From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
---|---|
To: | Haribabu Kommi <kommi(dot)haribabu(at)gmail(dot)com> |
Cc: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Parallel Seq Scan |
Date: | 2015-11-05 18:24:06 |
Message-ID: | CA+Tgmoa4=KaObDcnvADrKY5WwEWDN+rnGAfjzrc=d3UG0sz22w@mail.gmail.com |
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On Thu, Nov 5, 2015 at 12:52 AM, Haribabu Kommi
<kommi(dot)haribabu(at)gmail(dot)com> wrote:
>> Now instead of displaying Partial Seq Scan, if we just display Seq Scan,
>> then it might confuse user, so it is better to add some thing indicating
>> parallel node if we want to go this route.
>
> IMO, the change from Partial Seq Scan to Seq Scan may not confuse user,
> if we clearly specify in the documentation that all plans under a Gather node
> are parallel plans.
>
> This is possible for the execution nodes that executes fully under a
> Gather node.
> The same is not possible for parallel aggregates, so we have to mention the
> aggregate node below Gather node as partial only.
>
> I feel this suggestion arises as may be because of some duplicate code between
> Partial Seq Scan and Seq scan. By using Seq Scan node only if we display as
> Partial Seq Scan by storing some flag in the plan? This avoids the
> need of adding
> new plan nodes.
I was thinking about this idea:
1. Add a parallel_aware flag to each plan.
2. If the flag is set, have EXPLAIN print the word "Parallel" before
the node name.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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