Re: [PoC] Reducing planning time when tables have many partitions

On Wed, Sep 20, 2023 at 3:35 PM Yuya Watari <watari(dot)yuya(at)gmail(dot)com> wrote:

> I think we may be able to remove the eclass_child_members field by
> making child members on demand. v20 makes child members at
> add_[child_]join_rel_equivalences() and adds them into
> RelOptInfo->eclass_child_members. Instead of doing that, if we
> translate on demand when child members are requested,
> RelOptInfo->eclass_child_members is no longer necessary. After that,
> there is only ec_members, which consists of parent members, so
> removing clauses will still be simple. Do you think this idea will
> solve your problem? If so, I will experiment with this and share a new
> patch version. The main concern with this idea is that the same child
> member will be created many times, wasting time and memory. Some
> techniques like caching might solve this.
>

While working on RestrictInfo translations patch I was thinking on
these lines. [1] uses hash table for storing translated RestrictInfo.
An EC can have a hash table to store ec_member translations. The same
patchset also has some changes in the code which generates
RestrictInfo clauses from ECs. I think that code will be simplified by
your approach.

[1] https://www.postgresql.org/message-id/CAExHW5u0Yyyr2mwvLrvVy_QnLd65kpc9u-bO0Ox7bgLkgbac8A@mail.gmail.com

--
Best Wishes,
Ashutosh Bapat