2014-09-28 21:29 GMT+02:00 Gerardo Herzig <gherzig@xxxxxxxxxxx>:
Thanks Pavel! Im not (directly) concerned about speed, im concerned about resources usage.> Hi all. I see an entire database, with all the stored procedures
> writen in plpgsql. Off course, many (if not all) of that SP are
> simple inserts, updates, selects and so on.
>
> So, i want to test and show the differences between doing the same
> function in pgpgsql vs. plain sql.
> Im getting statistics (via collectd if that matters) and doing a
> modified version of the pgbench tests, just using pl (and sql)
> functions instead of the plain query:
>
> \setrandom delta -5000 5000
> BEGIN;
> SELECT pgbench_accounts_upd_pl(:delta, :aid);
> SELECT get_pgbench_accounts_pl(:aid);
> SELECT pgbench_tellers_upd_pl(:delta, :tid);
> SELECT pgbench_branches_upd_pl(:delta, :bid);
> select pgbench_history_ins_pl(:tid, :bid, :aid, :delta);
> END;
>
> At first, pgbench is showing a difference between the "pl" and de
> "sql" versions:
>
> (pl.scripts own the "PL" version, sql.script owns the "SQL" version
> of the test)
> (This is a tiny netbook, with a dual core procesor)
>
> gherzig@via:~> pgbench -c 2 -C -T 300 -f pl.script -U postgres test
> duration: 300 s
> number of transactions actually processed: 13524
> tps = 45.074960 (including connections establishing)
> tps = 75.260741 (excluding connections establishing)
>
> gherzig@via:~> pgbench -c 2 -C -T 300 -f sql.script -U postgres test
> starting vacuum...end.
> duration: 300 s
> number of transactions actually processed: 15125
> tps = 50.412852 (including connections establishing)
> tps = 92.058245 (excluding connections establishing)
>
> So yeah, it looks like the "SQL" version is able to do a 10% more
> transactions.
> However, i was hoping to see anothers "efects" of using sql (perhaps
> less load avg in the SQL version), at the OS level.
>
> So, finnaly, the actual question:
> ¿Wich signals should i monitor, in order to show that PGPLSQL uses
> more resources than SQL?
>
>
>
> It is hard question. It is invisible feature of SQL proc - inlining.
> What I know, a SQL function is faster than PLpgSQL function, when it
> is inlined. But there is nothing visible metric, that inform you
> about inlining.
>
>
> Regards
>
>
> Pavel
>
>
May be there is a value that shows the "PGSQL machine necesary for plpgsql execution"
This is little bit more wide topic. The performance is only one point, second is a readability, robustness, .. and there are questions about plan caching, query optimization,
Usually, PLpgSQL should not be used for one line SELECT based functions or one line _expression_ based functions. But there are some exceptions.
The best way is slow queries monitoring, and slow queries analyse - it is base for decision for changing language.
Regards
Pavel
Pavel
Thanks again for your time.
Gerardo
