Re: Patch for 8.5, transformationHook

2009/4/18 Tom Lane <tgl@sss.pgh.pa.us>:
> Pavel Stehule <pavel.stehule@gmail.com> writes:
>> 2009/4/11 Tom Lane <tgl@sss.pgh.pa.us>:
>>> No, I was complaining that a hook right there is useless and expensive.
>>> transformExpr() is executed multiple times per query, potentially a very
>>> large number of times per query; so even testing to see if a hook exists
>>> is not a negligible cost.
>
>> I did some tests based on pgbench.
>
> The queries done by pgbench are completely trivial and do not stress
> parser performance.  Even if they did (consider cases likw an IN with a
> few thousand list items), the parser is normally not a bottleneck
> compared to transaction overhead, network round trips, and pgbench
> itself.
>
>> I though about different position of hook, but only in this place the
>> hook is useful (because expressions are recursive).
>
> As I keep saying, a hook there is useless, at least by itself.  You
> have no control over the grammar and no ability to modify what the
> rest of the system understands.  The only application I can think of is
> to fool with the transformation of FuncCall nodes, which you could do in
> a much lower-overhead way by hooking into transformFuncCall.  Even that
> seems pretty darn marginal for real-world problems.
>

Hello

I am sending modified patch - it hooking parser via transformFuncCall

regards
Pavel Stehule


>                        regards, tom lane
>