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From Ronald Rudy <ronchal...@gmail.com>
Subject Re: OutOfMemoryErrors on group by select
Date Mon, 08 Feb 2010 15:42:04 GMT
Kristian,

Yes, I actually do have a heap dump just like you mentioned - sorry I had completely forgotten
I retrieved one earlier (it was done so late last evening and I am still getting my bearings
this morning :))

Here is the top 17 or so from the histogram: (view the email w/ fixed width and it should
be ok)

Class                                            Instance Count    Total Size
[C                                                      1596861    307166530
[B                                                        10719    69009057
org.apache.derby.iapi.types.SQLVarchar                  1391370    38958360
java.lang.String                                        1397786    22364576
[[C                                                     1392460    16709932
[Lorg.apache.derby.iapi.types.DataValueDescriptor;       200932    8796896
org.apache.derby.impl.store.access.sort.Node             198342    5553576
org.apache.derby.iapi.types.SQLInteger                   398201    1991005
org.apache.derby.impl.store.raw.data.StoredRecordHeader   93119    1583023
[Lorg.apache.derby.impl.store.access.sort.Node;               9    1049092
org.apache.derby.impl.store.raw.data.RecordId             48191    578292
[Ljava.util.concurrent.ConcurrentHashMap$HashEntry;         192    425876
[Lorg.apache.derby.impl.store.raw.data.StoredRecordHeader; 2000    404880
org.apache.derby.impl.store.raw.data.StoredPage            2000    352000
[Ljava.util.HashMap$Entry;                                  837    303432
[I                                                         4839    286212
java.lang.Class                                            2584    196384

It looks like it's keeping a ton of SQLVarchar's in memory.. 

-Ron



On Feb 8, 2010, at 9:48:52 AM, Kristian Waagan wrote:
> Hi Ronald,
> 
> If you can easily control this process, can you run it with -XX:+HeapDumpOnOutOfMemoryError
and post a heap dump summary?
> (I don't remember off the top of my head how you extract a histogram from the binary
heap dump, but I guess maybe using jmap or HeapViewer)
> Are there many Derby classes in the top 10?
> You might only see a bunch of arrays up there, in which case more investigation may be
required to understand what's going on.
> 
> 
> Regards,
> -- 
> Kristian


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