Hi H2 developers and users,
I'm experiencing a disturbing issue that I cannot find a way to fix,
except for the unscalable solution of just increasing the heap size to
enourmous sizes. Currently I have 1gb of memory available, which
should be enough I hope.
What I have is a table with around 1.2 million records and 7 columns
in it. I need to make a query to find the unique records of the table,
so I do a COUNT(*) and GROUP BY query like this:
SELECT a,b,c,d,e,f,g,COUNT(*) FROM my_table GROUP BY a,b,c,d,e,f,g
And this runs out of memory :-(
I've tried tweaking by issuing this, but it didn't work:
SET MAX_MEMORY_ROWS 500
My connection type is local filebased, like this:
jdbc:h2:c:\my_db
Is there any way to prevent this from happening, by using a more disk-
oriented caching mechanism or such? I hope so because I expect the
table to grow in size without having to increase the heap size all the
time. Execution speed is a minor issue, so a lesser performing
solution is OK.
Here's the stack trace of H2:
Caused by: java.lang.OutOfMemoryError: Java heap space
at org.h2.value.Value.cache(Value.java:338)
at org.h2.value.ValueString.get(ValueString.java:127)
at org.h2.store.Data.readValue(Data.java:747)
at org.h2.index.PageDataIndex.readRow(PageDataIndex.java:416)
at org.h2.index.PageDataLeaf.getRowAt(PageDataLeaf.java:327)
at org.h2.index.PageDataCursor.nextRow(PageDataCursor.java:97)
at org.h2.index.PageDataCursor.next(PageDataCursor.java:49)
at org.h2.index.IndexCursor.next(IndexCursor.java:222)
at org.h2.table.TableFilter.next(TableFilter.java:342)
at org.h2.command.dml.Select.queryGroup(Select.java:311)
at org.h2.command.dml.Select.queryWithoutCache(Select.java:592)
at org.h2.command.dml.Query.query(Query.java:257)
at org.h2.command.dml.Query.query(Query.java:227)
at org.h2.command.CommandContainer.query(CommandContainer.java:78)
at org.h2.command.Command.executeQuery(Command.java:178)
at org.h2.jdbc.JdbcStatement.executeQuery(JdbcStatement.java:77)
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