[jira] [Created] (CASSANDRA-10314) Update index file format

["Robert Stupp (JIRA)" <ji...@apache.org>]

Robert Stupp created CASSANDRA-10314:
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             Summary: Update index file format
                 Key: CASSANDRA-10314
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-10314
             Project: Cassandra
          Issue Type: Improvement
            Reporter: Robert Stupp
            Assignee: Robert Stupp
             Fix For: 3.0.0 rc1


As CASSANDRA-9738 may not make it into 3.0rc1, but having an off-heap key-cache is still a goal, we should change the index file format to meet off-heap requirements (so I've set fixver to 3.0rc1).

Off-heap (and mmap'd index files) need the offsets of the individual IndexInfo objects and the at least the offset field of IndexInfo structures.

The format I propose is as follows:

{noformat}
 (long) position (64 bit long)
  (int) serialized size of data that follows (32 bit int)
 -- following for indexed entries only (so serialized size > 0)
  (int) DeletionTime.localDeletionTime (32 bit int)
 (long) DeletionTime.markedForDeletionAt (64 bit long)
  (int) number of IndexInfo objects (32 bit int)
    (*) serialized IndexInfo objects, see below
    (*) offsets of serialized IndexInfo objects, since version "ma" (3.0)
        Each IndexInfo object's offset is relative to the first IndexInfo object.
{noformat}

{noformat}
    (*) IndexInfo.firstName (ClusteringPrefix serializer, either Clustering.serializer.serialize or Slice.Bound.serializer.serialize)
    (*) IndexInfo.lastName (ClusteringPrefix serializer, either Clustering.serializer.serialize or Slice.Bound.serializer.serialize)
 (long) IndexInfo.offset (vint encoded since 3.0, 64bit int before)
 (long) IndexInfo.width (vint encoded since 3.0, 64bit int before)
 (bool) IndexInfo.endOpenMarker != null              (if 3.0)
  (int) IndexInfo.endOpenMarker.localDeletionTime    (if 3.0 && IndexInfo.endOpenMarker != null)
 (long) IndexInfo.endOpenMarker.markedForDeletionAt  (if 3.0 && IndexInfo.endOpenMarker != null)
{noformat}

Regarding the {{IndexInfo.offset}} and {{.width}} fields there are two options. 
* Serialize both of them or
* Serialize only the offset field plus a _last byte offset_ to be able to recalculate the width of the last IndexInfo

The first option is probably the simpler one, the second saves a few bytes (those of the vint encoded width).



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