RE: Speeding up creating UPDATE/DELETE generic plan for partitioned table into a lot

From: Amit Langote [mailto:Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp]
> Maybe, we can invent new types of plans for queries on partitioned tables
> that can be constructed by only looking at the parent relation. We'd need
> new infrastructure before we can begin working on that though. For
> example, until we had partitioned tables and the new partition pruning
> module specialized for partitioned tables, we had to look at every child
> to use constraint exclusion to emulate partition pruning. Starting in PG
> 11, we now only look at the parent to perform pruning. To perform the
> *whole planning* by just looking at the parent relation would require us
> to build more infrastructure such that, for example, an appropriate scan
> method for underlying partitions can be selected without having to open
> the children.

Although I may say the same thing as you, I think a natural idea would be to create a generic plan gradually. The starting simple question is "why do we have to touch all partitions at first?" That is, can we behave like this:

* PREPARE just creates an aggregation plan node (e.g. Append for SELECT, Update for UPDATE). It doesn't create any plan for particular partitions. Say, call this a parent generic plan node.
* EXECUTE creates a generic plan for specific partitions if they don't exist yet, and attach them to the parent generic plan node.

Regards
Takayuki Tsunakawa