Queries to monitor your PostgreSQL database

These have been compiled from multiple sources like the postgresql wiki, and check_postgres.

Usage

These PREPAREd statements are essentially queries with names (and 0 arguments) for convenience. Once you have executed a PREPARE, you can run it using EXECUTE like so:

EXECUTE query_stats;

You can either copy/paste these in selectively, or use the full list of queries.

Cost

These queries can be run periodically to send data to your monitoring system. They are all cheap enough to be run every few seconds even during heavy load.

Queries

current_queries_status (pg9.x)

PREPARE current_queries_status AS
SELECT count(pid), query, waiting from pg_stat_activity group by query, waiting;

current_queries_status_with_locks (pg9.x)

PREPARE current_queries_status_with_locks AS
SELECT count(pg_stat_activity.pid) AS number_of_queries,
       substring(trim(LEADING
                      FROM regexp_replace(pg_stat_activity.query, '[\n\r]+'::text,
                       ' '::text, 'g'::text))
                 FROM 0
                 FOR 200) AS query_name,
       max(age(CURRENT_TIMESTAMP, query_start)) AS max_wait_time,
       waiting,
       usename,
       locktype,
       mode,
       granted
  FROM pg_stat_activity
  LEFT JOIN pg_locks ON pg_stat_activity.pid = pg_locks.pid
  WHERE query != '<IDLE>'
    AND query NOT ILIKE '%pg_%' AND query NOT ILIKE '%application_name%' AND query NOT ILIKE '%inet%'
    AND age(CURRENT_TIMESTAMP, query_start) > '5 milliseconds'::interval
  GROUP BY query_name,
           waiting,
           usename,
           locktype,
           mode,
           granted
  ORDER BY max_wait_time DESC;

current_queries_status_with_locks (pg10)

PREPARE current_queries_status_with_locks AS
SELECT count(pg_stat_activity.pid) AS number_of_queries,
       substring(trim(LEADING
                      FROM regexp_replace(pg_stat_activity.query, '[\n\r]+'::text,
                       ' '::text, 'g'::text))
                 FROM 0
                 FOR 200) AS query_name,
       max(age(CURRENT_TIMESTAMP, query_start)) AS max_wait_time,
       wait_event,
       usename,
       locktype,
       mode,
       granted
  FROM pg_stat_activity
  LEFT JOIN pg_locks ON pg_stat_activity.pid = pg_locks.pid
  WHERE query != '<IDLE>'
    AND query NOT ILIKE '%pg_%' AND query NOT ILIKE '%application_name%' AND query NOT ILIKE '%inet%'
    AND age(CURRENT_TIMESTAMP, query_start) > '5 milliseconds'::interval
  GROUP BY query_name,
           wait_event,
           usename,
           locktype,
           mode,
           granted
  ORDER BY max_wait_time DESC;

query_stats

PREPARE query_stats AS
SELECT LEFT(query,50) AS query,
       calls, total_time, rows, shared_blks_hit,
       local_blks_hit, blk_read_time, blk_write_time
FROM pg_stat_statements
WHERE EXISTS(SELECT * FROM pg_available_extensions
             WHERE name = 'pg_stat_statements')
ORDER BY calls DESC;

This requires pg_stat_statements to be set up. It's a part of the contrib package, and needs to be added to shared_preload_libraries in postgresql.conf.

Long Running Queries

sql
SELECT
  pid,
  user,
  pg_stat_activity.query_start,
  now() - pg_stat_activity.query_start AS query_time,
  query,
  state,
  wait_event_type,
  wait_event
FROM pg_stat_activity
WHERE (now() - pg_stat_activity.query_start) > interval '5 minutes';

This enables you to know the queries running for more than x Minutes (5 here). This gives you visibility as what might be hogging up your CPU and network pool. Crucial in determining what might take your DB down in high traffic.

Cache

cache_tables

PREPARE cache_tables AS
SELECT relname AS "relation",
       heap_blks_read AS heap_read,
       heap_blks_hit AS heap_hit,
       ( (heap_blks_hit*100) / NULLIF((heap_blks_hit + heap_blks_read), 0)) AS ratio
FROM pg_statio_user_tables;

cache_total

PREPARE cache_total AS
SELECT sum(heap_blks_read) AS heap_read,
       sum(heap_blks_hit)  AS heap_hit,
       (sum(heap_blks_hit)*100 / NULLIF((sum(heap_blks_hit) + sum(heap_blks_read)),0)) AS ratio
FROM pg_statio_user_tables;

