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From: Joe Conway <[email protected]>
To: Nathan Bossart <[email protected]>
To: Tom Lane <[email protected]>
Cc: Andrew Dunstan <[email protected]>
Cc: Davin Shearer <[email protected]>
Cc: PostgreSQL-development <[email protected]>
Subject: Re: Emitting JSON to file using COPY TO
Date: Thu, 7 Dec 2023 07:15:28 -0500
Message-ID: <[email protected]> (raw)
In-Reply-To: <20231207025622.GA3011676@nathanxps13>
References: <[email protected]>
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	<20231206163349.GA2873889@nathanxps13>
	<20231206164439.GC2873889@nathanxps13>
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	<20231207025622.GA3011676@nathanxps13>

On 12/6/23 21:56, Nathan Bossart wrote:
> On Wed, Dec 06, 2023 at 03:20:46PM -0500, Tom Lane wrote:
>> If Nathan's perf results hold up elsewhere, it seems like some
>> micro-optimization around the text-pushing (appendStringInfoString)
>> might be more useful than caching.  The 7% spent in cache lookups
>> could be worth going after later, but it's not the top of the list.
> 
> Hah, it turns out my benchmark of 110M integers really stresses the
> JSONTYPE_NUMERIC path in datum_to_json_internal().  That particular path
> calls strlen() twice: once for IsValidJsonNumber(), and once in
> appendStringInfoString().  If I save the result from IsValidJsonNumber()
> and give it to appendBinaryStringInfo() instead, the COPY goes ~8% faster.
> It's probably worth giving datum_to_json_internal() a closer look in a new
> thread.

Yep, after looking through that code I was going to make the point that 
your 11 integer test was over indexing on that one type. I am sure there 
are other micro-optimizations to be made here, but I also think that it 
is outside the scope of the COPY TO JSON patch.

-- 
Joe Conway
PostgreSQL Contributors Team
RDS Open Source Databases
Amazon Web Services: https://aws.amazon.com

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