| From: | Teodor Sigaev <teodor(at)sigaev(dot)ru> |
|---|---|
| To: | Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, Dmitry Ivanov <d(dot)ivanov(at)postgrespro(dot)ru> |
| Cc: | Shubham Barai <shubhambaraiss(at)gmail(dot)com>, Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Andrey Borodin <x4mmm(at)yandex-team(dot)ru>, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Andrew Borodin <amborodin86(at)gmail(dot)com>, Kevin Grittner <kgrittn(at)gmail(dot)com> |
| Subject: | Re: [HACKERS] GSoC 2017: weekly progress reports (week 6) |
| Date: | 2018-04-09 14:50:51 |
| Message-ID: | 0e3e4216-4288-49ef-57ee-7e1e7275c4d9@sigaev.ru |
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| Lists: | pgsql-hackers pgsql-www |
Hi!
> 1. Why do we lock all posting tree pages, even though they all represent the
> same value? Isn't it enough to lock the root of the posting tree?
> 2. Why do we lock any posting tree pages at all, if we lock the entry tree page
> anyway? Isn't the lock on the entry tree page sufficient to cover the key value?
> 3. Why do we *not* lock the entry leaf page, if there is no match? We still need
> a lock to remember that we probed for that value and there was no match, so that
> we conflict with a tuple that might be inserted later.
>
> At least #3 is a bug. The attached patch adds an isolation test that
> demonstrates it. #1 and #2 are weird, and cause unnecessary locking, so I think
> we should fix those too, even if they don't lead to incorrect results.
I can't find a hole here. Agree.
> I took a stab at fixing those issues, as well as the bug when fastupdate is
> turned on concurrently. Does the attached patch look sane to you?
I like an idea use metapage locking, thank you. Patch seems good, will you push it?
--
Teodor Sigaev E-mail: teodor(at)sigaev(dot)ru
WWW: http://www.sigaev.ru/
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