database/postgres
1
0
Fork 0
mirror of https://github.com/postgres/postgres.git synced 2025-11-16 15:02:33 +03:00
Code Activity

Allow read only connections during recovery, known as Hot Standby.

Browse Source 
Enabled by recovery_connections = on (default) and forcing archive recovery using a recovery.conf. Recovery processing now emulates the original transactions as they are replayed, providing full locking and MVCC behaviour for read only queries. Recovery must enter consistent state before connections are allowed, so there is a delay, typically short, before connections succeed. Replay of recovering transactions can conflict and in some cases deadlock with queries during recovery; these result in query cancellation after max_standby_delay seconds have expired. Infrastructure changes have minor effects on normal running, though introduce four new types of WAL record.

New test mode "make standbycheck" allows regression tests of static command behaviour on a standby server while in recovery. Typical and extreme dynamic behaviours have been checked via code inspection and manual testing. Few port specific behaviours have been utilised, though primary testing has been on Linux only so far.

This commit is the basic patch. Additional changes will follow in this release to enhance some aspects of behaviour, notably improved handling of conflicts, deadlock detection and query cancellation. Changes to VACUUM FULL are also required.

Simon Riggs, with significant and lengthy review by Heikki Linnakangas, including streamlined redesign of snapshot creation and two-phase commit.

Important contributions from Florian Pflug, Mark Kirkwood, Merlin Moncure, Greg Stark, Gianni Ciolli, Gabriele Bartolini, Hannu Krosing, Robert Haas, Tatsuo Ishii, Hiroyuki Yamada plus support and feedback from many other community members.
This commit is contained in:
Simon Riggs
2009-12-19 01:32:45 +00:00
parent 78a09145e0
commit efc16ea520
87 changed files with 6165 additions and 428 deletions
Download Patch File Download Diff File Expand all files Collapse all files

56
src/backend/access/nbtree/nbtpage.c
View File

@@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtpage.c,v 1.113 2009/05/05 19:02:22 tgl Exp $
* $PostgreSQL: pgsql/src/backend/access/nbtree/nbtpage.c,v 1.114 2009/12/19 01:32:33 sriggs Exp $
*
* NOTES
* Postgres btree pages look like ordinary relation pages. The opaque
@@ -653,19 +653,33 @@ _bt_page_recyclable(Page page)
*
* This routine assumes that the caller has pinned and locked the buffer.
* Also, the given itemnos *must* appear in increasing order in the array.
*
* We record VACUUMs and b-tree deletes differently in WAL. InHotStandby
* we need to be able to pin all of the blocks in the btree in physical
* order when replaying the effects of a VACUUM, just as we do for the
* original VACUUM itself. lastBlockVacuumed allows us to tell whether an
* intermediate range of blocks has had no changes at all by VACUUM,
* and so must be scanned anyway during replay. We always write a WAL record
* for the last block in the index, whether or not it contained any items
* to be removed. This allows us to scan right up to end of index to
* ensure correct locking.
*/
void
_bt_delitems(Relation rel, Buffer buf,
OffsetNumber *itemnos, int nitems)
OffsetNumber *itemnos, int nitems, bool isVacuum,
BlockNumber lastBlockVacuumed)
{
Page page = BufferGetPage(buf);
BTPageOpaque opaque;
Assert(isVacuum || lastBlockVacuumed == 0);
/* No ereport(ERROR) until changes are logged */
START_CRIT_SECTION();
/* Fix the page */
PageIndexMultiDelete(page, itemnos, nitems);
if (nitems > 0)
PageIndexMultiDelete(page, itemnos, nitems);
/*
* We can clear the vacuum cycle ID since this page has certainly been
@@ -688,15 +702,36 @@ _bt_delitems(Relation rel, Buffer buf,
/* XLOG stuff */
if (!rel->rd_istemp)
{
xl_btree_delete xlrec;
XLogRecPtr recptr;
XLogRecData rdata[2];
xlrec.node = rel->rd_node;
xlrec.block = BufferGetBlockNumber(buf);
if (isVacuum)
{
xl_btree_vacuum xlrec_vacuum;
xlrec_vacuum.node = rel->rd_node;
xlrec_vacuum.block = BufferGetBlockNumber(buf);
xlrec_vacuum.lastBlockVacuumed = lastBlockVacuumed;
rdata[0].data = (char *) &xlrec_vacuum;
rdata[0].len = SizeOfBtreeVacuum;
}
else
{
xl_btree_delete xlrec_delete;
xlrec_delete.node = rel->rd_node;
xlrec_delete.block = BufferGetBlockNumber(buf);
/*
* XXX: We would like to set an accurate latestRemovedXid, but
* there is no easy way of obtaining a useful value. So we punt
* and store InvalidTransactionId, which forces the standby to
* wait for/cancel all currently running transactions.
*/
xlrec_delete.latestRemovedXid = InvalidTransactionId;
rdata[0].data = (char *) &xlrec_delete;
rdata[0].len = SizeOfBtreeDelete;
}
rdata[0].data = (char *) &xlrec;
rdata[0].len = SizeOfBtreeDelete;
rdata[0].buffer = InvalidBuffer;
rdata[0].next = &(rdata[1]);
@@ -719,7 +754,10 @@ _bt_delitems(Relation rel, Buffer buf,
rdata[1].buffer_std = true;
rdata[1].next = NULL;
recptr = XLogInsert(RM_BTREE_ID, XLOG_BTREE_DELETE, rdata);
if (isVacuum)
recptr = XLogInsert(RM_BTREE_ID, XLOG_BTREE_VACUUM, rdata);
else
recptr = XLogInsert(RM_BTREE_ID, XLOG_BTREE_DELETE, rdata);
PageSetLSN(page, recptr);
PageSetTLI(page, ThisTimeLineID);