8000 Introduce pg_stat_checkpointer · postgrespro/postgres@96f0526 · GitHub
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Introduce pg_stat_checkpointer
Historically, the statistics of the checkpointer have been always part of pg_stat_bgwriter. This commit removes a few columns from pg_stat_bgwriter, and introduces pg_stat_checkpointer with equivalent, renamed columns (plus a new one for the reset timestamp): - checkpoints_timed -> num_timed - checkpoints_req -> num_requested - checkpoint_write_time -> write_time - checkpoint_sync_time -> sync_time - buffers_checkpoint -> buffers_written The fields of PgStat_CheckpointerStats and its SQL functions are renamed to match with the new field names, for consistency. Note that background writer and checkpointer have been split into two different processes in commits 806a2ae and bf405ba. The pgstat structures were already split, making this change straight-forward. Bump catalog version. Author: Bharath Rupireddy Reviewed-by: Bertrand Drouvot, Andres Freund, Michael Paquier Discussion: https://postgr.es/m/CALj2ACVxX2ii=66RypXRweZe2EsBRiPMj0aHfRfHUeXJcC7kHg@mail.gmail.com
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    +187
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    lines changed

    ‎doc/src/sgml/monitoring.sgml

    Lines changed: 75 additions & 23 deletions
    Original file line numberDiff line numberDiff line change
    @@ -451,6 +451,15 @@ postgres 27093 0.0 0.0 30096 2752 ? Ss 11:34 0:00 postgres: ser
    451451
    </entry>
    452452
    </row>
    453453

    454+
    <row>
    455+
    <entry><structname>pg_stat_checkpointer</structname><indexterm><primary>pg_stat_checkpointer</primary></indexterm></entry>
    456+
    <entry>One row only, showing statistics about the
    457+
    checkpointer process's activity. See
    458+
    <link linkend="monitoring-pg-stat-checkpointer-view">
    459+
    <structname>pg_stat_checkpointer</structname></link> for details.
    460+
    </entry>
    461+
    </row>
    462+
    454463
    <row>
    455464
    <entry><structname>pg_stat_database</structname><indexterm><primary>pg_stat_database</primary></indexterm></entry>
    456465
    <entry>One row per database, showing database-wide statistics. See
    @@ -2868,7 +2877,7 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    28682877

    28692878
    <para>
    28702879
    The <structname>pg_stat_bgwriter</structname> view will always have a
    2871-
    single row, containing global data for the cluster.
    2880+
    single row, containing data about the background writer of the cluster.
    28722881
    </para>
    28732882

    28742883
    <table id="pg-stat-bgwriter-view" xreflabel="pg_stat_bgwriter">
    @@ -2888,77 +2897,118 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    28882897
    <tbody>
    28892898
    <row>
    28902899
    <entry role="catalog_table_entry"><para role="column_definition">
    2891-
    <structfield>checkpoints_timed</structfield> <type>bigint</type>
    2900+
    <structfield>buffers_clean</structfield> <type>bigint</type>
    28922901
    </para>
    28932902
    <para>
    2894-
    Number of scheduled checkpoints that have been performed
    2903+
    Number of buffers written by the background writer
    28952904
    </para></entry>
    28962905
    </row>
    28972906

    28982907
    <row>
    28992908
    <entry role="catalog_table_entry"><para role="column_definition">
    2900-
    <structfield>checkpoints_req</structfield> <type>bigint</type>
    2909+
    <structfield>maxwritten_clean</structfield> <type>bigint</type>
    29012910
    </para>
    29022911
    <para>
    2903-
    Number of requested checkpoints that have been performed
    2912+
    Number of times the background writer stopped a cleaning
    2913+
    scan because it had written too many buffers
    29042914
    </para></entry>
    29052915
    </row>
    29062916

    29072917
    <row>
    29082918
    <entry role="catalog_table_entry"><para role="column_definition">
    2909-
    <structfield>checkpoint_write_time</structfield> <type>double precision</type>
    2919+
    <structfield>buffers_alloc</structfield> <type>bigint</type>
    29102920
    </para>
    29112921
    <para>
    2912-
    Total amount of time that has been spent in the portion of
    2913-
    checkpoint processing where files are written to disk, in milliseconds
    2922+
    Number of buffers allocated
    29142923
    </para></entry>
    29152924
    </row>
    29162925

