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Add information of total data processed to replication slot stats. 

This adds the statistics about total transactions count and total
transaction data logically sent to the decoding output plugin from
ReorderBuffer. Users can query the pg_stat_replication_slots view to check
these stats.

Suggested-by: Andres Freund
Author: Vignesh C and Amit Kapila
Reviewed-by: Sawada Masahiko, Amit Kapila
Discussion: https://postgr.es/m/20210319185247.ldebgpdaxsowiflw@alap3.anarazel.de
This commit is contained in:
Amit Kapila 2021-04-16 07:34:43 +05:30
parent 1bf946bd43
commit f5fc2f5b23
15 changed files with 256 additions and 52 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
contrib/test_decoding/Makefile
View File

@ -17,6 +17,8 @@ ISOLATION_OPTS = --temp-config $(top_srcdir)/contrib/test_decoding/logical.conf
# typical installcheck users do not have (e.g. buildfarm clients).
NO_INSTALLCHECK = 1
TAP_TESTS = 1
ifdef USE_PGXS
PG_CONFIG = pg_config
PGXS := $(shell $(PG_CONFIG) --pgxs)

79
contrib/test_decoding/expected/stats.out
View File

@ -8,7 +8,7 @@ SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_d
CREATE TABLE stats_test(data text);
-- function to wait for counters to advance
CREATE FUNCTION wait_for_decode_stats(check_reset bool) RETURNS void AS $$
CREATE FUNCTION wait_for_decode_stats(check_reset bool, check_spill_txns bool) RETURNS void AS $$
DECLARE
start_time timestamptz := clock_timestamp();
updated bool;
@ -16,12 +16,25 @@ BEGIN
-- we don't want to wait forever; loop will exit after 30 seconds
FOR i IN 1 .. 300 LOOP
-- check to see if all updates have been reset/updated
SELECT CASE WHEN check_reset THEN (spill_txns = 0)
ELSE (spill_txns > 0)
END
INTO updated
FROM pg_stat_replication_slots WHERE slot_name='regression_slot';
IF check_spill_txns THEN
-- check to see if all updates have been reset/updated
SELECT CASE WHEN check_reset THEN (spill_txns = 0)
ELSE (spill_txns > 0)
END
INTO updated
FROM pg_stat_replication_slots WHERE slot_name='regression_slot';
ELSE
-- check to see if all updates have been reset/updated
SELECT CASE WHEN check_reset THEN (total_txns = 0)
ELSE (total_txns > 0)
END
INTO updated
FROM pg_stat_replication_slots WHERE slot_name='regression_slot';
END IF;
exit WHEN updated;
@ -51,16 +64,16 @@ SELECT count(*) FROM pg_logical_slot_peek_changes('regression_slot', NULL, NULL,
-- Check stats, wait for the stats collector to update. We can't test the
-- exact stats count as that can vary if any background transaction (say by
-- autovacuum) happens in parallel to the main transaction.
SELECT wait_for_decode_stats(false);
SELECT wait_for_decode_stats(false, true);
wait_for_decode_stats
-----------------------
(1 row)
SELECT slot_name, spill_txns > 0 AS spill_txns, spill_count > 0 AS spill_count FROM pg_stat_replication_slots;
slot_name | spill_txns | spill_count
-----------------+------------+-------------
regression_slot | t | t