Disk usage

table_sizes

PREPARE table_sizes AS
SELECT relname AS "relation",
       pg_size_pretty(pg_total_relation_size(C.oid)) AS "total_size"
FROM pg_class C
LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace)
WHERE nspname NOT IN ('pg_catalog', 'information_schema')
      AND C.relkind <> 'i'
      AND nspname ='public'
ORDER BY pg_total_relation_size(C.oid) DESC;

relation_sizes

PREPARE relation_sizes AS
SELECT relname AS "relation",
    pg_size_pretty(pg_relation_size(C.oid)) AS "size"
FROM pg_class C
LEFT JOIN pg_namespace N ON (N.oid = C.relnamespace)
WHERE nspname = 'public'
ORDER BY pg_relation_size(C.oid) DESC;

db_size

PREPARE db_size AS
SELECT pg_size_pretty(pg_database_size(current_database()));

Bloat

table_bloat

PREPARE table_bloat AS
SELECT tblname as "relation", pg_size_pretty((bs*tblpages)::bigint) AS real_size,
  pg_size_pretty(((tblpages-est_tblpages)*bs)::bigint) AS extra_size,
  CASE WHEN tblpages - est_tblpages > 0
    THEN 100 * (tblpages - est_tblpages)/tblpages::float
    ELSE 0
  END AS extra_ratio, fillfactor, pg_size_pretty(((tblpages-est_tblpages_ff)*bs)::bigint) AS bloat_size,
  CASE WHEN tblpages - est_tblpages_ff > 0
    THEN 100 * (tblpages - est_tblpages_ff)/tblpages::float
    ELSE 0
  END AS bloat_ratio, is_na::varchar
  -- , (pst).free_percent + (pst).dead_tuple_percent AS real_frag
FROM (
  SELECT ceil( reltuples / ( (bs-page_hdr)/tpl_size ) ) + ceil( toasttuples / 4 ) AS est_tblpages,
    ceil( reltuples / ( (bs-page_hdr)*fillfactor/(tpl_size*100) ) ) + ceil( toasttuples / 4 ) AS est_tblpages_ff,
    tblpages, fillfactor, bs, tblid, schemaname, tblname, heappages, toastpages, is_na
    -- , stattuple.pgstattuple(tblid) AS pst
  FROM (
    SELECT
      ( 4 + tpl_hdr_size + tpl_data_size + (2*ma)
        - CASE WHEN tpl_hdr_size%ma = 0 THEN ma ELSE tpl_hdr_size%ma END
        - CASE WHEN ceil(tpl_data_size)::int%ma = 0 THEN ma ELSE ceil(tpl_data_size)::int%ma END
      ) AS tpl_size, bs - page_hdr AS size_per_block, (heappages + toastpages) AS tblpages, heappages,
      toastpages, reltuples, toasttuples, bs, page_hdr, tblid, schemaname, tblname, fillfactor, is_na
    FROM (
      SELECT
        tbl.oid AS tblid, ns.nspname AS schemaname, tbl.relname AS tblname, tbl.reltuples,
        tbl.relpages AS heappages, coalesce(toast.relpages, 0) AS toastpages,
        coalesce(toast.reltuples, 0) AS toasttuples,
        coalesce(substring(
          array_to_string(tbl.reloptions, ' ')
          FROM '%fillfactor=#"__#"%' FOR '#')::smallint, 100) AS fillfactor,
        current_setting('block_size')::numeric AS bs,
        CASE WHEN version()~'mingw32' OR version()~'64-bit|x86_64|ppc64|ia64|amd64' THEN 8 ELSE 4 END AS ma,
        24 AS page_hdr,
        23 + CASE WHEN MAX(coalesce(null_frac,0)) > 0 THEN ( 7 + count(*) ) / 8 ELSE 0::int END
          + CASE WHEN tbl.relhasoids THEN 4 ELSE 0 END AS tpl_hdr_size,
        sum( (1-coalesce(s.null_frac, 0)) * coalesce(s.avg_width, 1024) ) AS tpl_data_size,
        bool_or(att.atttypid = 'pg_catalog.name'::regtype) AS is_na
      FROM pg_attribute AS att
        JOIN pg_class AS tbl ON att.attrelid = tbl.oid
        JOIN pg_namespace AS ns ON ns.oid = tbl.relnamespace
        JOIN pg_stats AS s ON s.schemaname=ns.nspname AND ns.nspname = 'public'
          AND s.tablename = tbl.relname AND s.inherited=false AND s.attname=att.attname
        LEFT JOIN pg_class AS toast ON tbl.reltoastrelid = toast.oid
      WHERE att.attnum > 0 AND NOT att.attisdropped
        AND tbl.relkind = 'r'
      GROUP BY 1,2,3,4,5,6,7,8,9,10, tbl.relhasoids
      ORDER BY 2,3
    ) AS s
  ) AS s2
) AS s3;

