Thank you for your comment. I've removed the tabs. > I can think of at least a few use cases where this customscan is helpful and > not merely testing code.
IIUC, we already can use ctid in the where clause on the latest PostgreSQL, can't we? 2022年11月22日(火) 18:07 Ronan Dunklau <ronan.dunk...@aiven.io>: > > Le mardi 6 septembre 2022, 11:29:55 CET Etsuro Fujita a écrit : > > On Mon, Sep 5, 2022 at 10:32 PM Kazutaka Onishi <oni...@heterodb.com> wrote: > > > I'm sorry for my error on your name... > > > > No problem. > > > > > > IIUC, it uses the proposed > > > > > > > > APIs, but actually executes ctidscans *synchronously*, so it does not > > > > improve performance. Right? > > > > > > Exactly. > > > The actual CustomScan that supports asynchronous execution will > > > start processing in CustomScanAsyncRequest, > > > configure to detect completion via file descriptor in > > > CustomScanAsyncConfigureWait, > > > and receive the result in CustomScanAsyncNotify. > > > > Ok, thanks! > > Thanks for this patch, seems like a useful addition to the CustomScan API. > Just to nitpick: there are extraneous tabs in createplan.c on a blank line. > > Sorry for the digression, but I know your ctidscan module had been proposed > for inclusion in contrib a long time ago, and I wonder if the rationale for > not including it could have changed. We still don't have tests which cover > CustomScan, and I can think of at least a few use cases where this customscan > is helpful and not merely testing code. > > One of those use case is when performing migrations on a table, and one wants > to update the whole table by filling a new column with a computed value. You > obviously don't want to do it in a single transaction, so you end up batching > updates using an index looking for null values. If you want to do this, it's > much faster to update rows in a range of block, performing a first series of > batch updating all such block ranges, and then finally update the ones we > missed transactionally (inserted in a block we already processed while in the > middle of the batch, or in new blocks resulting from a relation extension). > > Best regards, > > -- > Ronan Dunklau > >
v3-0001-allow-custon-scan-asynchronous-execution.patch
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