| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | John Naylor <john(dot)naylor(at)enterprisedb(dot)com> |
| Cc: | Jelte Fennema <me(at)jeltef(dot)nl>, Merlin Moncure <mmoncure(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andrew Dunstan <andrew(dot)dunstan(at)2ndquadrant(dot)com>, Stephen Frost <sfrost(at)snowman(dot)net>, kevinvan(at)shift(dot)com, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: WIP Patch: Add a function that returns binary JSONB as a bytea |
| Date: | 2022-06-24 17:12:02 |
| Message-ID: | 20220624171202.vd7jf7n25nwvkkad@alap3.anarazel.de |
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| Lists: | pgsql-hackers |
Hi,
On 2022-06-24 14:33:00 +0700, John Naylor wrote:
> On Thu, Jun 23, 2022 at 9:06 PM Andres Freund <andres(at)anarazel(dot)de> wrote:
> > It looks like there's quite a bit of low hanging fruits to optimize...
>
> Yeah, if escapes and control characters are rare, adding an SSE2 fast
> path would give a boost to json_lex_string: check 16 bytes at a time
> for those chars (plus the ending double-quote).
The biggest thing I see is building the string in bigger chunks. Doing a
separate appendStringInfoChar() for each input character is obviously bad for
performance. I'd bet a good chunk of the time attributed to json_lex_string()
in Jelte's flamegraph is actually setting up the external function call to
appendStringInfoChar(). Which then proceeds to do a check whether the buffer
needs to be enlarged and maintains the trailing null byte on every call.
Greetings,
Andres Freund
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