On Mon, 2020-02-17 at 15:03 +0000, Lars Aksel Opsahl wrote: > I have tested in branch ( > https://github.com/larsop/resolve-overlap-and-gap/tree/add_postgis_topology_using_func) > where I use only have functions and no procedures and I still have the same > problem with subtransaction locks. > > Can I based on this assume that the problem is only related to exceptions ?
No, it is related to BEGIN ... EXCEPTION ... END blocks, no matter if an exception is thrown or not. As soon as execution enters such a block, a subtransaction is started. > Does this mean that if have 32 threads running in parallel and I get 2 > exceptions in each thread I have reached a state where I will get contention ? No, it means that if you enter a block with an EXCEPTION clause more than 64 times in a single transaction, performance will drop. > Is it any way increase from 64 to a much higher level, when compiling the > code ? Yes, you can increase PGPROC_MAX_CACHED_SUBXIDS in src/include/storage/proc.h > Basically what I do here is that I catch exceptions when get them and tries > to solve the problem in a alternative way. Either use shorter transactions, or start fewer subtransactions. Yours, Laurenz Albe -- Cybertec | https://www.cybertec-postgresql.com
