If you build Derby yourself you can test out a faster version of Derby
that has relaxed durability.
By relaxed durability I mean that:
- a commit no longer guarantees that the transaction's modifications
will survive a system crash or JVM termination.
- the database may not recover successfully upon re-start
- a near full disk at runtime may cause unexpected errors (currently
Derby ensures that space exists on the disk
for a transaction's data before commit)
This is useful for unit testing or development time.
I would not recommend it for production if your data is important.
I think this functionality should be added into the standard Derby but
in a simpler form,
maybe a single property
derby.storage.durable={full,none,???} [not supported currently, see below]
(or maybe even higher concept, derby.system.testMode=true??)
In the meantime ....
This will work on the 10.0 branch or the trunk
Set the variable MEASURE in
java/engine/org/apache/derby/iapi/services/diag/Performance to true
(see attached patch)
Clobber and then compile Derby
ant clobber
ant
Set these system properties when running Derby
derby.storage.dataNotSyncedAtCheckPoint=true
derby.storage.dataNotSyncedAtAllocation=true
derby.storage.logNotSynced=true
E.g.
java -Dderby.storage.dataNotSyncedAtCheckPoint=true
-Dderby.storage.dataNotSyncedAtAllocation=true
-Dderby.storage.logNotSynced=true your_application_class
If you are successful then you see this warnings in derby.log
Warning: derby.storage.dataNotSyncedAtCheckPointset to true.
Warning: derby.storage.dataNotSyncedAtAllocationset to true.
logNotSynced = true
This stops Derby flushing data all the way to disk, and thus in most
cases i/o cost is not involved as the operating file system cache keeps
all the data pages and log in memory.
If anyone tries this could they e-mail the list to say if it's
sufficient for their needs and if they would like to see this option
become part of a Derby release in its simpler form.
Thanks,
Dan.
Index: java/engine/org/apache/derby/iapi/services/diag/Performance.java
===================================================================
--- java/engine/org/apache/derby/iapi/services/diag/Performance.java
(revision 153426)
+++ java/engine/org/apache/derby/iapi/services/diag/Performance.java
(working copy)
@@ -26,5 +26,5 @@
// file and change the value of this to `true', then compile
// whichever other classes are depending on this. In general,
// such a check-out should only be temporary.
- public static final boolean MEASURE = false;
+ public static final boolean MEASURE = true;
}
