[infinispan-dev] Bucket-based cache stores not removing buckets when they're empty

[Martin Gencur]

I can't say how this will look in practice. You're right...if the
creation operation is not cheap, it will be probably better to not
delete buckets when they are empty but rather wait for the "purge"
operation. The database can hold lots of entries and remain efficient
anyway.

Martin



On Tue, 2011-12-06 at 10:28 +0000, Sanne Grinovero wrote:
> Hi Martin,
> I would expect that a bucket has a good likelihood to be reused, so
> that performance would be better to avoid both deletion and subsequent
> re-creation; concurrent creation might need a lock to ensure a single
> instance is created, so that's not a very cheap operation.
> 
> That said, I don't know how bad situation can get in practice; are you
> seeing this happening very often, to the point that many empty buckets
> might become inefficient usage of space or indexes in the store ? We
> might think of clearing them in background, but creation would need to
> be a blocking operation.
> 
> Sanne
> 
> On 6 December 2011 09:35, Martin Gencur <mgencur at redhat.com> wrote:
> > I found out through our tests that bucket-based cache stores
> > (JdbcBinaryCacheStore and FileCacheStore) are not removing buckets (this
> > is either a database table row or a file) when they remove last
> > entry from the bucket and they remain empty in the database/filesystem.
> >
> > (https://github.com/infinispan/infinispan/blob/master/core/src/main/java/org/infinispan/loaders/bucket/BucketBasedCacheStore.java#L105)
> >
> > Buckets are removed only when the cache store is purged (purge
> > attribute==true) so when the purge attribute is not set then the number
> > of buckets will only grow.
> >
> > Shouldn't we change this to remove buckets when removing last entry from
> > them?
> >
> >
> > Thanks for any thoughts
> >
> >
> >
> > --
> > Martin Gencur
> > --
> > JBoss QE, Enterprise Data Grid
> > Desk phone: +420 532 294 192, ext. 62192
> >
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-- 
Martin Gencur
--
JBoss QE, Enterprise Data Grid
Desk phone: +420 532 294 192, ext. 62192