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Pavel Yaskevich commented on CASSANDRA-3143:
--------------------------------------------
bq. I'm not a fan of that idea. We just cannot release this without a way to
deactivate the row cache as this would make the row cache unusable for most
users. IMHO, that's a good definition of something that should not be moved to
a separate task.
Couldn't we do that the same way we did with compression options? I'm happy to
make it a sub-task, I just want the main code to be settled before starting
with that.
bq. Why does the getRowCacheKeysToSave() option disappeared?
Is that going to have the same use case as it did per-CF? Meaning we would be
saving a top of the cache and it doesn't guarantee that system doesn't start
almost cold...
{quote}
Talking of the key cache save, the format used by the patch is really really
not compact. For each key we save the full path to the sstable, which can
easily be > 50 bytes. Maybe we could associate an int to each descriptor during
the save and save the association of descriptor -> id separately. * Still worth
allowing to chose how may keys to save
{quote}
Do you think that it worse the effort of maintaining (also persisting) such
descriptor -> id relationship exclusively for key cache? Meaning it's already
very compact cache e.g. even with descriptor > 50 bytes we would need ~20 mb to
store 200000 keys...
bq. The cache sizings don't take the keys into account. For the row cache, one
could make the argument that the overhead of the keys is negligible compared to
the values. For the key cache however, the key are bigger than the values.
We do that because CLHM only allows to measure values, to do something about it
we would need to re-write Weighter interface and change core semantics of
CLHM...
> Global caches (key/row)
> -----------------------
>
> Key: CASSANDRA-3143
> URL: https://issues.apache.org/jira/browse/CASSANDRA-3143
> Project: Cassandra
> Issue Type: Improvement
> Reporter: Pavel Yaskevich
> Assignee: Pavel Yaskevich
> Priority: Minor
> Labels: Core
> Fix For: 1.1
>
> Attachments: 0001-global-key-cache.patch,
> 0002-global-row-cache-and-ASC.readSaved-changed-to-abstra.patch,
> 0003-CacheServiceMBean-and-correct-key-cache-loading.patch,
> 0004-key-row-cache-tests-and-tweaks.patch,
> 0005-cleanup-of-the-CFMetaData-and-thrift-avro-CfDef-and-.patch,
> 0006-row-key-cache-improvements-according-to-Sylvain-s-co.patch
>
>
> Caches are difficult to configure well as ColumnFamilies are added, similar
> to how memtables were difficult pre-CASSANDRA-2006.
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