Laracon EU 2018: Things every developer absolutely, positively needs to know about database indexing
- 1. THINGS EVERY DEVELOPER ABSOLUTELY, POSITIVELY NEEDS TO KNOW ABOUT database indexing
- 5. WHY indexing? ▸ Improve query performance ▸ ... ▸ That's about it
- 6. Slow QueriesARE ONE THE MOST COMMON CAUSES OF POOR PERFORMANCE
- 7. DEVELOPERS DON'T KNOW (ENOUGH) ABOUT indexing
- 9. WHAT WE WILL LEARN 1. What's an index? 2. Understanding the execution plan 3. Common pitfalls
- 10. WHAT'S AN index?
- 13. An index is an ordered representation of the indexed data
- 14. B-TREE
- 18. EMPLOYEE_ID NAME 23 Kai 700 Marcel 12 Oliver 1 Taylor 18 Franz
- 22. ▸ Searching for a value is fast ▸ Logarithmic scalability
- 24. INDEXING MAKES READING faster BUT WRITING slower
- 25. UNDERSTANDING THE execution plan(MYSQL VERSION)
- 26. GETTING AN EXECUTION PLAN EXPLAIN SELECT * FROM users WHERE id = 1;
- 27. mysql> explain select * from users where id = 1 G; *************************** 1. row *************************** id: 1 select_type: SIMPLE table: users partitions: NULL type: const possible_keys: PRIMARY key: PRIMARY key_len: 4 ref: const rows: 1 filtered: 100.00 Extra: NULL
- 28. ACCESS TYPES
- 29. CONST / EQ_REF ▸ Performs a B-Tree traversal to find a single value ▸ Basically binary search ▸ Can only get used if uniqueness is guaranteed ▸ Super fast
- 30. REF / RANGE ▸ Also known as an index range scan ▸ Performs a B-Tree traversal to find the starting point ▸ Scans values from that point on ▸ Stops if it finds a value that does not meed the criteria
- 31. INDEX ▸ Also known as a Full Index Scan ▸ Starts at the first leaf node ▸ Traverses through the entire index
- 32. ALL ▸ Also known as a Full Table Scan ▸ Does not use an index at all ▸ Loads every column of every row from the table ▸ Scans through all of them and emits or discards accordingly
- 33. ACCESS TYPES ▸ const / eq_ref ▸ ref /range ▸ index ▸ ALL
- 34. COMMON Pitfalls
- 35. Functions
- 36. SELECT SUM(total) FROM orders WHERE YEAR(created_at) = '2012';
- 37. SELECT SUM(total) FROM orders WHERE YEAR(...) = '2012';
- 38. CREATED AT TOTAL USER ID 2008-02-19 00:00:00 1315 4685 2008-02-19 00:00:00 1755 6603 2008-03-06 00:00:00 18313 9266 2008-03-06 00:00:00 18395 5688 2018-02-16 00:00:00 2689 8656 2018-02-16 00:00:00 2692 8657
- 39. CREATED AT TOTAL USER ID 2008-02-19 00:00:00 1315 4685 2008-02-19 00:00:00 1755 6603 2008-03-06 00:00:00 18313 9266 2008-03-06 00:00:00 18395 5688 2018-02-16 00:00:00 2689 8656 2018-02-16 00:00:00 2692 8657
- 40. CREATED AT TOTAL USER ID 2008-02-19 00:00:00 1315 4685 2008-02-19 00:00:00 1755 6603 2008-03-06 00:00:00 18313 9266 2008-03-06 00:00:00 18395 5688 2018-02-16 00:00:00 2689 8656 2018-02-16 00:00:00 2692 8657
- 41. CREATED AT TOTAL USER ID 2008-02-19 00:00:00 1315 4685 2008-02-19 00:00:00 1755 6603 2008-03-06 00:00:00 18313 9266 2008-03-06 00:00:00 18395 5688 2018-02-16 00:00:00 2689 8656 2018-02-16 00:00:00 2692 8657
- 44. THANKS