How do you determine the number of buckets in the Hive?

In general, the bucket number is determined by the expression hash_function(bucketing_column) mod num_buckets. (There’s a ‘0x7FFFFFFF in there too, but that’s not that important). The hash_function depends on the type of the bucketing column.

How many number of buckets can be created in Hive?

Buckets can help with the predicate pushdown since every value belonging to one value will end up in one bucket. So if you bucket by 31 days and filter for one day Hive will be able to more or less disregard 30 buckets.

How do you determine the number of buckets in spark?

There is no general formula. It depends on volumes, available executors, etc. The main point is avoiding shuffling. As a guideline defaults for JOINing and AGGr are set to 200, so 200 or greater could be an approach, but again how many resources do you have on your cluster?

What are buckets in Hive?

Bucketing in hive is the concept of breaking data down into ranges, which are known as buckets, to give extra structure to the data so it may be used for more efficient queries. The range for a bucket is determined by the hash value of one or more columns in the dataset (or Hive metastore table).

Can we create buckets without partition in Hive?

Generally, in the table directory, each bucket is just a file, and Bucket numbering is 1-based. Along with Partitioning on Hive tables bucketing can be done and even without partitioning. vi. Moreover, Bucketed tables will create almost equally distributed data file parts.

Can we do partitioning and bucketing on same column?

To conclude, you can partition and use bucketing for storing results of the same CTAS query. These techniques for writing data do not exclude each other. Typically, the columns you use for bucketing differ from those you use for partitioning.

What is the difference between bucketing and partitioning in hive?

At a high level, Hive Partition is a way to split the large table into smaller tables based on the values of a column(one partition for each distinct values) whereas Bucket is a technique to divide the data in a manageable form (you can specify how many buckets you want).

What is the syntax for creating a bucket in Hive?

Below is the syntax to create bucket on Hive tables: CREATE TABLE bucketed_table ( Col1 integer, col2 string, col3 string, ) PARTITIONED BY (col4 date) CLUSTERED BY (col1) INTO 32 BUCKETS STORED AS TEXTFILE; You can create buckets on only one column, you cannot specify more than one column.

Can we create bucket without partition in Hive?

What is bucket in big data?

The bucketing in Hive is a data organizing technique. It is similar to partitioning in Hive with an added functionality that it divides large datasets into more manageable parts known as buckets. So, we can use bucketing in Hive when the implementation of partitioning becomes difficult.