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Update the PLPGSQL queries to resolve duplicate queries #1013

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Update the PLPGSQL queries to resolve duplicate queries #1013

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76 changes: 36 additions & 40 deletions collector/pg_stat_statements.go
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Original file line number Diff line number Diff line change
Expand Up @@ -71,47 +71,43 @@ var (
prometheus.Labels{},
)

pgStatStatementsQuery = `SELECT
pg_get_userbyid(userid) as user,
pg_database.datname,
pg_stat_statements.queryid,
pg_stat_statements.calls as calls_total,
pg_stat_statements.total_time / 1000.0 as seconds_total,
pg_stat_statements.rows as rows_total,
pg_stat_statements.blk_read_time / 1000.0 as block_read_seconds_total,
pg_stat_statements.blk_write_time / 1000.0 as block_write_seconds_total
FROM pg_stat_statements
JOIN pg_database
ON pg_database.oid = pg_stat_statements.dbid
WHERE
total_time > (
SELECT percentile_cont(0.1)
WITHIN GROUP (ORDER BY total_time)
FROM pg_stat_statements
pgStatStatementsQuery = `WITH percentiles AS (
SELECT percentile_cont(0.1) WITHIN GROUP (ORDER BY total_time) AS percentile
FROM pg_stat_statements
)
ORDER BY seconds_total DESC
LIMIT 100;`

pgStatStatementsNewQuery = `SELECT
pg_get_userbyid(userid) as user,
pg_database.datname,
pg_stat_statements.queryid,
pg_stat_statements.calls as calls_total,
pg_stat_statements.total_exec_time / 1000.0 as seconds_total,
pg_stat_statements.rows as rows_total,
pg_stat_statements.blk_read_time / 1000.0 as block_read_seconds_total,
pg_stat_statements.blk_write_time / 1000.0 as block_write_seconds_total
FROM pg_stat_statements
JOIN pg_database
ON pg_database.oid = pg_stat_statements.dbid
WHERE
total_exec_time > (
SELECT percentile_cont(0.1)
WITHIN GROUP (ORDER BY total_exec_time)
FROM pg_stat_statements
)
ORDER BY seconds_total DESC
LIMIT 100;`
SELECT DISTINCT ON (pss.queryid, pg_get_userbyid(pss.userid), pg_database.datname)
pg_get_userbyid(pss.userid) as user,
pg_database.datname,
pss.queryid,
pss.calls as calls_total,
pss.total_time / 1000.0 as seconds_total,
pss.rows as rows_total,
pss.blk_read_time / 1000.0 as block_read_seconds_total,
pss.blk_write_time / 1000.0 as block_write_seconds_total
FROM pg_stat_statements pss
JOIN pg_database ON pg_database.oid = pss.dbid
CROSS JOIN percentiles
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Can you explain the CROSS JOIN here? I'm having trouble understanding the why. My understanding is that CROSS JOIN will produce a cartesian product where every possible combination of table A and B will exist.

WHERE pss.total_time > (SELECT percentile FROM percentiles)
ORDER BY pss.queryid, pg_get_userbyid(pss.userid) DESC, pg_database.datname
LIMIT 100;`

pgStatStatementsNewQuery = `SELECT DISTINCT ON (pss.queryid, pg_get_userbyid(pss.userid), pg_database.datname)
pg_get_userbyid(pss.userid) AS user,
pg_database.datname AS database_name,
pss.queryid,
pss.calls AS calls_total,
pss.total_exec_time / 1000.0 AS seconds_total,
pss.rows AS rows_total,
pss.blk_read_time / 1000.0 AS block_read_seconds_total,
pss.blk_write_time / 1000.0 AS block_write_seconds_total
FROM pg_stat_statements pss
JOIN pg_database ON pg_database.oid = pss.dbid
JOIN (
SELECT percentile_cont(0.1) WITHIN GROUP (ORDER BY total_exec_time) AS percentile_val
FROM pg_stat_statements
) AS perc ON pss.total_exec_time > perc.percentile_val
ORDER BY pss.queryid, pg_get_userbyid(pss.userid) DESC, pg_database.datname
LIMIT 100;`
)

func (PGStatStatementsCollector) Update(ctx context.Context, instance *instance, ch chan<- prometheus.Metric) error {
Expand Down