The JCS hierarchical remove is more powerful than
groups. JCS grouping needs an overhaul.
The old JCS grouping was designed for fast removal and
gets, faster than hierarchical removal. We stored the
keys for groups in a hashtable in the systemgroupid
region. This allowed for quick lookups of group keys
and fast removal. To get the keys for a group, the
map for the group ids was retrieved and all the values
were spit out. This didn't require locking the entire
map for a region to retrieve group keys.
There were some synchronization problems in the old
group implementation, so it was changed. Currently,
the systemgroupid region is not used. Groups are
referenced by a special key. When you want a list of
the keys in a group, the cache iterates through all
the keys in a region. The current implementation does
not allow grouped items to be retrieved by their key
alone. As a result, groups function as mini regions
with slow removal times. It would be better to use
another region than the current groups.
Alternatively, the hierarchical removal can do most of
what you need.
Ideally, none of the auxiliaries needs to know about
groups. The CompositeCache should be able to manage
it all.
The group functionality needs to be changed.
Items in a group within a region should be able to be
referenced by the key alone. We can make this happen
by putting an object, CacheKey, in the CacheElement
and have it equal an object with a similar key in a
GroupAttrName, but this adds some complexity.
One alternative is to completely remove groups until
we work out a way to bring back the group key map.
Another option, if we only want to support single
groups, is to add a groupname or a list of group names
to the ElementAttributes. We could continue to
iterate through the map for group reference. We could
allow for multiple groups this way, but it would have
the same slowness problems. It would allow grouped
items to be retrieved by their common keys. All in
all, I think this is the best alternative for now.
Let's scrap the GroupAttrName and just put the group
information in the ElementAttributes until, or if, we
decide to use the group key maps again. This does
still require the auxiliaries to be able to handle
getGroupKeys requests.
Aaron
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