On 22/03/2019 10:00, Andrey Borodin wrote:
22 марта 2019 г., в 1:04, Heikki Linnakangas <hlinn...@iki.fi>
написал(а):
PS. for Gist, we could almost use the LSN / NSN mechanism to detect
the case that a deleted page is reused: Add a new field to the GiST
page header, to store a new "deleteNSN" field. When a page is
deleted, the deleted page's deleteNSN is set to the LSN of the
deletion record. When the page is reused, the deleteNSN field is
kept unchanged. When you follow a downlink during search, if you
see that the page's deleteNSN > parent's LSN, you know that it was
concurrently deleted and recycled, and should be ignored. That
would allow reusing deleted pages immediately. Unfortunately that
would require adding a new field to the gist page header/footer,
which requires upgrade work :-(. Maybe one day, we'll bite the
bullet. Something to keep in mind, if we have to change the page
format anyway, for some reason.
Yeah, the same day we will get rid of invalid tuples. I can make a
patch for v13. Actually, I have a lot of patches that I want in GiST
in v13. Or v14.
Cool! Here's my wishlist:
* That deleteNSN thing
* Add a metapage to blk #0.
* Add a "level"-field to page header.
* Currently, a search needs to scan all items on a page. If the keys are
small, that can be pretty slow. Divide each page further into e.g. 4
sub-pages, with a "bounding box" key for each sub-page, to speed up search.
- Heikki
