IBM Db2 Big SQL 7.1.0

Query runtime performance

Use these guidelines to tune query runtime performance.

The ANALYZE command
You can use the ANALYZE command to gather statistics for Hadoop and HBase tables. These statistics are used by the Db2® Big SQL optimizer to determine the most optimal access plans to efficiently process your queries. The more statistics that you collect on your tables, the better decisions the optimizer can make to provide the best possible access plans. When you run ANALYZE on a table to collect these statistics, the query generally runs faster.
Statistics
The Db2 Big SQL query optimizer uses statistics to determine an efficient data access strategy.
Registries for compiler and runtime performance improvement
You can improve the performance of your Db2 Big SQL environment by using the db2set command to change the values of certain registry variables. These registry variables can provide some performance benefit for specific queries such as SELECT DISTINCT queries.
Detection and compaction of small files in HDFS
Query performance can suffer when the file layout is fragmented into multiple small files. A tool that detects this condition and recommends corrective action to optimize file size and layout is available.

Parent topic: Query tuning