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From "Jonathan Ellis (JIRA)" <>
Subject [jira] Resolved: (CASSANDRA-226) Make time-sorted CFs behave consistently
Date Thu, 18 Jun 2009 18:34:07 GMT


Jonathan Ellis resolved CASSANDRA-226.

    Resolution: Won't Fix

Discussed with Sandeep and Eric in IRC.  Sandeep pointed out that it's a lot simpler if we
just drop the time-sorted concept, move to byte[] column names, and allow user-defined Comparators,
giving you whatever type of indexing you want.  There was general agreement that this is a
better solution.

> Make time-sorted CFs behave consistently
> ----------------------------------------
>                 Key: CASSANDRA-226
>                 URL:
>             Project: Cassandra
>          Issue Type: Bug
>            Reporter: Jonathan Ellis
>             Fix For: 0.4
> Time-sorted CFs are indexed and sorted by time in the SSTable.  So lookup by name is
inefficient, and compaction sucks (i.e., we can run out of memory), because we combine by
name even though we sort by time. (see CASSANDRA-16)
> The right fix is, for time-sorted columns we need to recognize that the right "key" as
it were is (time, name) not name.  We should allow slice by time and lookup by time or time,name
but not just name.  (Similarly, we should not allow lookup by time on name-sorted CFs.)  This
means that name will not necessarily be unique in time-sorted CFs but that is the right behavior!
 Time-based CFs are more like appending to a list than putting to a map.
> (As part of this we could track the most recent append in time-sorted CFs to prevent
the bug in CASSANDRA-223.  I am not sure that is the "right" way to go but I do mention it
as a possibility that this change enables.)
> In the code, this will allow more regular treatment of CFs and less special casing. 
(It will also allow using only a single map for memtable columns, reducing memory usage --
see CASSANDRA-51.)
> Implementation notes: we may be able to represent both types of CF with a pluggable Comparator
+ Indexer combination, which would solve CASSANDRA-185 and CASSANDRA-189 at the same time.

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