Negative imact of maintenance_work_mem to GIN size

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.

http://mira.sai.msu.ru/~megera/tmp/js.copy.gz

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.