Re: what specifically does vacuum have to scan / why does it need to rescan the same indexes many, many times

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От Jeff Janes
Тема Re: what specifically does vacuum have to scan / why does it need to rescan the same indexes many, many times
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Msg-id CAMkU=1w-=Wqau8Z8V_t-byo4wv9mt=PoZUQ1ucD7PGg5UL6qzw@mail.gmail.com
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Ответ на what specifically does vacuum have to scan / why does it need to rescan the same indexes many, many times  (john gale <john@smadness.com>)
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On Tuesday, July 1, 2014, john gale <john@smadness.com> wrote:

What does vacuum have to scan to be able to reclaim space, and how many times does it need to scan to finalize ?

More specifically, my VACUUM VERBOSE <table> is taking a long time and seems to be rescanning the same indexes / fields multiple times without finishing.

vacuum can only memorize one dead tuple for every 6 bytes of maintenance_work_mem.  If there are more dead tuples than that, it needs to make multiple passes over the indexes.
 
Increase maintenance_work_mem to improve the efficiency.

Cheers,

Jeff

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