Re: index prefetching

On 7/16/25 18:39, Peter Geoghegan wrote:
> On Wed, Jul 16, 2025 at 11:29 AM Peter Geoghegan <pg(at)bowt(dot)ie> wrote:
>> For example, with "linear_10 / eic=16 / sync", it looks like "complex"
>> has about half the latency of "simple" in tests where selectivity is
>> 10. The advantage for "complex" is even greater at higher
>> "selectivity" values. All of the other "linear" test results look
>> about the same.
>
> It's hard to interpret the raw data that you've provided. For example,
> I cannot figure out where "selectivity" appears in the raw CSV file
> from your results repro.
>
> Can you post a single spreadsheet or CSV file, with descriptive column
> names, and a row for every test case you ran? And with the rows
> ordered such that directly comparable results/rows appear close
> together?
>

That's a good point, sorry about that. I forgot the CSV files don't have
proper headers, I'll fix that and document the structure better.

The process.sh script starts by loading the CSV(s) into sqlite, in order
to do the processing / aggregations. If you copy the first couple lines,
you'll get scans.db, with nice column names and all that..

The selectivity is calculated as

(rows / total_rows)

where rows is the rowcount returned by the query, and total_rows is
reltuples. I also had charts with "page selectivity", but that often got
a bunch of 100% points squashed on the right edge, so I stopped
generating those.

regards

--
Tomas Vondra