From: | Dmitry Tkach <dmitry(at)openratings(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | pgsql-sql <pgsql-sql(at)postgresql(dot)org> |
Subject: | Re: Trouble with explicit joins |
Date: | 2004-10-21 23:36:41 |
Message-ID: | 41784809.4070009@openratings.com |
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Thread: | |
Lists: | pgsql-sql |
Tom Lane wrote:
>Dmitry Tkach <dmitry(at)openratings(dot)com> writes:
>
>
>>I suppose, this is because the planner takes the order, in which the
>>tables appear in the explicit joins as some kind of a hint to how I want
>>that query to be executed,
>>
>>
>
>It's not a "hint", it's a requirement. In general, changing the order
>in which outer joins are executed changes the results.
>
>There are some cases in which it is safe to rearrange the order, but
>determining this takes close analysis of the join conditions, and we
>don't (yet) have any code to do that. So the planner must be
>conservative and take your join order as gospel.
>
> regards, tom lane
>
>
Yeah.. that's what I figured.
Are you saying there is no way around it at all? Isn't there a syntax
supported to write a left join with implicit joins?
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