diff options
| author | Simon Riggs <simon@2ndQuadrant.com> | 2011-03-06 22:49:16 +0000 |
|---|---|---|
| committer | Simon Riggs <simon@2ndQuadrant.com> | 2011-03-06 22:49:16 +0000 |
| commit | a8a8a3e0965201df88bdfdff08f50e5c06c552b7 (patch) | |
| tree | c29687748fa9d5e9bc335e11bf3d8446563184c3 /src/backend/storage/ipc | |
| parent | 149b2673c244b92b59411dd2292d6ddcfb03d5d4 (diff) | |
Efficient transaction-controlled synchronous replication.
If a standby is broadcasting reply messages and we have named
one or more standbys in synchronous_standby_names then allow
users who set synchronous_replication to wait for commit, which
then provides strict data integrity guarantees. Design avoids
sending and receiving transaction state information so minimises
bookkeeping overheads. We synchronize with the highest priority
standby that is connected and ready to synchronize. Other standbys
can be defined to takeover in case of standby failure.
This version has very strict behaviour; more relaxed options
may be added at a later date.
Simon Riggs and Fujii Masao, with reviews by Yeb Havinga, Jaime
Casanova, Heikki Linnakangas and Robert Haas, plus the assistance
of many other design reviewers.
Diffstat (limited to 'src/backend/storage/ipc')
| -rw-r--r-- | src/backend/storage/ipc/shmqueue.c | 21 |
1 files changed, 19 insertions, 2 deletions
diff --git a/src/backend/storage/ipc/shmqueue.c b/src/backend/storage/ipc/shmqueue.c index 1cf69a09c83..5d684b2b85f 100644 --- a/src/backend/storage/ipc/shmqueue.c +++ b/src/backend/storage/ipc/shmqueue.c @@ -104,7 +104,6 @@ SHMQueueInsertBefore(SHM_QUEUE *queue, SHM_QUEUE *elem) * element. Inserting "after" the queue head puts the elem * at the head of the queue. */ -#ifdef NOT_USED void SHMQueueInsertAfter(SHM_QUEUE *queue, SHM_QUEUE *elem) { @@ -118,7 +117,6 @@ SHMQueueInsertAfter(SHM_QUEUE *queue, SHM_QUEUE *elem) queue->next = elem; nextPtr->prev = elem; } -#endif /* NOT_USED */ /*-------------------- * SHMQueueNext -- Get the next element from a queue @@ -156,6 +154,25 @@ SHMQueueNext(const SHM_QUEUE *queue, const SHM_QUEUE *curElem, Size linkOffset) return (Pointer) (((char *) elemPtr) - linkOffset); } +/*-------------------- + * SHMQueuePrev -- Get the previous element from a queue + * + * Same as SHMQueueNext, just starting at tail and moving towards head + * All other comments and usage applies. + */ +Pointer +SHMQueuePrev(const SHM_QUEUE *queue, const SHM_QUEUE *curElem, Size linkOffset) +{ + SHM_QUEUE *elemPtr = curElem->prev; + + Assert(ShmemAddrIsValid(curElem)); + + if (elemPtr == queue) /* back to the queue head? */ + return NULL; + + return (Pointer) (((char *) elemPtr) - linkOffset); +} + /* * SHMQueueEmpty -- TRUE if queue head is only element, FALSE otherwise */ |