Make DISCARD SEQUENCES also discard the last used sequence.

robertmhaas · robertmhaas · commit 16a906f53508 · 2013-10-07T15:55:56.000-04:00
Otherwise, we access already-freed memory.  Oops.

Report by Michael Paquier.  Fix by me.
diff --git a/src/backend/commands/sequence.c b/src/backend/commands/sequence.c
@@ -1617,4 +1617,6 @@ ResetSequenceCaches(void)
 		free(seqtab);
 		seqtab = next;
 	}
+
+	last_used_seq = NULL;
 }
diff --git a/src/test/regress/expected/sequence.out b/src/test/regress/expected/sequence.out
@@ -344,6 +344,9 @@ SELECT lastval();
       99
 (1 row)
 
+DISCARD SEQUENCES;
+SELECT lastval();
+ERROR:  lastval is not yet defined in this session
 CREATE SEQUENCE seq2;
 SELECT nextval('seq2');
  nextval 
diff --git a/src/test/regress/sql/sequence.sql b/src/test/regress/sql/sequence.sql
@@ -154,6 +154,8 @@ SELECT nextval('seq');
 SELECT lastval();
 SELECT setval('seq', 99);
 SELECT lastval();
+DISCARD SEQUENCES;
+SELECT lastval();
 
 CREATE SEQUENCE seq2;
 SELECT nextval('seq2');

Original file line number	Diff line number	Diff line change
`@@ -344,6 +344,9 @@ SELECT lastval();`
`344`	`344`	`99`
`345`	`345`	`(1 row)`
`346`	`346`
	`347`	`+DISCARD SEQUENCES;`
	`348`	`+SELECT lastval();`
	`349`	`+ERROR: lastval is not yet defined in this session`
`347`	`350`	`CREATE SEQUENCE seq2;`
`348`	`351`	`SELECT nextval('seq2');`
`349`	`352`	`nextval`