Gopal V created HIVE-4488:
-----------------------------
Summary: BucketizedHiveInputFormat is pessimistic with SMB split
generation
Key: HIVE-4488
URL: https://issues.apache.org/jira/browse/HIVE-4488
Project: Hive
Issue Type: Bug
Components: Query Processor
Affects Versions: 0.12.0
Environment: Ubuntu LXC
Reporter: Gopal V
BucketizedHiveInputFormat generates fewer splits than possible when faced with
a table structure where both tables are partitioned.
When debugging query82 from the TPC-DS spec, there were 7 partitions in the lhs
(store_sales) & 8 partitions in the rhs (inventory), with 1 bucket each.
Only 7 splits are generated from the mapper, instead of a potential 56 mappers.
{code}
13/05/01 07:08:22 INFO mapred.FileInputFormat: Total input paths to process : 1
13/05/01 07:08:22 INFO io.BucketizedHiveInputFormat: 7 bucketized splits
generated from 344 original splits.
{code}
The loop that generates the splits is as follows
{code}
InputSplit[] iss = inputFormat.getSplits(newjob, 0);
if (iss != null && iss.length > 0) {
numOrigSplits += iss.length;
result.add(new BucketizedHiveInputSplit(iss, inputFormatClass
.getName()));
}
{code}
As is clear from above, even though the more granular (per-file/per-partition)
splits coming off the getSplits() is being added to a single bucket split.
Logically, in our mapper we get
{code}
store_sales(2003)/000000_1)
join MergeQueue(
inv(1998-01-01)/000000_0
inv(1998-01-08)/000000_0
inv(1998-01-15)/000000_0
inv(1998-01-22)/000000_0
inv(1998-01-29)/000000_0
inv(1998-02-05)/000000_0
inv(1998-02-12)/000000_0
inv(1998-02-19)/000000_0
inv(1998-02-26)/000000_0
)
{code}
Where ideally, we could've used a CombineFileInputFormat to get node locality
for the merge queue inputs (viz BucketizedHiveInputSplit).
This would be far better in generating splits & in getting more out of
short-circuit reads.
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators
For more information on JIRA, see: http://www.atlassian.com/software/jira