table_and_index_bloat

PREPARE table_and_index_bloat AS
SELECT
  tablename AS "relation", reltuples::bigint AS tups, relpages::bigint AS pages, otta,
  ROUND(CASE WHEN otta=0 OR sml.relpages=0 OR sml.relpages=otta THEN 0.0 ELSE sml.relpages/otta::numeric END,1) AS tbloat,
  CASE WHEN relpages < otta THEN 0 ELSE relpages::bigint - otta END AS wastedpages,
  CASE WHEN relpages < otta THEN 0 ELSE bs*(sml.relpages-otta)::bigint END AS wastedbytes,
  CASE WHEN relpages < otta THEN 0 ELSE (bs*(relpages-otta))::bigint END AS wastedsize,
  iname, ituples::bigint AS itups, ipages::bigint AS ipages, iotta,
  ROUND(CASE WHEN iotta=0 OR ipages=0 OR ipages=iotta THEN 0.0 ELSE ipages/iotta::numeric END,1) AS ibloat,
  CASE WHEN ipages < iotta THEN 0 ELSE ipages::bigint - iotta END AS wastedipages,
  CASE WHEN ipages < iotta THEN 0 ELSE bs*(ipages-iotta) END AS wastedibytes,
  CASE WHEN ipages < iotta THEN 0 ELSE (bs*(ipages-iotta))::bigint END AS wastedisize,
  CASE WHEN relpages < otta THEN
    CASE WHEN ipages < iotta THEN 0 ELSE bs*(ipages-iotta::bigint) END
    ELSE CASE WHEN ipages < iotta THEN bs*(relpages-otta::bigint)
      ELSE bs*(relpages-otta::bigint + ipages-iotta::bigint) END
  END AS totalwastedbytes
FROM (
  SELECT
    nn.nspname AS schemaname,
    cc.relname AS tablename,
    COALESCE(cc.reltuples,0) AS reltuples,
    COALESCE(cc.relpages,0) AS relpages,
    COALESCE(bs,0) AS bs,
    COALESCE(CEIL((cc.reltuples*((datahdr+ma-
      (CASE WHEN datahdr%ma=0 THEN ma ELSE datahdr%ma END))+nullhdr2+4))/(bs-20::float)),0) AS otta,
    COALESCE(c2.relname,'?') AS iname, COALESCE(c2.reltuples,0) AS ituples, COALESCE(c2.relpages,0) AS ipages,
    COALESCE(CEIL((c2.reltuples*(datahdr-12))/(bs-20::float)),0) AS iotta -- very rough approximation, assumes all cols
  FROM
     pg_class cc
  JOIN pg_namespace nn ON cc.relnamespace = nn.oid AND nn.nspname = 'public'
  LEFT JOIN
  (
    SELECT
      ma,bs,foo.nspname,foo.relname,
      (datawidth+(hdr+ma-(case when hdr%ma=0 THEN ma ELSE hdr%ma END)))::numeric AS datahdr,
      (maxfracsum*(nullhdr+ma-(case when nullhdr%ma=0 THEN ma ELSE nullhdr%ma END))) AS nullhdr2
    FROM (
      SELECT
        ns.nspname, tbl.relname, hdr, ma, bs,
        SUM((1-coalesce(null_frac,0))*coalesce(avg_width, 2048)) AS datawidth,
        MAX(coalesce(null_frac,0)) AS maxfracsum,
        hdr+(
          SELECT 1+count(*)/8
          FROM pg_stats s2
          WHERE null_frac<>0 AND s2.schemaname = ns.nspname AND s2.tablename = tbl.relname
        ) AS nullhdr
      FROM pg_attribute att
      JOIN pg_class tbl ON att.attrelid = tbl.oid
      JOIN pg_namespace ns ON ns.oid = tbl.relnamespace
      LEFT JOIN pg_stats s ON s.schemaname=ns.nspname
      AND s.tablename = tbl.relname
      AND s.inherited=false
      AND s.attname=att.attname,
      (
        SELECT
          (SELECT current_setting('block_size')::numeric) AS bs,
            CASE WHEN SUBSTRING(SPLIT_PART(v, ' ', 2) FROM '#"[0-9]+.[0-9]+#"%' for '#')
              IN ('8.0','8.1','8.2') THEN 27 ELSE 23 END AS hdr,
          CASE WHEN v ~ 'mingw32' OR v ~ '64-bit' THEN 8 ELSE 4 END AS ma
        FROM (SELECT version() AS v) AS foo
      ) AS constants
      WHERE att.attnum > 0 AND tbl.relkind='r'
      GROUP BY 1,2,3,4,5
    ) AS foo
  ) AS rs
  ON cc.relname = rs.relname AND nn.nspname = rs.nspname AND nn.nspname = 'public'
  LEFT JOIN pg_index i ON indrelid = cc.oid
  LEFT JOIN pg_class c2 ON c2.oid = i.indexrelid
) AS sml;

