diff options
Diffstat (limited to 'src/backend/access/transam/twophase.c')
| -rw-r--r-- | src/backend/access/transam/twophase.c | 33 |
1 files changed, 32 insertions, 1 deletions
diff --git a/src/backend/access/transam/twophase.c b/src/backend/access/transam/twophase.c index 321fa247233..4ceb05c8531 100644 --- a/src/backend/access/transam/twophase.c +++ b/src/backend/access/transam/twophase.c @@ -7,7 +7,7 @@ * Portions Copyright (c) 1994, Regents of the University of California * * IDENTIFICATION - * $PostgreSQL: pgsql/src/backend/access/transam/twophase.c,v 1.25.2.2 2008/05/19 18:17:03 heikki Exp $ + * $PostgreSQL: pgsql/src/backend/access/transam/twophase.c,v 1.25.2.3 2009/11/23 09:59:11 heikki Exp $ * * NOTES * Each global transaction is associated with a global transaction @@ -106,6 +106,7 @@ int max_prepared_xacts = 5; typedef struct GlobalTransactionData { PGPROC proc; /* dummy proc */ + BackendId dummyBackendId; /* similar to backend id for backends */ TimestampTz prepared_at; /* time of preparation */ XLogRecPtr prepare_lsn; /* XLOG offset of prepare record */ Oid owner; /* ID of user that executed the xact */ @@ -197,6 +198,20 @@ TwoPhaseShmemInit(void) { gxacts[i].proc.links.next = TwoPhaseState->freeGXacts; TwoPhaseState->freeGXacts = MAKE_OFFSET(&gxacts[i]); + + /* + * Assign a unique ID for each dummy proc, so that the range of + * dummy backend IDs immediately follows the range of normal + * backend IDs. We don't dare to assign a real backend ID to + * dummy procs, because prepared transactions don't take part in + * cache invalidation like a real backend ID would imply, but + * having a unique ID for them is nevertheless handy. This + * arrangement allows you to allocate an array of size + * (MaxBackends + max_prepared_xacts + 1), and have a slot for + * every backend and prepared transaction. Currently multixact.c + * uses that technique. + */ + gxacts[i].dummyBackendId = MaxBackends + 1 + i; } } else @@ -635,6 +650,22 @@ pg_prepared_xact(PG_FUNCTION_ARGS) /* * TwoPhaseGetDummyProc + * Get the dummy backend ID for prepared transaction specified by XID + * + * Dummy backend IDs are similar to real backend IDs of real backends. + * They start at MaxBackends + 1, and are unique across all currently active + * real backends and prepared transactions. + */ +BackendId +TwoPhaseGetDummyBackendId(TransactionId xid) +{ + PGPROC *proc = TwoPhaseGetDummyProc(xid); + + return ((GlobalTransaction) proc)->dummyBackendId; +} + +/* + * TwoPhaseGetDummyProc * Get the PGPROC that represents a prepared transaction specified by XID */ PGPROC * |