/* Table and index bloat in your database ordered by most wasteful */

WITH constants AS (

SELECT current_setting('block_size')::numeric AS bs, 23 AS hdr, 4 AS ma

), bloat_info AS (

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, constants
  GROUP BY 1,2,3,4,5
) AS foo

), table_bloat AS (

SELECT
  schemaname, tablename, 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
FROM bloat_info
JOIN pg_class cc ON cc.relname = bloat_info.tablename
JOIN pg_namespace nn ON cc.relnamespace = nn.oid AND nn.nspname = bloat_info.schemaname AND nn.nspname <> 'information_schema'

), index_bloat AS (

SELECT
  schemaname, tablename, bs,
  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 bloat_info
JOIN pg_class cc ON cc.relname = bloat_info.tablename
JOIN pg_namespace nn ON cc.relnamespace = nn.oid AND nn.nspname = bloat_info.schemaname AND nn.nspname <> 'information_schema'
JOIN pg_index i ON indrelid = cc.oid
JOIN pg_class c2 ON c2.oid = i.indexrelid

) SELECT

type, schemaname, object_name, bloat, pg_size_pretty(raw_waste) as waste

FROM (SELECT

'table' as type,
schemaname,
tablename as object_name,
ROUND(CASE WHEN otta=0 THEN 0.0 ELSE table_bloat.relpages/otta::numeric END,1) AS bloat,
CASE WHEN relpages < otta THEN '0' ELSE (bs*(table_bloat.relpages-otta)::bigint)::bigint END AS raw_waste

FROM

table_bloat
  UNION

SELECT

'index' as type,
schemaname,
tablename || '::' || iname as object_name,
ROUND(CASE WHEN iotta=0 OR ipages=0 THEN 0.0 ELSE ipages/iotta::numeric END,1) AS bloat,
CASE WHEN ipages < iotta THEN '0' ELSE (bs*(ipages-iotta))::bigint END AS raw_waste

FROM

index_bloat) bloat_summary

ORDER BY raw_waste DESC, bloat DESC;