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Avoid using STRAIGHT_JOIN

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Problem Definition​

STRAIGHT_JOIN is a table join method in MySQL that forces joining tables in the order defined, equivalent to an inner join in result. It gives developers some control over how the database executes the SQL query. However, it also loses out on join order optimizations by the optimizer, so should be used carefully based on the scenario. PawSQL provides a risk warning for statements using STRAIGHT_JOIN to avoid potential performance issues caused by it.

Taking the lineitem and orders tables in the tpch database as an example, the following query will join the lineitem table first and orders table second directly, indicating the database should take lineitem as the driving table and orders as the driven table for the join operation, without optimizing the table order.

SELECT *
FROM lineitem 
STRAIGHT_JOIN orders ON lineitem.l_orderkey = orders.o_orderkey;

PawSQL Auditing​

PawSQL provides a corresponding SQL review warning for this case.

Default Warning Level​

  • Warning

There are 3 warning levels in ascending order: Note < Warning < Error

Conditions​

  • SQL statement contains STRAIGHT_JOIN syntax

Database Types and Versions​

  • MySQL 5.0.1 and above

About PawSQL​

PawSQL is dedicated to automatic and intelligent database performance optimization. The database types supported include MySQL, PostgreSQL, Oracle, and openGauss; and the products provided by PawSQL include:

  • PawSQL Cloud, an online automated SQL optimization tool that supports SQL auditing, intelligent query rewriting, cost-based index recommendations, suitable for database administrators and data application developers.
  • PawSQL Advisor, an IntelliJ plugin that is suitable for data application developers and can be installed via the IDEA/DataGrip marketplace by searching for "PawSQL Advisor" by name.
  • PawSQL Engine, which is the backend optimization engine of the PawSQL series of products, can be installed and deployed independently, and provides SQL optimization services through http/json interfaces. PawSQL Engine is provided for deployment and installation as a docker image.

Contact Us​

Website: https://docs.pawsql.com

Email: service@pawsql.com

Twitter: https://twitter.com/pawsql