Skip to content

Instantly share code, notes, and snippets.

Last active August 28, 2019 05:56
  • Star 36 You must be signed in to star a gist
  • Fork 10 You must be signed in to fork a gist
Star You must be signed in to star a gist
Save jberkus/9923948 to your computer and use it in GitHub Desktop.
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'
index_item_sizes AS (
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 ?) */
WHEN version() ~ 'mingw32' OR version() ~ '64-bit' THEN 8
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
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
+ nulldatawidth + maxalign - CASE /* Add padding to the data to align on MAXALIGN */
WHEN nulldatawidth::integer%maxalign = 0 THEN maxalign
ELSE nulldatawidth::integer%maxalign
)::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,
WHEN sub.relpages <= otta THEN 0
ELSE bs*(sub.relpages-otta)::bigint END
AS wastedbytes,
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, pg_size_pretty(wastedbytes::bigint) as bloat_size,
totalbytes as index_bytes, pg_size_pretty(totalbytes::bigint) as index_size,
table_bytes, pg_size_pretty(table_bytes) as table_size,
FROM raw_bloat
WHERE ( realbloat > 50 and wastedbytes > 50000000 )
ORDER BY wastedbytes DESC;
Copy link

mbanck commented Apr 4, 2014

I've applied Bernd Helmle's patch so the query uses only pg_stats, not pg_statistics (and thus can be executed by non-superusers) here:

Copy link

I changed the last where, so it not only shows size and percentage triggered ones, but also sized ones (bigger the current wastedbytes)

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment