Hive – Hadoop merged file

set hive.execution.engine=tez; - TEZ execution engine
set hive.merge.tezfiles= true; - Notifying that merge step is required
set hive.merge.smallfiles.avgsize=128000000; --128MB
set hive.merge.size.per.task=128000000; - 128MB 
If you want to use the MR engine, then add the following settings (I haven't tried it myself)
 
 
set hive.merge.mapredfiles=true; - Notifying that merge step is required
set hive.merge.smallfiles.avgsize=128000000; --128MB
set hive.merge.size.per.task=128000000; - 128MB
above The setting will generate a merge file step, the size of each part file should be 128MB.
Reference:
> Settings description

I have run a map job with only 674 mappers, in which hive generated 674 .gz files, I want to merge these files into 30-35 files. By not getting the merged output, I tried hive megre mapfilse attribute

Try to use the TEZ execution engine, and then use hive.merge.tezfiles. You You may also want to specify the size.

set hive.execution.engine=tez; - TEZ execution engine
set hive.merge.tezfiles=true; - Notifying that merge step is required
set hive.merge.smallfiles.avgsize=128000000; --128MB
set hive.merge.size.per.task=128000000; - 128MB

If you want to use the MR engine, then add the following settings (I haven't tried it myself)

set hive.merge.mapredfiles=true; - Notifying that merge step is required
set hive.merge.smallfiles.avgsize=128000000; --128MB
set hive.merge.size.per.task=128000000; - 128MB

The above setting Steps to generate a combined file, the size of each part file should be 128MB.

Reference:

> Settings description