Re: Adding skip scan (including MDAM style range skip scan) to nbtree

On Sat, Aug 3, 2024 at 6:14 PM Peter Geoghegan <pg(at)bowt(dot)ie> wrote:
> Displaying the number of primitive scans would already be useful for
> index scans with SAOPs, even without this patch. The same general
> concepts (estimated vs. actual primitive index scans) already exist,
> as of Postgres 17. That's really nothing new.

We actually expose this via instrumentation, in a certain sense. This
is documented by a "Note":

https://www.postgresql.org/docs/devel/monitoring-stats.html#MONITORING-PG-STAT-ALL-INDEXES-VIEW

That is, we already say "Each internal primitive index scan increments
pg_stat_all_indexes.idx_scan, so it's possible for the count of index
scans to significantly exceed the total number of index scan executor
node executions". So, as I said in the last email, advertising the
difference between # of primitive index scans and # of index scan
executor node executions in EXPLAIN ANALYZE is already a good idea.

--
Peter Geoghegan