Indexes: The neglected performance all rounder
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The document discusses improper index use as a common cause of poor database performance. It argues that indexing is often treated as an administrative task rather than a development task, but developers do not fully understand how to properly use indexes. As a result, indexes are not designed to match the overall needs of an application's queries. The document advocates that indexing should be viewed as a design task and that developers need to more fully learn how to utilize indexes to improve performance.
Indexes: The neglected performance all rounder
- 1. © 2013 by Markus Winand Indexes The Neglected Performance All-Rounder Not always that obvious, unfortunately! iStockPhoto wildpixel
- 2. Takeaway #1: Pandemic Scale It affects you! (Symbolic image; not real data) http://upload.wikimedia.org/wikipedia/commons/c/c7/2009_world_subdivisions_flu_pandemic.png
- 3. Takeaway #2: Caused by Success Copyright © 2013 Telerik, Inc. All rights reserved
- 4. Takeaway #3: It’s Not Your Fault http://simpsonswiki.com/wiki/File:I_Didn%27t_Do_It!_Volume_III.png
- 5. © 2013 by Markus Winand The Problem Improper Index Use
- 6. The Problem: Improper Index Use “A very common cause of performance problems is lack of proper indexes or the use of queries that are not using existing indexes.” —Buda Consulting http://www.budaconsulting.com/Portals/52677/docs/top_5_tech_brief.pdf
- 7. The Problem: Improper Index Use “A very common cause of performance problems is lack of proper indexes or the use of queries that are not using existing indexes.” —Buda Consulting http://www.budaconsulting.com/Portals/52677/docs/top_5_tech_brief.pdf
- 8. Quantifying the Problem Percona White Paper: Reasons of performance problems that caused production downtime: 38% bad SQL 15% schema and indexing http://www.percona.com/files/white-papers/causes-of-downtime-in-mysql.pdf
- 9. Quantifying the Problem Survey by sqlskills.com: Root causes of the last few SQL Server performance problems: 27% T-SQL 19% Poor indexing http://www.sqlskills.com/blogs/paul/survey-what-are-the-most-common-causes-of-performance-problems/
- 10. Quantifying the Problem Craig S. Mullins (strategist and researcher): „As much as 75% of poor relational performance is caused by "bad" SQL and application code.” Noel Yuhanna (Forrester Research): „The key difficulties surrounding performance continue to be poorly written SQL statements, improper DBMS configuration and a lack of clear understanding of how to tune databases to solve performance issues.”
- 11. Quantifying the Problem My observation: ~50% of SQL performance problems are caused by improper index use
- 12. © 2013 by Markus Winand The Root Cause
- 13. © 2013 by Markus Winand The Root Cause Admins are Indexing
- 14. The Root Cause: DBAs are Indexing How did databases work before SQL?
- 15. The Root Cause: DBAs are Indexing Index use was intrinsically tied to the queries.
- 16. The Root Cause: DBAs are Indexing Example: dBase Developers had to... ...use indexes explicitly when searching: !"#$%&'"($#)$*+!#,&+-" $$$.%&'$/%&+&' ...take care of index maintenance: !"#$%&'"($#)$*+!#,&+-"0$%'(1 $$$$+22"&'
- 17. The Root Cause: DBAs are Indexing SQL is an abstraction that only defines the logical view. The actual SQL implementation takes care of everything else.
- 18. The Root Cause: DBAs are Indexing Transactions Constraints Views Tables Data manipulation Queries SQL (language) has: SQL Databases (software) have:
- 19. The Root Cause: DBAs are Indexing Backup & recovery Storage management Bugs & patches Tuning parameters Transactions Constraints Views Tables Data manipulation Queries SQL (language) has: SQL Databases (software) have: High Availability
- 20. The Root Cause: DBAs are Indexing Indexes Backup & recovery Storage management Bugs & patches Tuning parameters Transactions Constraints Views Tables Data manipulation Queries SQL (language) has: SQL Databases (software) have: High Availability
- 21. The Root Cause: DBAs are Indexing Indexes Backup & recovery Storage management Bugs & patches Tuning parameters Transactions Constraints Views Tables Data manipulation Queries SQL Databases (software) have: Developers High Availability
- 22. The Root Cause: DBAs are Indexing Indexes Backup & recovery Storage management Bugs & patches Tuning parameters Transactions Constraints Views Tables Data manipulation Queries Developers Administrators High Availability
- 23. The Root Cause: DBAs are Indexing Indexing is considered a system tuning task that belongs to the administrators responsibilities.
- 24. The Root Cause: DBAs are Indexing A misconception that causes new problems:
- 25. The Root Cause: DBAs are Indexing A misconception that causes new problems: DBAs don’t know the queries Have to “investigate” to find the queries. It is time consuming and almost always incomplete. by G-10gian82 deviantart.com
- 26. The Root Cause: DBAs are Indexing A misconception that causes new problems: DBAs don’t know the queries Have to “investigate” to find the queries. It is time consuming and almost always incomplete. DBAs can’t change the queries Can make the index match the query. Can’t make the query match the index!
