Re: JDBC slow performance on resultSet iteration?

Well I can speak from experience…

When I was comparing the performance of my implementation with pgjdbc I was very disheartened at the beginning as pgjdbc was seemingly much faster. It was only after I switched the test to take into account the getXXX calls that the true cost of using the driver was discovered. If you just execute a query and ignore the results pgjdbc is essentially just receiving a stream of text. It ignores all of the work of turning that text into Java objects/primitives.

My implementation uses binary protocol for this reason and that removes a lot of the overhead that pgjdbc has. If pgAdmin is using the binary protocol as well this could very well be the difference that is being seen, because it is a significant amount of time.

On Nov 5, 2013, at 11:03 AM, Dave Cramer <pg(at)fastcrypt(dot)com> wrote:

> I do not know, the best way to figure this out is to use explain analyze in pg_admin.
>
> What I am debating is the java code is using a cursor. pgAdmin is not.
>
> Try it without setFetchSize()
>
> Dave Cramer
>
> dave.cramer(at)credativ(dot)ca
> http://www.credativ.ca
>
>
> On Tue, Nov 5, 2013 at 1:00 PM, Rui Pedro Leal <rui(dot)pedro(dot)leal(at)gmail(dot)com> wrote:
> Dave,
>
> I understand what you are saying, but i must get the results, right? :)
>
> I think in pgAdmin the total query time, presented by the query execution windows, is also considering the rendering / presenting of the query results, so this is comparable ... right?
>
> [] Rui Pedro Leal
> [] rui(dot)pedro(dot)leal(at)gmail(dot)com
>
> On 2013/11/05, at 17:34, Dave Cramer wrote:
>
>> Rui Leal,
>>
>> You shouldn't see that much of a penatly, but I question how you are measuring it. Since you are timing the loop which is using cursors.
>>
>> Just run a simple query and time it without iterating through the result set. That would be equivalent
>>
>> Dave Cramer
>>
>> dave.cramer(at)credativ(dot)ca
>> http://www.credativ.ca
>>
>>
>> On Tue, Nov 5, 2013 at 12:16 PM, Rui Pedro Leal <rui(dot)pedro(dot)leal(at)gmail(dot)com> wrote:
>> Hello Dave, thanks for the quick reply.
>>
>> I'm just executing the same query on pgAdmin query interface. Just a way to measure performance of the query + getting results vs the JDBC way.
>>
>> I'm using fetchsize in order to get some faster results when iterating the resultSet. I've tried not to use fetchSize/cursor but the performance is naturally slower (and worser than the simple pgAdmin query).
>>
>> What i'm asking is .. is this performance penalty i'm getting using postgres JDBC normal and within what's expected? I'm i doing something wrong? Can i do it in any other way?
>>
>> Regards,
>>
>> Rui Leal
>>
>> [] Rui Pedro Leal
>> [] rui(dot)pedro(dot)leal(at)gmail(dot)com
>>
>>
>> On 2013/11/05, at 16:43, Dave Cramer wrote:
>>
>>> How can you measure the same query in pgAdmin ? JDBC will use a cursor when you set the fetchsize.
>>>
>>> Dave Cramer
>>>
>>> dave.cramer(at)credativ(dot)ca
>>> http://www.credativ.ca
>>>
>>>
>>> On Tue, Nov 5, 2013 at 11:12 AM, Rui Pedro Leal <rui(dot)pedro(dot)leal(at)gmail(dot)com> wrote:
>>> Just an quick info update: i'm using the postgresql-9.2-1003-jdbc4 driver
>>>
>>> On 2013/11/05, at 16:09, Rui Pedro Leal wrote:
>>>
>>> > Hello everyone,
>>> >
>>> > I'm having slow JDBC performance on iterating a resultSet obtained from a somewhat simple query.
>>> >
>>> > The query, although using PostGIS functions, is pretty straight forward:
>>> >
>>> > SELECT _id, _spatial_type, ST_AsBinary(_geometry), _attribute, _count, _references, countpersons, countfatals, countdrunks, density
>>> > FROM accidents_5
>>> > WHERE (_geometry && ST_MakeEnvelope(-126.60644531250001,26.43122806450644,-63.369140625,52.96187505907603, 4326) )
>>> > ORDER BY _pk_id
>>> >
>>> > The results are the following:
>>> > - Executing the query directly from pgAdmin: ~2807ms
>>> > - Executing from JVM + JDBC: 4184ms
>>> >
>>> > The code i'm executing is pretty much standard:
>>> >
>>> > -------------------- code --------------------
>>> >
>>> > public static void main(final String[] args) throws Exception {
>>> >
>>> > String sql = "SELECT _id, _spatial_type, ST_AsBinary(_geometry), _attribute, _count, _references, countpersons, countfatals, countdrunks, density";
>>> > sql += " FROM accidents_5";
>>> > sql += " WHERE (_geometry && ST_MakeEnvelope(-126.60644531250001,26.43122806450644,-63.369140625,52.96187505907603, 4326) )";
>>> > sql += " ORDER BY _pk_id";
>>> >
>>> > System.out.println(sql);
>>> >
>>> > Long time = System.currentTimeMillis();
>>> > try {
>>> > Connection connection = DataStoreInfo.getDataStores().get(0);
>>> > connection.setAutoCommit(false);
>>> >
>>> > System.out.println("[QUERY " + Thread.currentThread().getId()
>>> > + "] - connection in "
>>> > + (System.currentTimeMillis() - time) + "ms.");
>>> >
>>> > Statement st = connection.createStatement(
>>> > ResultSet.TYPE_FORWARD_ONLY, ResultSet.CONCUR_READ_ONLY,
>>> > ResultSet.CLOSE_CURSORS_AT_COMMIT);
>>> > st.setFetchSize(250);
>>> >
>>> > System.out.println("[QUERY " + Thread.currentThread().getId()
>>> > + "] - statement in " + (System.currentTimeMillis() - time)
>>> > + "ms.");
>>> >
>>> > ResultSet resultSet = st.executeQuery(sql);
>>> >
>>> > System.out.println("[QUERY " + Thread.currentThread().getId()
>>> > + "] - done in " + (System.currentTimeMillis() - time)
>>> > + "ms.");
>>> >
>>> > GeometryFactory geofact = new GeometryFactory(new PrecisionModel(),4326);
>>> > WKBReader wkbReader = new WKBReader(geofact);
>>> >
>>> > String id;
>>> > String spatialType;
>>> > Geometry geometry;
>>> > String attribute;
>>> > Long count;
>>> > String reference;
>>> > Map<String, Double> properties;
>>> > String granularSynthString = "GranularSynthesis";
>>> >
>>> > while (resultSet.next()) {
>>> > id = resultSet.getString(1);
>>> > spatialType = resultSet.getString(2);
>>> >
>>> > // geometry = wkbReader.read(resultSet.getBytes(3)); // ignored the WKBReader and the results are about the same.
>>> > attribute = resultSet.getString(4);
>>> > count = resultSet.getLong(5);
>>> > reference = resultSet.getString(6);
>>> >
>>> > properties = new HashMap<String, Double>();
>>> > Double aux = resultSet.getDouble(7);
>>> > properties.put("countpersons", aux);
>>> > aux = resultSet.getDouble(8);
>>> > properties.put("countfatals", aux);
>>> > aux = resultSet.getDouble(9);
>>> > properties.put("countdrunks", aux);
>>> > aux = resultSet.getDouble(10);
>>> > properties.put("density", aux);
>>> > }
>>> >
>>> > System.out.println("[QUERY " + Thread.currentThread().getId()
>>> > + "] - done & iterated in "
>>> > + (System.currentTimeMillis() - time) + "ms.");
>>> >
>>> > resultSet.close();
>>> > st.close();
>>> > connection.commit();
>>> > connection.close();
>>> > } catch (SQLException exception) {
>>> > exception.printStackTrace();
>>> > // } catch (ParseException exception) { // ignored from WKBreader
>>> > // exception.printStackTrace();
>>> > }
>>> >
>>> > System.out.println("[End " + Thread.currentThread().getId()
>>> > + "] - done in " + (System.currentTimeMillis() - time) + "ms.");
>>> > }
>>> >
>>> > -------------------- end code --------------------
>>> >
>>> > Although i'm executing this on slow MacbookPro (2.6 core duo, 2Gbs RAM but SSD) and have a 9.1.2 postgres, i've also tested this on a recent retina MBP and the ratio between pgAdmin and JDBC execution is similar.
>>> >
>>> > Is this expected? Can someone point if i'm doing something terrible wrong?
>>> >
>>> > I'm not concerned about the query performance per-se (i know it CAN be optimized), but the differences just using JDBC and iterating the resultSet are really annoying.
>>> >
>>> > Thanks in advance for any help.
>>> >
>>> > Kind regards,
>>> >
>>> > Rui Leal
>>> >
>>> >
>>>
>>>
>>>
>>> --
>>> Sent via pgsql-jdbc mailing list (pgsql-jdbc(at)postgresql(dot)org)
>>> To make changes to your subscription:
>>> http://www.postgresql.org/mailpref/pgsql-jdbc
>>>
>>
>>
>
>