    29172926
    <row>
    29182927
    <entry role="catalog_table_entry"><para role="column_definition">
    2919-
    <structfield>checkpoint_sync_time</structfield> <type>double precision</type>
    2928+
    <structfield>stats_reset</structfield> <type>timestamp with time zone</type>
    29202929
    </para>
    29212930
    <para>
    2922-
    Total amount of time that has been spent in the portion of
    2923-
    checkpoint processing where files are synchronized to disk, in
    2924-
    milliseconds
    2931+
    Time at which these statistics were last reset
    29252932
    </para></entry>
    29262933
    </row>
    2934+
    </tbody>
    2935+
    </tgroup>
    2936+
    </table>
    2937+
    2938+
    </sect2>
    2939+
    2940+
    <sect2 id="monitoring-pg-stat-checkpointer-view">
    2941+
    <title><structname>pg_stat_checkpointer</structname></title>
    29272942

    2943+
    <indexterm>
    2944+
    <primary>pg_stat_checkpointer</primary>
    2945+
    </indexterm>
    2946+
    2947+
    <para>
    2948+
    The <structname>pg_stat_checkpointer</structname> view will always have a
    2949+
    single row, containing data about the checkpointer process of the cluster.
    2950+
    </para>
    2951+
    2952+
    <table id="pg-stat-checkpointer-view" xreflabel="pg_stat_checkpointer">
    2953+
    <title><structname>pg_stat_checkpointer</structname> View</title>
    2954+
    <tgroup cols="1">
    2955+
    <thead>
    29282956
    <row>
    29292957
    <entry role="catalog_table_entry"><para role="column_definition">
    2930-
    <structfield>buffers_checkpoint</structfield> <type>bigint</type>
    2958+
    Column Type
    29312959
    </para>
    29322960
    <para>
    2933-
    Number of buffers written during checkpoints
    2961+
    Description
    29342962
    </para></entry>
    29352963
    </row>
    2964+
    </thead>
    29362965

    2966+
    <tbody>
    29372967
    <row>
    29382968
    <entry role="catalog_table_entry"><para role="column_definition">
    2939-
    <structfield>buffers_clean</structfield> <type>bigint</type>
    2969+
    <structfield>num_timed</structfield> <type>bigint</type>
    29402970
    </para>
    29412971
    <para>
    2942-
    Number of buffers written by the background writer
    2972+
    Number of scheduled checkpoints that have been performed
    29432973
    </para></entry>
    29442974
    </row>
    29452975

    29462976
    <row>
    29472977
    <entry role="catalog_table_entry"><para role="column_definition">
    2948-
    <structfield>maxwritten_clean</structfield> <type>bigint</type>
    2978+
    <structfield>num_requested</structfield> <type>bigint</type>
    29492979
    </para>
    29502980
    <para>
    2951-
    Number of times the background writer stopped a cleaning
    2952-
    scan because it had written too many buffers
    2981+
    Number of requested checkpoints that have been performed
    29532982
    </para></entry>
    29542983
    </row>
    29552984

    29562985
    <row>
    29572986
    <entry role="catalog_table_entry"><para role="column_definition">
    2958-
    <structfield>buffers_alloc</structfield> <type>bigint</type>
    2987+
    <structfield>write_time</structfield> <type>double precision</type>
    29592988
    </para>
    29602989
    <para>
    2961-
    Number of buffers allocated
    2990+
    Total amount of time that has been spent in the portion of
    2991+
    checkpoint processing where files are written to disk, in milliseconds
    2992+
    </para></entry>
    2993+
    </row>
    2994+
    2995+
    <row>
    2996+
    <entry role="catalog_table_entry"><para role="column_definition">
    2997+
    <structfield>sync_time</structfield> <type>double precision</type>
    2998+
    </para>
    2999+
    <para>
    3000+
    Total amount of time that has been spent in the portion of
    3001+
    checkpoint processing where files are synchronized to disk, in
    3002+
    milliseconds
    3003+
    </para></entry>
    3004+
    </row>
    3005+
    3006+
    <row>
    3007+
    <entry role="catalog_table_entry"><para role="column_definition">
    3008+
    <structfield>buffers_written</structfield> <type>bigint</type>
    3009+
    </para>
    3010+
    <para>
    3011+
    Number of buffers written during checkpoints
    29623012
    </para></entry>
    29633013
    </row>
    29643014

    @@ -4669,8 +4719,10 @@ description | Waiting for a newly initialized WAL file to reach durable storage
    46694719
    Resets some cluster-wide statistics counters to zero, depending on the
    46704720
    argument. The argument can be <literal>bgwriter</literal> to reset
    46714721
    all the counters shown in
    4672-
    the <structname>pg_stat_bgwriter</structname>
    4673-
    view, <literal>archiver</literal> to reset all the counters shown in
    4722+
    the <structname>pg_stat_bgwriter</structname> view,
    4723+
    <literal>checkpointer</literal> to reset all the counters shown in
    4724+
    the <structname>pg_stat_checkpointer</structname> view,
    4725+
    <literal>archiver</literal> to reset all the counters shown in
    46744726
    the <structname>pg_stat_archiver</structname> view,
    46754727
    <literal>io</literal> to reset all the counters shown in the
    46764728
    <structname>pg_stat_io</structname> view,

