Re: [HACKERS] GSoC 2017 : Patch for predicate locking in Gist index

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От Andrew Borodin
Тема Re: [HACKERS] GSoC 2017 : Patch for predicate locking in Gist index
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Msg-id CAAhFRxgJ6p8wodCp1m8gK9moO09NSN=WoJnXt8c=cMVYXS+Mug@mail.gmail.com
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Ответ на Re: [HACKERS] GSoC 2017 : Patch for predicate locking in Gist index  (Alexander Korotkov <a.korotkov@postgrespro.ru>)
Ответы Re: [HACKERS] GSoC 2017 : Patch for predicate locking in Gist index  (Alexander Korotkov <a.korotkov@postgrespro.ru>)
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Hi, Alexander!

Thanks for looking into the patch!

On Thu, Sep 28, 2017 at 3:59 PM, Alexander Korotkov <a.korotkov@postgrespro.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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