Re: [HACKERS] GSoC 2017: weekly progress reports (week 4) and patchfor hash index

On Mon, Mar 12, 2018 at 7:18 PM, Amit Kapila <amit.kapila16@gmail.com> wrote:
> On Mon, Mar 12, 2018 at 12:18 AM, Alexander Korotkov
> <a.korotkov@postgrespro.ru> wrote:
>> On Sat, Mar 3, 2018 at 2:53 PM, Amit Kapila <amit.kapila16@gmail.com> wrote:
>>>
>>> On Fri, Mar 2, 2018 at 9:27 AM, Thomas Munro
>>> >  If that is indeed a race, could it be fixed by
>>> > calling PredicateLockPageSplit() at the start of _hash_splitbucket()
>>> > instead?
>>> >
>>>
>>> Yes, but I think it would be better if we call this once we are sure
>>> that at least one tuple from the old bucket has been transferred
>>> (consider if all tuples in the old bucket are dead).
>>
>>
>> Is it really fair?  For example, predicate lock can be held by session
>> which queried some key, but didn't find any corresponding tuple.
>> If we imagine this key should be in new bucket while all existing
>> tuples would be left in old bucket.  As I get, in this case no locks
>> would be transferred since no tuples were moved to the new bucket.
>> So, further insertion to the new bucket wouldn't conflict with session,
>> which looked for non-existing key, while it should.  Do it make sense?
>>
>
> Valid point, I think on split we should always transfer locks from old
> bucket to new bucket.
>

Attached patch changes it as per above suggestion.


-- 
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com