Re: How to prevent jdbc from sending any results back to the client ?

Dimitris,

No it does not do query caching. The backend does cache so typically the
first query will take a while, then subsequent queries will take much less
time as the data is in RAM.

Dave Cramer

dave.cramer(at)credativ(dot)ca
http://www.credativ.ca

On 20 April 2014 14:46, Dimitris Karampinas <dkarampin(at)gmail(dot)com> wrote:

> Thanks, EXPLAIN ANALYSE might be an option for me.
>
> One more question, because in certain cases I get strange results.
> Does jdbc do any kind of result or query caching by default ?
>
> -dk
>
>
> On Sun, Apr 20, 2014 at 2:22 AM, Dave Cramer <pg(at)fastcrypt(dot)com> wrote:
>
>> Dimitris,
>>
>> You would be better off running queries such as explain analyze which do
>> not return results, but do time the query. Every postgresql client library
>> will have to wait for the results. That is essentially the way the protocol
>> works
>>
>> Dave
>>
>> Dave Cramer
>>
>> dave.cramer(at)credativ(dot)ca
>> http://www.credativ.ca
>>
>>
>> On 19 April 2014 15:02, Sehrope Sarkuni <sehrope(at)jackdb(dot)com> wrote:
>>
>>> The fetch size only comes into play if your are in a transaction. You
>>> have to disable auto commit and set the fetch size before executing your
>>> query. Otherwise the entire query result will be read and buffered in
>>> memory.
>>>
>>> An alternative is to run the command as an EXPLAIN ANALYZE[1]. The
>>> server will then execute the entire operation but instead of sending back
>>> the data it will send the query plan and runtime statistics.
>>>
>>> [1]: http://www.postgresql.org/docs/9.3/static/sql-explain.html
>>>
>>> Regards,
>>> Sehrope Sarkuni
>>> Founder & CEO | JackDB, Inc. | http://www.jackdb.com/
>>>
>>> On Apr 19, 2014, at 2:48 PM, Dimitris Karampinas <dkarampin(at)gmail(dot)com>
>>> wrote:
>>>
>>> Hi,
>>>
>>> I'm working on an academic project and I need to benchmark PostgreSQL.
>>> I'm intersted only about the performance of the DBMS itself and I'm
>>> trying to keep things simple in my measurements.
>>> Preferably I'd like to ignore the query results at the client side but
>>> jdbc seems to return results even if I don't call next() on the Resultset
>>> (is that true ?).
>>> As a consequence, I can't measure acurately a per query execution time
>>> since the time I get depends also on the time spent to send the answer (or
>>> part of it) to the client.
>>> setFetchSize(1) doesn't seem to help much.
>>> Can I hack the driver and diminish the overhead explained above ?
>>>
>>> Cheers,
>>> Dimitris
>>>
>>>
>>
>