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What are the best practices to improve Hive query performance?

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What are the best practices to improve Hive query performance?

Hive Performance – 10 Best Practices for Apache Hive

  • Partitioning Tables: Hive partitioning is an effective method to improve the query performance on larger tables.
  • De-normalizing data:
  • Compress map/reduce output:
  • Map join:
  • Input Format Selection:
  • Parallel execution:
  • Vectorization:
  • Unit Testing:

What is hive optimization techniques?

Vectorization In Hive – Hive Optimization Techniques, to improve the performance of operations we use Vectorized query execution. Here operations refer to scans, aggregations, filters, and joins. It happens by performing them in batches of 1024 rows at once instead of single row each time.

How do you optimize a join in hive?

Physical Optimizations:

  1. Partition Pruning.
  2. Scan pruning based on partitions and bucketing.
  3. Scan pruning if a query is based on sampling.
  4. Apply Group By on the map side in some cases.
  5. Optimize Union so that union can be performed on map side only.
  6. Decide which table to stream last, based on user hint, in a multiway join.
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How do I show a schema in hive?

Examples

  1. Issue the SHOW SCHEMAS command to see a list of available schemas.
  2. Issue the USE command to switch to a particular schema.
  3. Issue the SHOW TABLES command to see the views or tables that exist within workspace.
  4. Switch to the Hive schema and issue the SHOW TABLES command to see the Hive tables that exist.

How do I optimize group by query in Hive?

Best Practices to Optimize Hive Query Performance

  1. Use Column Names instead of * in SELECT Clause.
  2. Use SORT BY instead of ORDER BY Clause.
  3. Use Hive Cost Based Optimizer (CBO) and Update Stats.
  4. Hive Command to Enable CBO.
  5. Use WHERE instead of HAVING to Define Filters on non-aggregate Columns.

How do I practice Hive in SQL?

Practice Hive Queries ( HiveQL Practice )

  1. create a separate database named movielens. create database movielens; use movielens;
  2. create tables to hold data. CREATE EXTERNAL TABLE ratings ( userid INT, movieid INT, rating INT, tstamp STRING. ) ROW FORMAT DELIMITED. FIELDS TERMINATED BY ‘#’
  3. see if data is loaded.
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How partitioning and bucketing improves the performance of Hive?

Both Partitioning and Bucketing in Hive are used to improve performance by eliminating table scans when dealing with a large set of data on a Hadoop file system (HDFS). A table can have one or more partitions that correspond to a sub-directory for each partition inside a table directory.

How do you analyze a Hive query performance?

How do I display a schema?

To show the schema, we can use the DESC command. This gives the description about the table structure.

What is Hive schema?

Hive is a database technology that can define databases and tables to analyze structured data. The theme for structured data analysis is to store the data in a tabular manner, and pass queries to analyze it. This chapter explains how to create Hive database. Hive contains a default database named default.