Optimization Techniques for Complex Queries (Using Execution Plan Analysis)

Doris is an open-source column-stored relational database management system. Optimization techniques are crucial to ensure high performance and efficiency. In this article, we will introduce how to use execution plan analysis to optimize complex queries.

What is Execution Plan Analysis?

Execution plan analysis refers to the process of analyzing the internal execution plans of Doris to understand which operations need to be performed and which can be optimized. By analyzing execution plans, optimization strategies can be determined to improve system performance.

How to Use Execution Plan Analysis?

1. Obtain Execution Plan: Use the EXPLAIN command to retrieve the current execution plan.

2. Analyze Execution Plan: Use Doris execution plan analysis tools, such as Doris's internal tool dorisexec analyzer, or third-party tools like ExplainDB, to analyze the execution plan and determine optimization strategies.

Common Optimization Techniques:

1. Reduce Table Scans

• Use indexes and Coverage Optimizer to reduce table scans.
• Use Covering Indexes to avoid reading the entire table.

2. Use Join vs Subquery

• Using joins compared to Subqueries allows Doris internal optimization, reducing sub-QUERY execution time.

3. Avoid Full Table Scan

• Use Indexes to avoid full table scans.
• Use Partitioning to reduce full table scans.

4. Optimize Join Order

• Use join order optimization to improve system performance.
• Use Covering Indexes to avoid reading the entire table.

5. Optimize Filter Conditions

• Use filter condition optimization to improve system performance.
• Use Indexes to avoid full table scans.

Final Notes:

• Use execution plan analysis tools, such as Doris's internal tool dorisexec analyzer, or third-party tools like ExplainDB, to better understand Doris execution plans.
• Adjust according to system requirements; these optimization strategies may need to be adjusted based on specific scenarios and table structures.