Hello,
Suppose that I have "tall-narrow" HBase table with composite key e.g.
{class_id}#{student_id}.
The exemplary data will look like as follow:
ROW_KEY | ONE COLLUMN FAMILY
----------------------------------------------------------------
1 | name = "Object Oriented Programming"
| location = "Building A"
| semester = "Winter"
| // many other information about class
----------------------------------------------------------------
1_1 | name = "Alice White"
1_2 | name = "Betty Lipcon"
// many other records related to class with ID = 1
----------------------------------------------------------------
// many other records related to class with ID = 2, 3, 4, .. N
I would like to use this HBase table as input source for my MapReduce job,
where
the mapper will emit <key, value> pairs where:
key = ${class_id}#${student_id},
value = some information about corresponding class.
Thanks to lexicographically sorting of row keys, it would be easily to
implement
if I could split HBase table into regions where all colocated rows (with the
same row prefix i.e. {class_id}) will reside in the same region. Then for each
group of such collocated records, I could use its first row to get information
about class and emit this information with rowkey from each remaining row.
So I would like to ask, if such a custom split is easy to implement?
I know that:
1) I could model it with "flat-wide" table and I will have everything what I
need in separate rows,
2) use two MR jobs for that.
but I am interested in best solution for "tall-narrow" table with one MR job.
Many thanks in advance for any hints!
