2009/4/18 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:
> Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> writes:
>> 2009/4/11 Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)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
>> 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.
I am sending modified patch - it hooking parser via transformFuncCall
> regards, tom lane
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