Query to check Bloated Index - PostgreSQL

 

/*Query to check Bloated Index*/

———————————————————————————————————–

WITH btree_index_atts AS (

SELECT nspname, relname, reltuples, relpages, indrelid, relam,

regexp_split_to_table(indkey::text, ‘ ‘)::smallint AS attnum,

indexrelid as index_oid

FROM pg_index

JOIN pg_class ON pg_class.oid=pg_index.indexrelid

JOIN pg_namespace ON pg_namespace.oid = pg_class.relnamespace

JOIN pg_am ON pg_class.relam = pg_am.oid

WHERE pg_am.amname = ‘btree’

— AND pg_namespace.nspname IN (”)

AND pg_class.relname NOT LIKE ‘pk_%’

),

index_item_sizes AS (

SELECT

i.nspname, i.relname, i.reltuples, i.relpages, i.relam,

s.starelid, a.attrelid AS table_oid, index_oid,

current_setting(‘block_size’)::numeric AS bs,

/* MAXALIGN: 4 on 32bits, 8 on 64bits (and mingw32 ?) / CASE WHEN version() ~ ‘mingw32′ OR version() ~ ’64-bit’ THEN 8 ELSE 4 END AS maxalign, 24 AS pagehdr, / per tuple header: add index_attribute_bm if some cols are null-able / CASE WHEN max(coalesce(s.stanullfrac,0)) = 0 THEN 2 ELSE 6 END AS index_tuple_hdr, / data len: we remove null values save space using it fractionnal part from stats */

sum( (1-coalesce(s.stanullfrac, 0)) * coalesce(s.stawidth, 2048) ) AS nulldatawidth

FROM pg_attribute AS a

JOIN pg_statistic AS s ON s.starelid=a.attrelid AND s.staattnum = a.attnum

JOIN btree_index_atts AS i ON i.indrelid = a.attrelid AND a.attnum = i.attnum

WHERE a.attnum > 0

GROUP BY 1, 2, 3, 4, 5, 6, 7, 8, 9

),

index_aligned AS (

SELECT maxalign, bs, nspname, relname AS index_name, reltuples,

relpages, relam, table_oid, index_oid,

( 2 +

maxalign – CASE /* Add padding to the index tuple header to align on MAXALIGN / WHEN index_tuple_hdr%maxalign = 0 THEN maxalign ELSE index_tuple_hdr%maxalign END + nulldatawidth + maxalign – CASE / Add padding to the data to align on MAXALIGN / WHEN nulldatawidth::integer%maxalign = 0 THEN maxalign ELSE nulldatawidth::integer%maxalign END )::numeric AS nulldatahdrwidth, pagehdr FROM index_item_sizes AS s1 ), otta_calc AS ( SELECT bs, nspname, table_oid, index_oid, index_name, relpages, coalesce( ceil((reltuples(4+nulldatahdrwidth))/(bs-pagehdr::float)) +

CASE WHEN am.amname IN (‘hash’,’btree’) THEN 1 ELSE 0 END , 0 — btree and hash have a metadata reserved block

) AS otta

FROM index_aligned AS s2

LEFT JOIN pg_am am ON s2.relam = am.oid

),

raw_bloat AS (

SELECT current_database() as dbname, nspname, c.relname AS table_name, index_name,

bs(sub.relpages)::bigint AS totalbytes, CASE WHEN sub.relpages <= otta THEN 0 ELSE bs(sub.relpages-otta)::bigint END

AS wastedbytes,

CASE

WHEN sub.relpages <= otta THEN 0 ELSE bs*(sub.relpages-otta)::bigint * 100 / (bs*(sub.relpages)::bigint) END AS realbloat, pg_relation_size(sub.table_oid) as table_bytes, stat.idx_scan as index_scans FROM otta_calc AS sub JOIN pg_class AS c ON c.oid=sub.table_oid JOIN pg_stat_user_indexes AS stat ON sub.index_oid = stat.indexrelid ) SELECT dbname as database_name, nspname as schema_name, table_name, index_name, round(realbloat, 1) as bloat_pct, wastedbytes as bloat_bytes, replace(pg_size_pretty(wastedbytes::bigint),’ ‘,”) as bloat_size, totalbytes as index_bytes, replace(pg_size_pretty(totalbytes::bigint),’ ‘,”) as index_size, table_bytes, replace(pg_size_pretty(table_bytes),’ ‘,”) as table_size, index_scans FROM raw_bloat WHERE realbloat > 40

— AND wastedbytes > 50000000

ORDER BY wastedbytes DESC;