SELECT slot_name, spill_txns > 0 AS spill_txns, spill_count > 0 AS spill_count, total_txns > 0 AS total_txns, total_bytes > 0 AS total_bytes FROM pg_stat_replication_slots;
slot_name | spill_txns | spill_count | total_txns | total_bytes
-----------------+------------+-------------+------------+-------------
regression_slot | t | t | t | t
(1 row)
-- reset the slot stats, and wait for stats collector to reset
@ -70,16 +83,16 @@ SELECT pg_stat_reset_replication_slot('regression_slot');
(1 row)
SELECT wait_for_decode_stats(true);
SELECT wait_for_decode_stats(true, true);
wait_for_decode_stats
-----------------------
(1 row)
SELECT slot_name, spill_txns, spill_count FROM pg_stat_replication_slots;
slot_name | spill_txns | spill_count
-----------------+------------+-------------
regression_slot | 0 | 0
SELECT slot_name, spill_txns, spill_count, total_txns, total_bytes FROM pg_stat_replication_slots;
slot_name | spill_txns | spill_count | total_txns | total_bytes
-----------------+------------+-------------+------------+-------------
regression_slot | 0 | 0 | 0 | 0
(1 row)
-- decode and check stats again.
@ -89,16 +102,36 @@ SELECT count(*) FROM pg_logical_slot_peek_changes('regression_slot', NULL, NULL,
5002
(1 row)
SELECT wait_for_decode_stats(false);
SELECT wait_for_decode_stats(false, true);
wait_for_decode_stats
-----------------------
(1 row)
SELECT slot_name, spill_txns > 0 AS spill_txns, spill_count > 0 AS spill_count FROM pg_stat_replication_slots;
slot_name | spill_txns | spill_count
-----------------+------------+-------------
regression_slot | t | t
SELECT slot_name, spill_txns > 0 AS spill_txns, spill_count > 0 AS spill_count, total_txns > 0 AS total_txns, total_bytes > 0 AS total_bytes FROM pg_stat_replication_slots;
slot_name | spill_txns | spill_count | total_txns | total_bytes
-----------------+------------+-------------+------------+-------------
regression_slot | t | t | t | t
(1 row)
SELECT pg_stat_reset_replication_slot('regression_slot');
pg_stat_reset_replication_slot
--------------------------------
(1 row)
-- non-spilled xact
INSERT INTO stats_test values(generate_series(1, 10));
SELECT wait_for_decode_stats(false, false);
wait_for_decode_stats
-----------------------
(1 row)
SELECT slot_name, spill_txns = 0 AS spill_txns, spill_count = 0 AS spill_count, total_txns > 0 AS total_txns, total_bytes > 0 AS total_bytes FROM pg_stat_replication_slots;
slot_name | spill_txns | spill_count | total_txns | total_bytes
-----------------+------------+-------------+------------+-------------
regression_slot | f | f | t | t
(1 row)
-- Ensure stats can be repeatedly accessed using the same stats snapshot. See
@ -117,7 +150,7 @@ SELECT slot_name FROM pg_stat_replication_slots;
(1 row)
COMMIT;
DROP FUNCTION wait_for_decode_stats(bool);
DROP FUNCTION wait_for_decode_stats(bool, bool);
DROP TABLE stats_test;
SELECT pg_drop_replication_slot('regression_slot');
pg_drop_replication_slot

