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Check for conflicting queries during replay of gistvacuumpage()

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013ebc0a7b implements so-called GiST microvacuum.  That is gistgettuple() marks
index tuples as dead when kill_prior_tuple is set.  Later, when new tuple
insertion claims page space, those dead index tuples are physically deleted
from page.  When this deletion is replayed on standby, it might conflict with
read-only queries.  But 013ebc0a7b doesn't handle this.  That may lead to
disappearance of some tuples from read-only snapshots on standby.

This commit implements resolving of conflicts between replay of GiST microvacuum
and standby queries.  On the master we implement new WAL record type
XLOG_GIST_DELETE, which comprises necessary information.  On stable releases
we've to be tricky to keep WAL compatibility.  Information required for conflict
processing is just appended to data of XLOG_GIST_PAGE_UPDATE record.  So,
PostgreSQL version, which doesn't know about conflict processing, will just
ignore that.

Reported-by: Andres Freund
Diagnosed-by: Andres Freund
Discussion: https://postgr.es/m/20181212224524.scafnlyjindmrbe6%40alap3.anarazel.de
Author: Alexander Korotkov
Backpatch-through: 9.6
This commit is contained in:
Alexander Korotkov
2018-12-21 02:37:37 +03:00
parent 7c15cef86d
commit c952eae52a
6 changed files with 298 additions and 13 deletions
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11
src/backend/access/rmgrdesc/gistdesc.c
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@@ -23,6 +23,11 @@ out_gistxlogPageUpdate(StringInfo buf, gistxlogPageUpdate *xlrec)
{
}
static void
out_gistxlogDelete(StringInfo buf, gistxlogPageUpdate *xlrec)
{
}
static void
out_gistxlogPageSplit(StringInfo buf, gistxlogPageSplit *xlrec)
{
@@ -41,6 +46,9 @@ gist_desc(StringInfo buf, XLogReaderState *record)
case XLOG_GIST_PAGE_UPDATE:
out_gistxlogPageUpdate(buf, (gistxlogPageUpdate *) rec);
break;
case XLOG_GIST_DELETE:
out_gistxlogDelete(buf, (gistxlogPageUpdate *) rec);
break;
case XLOG_GIST_PAGE_SPLIT:
out_gistxlogPageSplit(buf, (gistxlogPageSplit *) rec);
break;
@@ -59,6 +67,9 @@ gist_identify(uint8 info)
case XLOG_GIST_PAGE_UPDATE:
id = "PAGE_UPDATE";
break;
case XLOG_GIST_DELETE:
id = "DELETE";
break;
case XLOG_GIST_PAGE_SPLIT:
id = "PAGE_SPLIT";
break;