Re: Existence check for suitable index in advance when concurrently refreshing.

On Thu, Jan 28, 2016 at 1:01 AM, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
> On Wed, Jan 27, 2016 at 4:42 PM, Fujii Masao <masao(dot)fujii(at)gmail(dot)com> wrote:
>> On Tue, Jan 26, 2016 at 9:33 PM, Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com> wrote:
>>> Hi all,
>>>
>>> In concurrently refreshing materialized view, we check whether that
>>> materialized view has suitable index(unique and not having WHERE
>>> condition), after filling data to new snapshot
>>> (refresh_matview_datafill()).
>>> This logic leads to taking a lot of time until postgres returns ERROR
>>> log if that table doesn't has suitable index and table is large. it
>>> wastes time.
>>> I think we should check whether that materialized view can use
>>> concurrently refreshing or not in advance.
>>
>> +1
>>
>>> The patch is attached.
>>>
>>> Please give me feedbacks.
>
> Thank you for having look at this patch.
>
>> + indexRel = index_open(indexoid, RowExclusiveLock);
>>
>> Can we use AccessShareLock here, instead?
>
> Yeah, I think we can use it. Fixed.
>
>> + if (indexStruct->indisunique &&
>> + IndexIsValid(indexStruct) &&
>> + RelationGetIndexExpressions(indexRel) == NIL &&
>> + RelationGetIndexPredicate(indexRel) == NIL)
>> + hasUniqueIndex = true;
>> +
>> + index_close(indexRel, RowExclusiveLock);
>>
>> In the case where hasUniqueIndex = true, ISTM that we can get out of
>> the loop immediately just after calling index_close(). No?
>
> Fixed.
>
>> + /* Must have at least one unique index */
>> + Assert(foundUniqueIndex);
>>
>> Can we guarantee that there is at least one valid unique index here?
>> If yes, it's better to write the comment about that.
>>
>
> Added.
>
> Attached latest patch. Please review it.

Thanks for updating the patch!
Attached is the updated version of the patch.
I removed unnecessary assertion check and change of source code
that you added, and improved the source comment.
Barring objection, I'll commit this patch.

Regards,

--
Fujii Masao