| From: | Andrew Borodin <amborodin86(at)gmail(dot)com> |
|---|---|
| To: | Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru> |
| Cc: | Shubham Barai <shubhambaraiss(at)gmail(dot)com>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Kevin Grittner <kgrittn(at)gmail(dot)com> |
| Subject: | Re: GSoC 2017 : Patch for predicate locking in Gist index |
| Date: | 2017-10-02 10:40:29 |
| Message-ID: | CAAhFRxgJ6p8wodCp1m8gK9moO09NSN=WoJnXt8c=cMVYXS+Mug@mail.gmail.com |
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| Lists: | pgsql-hackers |
Hi, Alexander!
Thanks for looking into the patch!
On Thu, Sep 28, 2017 at 3:59 PM, Alexander Korotkov <
a(dot)korotkov(at)postgrespro(dot)ru> wrote:
>
>
> In gistdoinsert() you do CheckForSerializableConflictIn() only if page
> wasn't exclusively locked before (xlocked is false).
>
> if (!xlocked)
>> {
>> LockBuffer(stack->buffer, GIST_UNLOCK);
>> LockBuffer(stack->buffer, GIST_EXCLUSIVE);
>> CheckForSerializableConflictIn(r, NULL, stack->buffer);
>> xlocked = true;
>
>
> However, page might be exclusively locked before. And in this case
> CheckForSerializableConflictIn() would be skipped. That happens very
> rarely (someone fixes incomplete split before we did), but nevertheless.
>
if xlocked = true, page was already checked for conflict after setting
exclusive lock on it's buffer. I still do not see any problem here...
Best regards, Andrey Borodin.
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