Negative imact of maintenance_work_mem to GIN size

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От Alexander Korotkov
Тема Negative imact of maintenance_work_mem to GIN size
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Msg-id CAPpHfdt8Yxbj9sJ_9V15Rne1qu08+F+HFnvqceYuVxLXev42ww@mail.gmail.com
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Ответы Re: Negative imact of maintenance_work_mem to GIN size
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Hi!

I found that sometimes larger maintenance_work_mem leads to larger GIN index. That is quite strange. ISTM that it's related to posting lists compression but I can't figure out how exactly it is.

See example on delicious bookmarks dataset.


set maintenance_work_mem = '1GB';
create index js_idx1 on js using gin(v jsonb_path_idx);
set maintenance_work_mem = '16MB';
create index js_idx2 on js using gin(v jsonb_path_ops);

                        List of relations
 Schema |  Name   | Type  | Owner  | Table |  Size  | Description
--------+---------+-------+--------+-------+--------+-------------
 public | js_idx1 | index | smagen | js    | 432 MB |
 public | js_idx2 | index | smagen | js    | 309 MB |
(2 rows)

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With best regards,
Alexander Korotkov.

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