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Date: Fri, 5 Nov 2021 18:29:37 +0100
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Subject: Re: PostgreSQLv14 TPC-H performance GCC vs Clang
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To: arjun shetty <arjunshetty955@gmail.com>, Imre Samu <pella.samu@gmail.com>
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From: Tomas Vondra <tomas.vondra@enterprisedb.com>
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Hi,

IMO this thread provides so little information it's almost impossible to 
answer the question. There's almost no information about the hardware, 
scale of the test, configuration of the Postgres instance, the exact 
build flags, differences in generated asm code, etc.

I find it hard to believe merely switching from clang to gcc yields 22% 
speedup - that's way higher than any differences we've seen in the past.

In my experience, the speedup is unlikely to be "across the board". 
There will be a handful of affected queries, while most remaining 
queries will be about the same. In that case you need to focus on those 
queries, see if the plans are the same, do some profiling, etc.


regards

-- 
Tomas Vondra
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company