pgsql: Speedup COPY FROM with additional function inlining.

Speedup COPY FROM with additional function inlining.

Following the example set by commit 58a359e585, we can squeeze out
a little more performance from COPY FROM (FORMAT {text,csv}) by
inlining CopyReadLineText() and passing the is_csv parameter as a
constant. This allows the compiler to emit specialized code with
fewer branches.

This is preparatory work for a proposed follow-up commit that would
further optimize this code with SIMD instructions.

Author: Nazir Bilal Yavuz <byavuz81(at)gmail(dot)com>
Reviewed-by: Ayoub Kazar <ma_kazar(at)esi(dot)dz>
Tested-by: Manni Wood <manni(dot)wood(at)enterprisedb(dot)com>
Discussion: https://postgr.es/m/CAOzEurSW8cNr6TPKsjrstnPfhf4QyQqB4tnPXGGe8N4e_v7Jig%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/dc592a41557b072178f1798700bf9c69cd8e4235

Modified Files
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src/backend/commands/copyfromparse.c | 18 ++++++++++++++----
1 file changed, 14 insertions(+), 4 deletions(-)