On May 11, 2017 11:31:02 AM PDT, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>Bruce Momjian <bruce@momjian.us> writes:
>> Good point. I think we need to do some measurements to see if the
>> parser-only stage is actually significant. I have a hunch that
>> commercial databases have much heavier parsers than we do.
>
>FWIW, gram.y does show up as significant in many of the profiles I
>take.
>I speculate that this is not so much that it eats many CPU cycles, as
>that
>the constant tables are so large as to incur lots of cache misses.
>scan.l
>is not quite as big a deal for some reason, even though it's also
>large.
And that there's a lot of unpredictable branches, leading to a lot if pipeline stalls.
Andres
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