How to optimize SQLite database performance?

SQLite performance optimization needs to be considered from multiple aspects:

1. Database Design Optimization

   • Design table structures reasonably, avoid over-normalization
   • Use appropriate data types to reduce storage space
   • Create indexes for frequently queried columns
   • Use WITHOUT ROWID tables to reduce storage overhead

2. Query Optimization

   • Use EXPLAIN QUERY PLAN to analyze query execution plans
   • Avoid using SELECT *, only query needed columns
   • Use indexed columns for WHERE, JOIN, ORDER BY, GROUP BY operations
   • Avoid using functions or expressions on indexed columns
   • Use LIMIT to limit the number of returned results

3. Transaction Optimization

   • Wrap multiple operations in one transaction to reduce disk I/O
   • Use WAL mode to improve concurrency performance
   • Keep transactions short to reduce lock holding time
   • Use appropriate isolation modes (DEFERRED, IMMEDIATE, EXCLUSIVE)

4. Connection and Statement Optimization

   • Use prepared statements to improve performance
   • Reuse database connections, avoid frequent opening and closing
   • Use transactions when batch inserting data
   • Use parameterized queries to prevent SQL injection and improve performance

5. Configuration Optimization

   sql
   -- Enable WAL mode
   PRAGMA journal_mode = WAL;
   
   -- Set synchronous mode (FULL, NORMAL, OFF)
   PRAGMA synchronous = NORMAL;
   
   -- Set cache size (number of pages)
   PRAGMA cache_size = -20000;  -- 20MB
   
   -- Set temporary storage to memory
   PRAGMA temp_store = MEMORY;
   
   -- Set page size
   PRAGMA page_size = 4096;

6. Regular Maintenance

   • Use VACUUM to rebuild the database and reclaim space
   • Use ANALYZE to update statistics to help the query optimizer
   • Use REINDEX to rebuild fragmented indexes
   • Regularly backup the database

7. Application Layer Optimization

   • Use connection pools to manage database connections
   • Implement query caching mechanisms
   • Execute time-consuming operations asynchronously
   • Reasonably use in-memory databases (:memory:) for temporary data

By comprehensively applying these optimization techniques, you can significantly improve the performance of SQLite databases.