On Fri, Dec 8, 2023 at 3:13 PM Alexander Pyhalov <a.pyha...@postgrespro.ru> wrote:
> Andrei Lepikhov писал(а) 2023-12-08 07:37: > > I'd already clashed with Tom on copying the required_relids field and > > voluntarily made unnecessary copies in the project [1]. > > And ... stuck into huge memory consumption. The reason was in > > Bitmapsets: > > When we have 1E3-1E4 partitions and try to reparameterize a join, one > > bitmapset field can have a size of about 1kB. Having bitmapset > > referencing Relation with a large index value, we had a lot of (for > > example, 1E4 * 1kB) copies on each reparametrization of such a field. > > Alexander Pyhalov should remember that case. > > Yes. If it matters, this happened during reparametrization when 2 > partitioned tables with 1000 partitions each were joined. Then > asymmetric pw join managed to eat lots of memory for bitmapsets (by > lots of memory I mean all available on the test VM). By reparametrization did you mean the work done in reparameterize_path_by_child()? If so maybe you'd be interested in the patch [1] which postpones reparameterization of paths until createplan.c and thus can help avoid unnecessary reparametrization work. [1] https://www.postgresql.org/message-id/CAMbWs48PBwe1YadzgKGW_ES%3DV9BZhq00BaZTOTM6Oye8n_cDNg%40mail.gmail.com Thanks Richard