    ‎src/backend/access/transam/xlog.c

    Lines changed: 2 additions & 2 deletions
    Original file line numberDiff line numberDiff line change
    @@ -6349,8 +6349,8 @@ LogCheckpointEnd(bool restartpoint)
    63496349
    CheckpointStats.ckpt_sync_end_t);
    63506350

    63516351
    /* Accumulate checkpoint timing summary data, in milliseconds. */
    6352-
    PendingCheckpointerStats.checkpoint_write_time += write_msecs;
    6353-
    PendingCheckpointerStats.checkpoint_sync_time += sync_msecs;
    6352+
    PendingCheckpointerStats.write_time += write_msecs;
    6353+
    PendingCheckpointerStats.sync_time += sync_msecs;
    63546354

    63556355
    /*
    63566356
    * All of the published timing statistics are accounted for. Only

    ‎src/backend/catalog/system_views.sql

    Lines changed: 9 additions & 5 deletions
    Original file line numberDiff line numberDiff line change
    @@ -1111,16 +1111,20 @@ CREATE VIEW pg_stat_archiver AS
    11111111

    11121112
    CREATE VIEW pg_stat_bgwriter AS
    11131113
    SELECT
    1114-
    pg_stat_get_bgwriter_timed_checkpoints() AS checkpoints_timed,
    1115-
    pg_stat_get_bgwriter_requested_checkpoints() AS checkpoints_req,
    1116-
    pg_stat_get_checkpoint_write_time() AS checkpoint_write_time,
    1117-
    pg_stat_get_checkpoint_sync_time() AS checkpoint_sync_time,
    1118-
    pg_stat_get_bgwriter_buf_written_checkpoints() AS buffers_checkpoint,
    11191114
    pg_stat_get_bgwriter_buf_written_clean() AS buffers_clean,
    11201115
    pg_stat_get_bgwriter_maxwritten_clean() AS maxwritten_clean,
    11211116
    pg_stat_get_buf_alloc() AS buffers_alloc,
    11221117
    pg_stat_get_bgwriter_stat_reset_time() AS stats_reset;
    11231118

    1119+
    CREATE VIEW pg_stat_checkpointer AS
    1120+
    SELECT
    1121+
    pg_stat_get_checkpointer_num_timed() AS num_timed,
    1122+
    pg_stat_get_checkpointer_num_requested() AS num_requested,
    1123+
    pg_stat_get_checkpointer_write_time() AS write_time,
    1124+
    pg_stat_get_checkpointer_sync_time() AS sync_time,
    1125+
    pg_stat_get_checkpointer_buffers_written() AS buffers_written,
    1126+
    pg_stat_get_checkpointer_stat_reset_time() AS stats_reset;
    1127+
    11241128
    CREATE VIEW pg_stat_io AS
    11251129
    SELECT
    11261130
    b.backend_type,

    ‎src/backend/postmaster/checkpointer.c

    Lines changed: 3 additions & 3 deletions
    Original file line numberDiff line numberDiff line change
    @@ -358,7 +358,7 @@ CheckpointerMain(void)
    358358
    if (((volatile CheckpointerShmemStruct *) CheckpointerShmem)->ckpt_flags)
    359359
    {
    360360
    do_checkpoint = true;
    361-
    PendingCheckpointerStats.requested_checkpoints++;
    361+
    PendingCheckpointerStats.num_requested++;
    362362
    }
    363363

    364364
    /*
    @@ -372,7 +372,7 @@ CheckpointerMain(void)
    372372
    if (elapsed_secs >= CheckPointTimeout)
    373373
    {
    374374
    if (!do_checkpoint)
    375-
    PendingCheckpointerStats.timed_checkpoints++;
    375+
    PendingCheckpointerStats.num_timed++;
    376376
    do_checkpoint = true;
    377377
    flags |= CHECKPOINT_CAUSE_TIME;
    378378
    }
    @@ -569,7 +569,7 @@ HandleCheckpointerInterrupts(void)
    569569
    * updates the statistics, increment the checkpoint request and flush
    570570
    * out pending statistic.
    571571
    */
    572-
    PendingCheckpointerStats.requested_checkpoints++;
    572+
    PendingCheckpointerStats.num_requested++;
    573573
    ShutdownXLOG(0, 0);
    574574
    pgstat_report_checkpointer();
    575575
    pgstat_report_wal(true);

