Re: TOAST pointer size

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: hus(dot)mhd(at)gmail(dot)com
Cc: pgsql-docs(at)lists(dot)postgresql(dot)org
Subject: Re: TOAST pointer size
Date: 2020-12-05 18:09:34
Message-ID: 2303584.1607191774@sss.pgh.pa.us
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PG Doc comments form <noreply(at)postgresql(dot)org> writes:
> It would be nice to add a break-down of why the TOAST Pointer size is 18
> bytes

Use the source, Luke. The useful pointer data is indeed 16 bytes:

https://git.postgresql.org/gitweb/?p=postgresql.git;a=blob;f=src/include/postgres.h;h=c48f47e930ad05d3ae2e24b0c0c85662cd058a7b;hb=HEAD#l67

but there's varlena tag overhead:

https://git.postgresql.org/gitweb/?p=postgresql.git;a=blob;f=src/include/postgres.h;h=c48f47e930ad05d3ae2e24b0c0c85662cd058a7b;hb=HEAD#l159

This doesn't seem like appropriate detail for the user docs.

regards, tom lane

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