Jesse Yates created HBASE-7958:
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Summary: Statistics per-column family per-region
Key: HBASE-7958
URL: https://issues.apache.org/jira/browse/HBASE-7958
Project: HBase
Issue Type: New Feature
Affects Versions: 0.96.0
Reporter: Jesse Yates
Fix For: 0.96.0
Originating from this discussion on the dev list:
http://search-hadoop.com/m/coDKU1urovS/Simple+stastics+per+region/v=plain
Essentially, we should have built-in statistics gathering for HBase tables.
This allows clients to have a better understanding of the distribution of keys
within a table and a given region. We could also surface this information via
the UI.
There are a couple different proposals from the email, the overview is this:
We add in something on compactions that gathers stats about the keys that are
written and then we surface them to a table.
The possible proposals include:
*How to implement it?*
# Coprocessors -
** advantage - it easily plugs in and people could pretty easily add their own
statistics.
** disadvantage - UI elements would also require this, we get into dependent
loading, which leads down the OSGi path. Also, these CPs need to be installed
_after_ all the other CPs on compaction to ensure they see exactly what gets
written (doable, but a pain)
# Built into HBase as a custom scanner
** advantage - always goes in the right place and no need to muck about with
loading CPs etc.
** disadvantage - less pluggable, at least for the initial cut
*Where do we store data?*
# .META.
** advantage - its an existing table, so we can jam it into another CF there
** disadvantage - this would make META much larger, possibly leading to splits
AND will make it much harder for other processes to read the info
# A new stats table
** advantage - cleanly separates out the information from META
** disadvantage - should use a 'system table' idea to prevent accidental
deletion, manipulation by arbitrary clients, but still allow clients to read it.
Once we have this framework, we can then move to an actual implementation of
various statistics.
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