Re: Report buffer access strategies in EXPLAIN

On Thu, Nov 05, 2026 at 12:17:42PM +0000, Bertrand Drouvot wrote:
> Right, that's why the text refers specifically to the 256KB target. Do you
> mean that the L2 cache rationale should be dropped now that it does not
> necessarily apply to the resulting ring size?

v4 still has the same text:

+For bulk reads, the requested ring size is at least 256KB. The 256KB target is
+small enough to fit in L2 cache, which makes transferring pages from OS cache
+to shared buffer cache efficient.

L2 caches can be larger than 256kB, so having a larger size could
still be effective. The current wording sounds slightly confusing to
me here due to that. But perhaps your wording is fine enough. I
suspect that Andres and other folks involved in this area of the code
would have comments about these parts. Better to wait for inputs from
them.

> That makes sense. I've listed the commands under each applicable strategy. Note
> that some appear in both lists: for example, CREATE DATABASE uses bulkread for
> the source and bulkwrite for the destination. I did not go as far as explaining
> why in the glossary.

The checksumming part is missing for checksums where BAS_VACUUM is in
use.

v4-0002 seems mostly OK here, with your previous adjustments included.

+ <literal>vacuum</literal>: I/O operations performed using the
+ <literal>vacuum</literal>
+ <glossterm linkend="glossary-buffer-access-strategy">buffer access
+ strategy</glossterm>

In v4-0003, too many vacuum references perhaps? This is the same as
my previous comment when I have looked at the v3 series. I'm
wondering if you should make it simpler, by the addition of linkend
once within parenthesis like a simpler "(see also <linkend>BAS</>)",
with a set of <literal>s for the follow-up references.
--
Michael