Re: Cache Hash Index meta page.

On 07/22/2016 06:02 AM, Mithun Cy wrote:
> I have created a patch to cache the meta page of Hash index in
> backend-private memory. This is to save reading the meta page buffer every
> time when we want to find the bucket page. In “_hash_first” call, we try to
> read meta page buffer twice just to make sure bucket is not split after we
> found bucket page. With this patch meta page buffer read is not done, if
> the bucket is not split after caching the meta page.
>
> Idea is to cache the Meta page data in rd_amcache and store maxbucket
> number in hasho_prevblkno of bucket primary page (which will always be NULL
> other wise, so reusing it here for this cause!!!). So when we try to do
> hash lookup for bucket page if locally cached maxbucket number is greater
> than or equal to bucket page's maxbucket number then we can say given
> bucket is not split after we have cached the meta page. Hence avoid reading
> meta page buffer.
>
> I have attached the benchmark results and perf stats (refer
> hash_index_perf_stat_and_benchmarking.odc [sheet 1: perf stats; sheet 2:
> Benchmark results). There we can see improvements at higher clients, as
> lwlock contentions due to buffer read are more at higher clients. If I
> apply the same patch on Amit's concurrent hash index patch [1] we can see
> improvements at lower clients also. Amit's patch has removed a heavy weight
> page lock which was the bottle neck at lower clients.
>

Could you provide a rebased patch based on Amit's v5 ?

Best regards,
Jesper