48
contrib/test_decoding/sql/stats.sql
View File

@ -6,7 +6,7 @@ SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_d
CREATE TABLE stats_test(data text);
-- function to wait for counters to advance
CREATE FUNCTION wait_for_decode_stats(check_reset bool) RETURNS void AS $$
CREATE FUNCTION wait_for_decode_stats(check_reset bool, check_spill_txns bool) RETURNS void AS $$
DECLARE
start_time timestamptz := clock_timestamp();
updated bool;
@ -14,12 +14,25 @@ BEGIN
-- we don't want to wait forever; loop will exit after 30 seconds
FOR i IN 1 .. 300 LOOP
-- check to see if all updates have been reset/updated
SELECT CASE WHEN check_reset THEN (spill_txns = 0)
ELSE (spill_txns > 0)
END
INTO updated
FROM pg_stat_replication_slots WHERE slot_name='regression_slot';
IF check_spill_txns THEN
-- check to see if all updates have been reset/updated
SELECT CASE WHEN check_reset THEN (spill_txns = 0)
ELSE (spill_txns > 0)
END
INTO updated
FROM pg_stat_replication_slots WHERE slot_name='regression_slot';
ELSE
-- check to see if all updates have been reset/updated
SELECT CASE WHEN check_reset THEN (total_txns = 0)
ELSE (total_txns > 0)
END
INTO updated
FROM pg_stat_replication_slots WHERE slot_name='regression_slot';
END IF;
exit WHEN updated;
@ -46,18 +59,25 @@ SELECT count(*) FROM pg_logical_slot_peek_changes('regression_slot', NULL, NULL,
-- Check stats, wait for the stats collector to update. We can't test the
-- exact stats count as that can vary if any background transaction (say by
-- autovacuum) happens in parallel to the main transaction.
SELECT wait_for_decode_stats(false);
SELECT slot_name, spill_txns > 0 AS spill_txns, spill_count > 0 AS spill_count FROM pg_stat_replication_slots;
SELECT wait_for_decode_stats(false, true);
SELECT slot_name, spill_txns > 0 AS spill_txns, spill_count > 0 AS spill_count, total_txns > 0 AS total_txns, total_bytes > 0 AS total_bytes FROM pg_stat_replication_slots;
-- reset the slot stats, and wait for stats collector to reset
SELECT pg_stat_reset_replication_slot('regression_slot');
SELECT wait_for_decode_stats(true);
SELECT slot_name, spill_txns, spill_count FROM pg_stat_replication_slots;
SELECT wait_for_decode_stats(true, true);
SELECT slot_name, spill_txns, spill_count, total_txns, total_bytes FROM pg_stat_replication_slots;
-- decode and check stats again.
SELECT count(*) FROM pg_logical_slot_peek_changes('regression_slot', NULL, NULL, 'skip-empty-xacts', '1');
SELECT wait_for_decode_stats(false);
SELECT slot_name, spill_txns > 0 AS spill_txns, spill_count > 0 AS spill_count FROM pg_stat_replication_slots;
SELECT wait_for_decode_stats(false, true);
SELECT slot_name, spill_txns > 0 AS spill_txns, spill_count > 0 AS spill_count, total_txns > 0 AS total_txns, total_bytes > 0 AS total_bytes FROM pg_stat_replication_slots;
SELECT pg_stat_reset_replication_slot('regression_slot');
-- non-spilled xact
INSERT INTO stats_test values(generate_series(1, 10));
SELECT wait_for_decode_stats(false, false);
SELECT slot_name, spill_txns = 0 AS spill_txns, spill_count = 0 AS spill_count, total_txns > 0 AS total_txns, total_bytes > 0 AS total_bytes FROM pg_stat_replication_slots;
-- Ensure stats can be repeatedly accessed using the same stats snapshot. See
-- https://postgr.es/m/20210317230447.c7uc4g3vbs4wi32i%40alap3.anarazel.de
@ -66,6 +86,6 @@ SELECT slot_name FROM pg_stat_replication_slots;
SELECT slot_name FROM pg_stat_replication_slots;
COMMIT;
DROP FUNCTION wait_for_decode_stats(bool);
DROP FUNCTION wait_for_decode_stats(bool, bool);
DROP TABLE stats_test;
SELECT pg_drop_replication_slot('regression_slot');

