>From cb12f56b401bba484ad82f14079450cd83dfe673 Mon Sep 17 00:00:00 2001 From: Andres Freund Date: Tue, 11 Jun 2013 23:25:26 +0200 Subject: [PATCH 06/17] wal_decoding: Introduce InvalidCommandId and declare that to be the new maximum for CommandCounterIncrement This is useful to be able to represent a CommandId thats invalid. There was no such value before. This decreases the possible number of subtransactions by one which seems unproblematic. Its also not a problem for pg_upgrade because cmin/cmax are never looked at outside the context of their own transaction (spare timetravel access, but thats new anyway). --- src/backend/access/transam/xact.c | 4 ++-- src/include/c.h | 1 + 2 files changed, 3 insertions(+), 2 deletions(-) diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c index 31e868d..0591f3f 100644 --- a/src/backend/access/transam/xact.c +++ b/src/backend/access/transam/xact.c @@ -766,12 +766,12 @@ CommandCounterIncrement(void) if (currentCommandIdUsed) { currentCommandId += 1; - if (currentCommandId == FirstCommandId) /* check for overflow */ + if (currentCommandId == InvalidCommandId) { currentCommandId -= 1; ereport(ERROR, (errcode(ERRCODE_PROGRAM_LIMIT_EXCEEDED), - errmsg("cannot have more than 2^32-1 commands in a transaction"))); + errmsg("cannot have more than 2^32-2 commands in a transaction"))); } currentCommandIdUsed = false; diff --git a/src/include/c.h b/src/include/c.h index 7193af6..e4940a9 100644 --- a/src/include/c.h +++ b/src/include/c.h @@ -368,6 +368,7 @@ typedef uint32 MultiXactOffset; typedef uint32 CommandId; #define FirstCommandId ((CommandId) 0) +#define InvalidCommandId (~(CommandId)0) /* * Array indexing support -- 1.8.2.rc2.4.g7799588.dirty