At Tue, 5 Apr 2016 20:17:21 +0900, Fujii Masao <[email protected]> wrote in
<CAHGQGwE8_F79BUpC5TmJ7aazXU=uju0vznfcckdk57-wnph...@mail.gmail.com>
> >> list_member_int() performs the loop internally. So I'm not sure how much
> >> adding extra list_member_int() here can optimize this processing.
> >> Another idea is to make SyncRepGetSyncStandby() check whether I'm sync
> >> standby or not. In this idea, without adding extra loop, we can exit
> >> earilier
> >> in the case where I'm not a sync standby. Does this make sense?
> >
> > The list_member_int() is also performed in the "(snip)" part. So
> > SyncRepGetSyncStandbys() returning am_sync seems making sense.
> >
> > sync_standbys = SyncRepGetSyncStandbys(am_sync);
> >
> > /*
> > * Quick exit if I am not synchronous or there's not
> > * enough synchronous standbys
> > * /
> > if (!*am_sync || list_length(sync_standbys) < SyncRepConfig->num_sync)
> > {
> > list_free(sync_standbys);
> > return false;
> > }
>
> Thanks for the comment! I changed SyncRepGetSyncStandbys() so that
> it checks whether we're managing a sync standby or not.
> Attached is the updated version of the patch. I also applied several
> review comments to the patch.
It still does list_member_int but it can be gotten rid of as the
attached patch.
regards,
diff --git a/src/backend/replication/syncrep.c b/src/backend/replication/syncrep.c
index 9b2137a..6998bb8 100644
--- a/src/backend/replication/syncrep.c
+++ b/src/backend/replication/syncrep.c
@@ -590,6 +590,10 @@ SyncRepGetSyncStandbys(bool *am_sync)
if (XLogRecPtrIsInvalid(walsnd->flush))
continue;
+ /* Notify myself as 'synchonized' if I am */
+ if (am_sync != NULL && walsnd == MyWalSnd)
+ *am_sync = true;
+
/*
* If the priority is equal to 1, consider this standby as sync
* and append it to the result. Otherwise append this standby
@@ -598,8 +602,6 @@ SyncRepGetSyncStandbys(bool *am_sync)
if (this_priority == 1)
{
result = lappend_int(result, i);
- if (am_sync != NULL && walsnd == MyWalSnd)
- *am_sync = true;
if (list_length(result) == SyncRepConfig->num_sync)
{
list_free(pending);
@@ -630,9 +632,6 @@ SyncRepGetSyncStandbys(bool *am_sync)
{
bool needfree = (result != NIL && pending != NIL);
- if (am_sync != NULL && !(*am_sync))
- *am_sync = list_member_int(pending, MyWalSnd->slotno);
-
result = list_concat(result, pending);
if (needfree)
pfree(pending);
@@ -640,6 +639,13 @@ SyncRepGetSyncStandbys(bool *am_sync)
}
/*
+ * The pending list contains eventually potentially-synchronized standbys
+ * and this walsender may be one of them. So once reset am_sync.
+ */
+ if (am_sync != NULL)
+ *am_sync = false;
+
+ /*
* Find the sync standbys from the pending list.
*/
priority = next_highest_priority;
--
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