"%s\" is not a table",
                        RelationGetRelationName(rel))));
+   else if (rel->rd_rel->relam != HEAP_TABLE_AM_OID)
+       ereport(ERROR,
+               (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+                errmsg("only heap AM is supported")));
 
    /*
     * check permissions: must have SELECT on table or be in