    ‎src/backend/storage/buffer/bufmgr.c

    Lines changed: 1 addition & 1 deletion
    Original file line numberDiff line numberDiff line change
    @@ -2751,7 +2751,7 @@ BufferSync(int flags)
    27512751
    if (SyncOneBuffer(buf_id, false, &wb_context) & BUF_WRITTEN)
    27522752
    {
    27532753
    TRACE_POSTGRESQL_BUFFER_SYNC_WRITTEN(buf_id);
    2754-
    PendingCheckpointerStats.buf_written_checkpoints++;
    2754+
    PendingCheckpointerStats.buffers_written++;
    27552755
    num_written++;
    27562756
    }
    27572757
    }

    ‎src/backend/utils/activity/pgstat_checkpointer.c

    Lines changed: 11 additions & 10 deletions
    Original file line numberDiff line numberDiff line change
    @@ -47,11 +47,11 @@ pgstat_report_checkpointer(void)
    4747
    pgstat_begin_changecount_write(&stats_shmem->changecount);
    4848

    4949
    #define CHECKPOINTER_ACC(fld) stats_shmem->stats.fld += PendingCheckpointerStats.fld
    50-
    CHECKPOINTER_ACC(timed_checkpoints);
    51-
    CHECKPOINTER_ACC(requested_checkpoints);
    52-
    CHECKPOINTER_ACC(checkpoint_write_time);
    53-
    CHECKPOINTER_ACC(checkpoint_sync_time);
    54-
    CHECKPOINTER_ACC(buf_written_checkpoints);
    50+
    CHECKPOINTER_ACC(num_timed);
    51+
    CHECKPOINTER_ACC(num_requested);
    52+
    CHECKPOINTER_ACC(write_time);
    53+
    CHECKPOINTER_ACC(sync_time);
    54+
    CHECKPOINTER_ACC(buffers_written);
    5555
    #undef CHECKPOINTER_ACC
    5656

    5757
    pgstat_end_changecount_write(&stats_shmem->changecount);
    @@ -92,6 +92,7 @@ pgstat_checkpointer_reset_all_cb(TimestampTz ts)
    9292
    &stats_shmem->stats,
    9393
    sizeof(stats_shmem->stats),
    9494
    &stats_shmem->changecount);
    95+
    stats_shmem->stats.stat_reset_timestamp = ts;
    9596
    LWLockRelease(&stats_shmem->lock);
    9697
    }
    9798

    @@ -113,10 +114,10 @@ pgstat_checkpointer_snapshot_cb(void)
    113114

    114115
    /* compensate by reset offsets */
    115116
    #define CHECKPOINTER_COMP(fld) pgStatLocal.snapshot.checkpointer.fld -= reset.fld;
    116-
    CHECKPOINTER_COMP(timed_checkpoints);
    117-
    CHECKPOINTER_COMP(requested_checkpoints);
    118-
    CHECKPOINTER_COMP(checkpoint_write_time);
    119-
    CHECKPOINTER_COMP(checkpoint_sync_time);
    120-
    CHECKPOINTER_COMP(buf_written_checkpoints);
    117+
    CHECKPOINTER_COMP(num_timed);
    118+
    CHECKPOINTER_COMP(num_requested);
    119+
    CHECKPOINTER_COMP(write_time);
    120+
    CHECKPOINTER_COMP(sync_time);
    121+
    CHECKPOINTER_COMP(buffers_written);
    121122
    #undef CHECKPOINTER_COMP
    122123
    }

    ‎src/backend/utils/adt/pgstatfuncs.c

    Lines changed: 18 additions & 17 deletions
    Original file line numberDiff line numberDiff line change
    @@ -1182,21 +1182,21 @@ PG_STAT_GET_DBENTRY_FLOAT8_MS(idle_in_transaction_time)
    11821182
    PG_STAT_GET_DBENTRY_FLOAT8_MS(session_time)
    11831183

    11841184
    Datum
    1185-
    pg_stat_get_bgwriter_timed_checkpoints(PG_FUNCTION_ARGS)
    1185+
    pg_stat_get_checkpointer_num_timed(PG_FUNCTION_ARGS)
    11861186
    {
    1187-
    PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->timed_checkpoints);
    1187+
    PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->num_timed);
    11881188
    }
    11891189

