Voir le 'gonflement des tables , la requête provient de la sonde nagios / icinga check_postgres de bucardo.org.
requête complexe triée (tables non bloatée n'apparaissent pas):
| WITH constants AS ( -- definition de constantes pour les tailles -- pour référence dans la requête et avoir un entretien facilité SELECT current_setting('block_size')::numeric AS bs, 23 AS hdr, 8 AS ma ), no_stats AS ( -- exclusion des tables qui ont des attributs -- qui n'ont pas de statistiques, telles que JSON SELECT table_schema, table_name, n_live_tup::numeric as est_rows, pg_table_size(relid)::numeric as table_size FROM information_schema.columns JOIN pg_stat_user_tables as psut ON table_schema = psut.schemaname AND table_name = psut.relname LEFT OUTER JOIN pg_stats ON table_schema = pg_stats.schemaname AND table_name = pg_stats.tablename AND column_name = attname WHERE attname IS NULL AND table_schema NOT IN ('pg_catalog', 'information_schema') GROUP BY table_schema, table_name, relid, n_live_tup ), null_headers AS ( -- trouver les en-têtes nulles -- omission des tables qui n'ont pas de statistiques complètes -- et des attributs qui ne sont pas visibles SELECT hdr+1+(sum(case when null_frac <> 0 THEN 1 else 0 END)/8) as nullhdr, SUM((1-null_frac)*avg_width) as datawidth, MAX(null_frac) as maxfracsum, schemaname, tablename, hdr, ma, bs FROM pg_stats CROSS JOIN constants LEFT OUTER JOIN no_stats ON schemaname = no_stats.table_schema AND tablename = no_stats.table_name WHERE schemaname NOT IN ('pg_catalog', 'information_schema') AND no_stats.table_name IS NULL AND EXISTS ( SELECT 1 FROM information_schema.columns WHERE schemaname = columns.table_schema AND tablename = columns.table_name ) GROUP BY schemaname, tablename, hdr, ma, bs ), data_headers AS ( -- estimation de la taille de l'en-tête et de la ligne SELECT ma, bs, hdr, schemaname, tablename, (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 null_headers ), table_estimates AS ( -- estimations de la taille des tables -- en fonctionde la taille de la ligne et de la page SELECT schemaname, tablename, bs, reltuples::numeric as est_rows, relpages * bs as table_bytes, CEIL((reltuples* (datahdr + nullhdr2 + 4 + ma - (CASE WHEN datahdr%ma=0 THEN ma ELSE datahdr%ma END) )/(bs-20))) * bs AS expected_bytes, reltoastrelid FROM data_headers JOIN pg_class ON tablename = relname JOIN pg_namespace ON relnamespace = pg_namespace.oid AND schemaname = nspname WHERE pg_class.relkind = 'r' ), estimates_with_toast AS ( -- ajouter les tailles estimées des tables 'TOAST' -- estimation basée sur 4 toast tuples par page car on a rien de mieux -- ajout également des tables no_data SELECT schemaname, tablename, TRUE as can_estimate, est_rows, table_bytes + ( coalesce(toast.relpages, 0) * bs ) as table_bytes, expected_bytes + ( ceil( coalesce(toast.reltuples, 0) / 4 ) * bs ) as expected_bytes FROM table_estimates LEFT OUTER JOIN pg_class as toast ON table_estimates.reltoastrelid = toast.oid AND toast.relkind = 't' ), table_estimates_plus AS ( -- ajout des métadonnées supplémentaire aux données de la table -- et aux calculs à réutiliser -- y compris si nous ne pouvons pas l'estimer -- ou si nous pensons qu'elles pourraient être compressées SELECT current_database() as