From: Justin Pryzby <pryzby@telsasoft.com>
To: Alex <cdalxndr@yahoo.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: 15x slower PreparedStatement vs raw query
Date: Mon, 3 May 2021 15:18:12 -0500
Message-ID: <20210503201811.GA27406@telsasoft.com> (raw)
In-Reply-To: <3f8c88d8a6ef9.d82fa04cf610d@yahoo.com>
References: <3f8c88d8a6ef9.d82fa04cf610d.ref@yahoo.com>
<3f8c88d8a6ef9.d82fa04cf610d@yahoo.com>
On Sun, May 02, 2021 at 07:45:26PM +0000, Alex wrote:
> PreparedStatement: 15s
> Raw query with embedded params: 1s
> See issue on github with query and explain analyze:
> https://github.com/pgjdbc/pgjdbc/issues/2145
| ..PostgreSQL Version? 12
|Prepared statement
|...
|Planning Time: 11.596 ms
|Execution Time: 14799.266 ms
|
|Raw statement
|Planning Time: 22.685 ms
|Execution Time: 1012.992 ms
The prepared statemnt has 2x faster planning time, which is what it's meant to
improve.
The execution time is slower, and I think you can improve it with this.
https://www.postgresql.org/docs/12/runtime-config-query.html#GUC-PLAN-CACHE_MODE
|plan_cache_mode (enum)
| Prepared statements (either explicitly prepared or implicitly generated, for example by PL/pgSQL) can be executed using custom or generic plans. Custom plans are made afresh for each execution using its specific set of parameter values, while generic plans do not rely on the parameter values and can be re-used across executions. Thus, use of a generic plan saves planning time, but if the ideal plan depends strongly on the parameter values then a generic plan may be inefficient. The choice between these options is normally made automatically, but it can be overridden with plan_cache_mode. The allowed values are auto (the default), force_custom_plan and force_generic_plan. This setting is considered when a cached plan is to be executed, not when it is prepared. For more information see PREPARE.
--
Justin
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To: pgsql-performance@postgresql.org
Cc: pryzby@telsasoft.com, cdalxndr@yahoo.com
Subject: Re: 15x slower PreparedStatement vs raw query
In-Reply-To: <20210503201811.GA27406@telsasoft.com>
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