Update the patch. 1. The STANDBY_SNAPSHOT_PENDING state is set when we replay the first XLOG_RUNNING_XACTS and the sub transaction ids are overflow. 2. When we log XLOG_RUNNING_XACTS in master node, can we assume that all xact IDS < oldestRunningXid are considered finished? 3. If we can assume this, when we replay XLOG_RUNNING_XACTS and change standbyState to STANDBY_SNAPSHOT_PENDING, can we record oldestRunningXid to a shared variable, like procArray->oldest_running_xid? 4. In standby node when call GetSnapshotData if procArray->oldest_running_xid is valid, can we set xmin to be procArray->oldest_running_xid?
Appreciate any suggestion to this issue. At 2019-10-22 01:27:58, "Robert Haas" <robertmh...@gmail.com> wrote: >On Mon, Oct 21, 2019 at 4:13 AM Thunder <thund...@126.com> wrote: >> Can we fix this issue like the following patch? >> >> $git diff src/backend/access/transam/xlog.c >> diff --git a/src/backend/access/transam/xlog.c >> b/src/backend/access/transam/xlog.c >> index 49ae97d4459..0fbdf6fd64a 100644 >> --- a/src/backend/access/transam/xlog.c >> +++ b/src/backend/access/transam/xlog.c >> @@ -8365,7 +8365,7 @@ CheckRecoveryConsistency(void) >> * run? If so, we can tell postmaster that the database is >> consistent now, >> * enabling connections. >> */ >> - if (standbyState == STANDBY_SNAPSHOT_READY && >> + if ((standbyState == STANDBY_SNAPSHOT_READY || standbyState == >> STANDBY_SNAPSHOT_PENDING) && >> !LocalHotStandbyActive && >> reachedConsistency && >> IsUnderPostmaster) > >I think that the issue you've encountered is design behavior. In >other words, it's intended to work that way. > >The comments for the code you propose to change say that we can allow >connections once we've got a valid snapshot. So presumably the effect >of your change would be to allow connections even though we don't have >a valid snapshot. > >That seems bad. > >-- >Robert Haas >EnterpriseDB: http://www.enterprisedb.com >The Enterprise PostgreSQL Company
standby_service.patch
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