On Mon, Aug 7, 2023 at 10:25 AM Amit Langote <amitlangot...@gmail.com> wrote: > Note we’re talking here about “initial” pruning that occurs during > ExecInitNode(). Workers are only launched during ExecGather[Merge]() which > thereafter do ExecInitNode() on their copy of the the plan tree. So if we > are to pass the pruning results for cross-checking, it will have to be from > the leader to workers.
That doesn't seem like a big problem because there aren't many node types that do pruning, right? I think we're just talking about Append and MergeAppend, or something like that, right? You just need the ExecWhateverEstimate function to budget some DSM space to store the information, which can basically just be a bitmap over the set of child plans, and the ExecWhateverInitializeDSM copies the information into that DSM space, and ExecWhateverInitializeWorker() copies the information from the shared space back into the local node (or maybe just points to it, if the representation is sufficiently compatible). I feel like this is an hour or two's worth of coding, unless I'm missing something, and WAY easier than trying to reason about what happens if expression evaluation isn't as stable as we'd like it to be. -- Robert Haas EDB: http://www.enterprisedb.com
