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Need to select indexes which are fragmented for a certain level. Can someone help me with the query for that?

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  • What exactly is a "fragmented index"? Are you referring to index bloat?
    – user1822
    Commented Aug 11, 2020 at 9:03
  • yes. the bloated indexes for a table due to deletion of large number of records. Need to fetch the indexes for a given table which are bloated above 30 % or so. Commented Aug 11, 2020 at 9:41
  • Also this given query SELECT * FROM pgstatindex('index_name'); fetches the leaf_fragmentation percentage for a given index. not sure how to use this function to select the indexes for a table with leaf_fragmentation above 30 % Commented Aug 11, 2020 at 9:43

1 Answer 1

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You can use pgstatindex from the pgstattuple extension to get the leaf fragmentation of all B-tree indexes:

SELECT i.indexrelid::regclass,
       s.leaf_fragmentation
FROM pg_index AS i
   JOIN pg_class AS t ON i.indexrelid = t.oid
   JOIN pg_opclass AS opc ON i.indclass[0] = opc.oid
   JOIN pg_am ON opc.opcmethod = pg_am.oid
   CROSS JOIN LATERAL pgstatindex(i.indexrelid) AS s
WHERE t.relkind = 'i'
  AND pg_am.amname = 'btree';

This will scan through all these indexes and might take a long time.

Note that it is normal for an index to be up to 70% fragmented.

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