On 17-Oct-06, at 3:05 PM, Behl, Rohit ((Infosys)) wrote:
Hi
We are facing performance problems in postgres while executing a query. When I execute this query on the server it takes 5-10 seconds. Also I get good performance while executing this query from my code in java with the hard codes values. I face severe performance problems when I run it using a prepared statement.
The query is as follows:
Select events.event_id, ctrl.real_name, events.tsds, events.value, events.lds, events.correction, ctrl.type, ctrl.freq from iso_midw_data_update_events events, iso_midw_control ctrl where events.obj_id = ctrl.obj_id and events.event_id > 68971124 order by events.event_id limit 2000
The above query executes in 5-10 seconds.
However the below query executes in 8 mins:
Select events.event_id, ctrl.real_name, events.tsds, events.value, events.lds, events.correction, ctrl.type, ctrl.freq from table events, iso_midw_control ctrl where events.obj_id = ctrl.obj_id and events.event_id > ?::bigint order by events.event_id limit ?
setLong(1, 68971124);
setInt(2, 2000);
The table has close to 5 million rows. The table has the following index:
iso_midw_data_update_events_event_id_key
iso_midw_data_update_events_lds_idx
iso_midw_data_update_events_obj_id_idx
The table is described as follows:
Columns_name data_type type_name column_size
lds 2 numeric 13
obj_id 2 numeric 6
tsds 2 numeric 13
value 12 varchar 22
correction 2 numeric 1
delta_lds_tsds 2 numeric 13
event_id -5 bigserial 8
Please tell me what I am missing while setting the prepared statement. I am using postgres7.4.2. and postgresql-8.1-407.jdbc3.jar.
Try the same query with protocolVersion=2. There are some issues with prepared statements being slower if the parameters are not the same type as the column being compared to.
protocol version 2 will issue the query exactly the same as psql does. Also note that your two queries are not identical. In the prepared query you cast to bigint ?