76
contrib/test_decoding/t/001_repl_stats.pl Normal file
View File

@ -0,0 +1,76 @@
# Test replication statistics data in pg_stat_replication_slots is sane after
# drop replication slot and restart.
use strict;
use warnings;
use PostgresNode;
use TestLib;
use Test::More tests => 1;
# Test set-up
my $node = get_new_node('test');
$node->init(allows_streaming => 'logical');
$node->append_conf('postgresql.conf', 'synchronous_commit = on');
$node->start;
# Create table.
$node->safe_psql('postgres',
"CREATE TABLE test_repl_stat(col1 int)");
# Create replication slots.
$node->safe_psql(
'postgres', qq[
SELECT pg_create_logical_replication_slot('regression_slot1', 'test_decoding');
SELECT pg_create_logical_replication_slot('regression_slot2', 'test_decoding');
SELECT pg_create_logical_replication_slot('regression_slot3', 'test_decoding');
SELECT pg_create_logical_replication_slot('regression_slot4', 'test_decoding');
]);
# Insert some data.
$node->safe_psql('postgres', "INSERT INTO test_repl_stat values(generate_series(1, 5));");
$node->safe_psql(
'postgres', qq[
SELECT data FROM pg_logical_slot_get_changes('regression_slot1', NULL,
NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
SELECT data FROM pg_logical_slot_get_changes('regression_slot2', NULL,
NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
SELECT data FROM pg_logical_slot_get_changes('regression_slot3', NULL,
NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
SELECT data FROM pg_logical_slot_get_changes('regression_slot4', NULL,
NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
]);
# Wait for the statistics to be updated.
$node->poll_query_until(
'postgres', qq[
SELECT count(slot_name) >= 4 FROM pg_stat_replication_slots
WHERE slot_name ~ 'regression_slot'
AND total_txns > 0 AND total_bytes > 0;
]) or die "Timed out while waiting for statistics to be updated";
# Test to drop one of the replication slot and verify replication statistics data is
# fine after restart.
$node->safe_psql('postgres', "SELECT pg_drop_replication_slot('regression_slot4')");
$node->stop;
$node->start;
# Verify statistics data present in pg_stat_replication_slots are sane after
# restart.
my $result = $node->safe_psql('postgres',
"SELECT slot_name, total_txns > 0 AS total_txn,
total_bytes > 0 AS total_bytes FROM pg_stat_replication_slots
ORDER BY slot_name"
);
is($result, qq(regression_slot1|t|t
regression_slot2|t|t
regression_slot3|t|t), 'check replication statistics are updated');
# cleanup
$node->safe_psql('postgres', "DROP TABLE test_repl_stat");
$node->safe_psql('postgres', "SELECT pg_drop_replication_slot('regression_slot1')");
$node->safe_psql('postgres', "SELECT pg_drop_replication_slot('regression_slot2')");
$node->safe_psql('postgres', "SELECT pg_drop_replication_slot('regression_slot3')");
# shutdown
$node->stop;

25
doc/src/sgml/monitoring.sgml
View File

@ -2716,6 +2716,31 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
</entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>total_txns</structfield> <type>bigint</type>
</para>
<para>
Number of decoded transactions sent to the decoding output plugin for
this slot. This counter is used to maintain the top level transactions,
so the counter is not incremented for subtransactions. Note that this
includes the transactions that are streamed and/or spilled.
</para></entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>total_bytes</structfield><type>bigint</type>
</para>
<para>
Amount of decoded transactions data sent to the decoding output plugin
while decoding the changes from WAL for this slot. This can be used to
gauge the total amount of data sent during logical decoding. Note that
this includes the data that is streamed and/or spilled.
</para>
</entry>
</row>
<row>
<entry role="catalog_table_entry"><para role="column_definition">
<structfield>stats_reset</structfield> <type>timestamp with time zone</type>

2
src/backend/catalog/system_views.sql
View File

@ -875,6 +875,8 @@ CREATE VIEW pg_stat_replication_slots AS
s.stream_txns,
s.stream_count,
s.stream_bytes,
s.total_txns,
s.total_bytes,
s.stats_reset
FROM pg_stat_get_replication_slots() AS s;

6
src/backend/postmaster/pgstat.c
View File

@ -1829,6 +1829,8 @@ pgstat_report_replslot(const PgStat_ReplSlotStats *repSlotStat)
msg.m_stream_txns = repSlotStat->stream_txns;
msg.m_stream_count = repSlotStat->stream_count;
msg.m_stream_bytes = repSlotStat->stream_bytes;
msg.m_total_txns = repSlotStat->total_txns;
msg.m_total_bytes = repSlotStat->total_bytes;
pgstat_send(&msg, sizeof(PgStat_MsgReplSlot));
}
@ -5568,6 +5570,8 @@ pgstat_recv_replslot(PgStat_MsgReplSlot *msg, int len)
replSlotStats[idx].stream_txns += msg->m_stream_txns;
replSlotStats[idx].stream_count += msg->m_stream_count;
replSlotStats[idx].stream_bytes += msg->m_stream_bytes;
replSlotStats[idx].total_txns += msg->m_total_txns;
replSlotStats[idx].total_bytes += msg->m_total_bytes;
}
}
@ -5795,6 +5799,8 @@ pgstat_reset_replslot(int i, TimestampTz ts)
replSlotStats[i].stream_txns = 0;
replSlotStats[i].stream_count = 0;
replSlotStats[i].stream_bytes = 0;
replSlotStats[i].total_txns = 0;
replSlotStats[i].total_bytes = 0;
replSlotStats[i].stat_reset_timestamp = ts;
}

