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Add pg_stat_wal statistics view.

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This view shows the statistics about WAL activity. Currently it has only
two columns: wal_buffers_full and stats_reset. wal_buffers_full column
indicates the number of times WAL data was written to the disk because
WAL buffers got full. This information is useful when tuning wal_buffers.
stats_reset column indicates the time at which these statistics were
last reset.

pg_stat_wal view is also the basic infrastructure to expose other
various statistics about WAL activity later.

Bump PGSTAT_FILE_FORMAT_ID due to the change in pgstat format.

Bump catalog version.

Author: Masahiro Ikeda
Reviewed-by: Takayuki Tsunakawa, Kyotaro Horiguchi, Amit Kapila, Fujii Masao
Discussion: https://postgr.es/m/188bd3f2d2233cf97753b5ced02bb050@oss.nttdata.com
This commit is contained in:
Fujii Masao
2020-10-02 10:17:11 +09:00
parent 9d0bd95fa9
commit 8d9a935965
13 changed files with 276 additions and 11 deletions
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36
src/backend/utils/adt/pgstatfuncs.c
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@ -1697,6 +1697,42 @@ pg_stat_get_buf_alloc(PG_FUNCTION_ARGS)
PG_RETURN_INT64(pgstat_fetch_global()->buf_alloc);
}
/*
* Returns statistics of WAL activity
*/
Datum
pg_stat_get_wal(PG_FUNCTION_ARGS)
{
#define PG_STAT_GET_WAL_COLS 2
TupleDesc tupdesc;
Datum values[PG_STAT_GET_WAL_COLS];
bool nulls[PG_STAT_GET_WAL_COLS];
PgStat_WalStats *wal_stats;
/* Initialise values and NULL flags arrays */
MemSet(values, 0, sizeof(values));
MemSet(nulls, 0, sizeof(nulls));
/* Initialise attributes information in the tuple descriptor */
tupdesc = CreateTemplateTupleDesc(PG_STAT_GET_WAL_COLS);
TupleDescInitEntry(tupdesc, (AttrNumber) 1, "wal_buffers_full",
INT8OID, -1, 0);
TupleDescInitEntry(tupdesc, (AttrNumber) 2, "stats_reset",
TIMESTAMPTZOID, -1, 0);
BlessTupleDesc(tupdesc);
/* Get statistics about WAL activity */
wal_stats = pgstat_fetch_stat_wal();
/* Fill values and NULLs */
values[0] = Int64GetDatum(wal_stats->wal_buffers_full);
values[1] = TimestampTzGetDatum(wal_stats->stat_reset_timestamp);
/* Returns the record as Datum */
PG_RETURN_DATUM(HeapTupleGetDatum(heap_form_tuple(tupdesc, values, nulls)));
}
/*
* Returns statistics of SLRU caches.
*/