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Add a new WAL summarizer process.

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When active, this process writes WAL summary files to
$PGDATA/pg_wal/summaries. Each summary file contains information for a
certain range of LSNs on a certain TLI. For each relation, it stores a
"limit block" which is 0 if a relation is created or destroyed within
a certain range of WAL records, or otherwise the shortest length to
which the relation was truncated during that range of WAL records, or
otherwise InvalidBlockNumber. In addition, it stores a list of blocks
which have been modified during that range of WAL records, but
excluding blocks which were removed by truncation after they were
modified and never subsequently modified again.

In other words, it tells us which blocks need to copied in case of an
incremental backup covering that range of WAL records. But this
doesn't yet add the capability to actually perform an incremental
backup; the next patch will do that.

A new parameter summarize_wal enables or disables this new background
process.  The background process also automatically deletes summary
files that are older than wal_summarize_keep_time, if that parameter
has a non-zero value and the summarizer is configured to run.

Patch by me, with some design help from Dilip Kumar and Andres Freund.
Reviewed by Matthias van de Meent, Dilip Kumar, Jakub Wartak, Peter
Eisentraut, and Álvaro Herrera.

Discussion: http://postgr.es/m/CA+TgmoYOYZfMCyOXFyC-P+-mdrZqm5pP2N7S-r0z3_402h9rsA@mail.gmail.com
This commit is contained in:
Robert Haas
2023-12-20 08:41:09 -05:00
parent 00498b7185
commit 174c480508
30 changed files with 3743 additions and 11 deletions
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26
src/backend/utils/misc/guc_tables.c
View File

@ -63,6 +63,7 @@
#include "postmaster/postmaster.h"
#include "postmaster/startup.h"
#include "postmaster/syslogger.h"
#include "postmaster/walsummarizer.h"
#include "postmaster/walwriter.h"
#include "replication/logicallauncher.h"
#include "replication/slot.h"
@ -703,6 +704,8 @@ const char *const config_group_names[] =
gettext_noop("Write-Ahead Log / Archive Recovery"),
/* WAL_RECOVERY_TARGET */
gettext_noop("Write-Ahead Log / Recovery Target"),
/* WAL_SUMMARIZATION */
gettext_noop("Write-Ahead Log / Summarization"),
/* REPLICATION_SENDING */
gettext_noop("Replication / Sending Servers"),
/* REPLICATION_PRIMARY */
@ -1786,6 +1789,16 @@ struct config_bool ConfigureNamesBool[] =
NULL, NULL, NULL
},
{
{"summarize_wal", PGC_SIGHUP, WAL_SUMMARIZATION,
gettext_noop("Starts the WAL summarizer process to enable incremental backup."),
NULL
},
&summarize_wal,
false,
NULL, NULL, NULL
},
{
{"hot_standby", PGC_POSTMASTER, REPLICATION_STANDBY,
gettext_noop("Allows connections and queries during recovery."),
@ -3200,6 +3213,19 @@ struct config_int ConfigureNamesInt[] =
check_wal_segment_size, NULL, NULL
},
{
{"wal_summary_keep_time", PGC_SIGHUP, WAL_SUMMARIZATION,
gettext_noop("Time for which WAL summary files should be kept."),
NULL,
GUC_UNIT_MIN,
},
&wal_summary_keep_time,
10 * 24 * 60, /* 10 days */
0,
INT_MAX,
NULL, NULL, NULL
},
{
{"autovacuum_naptime", PGC_SIGHUP, AUTOVACUUM,
gettext_noop("Time to sleep between autovacuum runs."),