From: | Dimitri <dimitrik(dot)fr(at)gmail(dot)com> |
---|---|
To: | Alvaro Herrera <alvherre(at)commandprompt(dot)com> |
Cc: | Aidan Van Dyk <aidan(at)highrise(dot)ca>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Merlin Moncure <mmoncure(at)gmail(dot)com>, PostgreSQL Performance <pgsql-performance(at)postgresql(dot)org> |
Subject: | Re: Any better plan for this query?.. |
Date: | 2009-05-12 07:29:08 |
Message-ID: | 5482c80a0905120029s78d5595dp83a659238cd0cbea@mail.gmail.com |
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Thread: | |
Lists: | pgsql-performance |
>> So, why I don't use prepare here: let's say I'm testing the worst
>> stress case :-) Imagine you have thousands of such kind of queries -
>> you cannot prepare all of them! :-)
>
> Thousands? Surely there'll be a dozen or three of most common queries,
> to which you pass different parameters. You can prepare thoseu
Ok, and if each client just connect to the database, execute each kind
of query just *once* and then disconnect?.. - cost of prepare will
kill performance here if it's not reused at least 10 times within the
same session.
Well, I know, we always can do better, and even use stored procedures,
etc. etc.
>
>> Now, as you see from your explanation, the Part #2 is the most
>> dominant - so why instead to blame this query not to implement a QUERY
>> PLANNER CACHE??? - in way if any *similar* query is recognized by
>> parser we simply *reuse* the same plan?..
>
> This has been discussed in the past, but it turns out that a real
> implementation is a lot harder than it seems.
Ok. If I remember well, Oracle have it and it helps a lot, but for
sure it's not easy to implement..
Rgds,
-Dimitri
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