Ugly patch to make ALTER SEQUENCE OWNED BY not affect the currval() state

of the sequence.  Since OWNED BY never existed before 8.2, this seems
unlikely to create any compatibility issues.  Other forms of ALTER SEQUENCE
continue to do what they did before, namely update currval to match the
sequence's actual last_val.  That seems wrong on consideration, but we'll
not change it in a minor release --- 8.3 will make that fix.

diff --git a/src/backend/commands/sequence.c b/src/backend/commands/sequence.c
index b73069cf1b6e7b63506adfff34689b673ba54b9f..9404efa379f352b8b16efb3e32abd7f3d0d94436 100644 (file)
--- a/src/backend/commands/sequence.c
+++ b/src/backend/commands/sequence.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/commands/sequence.c,v 1.141 2006/10/06 17:13:58 petere Exp $
+ *       $PostgreSQL: pgsql/src/backend/commands/sequence.c,v 1.141.2.1 2007/10/25 19:15:01 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -315,6 +315,7 @@ AlterSequence(AlterSeqStmt *stmt)
        Form_pg_sequence seq;
        FormData_pg_sequence new;
        List       *owned_by;
+       int64           save_increment;
 
        /* open and AccessShareLock sequence */
        relid = RangeVarGetRelid(stmt->sequence, false);
@@ -325,6 +326,9 @@ AlterSequence(AlterSeqStmt *stmt)
                aclcheck_error(ACLCHECK_NOT_OWNER, ACL_KIND_CLASS,
                                           stmt->sequence->relname);
 
+       /* hack to keep ALTER SEQUENCE OWNED BY from changing currval state */
+       save_increment = elm->increment;
+
        /* lock page' buffer and read tuple into new sequence structure */
        seq = read_info(elm, seqrel, &buf);
        page = BufferGetPage(buf);
@@ -338,10 +342,18 @@ AlterSequence(AlterSeqStmt *stmt)
        /* Now okay to update the on-disk tuple */
        memcpy(seq, &new, sizeof(FormData_pg_sequence));
 
-       /* Clear local cache so that we don't think we have cached numbers */
-       elm->last = new.last_value; /* last returned number */
-       elm->cached = new.last_value;           /* last cached number (forget cached
+       if (owned_by)
+       {
+               /* Restore previous state of elm (assume nothing else changes) */
+               elm->increment = save_increment;
+       }
+       else
+       {
+               /* Clear local cache so that we don't think we have cached numbers */
+               elm->last = new.last_value; /* last returned number */
+               elm->cached = new.last_value;   /* last cached number (forget cached
                                                                                 * values) */
+       }
 
        START_CRIT_SECTION();