[ http://issues.apache.org/jira/browse/DERBY-1713?page=all ]
John H. Embretsen updated DERBY-1713:
-------------------------------------
Component/s: SQL
Urgency: Normal (was: Urgent)
Priority: Major (was: Critical)
This issue is seen when executing certain kinds of queries against large
tables. Two work-arounds have been identified and tested:
1. Increase max heap size (e.g. from 32 MB to 38 MB, -Xmx38M)
2. Reduce the size of Derby's page cache. With Derby1713repro.java, the
following command succeeded:
> java -Xmx32m -Dderby.storage.pageCacheSize=800 Derby1713repro haveDB
whereas it fails with the default pageCacheSize value (1000). Using different
values for derby.storage.pageSize only did not seem to have a noticeable effect
on memory usage.
See Derby's tuning guide for more information about these properties (
http://db.apache.org/derby/docs/dev/tuning/ ).
The reported problem of not being able to free memory following an
OutOfMemoryError is not a bug. Quoting the Java Language Specification, 3rd
edition, Chapter 11 (
http://java.sun.com/docs/books/jls/third_edition/html/exceptions.html ):
"The class Error and its subclasses are exceptions from which ordinary programs
are not ordinarily expected to recover. (...) recovery is typically not
possible".
If any of the reported work-arounds are not acceptable, the programmer probably
needs to handle such situations preemptively. There may be some useful advice
in the Tuning Guide (see
http://db.apache.org/derby/docs/dev/tuning/ctundepth10525.html ).
Lowering Priority (Major; work-arounds exist) and Urgency (Normal; "If this
issue scratches the itch of any particular developer, then they should help to
solve it and provide a patch").
> Memory do not return to the system after Shuting down derby 10.2.1.0,
> following an out of memory event
> ------------------------------------------------------------------------------------------------------
>
> Key: DERBY-1713
> URL: http://issues.apache.org/jira/browse/DERBY-1713
> Project: Derby
> Issue Type: Bug
> Components: Performance, SQL
> Affects Versions: 10.2.1.0
> Environment: Windows XP SP2
> JRE 1.6 beta2
> Reporter: Ibrahim
> Attachments: Derby1713repro.java, test.zip, Test1.java
>
>
> I face a problem when querying large tables. I run the below SQL and it stuck
> in this query and throws java heap exception OutOfMemory:
> SELECT count(*) FROM <table> WHERE .....
> N.B. I'm using a database of more than 90,000 records (40 MB). I set the
> maxHeap to 32 MB (all other settings have the default value, pageCache ...
> etc ).
> Then, I shutdown the database but the memory is not returned to the system
> (and remain 32 MB [max threshold]). I tried to increase the maxHeap to 128 MB
> in which it works and releases the memory, so I think the problem is when it
> reaches the maxHeap then it seems to not respond to anything such as closing
> the connection or shutting down the database. How can I get rid of this?
> (because i cannot increase the maxHeap as the database increases, I want to
> throw an exception and release the memory)
> I'm using this to shutdown the DB:
> try{DriverManager.getConnection("jdbc:derby:;shutdown=true");}
> catch(SQLException ex){System.err.println("SQLException: " +
> ex.getMessage());}
> I'm using a memory Profiler for monitoring the memory usage.
> Thanks in advanced.
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