18
src/backend/replication/logical/logical.c
View File

@ -1775,21 +1775,20 @@ UpdateDecodingStats(LogicalDecodingContext *ctx)
ReorderBuffer *rb = ctx->reorder;
PgStat_ReplSlotStats repSlotStat;
/*
* Nothing to do if we haven't spilled or streamed anything since the last
* time the stats has been sent.
*/
if (rb->spillBytes <= 0 && rb->streamBytes <= 0)
/* Nothing to do if we don't have any replication stats to be sent. */
if (rb->spillBytes <= 0 && rb->streamBytes <= 0 && rb->totalBytes <= 0)
return;
elog(DEBUG2, "UpdateDecodingStats: updating stats %p %lld %lld %lld %lld %lld %lld",
elog(DEBUG2, "UpdateDecodingStats: updating stats %p %lld %lld %lld %lld %lld %lld %lld %lld",
rb,
(long long) rb->spillTxns,
(long long) rb->spillCount,
(long long) rb->spillBytes,
(long long) rb->streamTxns,
(long long) rb->streamCount,
(long long) rb->streamBytes);
(long long) rb->streamBytes,
(long long) rb->totalTxns,
(long long) rb->totalBytes);
namestrcpy(&repSlotStat.slotname, NameStr(ctx->slot->data.name));
repSlotStat.spill_txns = rb->spillTxns;
@ -1798,12 +1797,17 @@ UpdateDecodingStats(LogicalDecodingContext *ctx)
repSlotStat.stream_txns = rb->streamTxns;
repSlotStat.stream_count = rb->streamCount;
repSlotStat.stream_bytes = rb->streamBytes;
repSlotStat.total_txns = rb->totalTxns;
repSlotStat.total_bytes = rb->totalBytes;
pgstat_report_replslot(&repSlotStat);
rb->spillTxns = 0;
rb->spillCount = 0;
rb->spillBytes = 0;
rb->streamTxns = 0;
rb->streamCount = 0;
rb->streamBytes = 0;
rb->totalTxns = 0;
rb->totalBytes = 0;
}

21
src/backend/replication/logical/reorderbuffer.c
View File

@ -350,6 +350,8 @@ ReorderBufferAllocate(void)
buffer->streamTxns = 0;
buffer->streamCount = 0;
buffer->streamBytes = 0;
buffer->totalTxns = 0;
buffer->totalBytes = 0;
buffer->current_restart_decoding_lsn = InvalidXLogRecPtr;
@ -1363,6 +1365,11 @@ ReorderBufferIterTXNNext(ReorderBuffer *rb, ReorderBufferIterTXNState *state)
dlist_delete(&change->node);
dlist_push_tail(&state->old_change, &change->node);
/*
* Update the total bytes processed before releasing the current set
* of changes and restoring the new set of changes.
*/
rb->totalBytes += rb->size;
if (ReorderBufferRestoreChanges(rb, entry->txn, &entry->file,
&state->entries[off].segno))
{
@ -2363,6 +2370,20 @@ ReorderBufferProcessTXN(ReorderBuffer *rb, ReorderBufferTXN *txn,
ReorderBufferIterTXNFinish(rb, iterstate);
iterstate = NULL;
/*
* Update total transaction count and total transaction bytes
* processed. Ensure to not count the streamed transaction multiple
* times.
*
* Note that the statistics computation has to be done after
* ReorderBufferIterTXNFinish as it releases the serialized change
* which we have already accounted in ReorderBufferIterTXNNext.
*/
if (!rbtxn_is_streamed(txn))
rb->totalTxns++;
rb->totalBytes += rb->size;
/*
* Done with current changes, send the last message for this set of
* changes depending upon streaming mode.

