Cursor functionality for results generated by Coprocessors
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Key: HBASE-3607
URL: https://issues.apache.org/jira/browse/HBASE-3607
Project: HBase
Issue Type: New Feature
Components: coprocessors
Reporter: Himanshu Vashishtha
I tried to come up with a scanner like functionality for results generated by
coprocessors at region level.
This is just a poc, and it will be good to have your comments on it.
It has support for both Incremental and In-memory Result sets. Attached is a
patch that has a test case for an incremental result (i.e., client receives a
cursorId from the CP core method, it instantiates a cursor object and iterates
over the result set. He can set a cache limit on the CursorCallable object to
reduce the number of rpc --> just like scanners.
In its current state, it has some limitations too :)), like, it is region
specific only, i.e., one can instantiate and use cursor at one region only (and
that region is determined by the input row while instantiating the cursor). I
will try to expand it so that it can have atleast a sequential access to other
regions, but as I said, I want the opinion of experts to know whether this
approach really makes some sense or not.
I have tested it with the inbuilt testing framework on my laptop only.
It will be good if I copy the use case here in the description too:
Test table has rows like:
/**
* The scenario is that I have these rows keys in the test table:
'aaa-123'
'aaa-456'
'abc-111'
'abd-111'
'abd-222'
& I want to return:
('aaa', 2)
('abc', 1)
('abd', 2)
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