What is cluster by and distribute by in Hive?

CLUSTER BY is a clause or command 4used in Hive queries to carry out DISTRIBUTE BY and SORT BY operations. This command ensures total ordering or sorting across all output data files. DISTRIBUTE BY has a similar job as a GROUP BY clause as it manages how the reducer will receive data or rows for processing.

What is distribute by in Hive?

Distribute BY clause used on tables present in Hive. Hive uses the columns in Distribute by to distribute the rows among reducers. All Distribute BY columns will go to the same reducer. It ensures each of N reducers gets non-overlapping ranges of column.

What is the use of cluster by in Hive?

“clustered by” clause is used to divide the table into buckets. Each bucket will be saved as a file under table directory. Bucketing can be done along with partitioning or without partitioning on Hive tables. Bucketed tables will create almost equally distributed data file parts.

What is the difference between ORDER BY Sort by and distribute by?

SORT BY x : orders data at each of N reducers, but each reducer can receive overlapping ranges of data. You end up with N or more sorted files with overlapping ranges. DISTRIBUTE BY x : ensures each of N reducers gets non-overlapping ranges of x , but doesn’t sort the output of each reducer.

What is distributed by clause?

DISTRIBUTE BY clause is used to distribute the input rows among reducers. It ensures that all rows for the same key columns are going to the same reducer.

Which is better sort by or order by?

Difference between Sort By and Order By The difference between “order by” and “sort by” is that the former guarantees total order in the output while the latter only guarantees ordering of the rows within a reducer. If there are more than one reducer, “sort by” may give partially ordered final results.

What does cluster by do?

The CLUSTER BY clause is used to first repartition the data based on the input expressions and then sort the data within each partition.

What is difference between order by and group by in SQL?

1. Group by statement is used to group the rows that have the same value. Whereas Order by statement sort the result-set either in ascending or in descending order.

What is cluster by in spark?

What is CLUSTER BY? CLUSTER BY is a Spark SQL syntax which is used to partition the data before writing it back to the disk. Please note that the number of partitions would depend on the value of spark parameter “spark.

What is the use of distribute by?