[jira] [Created] (HIVE-4486) FetchOperator slows down SMB map joins with many files

["Gopal V (JIRA)" <ji...@apache.org>]

Gopal V created HIVE-4486:
-----------------------------

             Summary: FetchOperator slows down SMB map joins with many files
                 Key: HIVE-4486
                 URL: https://issues.apache.org/jira/browse/HIVE-4486
             Project: Hive
          Issue Type: Bug
          Components: Query Processor
         Environment: Ubuntu LXC 12.10
            Reporter: Gopal V
            Priority: Minor


While looking at log files for SMB joins in hive, it was noticed that the actual join op didn't show up as a significant fraction of the time spent. Most of the time was spent parsing configuration files.

To confirm, I put log lines in the HiveConf constructor and eventually made the following edit to the code

{code}
--- ql/src/java/org/apache/hadoop/hive/ql/exec/FetchOperator.java
+++ ql/src/java/org/apache/hadoop/hive/ql/exec/FetchOperator.java
@@ -648,8 +648,7 @@ public ObjectInspector getOutputObjectInspector() throws HiveException {
    * @return list of file status entries
    */
   private FileStatus[] listStatusUnderPath(FileSystem fs, Path p) throws IOException {
-    HiveConf hiveConf = new HiveConf(job, FetchOperator.class);
-    boolean recursive = hiveConf.getBoolVar(HiveConf.ConfVars.HADOOPMAPREDINPUTDIRRECURSIVE);
+    boolean recursive = false;
     if (!recursive) {
       return fs.listStatus(p);
     }
{code}

And re-ran my query to compare timings.

||Before||After||
|Cumulative CPU| 731.07 sec|386.0 sec|
|Total time | 347.66 seconds | 218.855 seconds | 
|

The query used was 

{code}INSERT OVERWRITE LOCAL DIRECTORY
'/grid/0/smb/'
select inv_item_sk
from
     inventory inv
     join store_sales ss on (ss.ss_item_sk = inv.inv_item_sk)
limit 100000
;
{code}

On a scale=2 tpcds data-set, where both store_sales & inventory are bucketed into 4 buckets, with store_sales split into 7 partitions and inventory into 261 partitions.

78% of all CPU time was spent within new HiveConf(). The yourkit profiler runs are attached.

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