From: | Gregory Stark <stark(at)enterprisedb(dot)com> |
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To: | "Gavin Sherry" <swm(at)alcove(dot)com(dot)au> |
Cc: | "Jonah H(dot) Harris" <jonah(dot)harris(at)gmail(dot)com>, "PostgreSQL-development" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Status of Hierarchical Queries |
Date: | 2007-02-21 22:52:38 |
Message-ID: | 87mz37nmx5.fsf@stark.xeocode.com |
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Lists: | pgsql-hackers |
"Gavin Sherry" <swm(at)alcove(dot)com(dot)au> writes:
> The WITH support seems okay. I guess I'd thought it might be represented
> different internally (not a sub query) but the approach Greg has taken is
> probably more straight forward (in that you get a lot of proven code for
> free). It should work fine for recursive queries too, if you just re-seed
> the param keys for every scan of the 'sub-query'.
I don't think it works for recursive queries. Since you can't have the same
executor plan in motion for two different sets of parameters simultaneously.
That's why I was talking about a Memoize node.
It is sufficient for the non-recursive case which might make it worthwhile
putting it in 8.3. But even there user's expectations are probably that the
reason they're writing it as a cte is precisely to avoid duplicate execution.
--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com
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