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From Krishna <research...@gmail.com>
Subject Re: Salt buckets optimization
Date Fri, 27 Feb 2015 01:28:58 GMT
Puneet, In addition to creating an initial number of regions, it appears,
salt buckets is also used for determining the # of threads (?) while doing
skip scan. Explain plan shows something like "client 60-way skip scan...".
So, having a higher number of salt buckets should, theoretically, help
query performance. Could you explain what kind of issues could pop-up
having 150 to 200+ salt bytes?



On Thu, Feb 26, 2015 at 2:57 AM, Puneet Kumar Ojha <
puneet.kumar@pubmatic.com> wrote:

>  Yes you can have more salt buckets than no of regions servers. Salt
> buckets specififed will create thoe many number of regions.
>
>
>
> Depending upon what regions size is optimal –(dependent on table data) you
> need to opt the salt bucket numbers.
>
>
>
>
>
> *From:* Vamsi Krishna [mailto:vamsi.attluri@gmail.com]
> *Sent:* Thursday, February 26, 2015 11:25 AM
> *To:* user@phoenix.apache.org
> *Subject:* Re: Salt buckets optimization
>
>
>
> Can we have more no of salt buckets than the no of region servers?
>
> According to Phoenix documentation, I've read "*For optimal performance,
> number of salt buckets should match number of region servers*".
>
> http://phoenix.apache.org/performance.html
>
>
>
> In our case, we are evaluating on a small cluster with two region servers
> and we are observing better performance with 10 salt buckets compared to 2
> salt buckets and 20 salt buckets.
>
>
>
> Could someone please explain what's happening behind the scenes?
>
>
>
> Thanks,
>
> Vamsi Attluri.
>
>
>
> On Wed, Feb 25, 2015 at 6:56 PM, Puneet Kumar Ojha <
> puneet.kumar@pubmatic.com> wrote:
>
>  For big tables keep the salt bucket high, generally around 60-90.
>
> Smaller or join tables should have salt buckets as minimal may be 1-4.
>
>
>
>
>
> Thanks
>
>
>
>
>
> ------ Original message------
>
> *From: *Krishna
>
> *Date: *Thu, Feb 26, 2015 07:42
>
> *To: *dev@phoenix.apache.org;user@phoenix.apache.org;
>
> *Subject:*Salt buckets optimization
>
>
>
> Are there any recommendations for estimating and optimizing salt buckets
> during table creation time? What, if any, are the cons of having high
> number (200+) of salt buckets? Is it possible to update salt buckets after
> table is created?
>
>
>
> Thanks
>
>
>
>
>

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