PG Stat Statements helpers

v_pg_stat_statements_helpers.sql

\set common_pct 0.1
\set common_slow 10
\set other_slow 100

CREATE MATERIALIZED VIEW v_pg_stat_statements AS
WITH totals AS (
  SELECT sum(calls) as ttl_calls, sum(total_time) as ttl_time
  FROM pg_stat_statements
)
SELECT
  userid,
  dbid,
  queryid,
  -- shorten and clean up the query field
  substr(REGEXP_REPLACE(regexp_replace(query, '[ \t\n]+', ' ', 'g'), '^\s+|\s+$', ''), 1, 128) as short,
  -- Clean up the query field
  REGEXP_REPLACE(regexp_replace(query, '[ \t\n]+', ' ', 'g'), '^\s+|\s+$', '') as query,
  calls,
  total_time,
  min_time,
  max_time,
  mean_time,
  stddev_time,
  rows,
  shared_blks_hit,
  shared_blks_read,
  -- read comes from disk, hit comes from cache
  -- Shared blocks contain data from regular tables and indexes;
  -- local blocks contain data from temporary tables and indexes;
  -- cache hit rate: should be close to 1
  CASE
    WHEN (shared_blks_hit + shared_blks_read)::float = 0 THEN 0
    ELSE shared_blks_hit / (shared_blks_hit + shared_blks_read)::float
  END as hit_rate,
  shared_blks_dirtied,
  shared_blks_written,
  local_blks_hit,
  local_blks_read,
  local_blks_dirtied,
  local_blks_written,
  temp_blks_read,
  temp_blks_written,
  blk_read_time,
  blk_write_time,
  -- how many bytes of query text (not results) have been sent over the wire
  pg_size_pretty((calls*pg_column_size(query))::bigint) as query_bandwidth,
  (calls / totals.ttl_calls) AS pct_of_calls,
  (total_time / totals.ttl_time) AS pct_of_time
FROM pg_stat_statements, totals;

CREATE VIEW v_reads_pg_stat_statements AS
SELECT *
FROM v_pg_stat_statements
WHERE short ILIKE 'SELECT%' OR short ILIKE 'WITH%';

CREATE VIEW v_common_queries AS
SELECT *
FROM (
  SELECT percent_rank() OVER (ORDER BY calls DESC) AS pct, *
  FROM v_reads_pg_stat_statements
) AS ranked
WHERE pct <= :common_pct
ORDER BY calls DESC;

CREATE OR REPLACE VIEW v_slow_common_queries AS
SELECT *
FROM v_common_queries
WHERE mean_time > :common_slow
  OR stddev_time > :common_slow
ORDER BY calls DESC;

CREATE OR REPLACE VIEW v_slow_other_queries AS
SELECT *
FROM v_reads_pg_stat_statements
WHERE mean_time > :other_slow
  OR stddev_time > :other_slow
ORDER BY calls DESC;

CREATE OR REPLACE VIEW v_most_variance AS
SELECT *
FROM (
  SELECT percent_rank() OVER (ORDER BY stddev_time DESC) AS pct, *
  FROM v_reads_pg_stat_statements
) AS ranked
WHERE pct <= :common_pct
ORDER BY stddev_time DESC;


-- CREATE OR REPLACE FUNCTION pss_common_queries(IN max_pct float)
--   RETURNS TABLE (queryid bigint, pct double precision, calls bigint, total_time double precision) AS
-- $BODY$
-- BEGIN
--   return query
    -- SELECT ranked.queryid, ranked.pct, ranked.calls, ranked.total_time
    -- FROM (
    --   SELECT percent_rank() OVER (ORDER BY vr.calls DESC) AS pct, *
    --   FROM v_reads_pg_stat_statements AS vr
    -- ) AS ranked
    -- WHERE ranked.pct <= max_pct
    -- ORDER BY total_time DESC;
-- END;
-- $BODY$
-- LANGUAGE plpgsql VOLATILE;