Hi All,
Bucketing concept is based on the hash partition the bucketed column as per
configured bucket numbers. Records with same bucketed column always goes to
the same same bucket. Physically each bucket is a file/files in table
directory.
Advantages
Bucketed table is useful feature to do the map side joins and avoids
shuffling of data.
Carbondata can do driver level pruning on bucketed column to improve query
performance.
User can add bucketed table as follows
CREATE TABLE test(user_id BIGINT, firstname STRING, lastname STRING)
CLUSTERED BY(user_id) INTO 32 BUCKETS;
In the above example column user_id is hash partitioned and creates 32
buckets/partitions files in carbondata. So while doing the join with other
table on bucketed column it can select same buckets and do the join with
out shuffling.
Carbon creates following folder structure currently, since carbon is
already supporting partitioning in its file format
dbName -> tableName - > Fact ->
Part0 ->Segment_id ->
carbondatafiles
Part1 ->Segment_id ->
carbondatafiles
we can also move the partitionid to file metadata.But if we move the
partitionId to metadata then there would be complications in backward
compatibility.
--
Thanks & Regards,
Ravindra
