Database Optimization (MySQL)
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The document provides guidelines for database optimization, emphasizing the importance of verifying optimization efforts with actual data. It covers techniques such as query profiling, indexing strategies, and the use of caching to improve performance. Key advice includes avoiding cached results and optimizing queries by rewriting, selecting necessary columns, and correctly filtering rows.
Database Optimization (MySQL)
- 1. DATABASE OPTIMIZATION _by Oleksii Prohonnyi
- 2. The degree of normality in a database is inversely proportional to that of its DBA.
- 4. WHEN DO WE OPTIMIZE THE DATABASE?
- 6. You should get your home page down to 1.5 seconds. (Google’s threshold for being considered a “fast” website) Best Practices for Speeding Up Your Web Site by Yahoo
- 7. PROFILE FIRST, OPTIMIZE LAST
- 9. The basic rule of optimization is to never assume - always verify, using actual data.
- 10. PEAR_Benchmark Stores microtime() values before and after the query for later observation, and the difference would be the timing of the query with good accuracy. Package Information: Benchmark by The PHP Group
- 11. PEAR_Benchmark Example 1: Automatic profiling start, stop, and output.
- 13. PEAR_Benchmark Example 2: Manual profiling start, stop, and output.
- 15. Zend_Db_Profiler Built-in support for profiling in Zend Framework.
- 17. CWebLogRoute Built-in support for profiling in Yii Framework.
- 21. It's very important to profile using a relevant dataset. You should create a test machine that resembles your live dataset as much as possible to get relevant data.
- 22. Another important note is to avoid looking at cached results. - SQL_NO_CACHE - MySQL Caches - OS Caches - Hardware Caches Query Profiling with MySQL: Bypassing caches by Peter Zaitsev
- 23. The Slow Query Log Profiles queries that are used by daemons and cron jobs and log the results to a file. 5.2.5. The Slow Query Log by Oracle Corporation
- 26. There are 4 basic ways to optimize query performance: - Rewrite the queries - Change indexing strategy - Change schema - Use an external cache
- 27. EXAMINING QUERY EXECUTION PLANS
- 28. EXPLAIN Add the reserved word 'EXPLAIN' at the beginning of your query to get the execution plan for the query. 8.2.2. EXPLAIN Output Format by Oracle Corporation
- 31. EXPLAIN limitations: - EXPLAIN can be wrong - EXPLAIN works for SELECT only - EXPLAIN may take long time - Estimated number of rows may be very inaccurate …. MySQL EXPLAIN limits and errors by Peter Zaitsev
- 34. 1. Looping queries One of the most common mistakes is to query in a loop without need. Most likely looped SELECT queries can be rewritten as a JOIN.
- 36. 2. Picking only needed columns Picking only the needed columns is a good general practice to use, and avoids those problems.
- 38. 3. Filtering rows correctly and using indexes Our main goal is to select the smallest amount of rows we need and doing so in the fastest way possible.
- 39. Filtering rows correctly and using indexes Example - fetching users created in the last 4 weeks.
- 41. Filtering rows correctly and using indexes Example - select the lowest priced fruit from several fruit types.
- 43. 4. Indexing correctly Using more indexes than is necessary can have adverse affects - as it slows down the operation of INSERT and UPDATE queries, while taking up more memory. Do you always need index on WHERE column? by Vadim Tkachenko
- 44. 5. Picking the right engine for your data MySQL has a pluggable engine design, which allows you to use different engine types to store your data, each with its own advantages and drawbacks. Chapter 14. Storage Engines by Oracle Corporation
- 46. CACHING
- 47. There are many caching strategies. Common options include caching to disk (files) or caching to memory (using solutions such as memcache or APC). Another form of caching is to the database – by de-normalizing the schema to store data that is the result of expensive to run queries.
- 48. S4I8GMA UKRAINE
- 49. Oleksii Prohonnyi facebook.com/oprohonnyi linkedin.com/in/oprohonnyi