    11901190
    Datum
    1191-
    pg_stat_get_bgwriter_requested_checkpoints(PG_FUNCTION_ARGS)
    1191+
    pg_stat_get_checkpointer_num_requested(PG_FUNCTION_ARGS)
    11921192
    {
    1193-
    PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->requested_checkpoints);
    1193+
    PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()-> 10000 num_requested);
    11941194
    }
    11951195

    11961196
    Datum
    1197-
    pg_stat_get_bgwriter_buf_written_checkpoints(PG_FUNCTION_ARGS)
    1197+
    pg_stat_get_checkpointer_buffers_written(PG_FUNCTION_ARGS)
    11981198
    {
    1199-
    PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->buf_written_checkpoints);
    1199+
    PG_RETURN_INT64(pgstat_fetch_stat_checkpointer()->buffers_written);
    12001200
    }
    12011201

    12021202
    Datum
    @@ -1212,19 +1212,25 @@ pg_stat_get_bgwriter_maxwritten_clean(PG_FUNCTION_ARGS)
    12121212
    }
    12131213

    12141214
    Datum
    1215-
    pg_stat_get_checkpoint_write_time(PG_FUNCTION_ARGS)
    1215+
    pg_stat_get_checkpointer_write_time(PG_FUNCTION_ARGS)
    12161216
    {
    12171217
    /* time is already in msec, just convert to double for presentation */
    12181218
    PG_RETURN_FLOAT8((double)
    1219-
    pgstat_fetch_stat_checkpointer()->checkpoint_write_time);
    1219+
    pgstat_fetch_stat_checkpointer()->write_time);
    12201220
    }
    12211221

    12221222
    Datum
    1223-
    pg_stat_get_checkpoint_sync_time(PG_FUNCTION_ARGS)
    1223+
    pg_stat_get_checkpointer_sync_time(PG_FUNCTION_ARGS)
    12241224
    {
    12251225
    /* time is already in msec, just convert to double for presentation */
    12261226
    PG_RETURN_FLOAT8((double)
    1227-
    pgstat_fetch_stat_checkpointer()->checkpoint_sync_time);
    1227+
    pgstat_fetch_stat_checkpointer()->sync_time);
    1228+
    }
    1229+
    1230+
    Datum
    1231+
    pg_stat_get_checkpointer_stat_reset_time(PG_FUNCTION_ARGS)
    1232+
    {
    1233+
    PG_RETURN_TIMESTAMPTZ(pgstat_fetch_stat_checkpointer()->stat_reset_timestamp);
    12281234
    }
    12291235

    12301236
    Datum
    @@ -1684,14 +1690,9 @@ pg_stat_reset_shared(PG_FUNCTION_ARGS)
    16841690
    if (strcmp(target, "archiver") == 0)
    16851691
    pgstat_reset_of_kind(PGSTAT_KIND_ARCHIVER);
    16861692
    else if (strcmp(target, "bgwriter") == 0)
    1687-
    {
    1688-
    /*
    1689-
    * Historically checkpointer was part of bgwriter, continue to reset
    1690-
    * both for now.
    1691-
    */
    16921693
    pgstat_reset_of_kind(PGSTAT_KIND_BGWRITER);
    1694+
    else if (strcmp(target, "checkpointer") == 0)
    16931695
    pgstat_reset_of_kind(PGSTAT_KIND_CHECKPOINTER);
    1694-
    }
    16951696
    else if (strcmp(target, "io") == 0)
    16961697
    pgstat_reset_of_kind(PGSTAT_KIND_IO);
    16971698
    else if (strcmp(target, "recovery_prefetch") == 0)
    @@ -1702,7 +1703,7 @@ pg_stat_reset_shared(PG_FUNCTION_ARGS)
    17021703
    ereport(ERROR,
    17031704
    (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
    17041705
    errmsg("unrecognized reset target: \"%s\"", target),
    1705-
    errhint("Target must be \"archiver\", \"bgwriter\", \"io\", \"recovery_prefetch\", or \"wal\".")));
    1706+
    errhint("Target must be \"archiver\", \"bgwriter\", \"checkpointer\", \"io\", \"recovery_prefetch\", or \"wal\".")));
    17061707

    17071708
    PG_RETURN_VOID();
    17081709
    }

    ‎src/include/catalog/catversion.h

    Lines changed: 1 addition & 1 deletion
    Original file line numberDiff line numberDiff line change
    @@ -57,6 +57,6 @@
    5757
    */
    5858

    5959
    /* yyyymmddN */
    60-
    #define CATALOG_VERSION_NO 202310271
    60+
    #define CATALOG_VERSION_NO 202310301
    6161

    6262
    #endif

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