| From: | Heikki Linnakangas <hlinnaka(at)iki(dot)fi> |
|---|---|
| To: | feichanghong <feichanghong(at)qq(dot)com>, pgsql-hackers(at)lists(dot)postgresql(dot)org |
| Cc: | hu_yajun(at)qq(dot)com |
| Subject: | Re: Improve the efficiency of _bt_killitems. |
| Date: | 2024-11-01 08:24:02 |
| Message-ID: | 3c957e3b-1faf-4d11-aaef-d7b773c30046@iki.fi |
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| Thread: | |
| Lists: | pgsql-hackers |
On 01/11/2024 09:19, feichanghong wrote:
> Hi hackers,
>
> In the _bt_killitems function, the following logic is present: we
> search to the right for an index item that matches the heap TID and
> attempt to mark it as dead. If that index item has already been
> marked as dead by other concurrent processes, we will continue
> searching. However, there should not be any more matching index items
> on the current page.
Why could there not be more matching items on the page?
Are you assuming a unique index? Even then it's not right; you can have
multiple index entries point to different heap tuples with the same key,
as long as they're not visible at the same time. For example, if you
UPDATE or DELETE+INSERT a row.
--
Heikki Linnakangas
Neon (https://neon.tech)
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