Bug 1135630

+++ This bug was initially created as a clone of Bug #1135629 +++

Description of problem:
In RHQ 4.11 we had the metrics_index table which was replaced with the metrics_cache_index table in RHQ 4.12. With both tables the number of rows per (CQL) partition would be N, where N is the number of measurement schedules having data stored during a given time slice, e.g., 04:00 - 05:00. As N gets bigger, we wind up with increasingly large partitions, often referred to as "wide rows" in Cassandra terminology. The problem is even worse with the new metrics_cache_index table because we store even more data in each row.

Because of bug 1135603, we no longer need the metrics_cache_index table. We need to avoid really big wide rows and also deal with the read timeouts. The following schema change will address these concerns,

CREATE TABLE rhq.metrics_idx (
  bucket text,
  partition int,
  time timestamp,
  schedule_id int,
  PRIMARY KEY ((bucket, partition, time), schedule_id)
)

This is almost the same as the original metrics_index table except that it now has a partition column. We will need to track the number of partitions or possible values for the partition column. Let's say it is 5, which means the column can range from zero to four. Now the N schedule ids will be spread across N / 5 partitions instead of a single one. The index queries used during aggregation will also need to be refactored so avoid retrieving too much data at once.

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