Indexes

index_usage

PREPARE index_usage AS
SELECT
    t.tablename AS "relation",
    indexname,
    c.reltuples AS num_rows,
    pg_size_pretty(pg_relation_size(quote_ident(t.tablename)::text)) AS table_size,
    pg_size_pretty(pg_relation_size(quote_ident(indexrelname)::text)) AS index_size,
    idx_scan AS number_of_scans,
    idx_tup_read AS tuples_read,
    idx_tup_fetch AS tuples_fetched
FROM pg_tables t
LEFT OUTER JOIN pg_class c ON t.tablename=c.relname
LEFT OUTER JOIN
    ( SELECT c.relname AS ctablename, ipg.relname AS indexname, x.indnatts AS number_of_columns, idx_scan, idx_tup_read, idx_tup_fetch, indexrelname, indisunique FROM pg_index x
           JOIN pg_class c ON c.oid = x.indrelid
           JOIN pg_class ipg ON ipg.oid = x.indexrelid
           JOIN pg_stat_all_indexes psai ON x.indexrelid = psai.indexrelid )
    AS foo
    ON t.tablename = foo.ctablename
WHERE t.schemaname='public'
ORDER BY 1,2;

Tuples and Autovacuum

tuple_info

PREPARE tuple_info AS
SELECT relname as "relation", EXTRACT (EPOCH FROM current_timestamp-last_autovacuum) as since_last_av,
       autovacuum_count as av_count, n_tup_ins, n_tup_upd, n_tup_del, n_live_tup, n_dead_tup
FROM pg_stat_all_tables
WHERE schemaname = 'public'
ORDER BY relname;

Replication

replication_status (pg9.x)

PREPARE replication_status AS
SELECT application_name,client_addr,state,sent_location,write_location,replay_location,
                 (sent_offset - (replay_offset - (sent_xlog - replay_xlog) * 255 * 16 ^ 6 ))::text AS byte_lag
                  FROM (SELECT
                          application_name,client_addr,state,sync_state,sent_location,write_location,replay_location,
                          ('x' || lpad(split_part(sent_location::text,   '/', 1), 8, '0'))::bit(32)::bigint AS sent_xlog,
                          ('x' || lpad(split_part(replay_location::text, '/', 1), 8, '0'))::bit(32)::bigint AS replay_xlog,
                          ('x' || lpad(split_part(sent_location::text,   '/', 2), 8, '0'))::bit(32)::bigint AS sent_offset,
                          ('x' || lpad(split_part(replay_location::text, '/', 2), 8, '0'))::bit(32)::bigint AS replay_offset
                        FROM pg_stat_replication)
                  AS s;

replication_status (pg10)

PREPARE replication_status AS
SELECT application_name,client_addr,state, \\
                 (sent_offset - (replay_offset - (sent_xlog - replay_xlog) * 255 * 16 ^ 6 ))::text AS byte_lag \\
                  FROM (SELECT \\
                          application_name,client_addr,state,sync_state,sent_lsn,write_lsn,replay_lsn, \\
                          ('x' || lpad(split_part(sent_lsn::text,   '/', 1), 8, '0'))::bit(32)::bigint AS sent_xlog, \\
                          ('x' || lpad(split_part(replay_lsn::text, '/', 1), 8, '0'))::bit(32)::bigint AS replay_xlog, \\
                          ('x' || lpad(split_part(sent_lsn::text,   '/', 2), 8, '0'))::bit(32)::bigint AS sent_offset, \\
                          ('x' || lpad(split_part(replay_lsn::text, '/', 2), 8, '0'))::bit(32)::bigint AS replay_offset \\
                        FROM pg_stat_replication) \\
                  AS s;

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