On 3/24/25 23:45, Tom Lane wrote:
Lukas Fittl <lu...@fittl.com> writes:
The main argument I had initially when proposing this, is that Memoize is
different from other plan nodes, in that it makes the child node costs
"cheaper". Clearly seeing the expected cache hit/ratio (that drives that
costing modification) helps interpret why the planner came up with a given
plan.
As I said, I'm not necessarily averse to showing these numbers
somehow. But I don't think they belong in the default output,
and I'm not even convinced that VERBOSE is the right place.
pg_overexplain seems like it could be an ideal home for this
sort of detail.
I prefer not to see these numbers in the default EXPLAIN output, not
only because they can fluctuate but mainly because I like to view the
basic query structure without additional details.
As I mentioned earlier, most of the information we typically need to
explore query plans stays in path nodes and does not transfer to the
Plan node. I believe this should stay as is, as we deal with numerous
cases and a vast amount of data.
It would be beneficial to expose extra data in an external extension. By
implementing a `create_plan` hook and an extensible list node in both
Path and Plan structures, we could provide a machinery for writing an
extension that can expose any planning-stage information in EXPLAIN on
demand.
This could encourage developers to create a "pg_extended_explain"
extension, which would address most user needs without requiring
additional changes to the core system.
--
regards, Andrei Lepikhov
