• Re: [Info-ingres] Empty pages

    From Roy Hann@roy.hann@rationalcommerce.com to info-ingres@lists.planetingres.org on Mon Oct 25 14:08:32 2021
    From Newsgroup: comp.databases.ingres

    Monday, October 25, 2021, 1:48:29 PM, you wrote:
    IAve recently had a btree table which had grown to 8025535 pages
    with zero overflow. But after a modify it shrank to a little over 5000 pages.

    My suspicion is that this table had grown to this size because it
    is daily getting a few hundred thousand rows inserted and then
    deleted. The key of the table is increasing and so deleted rows
    on the pages are never reused.
    Deleted rows on the associated data page should get reused. My
    suspicion is MVCC is enabled on the database. That defeats the free
    page management in Btrees.
    Is there an easy way to determine the number of aemptyA pages? IAve
    started experimenting with modify table to table_debug [with
    table_option = 1|2|3], but IAm not seeing a smoking gun.
    I have written various scripts over the years to join iifile_info and
    iitables with the output from ls or dir, as appropriate.
    Roy
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