Major Description
I found this issue after debugging a performance problem on an OpenTSDB cluster, it was basically unusable after an upgrade from 0.94.2 to 0.94.6. It was caused by HBASE-7279 (ping lhofhansl).
The easiest way to see it is to run a simple 1 client PE:
$ ./bin/hbase org.apache.hadoop.hbase.PerformanceEvaluation sequentialWrite 1
Then in the shell do a filter scan (flush the table first and make sure if fits in your blockcache if you want stable numbers).
Pre HBASE-7279:
hbase(main):028:0> scan 'TestTable', {FILTER => "(RowFilter (=, 'regexstring:0000055872') )"}
ROW COLUMN+CELL
0000055872 column=info:data, timestamp=1378248850191, value=(blanked)
1 row(s) in 1.2780 seconds
Post HBASE-7279
hbase(main):037:0* scan 'TestTable', {FILTER => "(RowFilter (=, 'regexstring:0000055872') )"}
ROW COLUMN+CELL
0000055872 column=info:data, timestamp=1378248850191, value=(blanked)
1 row(s) in 24.2940 seconds
I tried a bunch of 0.94, up to 0.94.11, and the tip of 0.96. They are all slow like this.
It seems that since that jira went in we do a lot more row matching, and running the regex gets super expensive.