Re: [HACKERS] Cursor With_Hold Performance Workarounds/Optimization

2017-10-20 Thread Leon Winter
> When we declare a cursor for a select on the mentioned big table, it takes > multiple seconds and a big temp file is created which to me seems like the > materialization took place immediately. Since you mentioned, Postgres already postponed materialization until commit operations we checked aga

Re: [HACKERS] Cursor With_Hold Performance Workarounds/Optimization

2017-10-20 Thread Leon Winter
> > The calculations inside the loop are written in some dynamic high-level > > language and cannot easily be translated into SQL. > > You don't really have to --- PG supports functions written in non-SQL > languages. Not sure if your problem is big enough to justify developing > a new PL interfa

Re: [HACKERS] Cursor With_Hold Performance Workarounds/Optimization

2017-10-20 Thread Leon Winter
> > The calculations inside the loop are written in some dynamic high-level > > language and cannot easily be translated into SQL. > > > > ???Can you not simply create a second connection to perform the updates? That would be possibe, but I can see some problems: loop { update table1; select so

Re: [HACKERS] Cursor With_Hold Performance Workarounds/Optimization

2017-10-20 Thread Leon Winter
> I don't know quite how to put this, but it's not clear to me that the > difficulties in this situation are things PostgreSQL could resolve > even with much larger development resources than are currently > available. There does not seem to exist a cursor/portal/pointer semantic that can survive

Re: [HACKERS] Cursor With_Hold Performance Workarounds/Optimization

2017-10-19 Thread Leon Winter
> What other things did you try, and how did they fail? In particular, > what happened when you used > > UPDATE table2 > SET [things based on table1] > FROM table1 [qualified] JOIN table2 ON ([conditions]) well, it is not the ideal way of doing things but then again this SQL is merel

[HACKERS] Cursor With_Hold Performance Workarounds/Optimization

2017-10-19 Thread Leon Winter
Hi, I originally brought up this issue on the pgsql-performance mailing list [^] to no avail so I am trying again here. During implementation of a runtime environment and the adjoining database abstraction layer I noticed (like many before me [0] and as correctly mentioned in the documentation) t