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From nicolas maillard <nicolas.maill...@fifty-five.com>
Subject Counter and Coprocessor Musing
Date Tue, 11 Dec 2012 14:50:55 GMT
Hi everyone

While working with hbase and looking at what the tables and meta look like I 
thought of a couple things, maybe someone has insights.
My thoughts are around the count situation it is a current database process to 
count entries for a given query.
for example as a first check to see if everything is written or sometimes to get 
feel of a population.
I was wondering 2 things:
- Should'nt Hbase keep in the metrics for a table it's total entry count?
this would not take too much space and often comes in handy. Granted with a 
coprocessor you could easily create a table with counters for all the other 
tables in the system but it would be a nice have as a standard.

- I was also wondering maybe every region could know the number of entries it 
contains. Every region already knows the start and endkey of it's entries. For a 
count on a given scan this would speed up the count. Every region who's start 
and endkey are in the scan would just send back it's population count and only a 
region that is wider then the count would need to be scanned and counted.

Wondering if these thoughts are already implemented and if I'm missing something 
or would not be a good idea. Altenratly if this is a not a definite No for some 
reason could coprocessors allow to implement these thoughts. Can I with a 
coprocessor write in the metrics part, or on a given scan first check if, for a 
region smaller than my scan, I already have written somewhere the count instead 
scanning and couning.

Thnaks for any thoughts you may have  

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