databasename, schemaname, tablename, can_estimate, est_rows, CASE WHEN table_bytes > 0 THEN table_bytes::NUMERIC ELSE NULL::NUMERIC END AS table_bytes, CASE WHEN expected_bytes > 0 THEN expected_bytes::NUMERIC ELSE NULL::NUMERIC END AS expected_bytes, CASE WHEN expected_bytes > 0 AND table_bytes > 0 AND expected_bytes <= table_bytes THEN (table_bytes - expected_bytes)::NUMERIC ELSE 0::NUMERIC END AS bloat_bytes FROM estimates_with_toast UNION ALL SELECT current_database() as databasename, table_schema, table_name, FALSE, est_rows, table_size, NULL::NUMERIC, NULL::NUMERIC FROM no_stats ), bloat_data AS ( -- calculs finaux et formatage du résultat select current_database() as databasename, schemaname, tablename, can_estimate, table_bytes, round(table_bytes/(1024^2)::NUMERIC,3) as table_mb, expected_bytes, round(expected_bytes/(1024^2)::NUMERIC,3) as expected_mb, round(bloat_bytes*100/table_bytes) as pct_bloat, round(bloat_bytes/(1024::NUMERIC^2),2) as mb_bloat, table_bytes, expected_bytes, est_rows FROM table_estimates_plus ) -- sortie de filtre pour les tables bloatées SELECT databasename, schemaname, tablename, can_estimate, est_rows, pct_bloat, mb_bloat, table_mb FROM bloat_data -- ce where définit les tables qui apparaissent réellement -- dans le qraphique des bloat -- exemple ci-dessous les filtres pour les tables qui sont à 50% -- bloatée avec plus de 20mb , ou plus de 25% -- bloatée avec plus 1GB WHERE ( pct_bloat >= 1 AND mb_bloat >= 20 ) OR ( pct_bloat >= 1 AND mb_bloat >= 20 ) ORDER BY pct_bloat DESC; |
requête plus simple non triée
| SELECT current_database(), schemaname, tablename, /*reltuples::bigint, relpages::bigint, otta,*/ ROUND((CASE WHEN otta=0 THEN 0.0 ELSE sml.relpages::FLOAT/otta END)::NUMERIC,1) AS tbloat, CASE WHEN relpages < otta THEN 0 ELSE bs*(sml.relpages-otta)::BIGINT END AS wastedbytes, iname, /*ituples::bigint, ipages::bigint, iotta,*/ ROUND((CASE WHEN iotta=0 OR ipages=0 THEN 0.0 ELSE ipages::FLOAT/iotta END)::NUMERIC,1) AS ibloat, CASE WHEN ipages < iotta THEN 0 ELSE bs*(ipages-iotta) END AS wastedibytes FROM ( SELECT schemaname, tablename, cc.reltuples, cc.relpages, bs, CEIL((cc.reltuples*((datahdr+ma- (CASE WHEN datahdr%ma=0 THEN ma ELSE datahdr%ma END))+nullhdr2+4))/(bs-20::FLOAT)) 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 ( SELECT ma,bs,schemaname,tablename, (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 schemaname, tablename, hdr, ma, bs, SUM((1-null_frac)*avg_width) AS datawidth, MAX(null_frac) AS maxfracsum, hdr+( SELECT 1+COUNT(*)/8 FROM pg_stats s2 WHERE null_frac<>0 AND s2.schemaname = s.schemaname AND s2.tablename = s.tablename ) AS nullhdr FROM pg_stats s, ( SELECT (SELECT current_setting('block_size')::NUMERIC) AS bs, CASE WHEN SUBSTRING(v,12,3) IN ('8.0','8.1','8.2') THEN 27 ELSE 23 END AS hdr, CASE WHEN v ~ 'mingw32' THEN 8 ELSE 4 END AS ma FROM (SELECT version() AS v) AS foo ) AS constants GROUP BY 1,2,3,4,5 ) AS foo ) AS rs JOIN pg_class cc ON cc.relname = rs.tablename JOIN pg_namespace nn ON cc.relnamespace = nn.oid AND nn.nspname = rs.schemaname AND nn.nspname <> 'information_schema' LEFT JOIN pg_index i ON indrelid = cc.oid LEFT JOIN pg_class c2 ON c2.oid = i.indexrelid ) AS sml ORDER BY wastedbytes DESC |