EXPLAIN (ANALYZE, VERBOSE, BUFFERS)
SELECT current_database(), nspname AS schemaname, tblname, idxname, bs*(relpages)::bigint AS real_size,
  bs*(relpages-est_pages)::bigint AS extra_size,
  100 * (relpages-est_pages)::float / relpages AS extra_ratio,
  fillfactor,
  CASE WHEN relpages > est_pages_ff
    THEN bs*(relpages-est_pages_ff)
    ELSE 0
  END AS bloat_size,
  100 * (relpages-est_pages_ff)::float / relpages AS bloat_ratio,
  is_na
  -- , 100-(pst).avg_leaf_density AS pst_avg_bloat, est_pages, index_tuple_hdr_bm, maxalign, pagehdr, nulldatawidth, nulldatahdrwidth, reltuples, relpages -- (DEBUG INFO)
FROM (
  SELECT coalesce(1 +
         ceil(reltuples/floor((bs-pageopqdata-pagehdr)/(4+nulldatahdrwidth)::float)), 0 -- ItemIdData size + computed avg size of a tuple (nulldatahdrwidth)
      ) AS est_pages,
      coalesce(1 +
         ceil(reltuples/floor((bs-pageopqdata-pagehdr)*fillfactor/(100*(4+nulldatahdrwidth)::float))), 0
      ) AS est_pages_ff,
      bs, nspname, tblname, idxname, relpages, fillfactor, is_na
      -- , pgstatindex(idxoid) AS pst, index_tuple_hdr_bm, maxalign, pagehdr, nulldatawidth, nulldatahdrwidth, reltuples -- (DEBUG INFO)
  FROM (
      SELECT maxalign, bs, nspname, tblname, idxname, reltuples, relpages, idxoid, fillfactor,
            ( index_tuple_hdr_bm +
                maxalign - CASE -- Add padding to the index tuple header to align on MAXALIGN
                  WHEN index_tuple_hdr_bm%maxalign = 0 THEN maxalign
                  ELSE index_tuple_hdr_bm%maxalign
                END
              + nulldatawidth + maxalign - CASE -- Add padding to the data to align on MAXALIGN
                  WHEN nulldatawidth = 0 THEN 0
                  WHEN nulldatawidth::integer%maxalign = 0 THEN maxalign
                  ELSE nulldatawidth::integer%maxalign
                END
            )::numeric AS nulldatahdrwidth, pagehdr, pageopqdata, is_na
            -- , index_tuple_hdr_bm, nulldatawidth -- (DEBUG INFO)
      FROM (
          SELECT n.nspname, ct.relname AS tblname, i.idxname, i.reltuples, i.relpages,
              i.idxoid, i.fillfactor, current_setting('block_size')::numeric AS bs,
              CASE -- MAXALIGN: 4 on 32bits, 8 on 64bits (and mingw32 ?)
                WHEN version() ~ 'mingw32' OR version() ~ '64-bit|x86_64|ppc64|ia64|amd64' THEN 8
                ELSE 4
              END AS maxalign,
              /* per page header, fixed size: 20 for 7.X, 24 for others */
              24 AS pagehdr,
              /* per page btree opaque data */
              16 AS pageopqdata,
              /* per tuple header: add IndexAttributeBitMapData if some cols are null-able */
              CASE WHEN max(coalesce(s.stanullfrac,0)) = 0
                  THEN 2 -- IndexTupleData size
                  ELSE 2 + (( 32 + 8 - 1 ) / 8) -- IndexTupleData size + IndexAttributeBitMapData size ( max num filed per index + 8 - 1 /8)
              END AS index_tuple_hdr_bm,
              /* data len: we remove null values save space using it fractionnal part from stats */
              sum( (1-coalesce(s.stanullfrac, 0)) * coalesce(s.stawidth, 1024)) AS nulldatawidth,
              max( CASE WHEN a.atttypid = 'pg_catalog.name'::regtype THEN 1 ELSE 0 END ) > 0 AS is_na
          FROM (
              SELECT idxname, reltuples, relpages, tbloid, idxoid, fillfactor,
                  CASE WHEN indkey[i]=0 THEN idxoid ELSE tbloid END AS att_rel,
                  CASE WHEN indkey[i]=0 THEN i ELSE indkey[i] END AS att_pos
              FROM (
                  SELECT idxname, reltuples, relpages, tbloid, idxoid, fillfactor, indkey, generate_series(1,indnatts) AS i
                  FROM (
                      SELECT ci.relname AS idxname, ci.reltuples, ci.relpages, i.indrelid AS tbloid,
                          i.indexrelid AS idxoid,
                          coalesce(substring(
                              array_to_string(ci.reloptions, ' ')
                              from 'fillfactor=([0-9]+)')::smallint, 90) AS fillfactor,
                          i.indnatts,
                          string_to_array(textin(int2vectorout(i.indkey)),' ')::int[] AS indkey
                      FROM pg_index i
                      JOIN pg_class ci ON ci.oid=i.indexrelid
                      WHERE ci.relam=(SELECT oid FROM pg_am WHERE amname = 'btree')
                        AND ci.relpages > 0
                  ) AS idx_data
              ) AS idx_data_cross
          ) i
          JOIN pg_attribute a ON a.attrelid = i.att_rel
                             AND a.attnum = i.att_pos
          JOIN pg_statistic s ON s.starelid = i.att_rel
                             AND s.staattnum = i.att_pos
          JOIN pg_class ct ON ct.oid = i.tbloid
          JOIN pg_namespace n ON ct.relnamespace = n.oid
          GROUP BY 1,2,3,4,5,6,7,8,9,10
      ) AS rows_data_stats
  ) AS rows_hdr_pdg_stats
) AS relation_stats
ORDER BY nspname, tblname, idxname;