[Info-ingres] Empty pages

[Roy Hann]

Monday, October 25, 2021, 1:48:29 PM, you wrote:

> I’ve 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 ‘empty’ pages? I’ve
> started experimenting with modify table to table_debug [with
> table_option = 1|2|3], but I’m 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