This content originally appeared on DEV Community and was authored by Cong Li
SQL Optimization
1.1 Filter Out Unnecessary Data
When querying tables, filter data as much as possible. SQL can reduce data by minimizing projection columns and adding filter conditions, thereby improving the efficiency of subsequent computations.
1.2 Avoid Cartesian Products in Table Joins
Avoid joining tables without proper join conditions, as this will lead to a large result set and negatively impact performance.
1.3 SQL Rewriting
If performance analysis indicates that the GBase 8a optimizer is not generating the optimal plan, many performance issues can be avoided by rewriting the SQL.
1.4 Use UNION ALL Instead of UNION
Whenever possible, use UNION ALL instead of UNION. The UNION operation requires deduplication, which can significantly impact performance. Ensure that identical data is only inserted once and that there is no duplicate data between different tables to enhance performance with UNION ALL.
1.5 Avoid Table Operations in Custom Functions
Since functions are executed on the compute node, only replicated tables should be operated on within functions. It is recommended to avoid table operations within functions as much as possible.
1.6 Minimize the Use of Cursors
Minimize the use of cursors. Cursor operations are akin to retrieving and processing each row's value individually. If cursors can be replaced with a single SQL statement containing multiple related subqueries, performance will be greatly enhanced.
1.7 Prefer VARCHAR Over CHAR
Whenever possible, use VARCHAR instead of CHAR. The spaces in CHAR can affect performance, and joining CHAR and VARCHAR fields can lead to incorrect joins.
This content originally appeared on DEV Community and was authored by Cong Li
Cong Li | Sciencx (2024-06-27T06:59:58+00:00) GBase 8a Implementation Guide: Application Development Optimization. Retrieved from https://www.scien.cx/2024/06/27/gbase-8a-implementation-guide-application-development-optimization/
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