8
src/backend/utils/adt/pgstatfuncs.c
View File

@ -2284,7 +2284,7 @@ pg_stat_get_archiver(PG_FUNCTION_ARGS)
Datum
pg_stat_get_replication_slots(PG_FUNCTION_ARGS)
{
#define PG_STAT_GET_REPLICATION_SLOT_COLS 8
#define PG_STAT_GET_REPLICATION_SLOT_COLS 10
ReturnSetInfo *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
TupleDesc tupdesc;
Tuplestorestate *tupstore;
@ -2335,11 +2335,13 @@ pg_stat_get_replication_slots(PG_FUNCTION_ARGS)
values[4] = Int64GetDatum(s->stream_txns);
values[5] = Int64GetDatum(s->stream_count);
values[6] = Int64GetDatum(s->stream_bytes);
values[7] = Int64GetDatum(s->total_txns);
values[8] = Int64GetDatum(s->total_bytes);
if (s->stat_reset_timestamp == 0)
nulls[7] = true;
nulls[9] = true;
else
values[7] = TimestampTzGetDatum(s->stat_reset_timestamp);
values[9] = TimestampTzGetDatum(s->stat_reset_timestamp);
tuplestore_putvalues(tupstore, tupdesc, values, nulls);
}

2
src/include/catalog/catversion.h
View File

@ -53,6 +53,6 @@
*/
/* yyyymmddN */
#define CATALOG_VERSION_NO 202104151
#define CATALOG_VERSION_NO 202104161
#endif

6
src/include/catalog/pg_proc.dat
View File

@ -5315,9 +5315,9 @@
proname => 'pg_stat_get_replication_slots', prorows => '10',
proisstrict => 'f', proretset => 't', provolatile => 's', proparallel => 'r',
prorettype => 'record', proargtypes => '',
proallargtypes => '{text,int8,int8,int8,int8,int8,int8,timestamptz}',
proargmodes => '{o,o,o,o,o,o,o,o}',
proargnames => '{slot_name,spill_txns,spill_count,spill_bytes,stream_txns,stream_count,stream_bytes,stats_reset}',
proallargtypes => '{text,int8,int8,int8,int8,int8,int8,int8,int8,timestamptz}',
proargmodes => '{o,o,o,o,o,o,o,o,o,o}',
proargnames => '{slot_name,spill_txns,spill_count,spill_bytes,stream_txns,stream_count,stream_bytes,total_txns,total_bytes,stats_reset}',
prosrc => 'pg_stat_get_replication_slots' },
{ oid => '6118', descr => 'statistics: information about subscription',
proname => 'pg_stat_get_subscription', prorows => '10', proisstrict => 'f',

4
src/include/pgstat.h
View File

@ -548,6 +548,8 @@ typedef struct PgStat_MsgReplSlot
PgStat_Counter m_stream_txns;
PgStat_Counter m_stream_count;
PgStat_Counter m_stream_bytes;
PgStat_Counter m_total_txns;
PgStat_Counter m_total_bytes;
} PgStat_MsgReplSlot;
/* ----------
@ -924,6 +926,8 @@ typedef struct PgStat_ReplSlotStats
PgStat_Counter stream_txns;
PgStat_Counter stream_count;
PgStat_Counter stream_bytes;
PgStat_Counter total_txns;
PgStat_Counter total_bytes;
TimestampTz stat_reset_timestamp;
} PgStat_ReplSlotStats;

7
src/include/replication/reorderbuffer.h
View File

@ -618,6 +618,13 @@ struct ReorderBuffer
int64 streamTxns; /* number of transactions streamed */
int64 streamCount; /* streaming invocation counter */
int64 streamBytes; /* amount of data streamed */
/*
* Statistics about all the transactions sent to the decoding output
* plugin
*/
int64 totalTxns; /* total number of transactions sent */
int64 totalBytes; /* total amount of data sent */
};

4
src/test/regress/expected/rules.out
View File

@ -2068,8 +2068,10 @@ pg_stat_replication_slots| SELECT s.slot_name,
s.stream_txns,
s.stream_count,
s.stream_bytes,
s.total_txns,
s.total_bytes,
s.stats_reset
FROM pg_stat_get_replication_slots() s(slot_name, spill_txns, spill_count, spill_bytes, stream_txns, stream_count, stream_bytes, stats_reset);
FROM pg_stat_get_replication_slots() s(slot_name, spill_txns, spill_count, spill_bytes, stream_txns, stream_count, stream_bytes, total_txns, total_bytes, stats_reset);
pg_stat_slru| SELECT s.name,
s.blks_zeroed,
s.blks_hit,