From: Amit Langote [mailto:langote_amit...@lab.ntt.co.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
