Re: PoC Refactor AM analyse API - Mailing list pgsql-hackers

From Denis Smirnov
Subject Re: PoC Refactor AM analyse API
Date
Msg-id 29A6A06B-7CE8-4460-AA1F-33DB6709F6BD@arenadata.io
Whole thread Raw
In response to Re: PoC Refactor AM analyse API  (Zhihong Yu <zyu@yugabyte.com>)
Responses Re: PoC Refactor AM analyse API
List pgsql-hackers
Hello,  Zhihong.

Thanks for your comments.

1. I am afraid that an equivalence of "floor(val + 0.5)" to "cell(val)" is incorrect: "floor(2.1 + 0.5)" returns 2
while "cell(2.1)" returns 3. We can’t use such replacement, as you have suggested. 

2. >> For compare_rows(), it seems the computation of oa and ob can be delayed to when ba == bb (after the first two if
statements).
I have checked some examples of ASM code generated by different compilers with -O2/O3 flags on https://gcc.godbolt.org
anddidn’t see any big benefit in result CPU instructions. You can check yourself an attached example below. 



Best regards,
Denis Smirnov | Developer
sd@arenadata.io 
Arenadata | Godovikova 9-17, Moscow 129085 Russia


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