Re: Stored Procedure Performance

[Purav Chovatia <puravc@xxxxxxxxx>]

Thanks Pavel. Our SPs are not doing any mathematical calculations. Its mostly if-else, so I would expect good performance.

On 11 October 2017 at 19:50, Pavel Stehule <pavel.stehule@xxxxxxxxx> wrote:

2017-10-11 15:59 GMT+02:00 Purav Chovatia <puravc@xxxxxxxxx>:

Thanks Laurenz, am having a look at perf.

Can you pls help understand what exactly do you mean when you say "PL/pgSQL is not optimized for performance like PL/SQL". Do you mean to indicate that app firing queries/DMLs directly would be a better option as compared to putting those in Stored Procs?

PL/pgSQL is perfect glue for SQL. SQL queries has same speed without dependency on environment that executed it.

This sentence mean, so PLpgSQL is not designed for intensive mathematics calculation.  PL/SQL is self govering environment ... it has own data types, it has own implementation of logical and mathematics operators. PLpgSQL is layer over SQL engine - and has not own types, has not own operators. Any _expression_ is translated to SQL and then is interpreted by SQL _expression_ interpret. Maybe in next few years there will be a JIT compiler. But it is not now. This is current bottleneck of PLpgSQL. If your PL code is glue for SQL queries (implementation of some business processes), then PLpgSQL is fast enough. If you try to calculate numeric integration or derivation of some functions, then PLpgSQL is slow. It is not too slow - the speed is comparable with PHP, but it is significantly slower than C language.

PostgreSQL has perfect C API - so intensive numeric calculations are usually implemented as C extension.

Regards

Pavel

 

Regards

On 3 October 2017 at 20:24, Laurenz Albe <laurenz.albe@xxxxxxxxxxx> wrote:

Purav Chovatia wrote:
> I come from Oracle world and we are porting all our applications to postgresql.
>
> The application calls 2 stored procs, 
> - first one does a few selects and then an insert
> - second one does an update
>
> The main table on which the insert and the update happens is truncated before every performance test.
>
> We are doing about 100 executions of both of these stored proc per second.
>
> In Oracle each exec takes about 1millisec whereas in postgres its taking 10millisec and that eventually leads to a queue build up in our application.
>
> All indices are in place. The select, insert & update are all single row operations and use the PK.
>
> It does not look like any query taking longer but something else. How can I check where is the time being spent? There are no IO waits, so its all on the CPU.

You could profile the PostgreSQL server while it is executing the
workload,
see for example https://wiki.postgresql.org/wiki/Profiling_with_perf

That way you could see where the time is spent.

PL/pgSQL is not optimized for performance like PL/SQL.

Yours,
Laurenz Albe