[
https://issues.apache.org/jira/browse/DERBY-5066?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12999219#comment-12999219
]
Mike Matrigali commented on DERBY-5066:
---------------------------------------
there is probably some tuning that could be done on the sort, as bryan
mentions. It could be you need to start your jvm with some bigger initial
heaps. But as I understand the goal of the app derby is never going to give
you what you are looking for if it does a sort rather than
do sort avoidance.
You have 3 choices:
1) assuming PID is a unique key, first issue an order select to get all the
PID's of interest and then as you fill each row in the UI do a stored prepared
statement to look up the data associated with the PID. I believe if you just
select the stuff in the index it will never do a sort.
2) use optimizer hints to force the use of the index in your query.
3) use fetch/offset feature added recently to derby to get "chunks" of data. I
don't know much about this feature so am not sure if it will avoid
the sort or not.
> full table scan when index is used, taking extremely long time in JDBC
> ----------------------------------------------------------------------
>
> Key: DERBY-5066
> URL: https://issues.apache.org/jira/browse/DERBY-5066
> Project: Derby
> Issue Type: Bug
> Components: Eclipse Plug-in, JDBC
> Affects Versions: 10.7.1.1
> Environment: Windows XP environment
> Reporter: George Xu
> Attachments: LogXData.rar
>
>
> When a very large table (500k rows) is used with a column is indexed.
> select * from tab where pid > 0 order by pid takes extremely longer time than
> select * from tab order by pid. Actually, it is 100 times slower. However,
> in IJ, ther performance seems to be similar. PID column is indexed.
> Here is the code snipplet
> import java.sql.Connection;
> import java.sql.DriverManager;
> import java.sql.ResultSet;
> import java.sql.SQLException;
> import java.sql.Statement;
> public class TestPerformance {
> //20343 mill-sec
> static String s1 = "SELECT TIMESTAMP, HOSTPORT AS \"HOST ID\", PID,
> SESSIONID, REQUESTID, " +
> "SUBREQUESTID, STEPID, TID, COMPONENT, BUILDNUM, " +
> "LOGLEVELORIG AS \"LEVEL\", LOGGER, OPERATION, OBJECTTYPE, OBJECTPATH,
> " +
> "STATUS, MESSAGE, DATA, NDX FROM LOGDATA871218 where PID > 0 ORDER BY
> PID";
> //297 million sec.
> static String s2 = "SELECT TIMESTAMP, HOSTPORT AS \"HOST ID\", PID,
> SESSIONID, REQUESTID, " +
> "SUBREQUESTID, STEPID, TID, COMPONENT, BUILDNUM, " +
> "LOGLEVELORIG AS \"LEVEL\", LOGGER, OPERATION, OBJECTTYPE, OBJECTPATH,
> " +
> "STATUS, MESSAGE, DATA, NDX FROM LOGDATA871218 ORDER BY PID";
> public static void main(String[] args) throws InstantiationException,
> IllegalAccessException, ClassNotFoundException {
> Statement stmt3;
> try {
>
> //connect'jdbc:derby:C:/devroot/runtime-New_configuration/LogXData';
> String db =
> "C:/devroot/runtime-New_configuration/LogXData";
> String driver = "org.apache.derby.jdbc.EmbeddedDriver";
> Class.forName(driver).newInstance();
> Connection con =
> DriverManager.getConnection("jdbc:derby:"+db);
> stmt3 = con.createStatement(ResultSet.FETCH_FORWARD,
> ResultSet.TYPE_FORWARD_ONLY);
> long startTime3 = System.currentTimeMillis();
> ResultSet rs3 = stmt3.executeQuery(s1);
> long elapsed3 = System.currentTimeMillis() - startTime3;
> System.out.println("Statment.executeQuery Dup: " +
> elapsed3);
> } catch (SQLException e) {
> // TODO Auto-generated catch block
> e.printStackTrace();
> }
> }
> }
--
This message is automatically generated by JIRA.
-
For more information on JIRA, see: http://www.atlassian.com/software/jira