- 27. © 2013 by Markus Winand The Solution
- 28. © 2013 by Markus Winand The Solution Indexing is a Development Task
- 29. The Solution: It’s a Dev Task Indexes Backup & recovery Storage management Tuning parameters Transactions Constraints Views Tables Data manipulation Queries Developers Administrators High Availability Bugs & patches
- 30. The Solution: It’s a Dev Task Indexes Backup & recovery Storage management Tuning parameters Transactions Constraints Views Tables Data manipulation Queries Developers Administrators Must match! High Availability Bugs & patches
- 31. Another Problem: It’s not Taught Indexes are not part of the pure SQL (language) literature because indexes are not part of the SQL standard. 11 SQL books analyzed: only 1.0% of the pages are about indexes (70 out of 7330 pages). Examples: Oracle SQL by Example: 2.0% (19/960) Beginning DBs with PostgreSQL: 0.8% (5/664) Learning SQL: 3.3% (11/336 — highest rate in class)
- 32. Another Problem: It’s not Taught Proper index usage is sometimes covered in database tuning books but is always buried between hundreds of pages of HW, OS and DB parameterization topics. 14 database administration books analyzed: 5.1% of the pages are about indexes (307 out of 6069 pages). Examples: Oracle Performance Survival Guide: 5.2% (38/730) High Performance MySQL: 8% (55/684) PostgreSQL 9 High Performance: 5.8% (27/468)
- 33. Another Problem: It’s not Taught Consequence: Developers don’t know how to use indexes properly.
- 34. Another Problem: It’s not Taught Consequence: Developers don’t know how to use indexes properly. Results of the 3-minute online quiz: http://use-the-index-luke.com/3-minute-test 5 questions: each about a specific index usage pattern. Non-representative!
- 35. Q1: Good or Bad? (Function use) 345675$89:5;$#<*,%'($=9$#<*$>!"#$%&'()*+?@ A5B537$#"(#0$'+#",C)*D-& $$E4=F$#<* $/G545$,-%./012!"#$%&'()*+0$HIIIIH?$J$H1KLMH@ 3-Minute Quiz: Indexing Skills
- 36. Q1: Good or Bad? (Function use) 345675$89:5;$#<*,%'($=9$#<*$>!"#$%&'()*+?@ A5B537$#"(#0$'+#",C)*D-& $$E4=F$#<* $/G545$,-%./012!"#$%&'()*+0$HIIIIH?$J$H1KLMH@ 3-Minute Quiz: Indexing Skills
- 37. Q1: Good or Bad? (Function use) 345675$89:5;$#*,%'($=9$#*$!#$%'()*+?@ A5B537$#(#0$'+#,C)*D- $$E4=F$#* $/G545$,-%./012!#$%'()*+0$HIIIIH?$J$H1KLMH@ 3-Minute Quiz: Indexing Skills
- 38. 3-Minute Quiz: Indexing Skills Q2: Good or Bad? (Indexed Top-N, no IOS) 345675$89:5;$#*,%'($=9$#*$+0$'+#,C)*?@ A5B537$%'0$+0$'+#,C)* $$E4=F$#* $/G545$+$J$NL $=4:54$OI$'+#,C)*$:5A3 $3454,67@
- 39. 3-Minute Quiz: Indexing Skills Q2: Good or Bad? (Indexed Top-N, no IOS) 345675$89:5;$#*,%'($=9$#*$+0$'+#,C)*?@ A5B537$%'0$+0$'+#,C)* $$E4=F$#* $/G545$+$J$NL $=4:54$OI$'+#,C)*$:5A3 $3454,67@ Understandable controversy!
- 40. 3-Minute Quiz: Indexing Skills Q3: Good or Bad? (Column order) CREATE INDEX tbl_idx ON tbl (a, b); SELECT id, a, b FROM tbl WHERE a = $1 AND b = $2; SELECT id, a, b FROM tbl WHERE b = $1;
- 41. 3-Minute Quiz: Indexing Skills Q3: Good or Bad? (Column order) CREATE INDEX tbl_idx ON tbl (a, b); SELECT id, a, b FROM tbl WHERE a = $1 AND b = $2; SELECT id, a, b FROM tbl WHERE b = $1;
- 42. 3-Minute Quiz: Indexing Skills Q4: Good or Bad? (Indexing LIKE) CREATE INDEX tbl_idx ON tbl (text varchar_pattern_ops); SELECT id, text FROM tbl WHERE text LIKE '%TERM%';
- 43. 3-Minute Quiz: Indexing Skills Q4: Good or Bad? (Indexing LIKE) CREATE INDEX tbl_idx ON tbl (text varchar_pattern_ops); SELECT id, text FROM tbl WHERE text LIKE '%TERM%';
- 44. 3-Minute Quiz: Indexing Skills Q5: Good or Bad? (equality vs. ranges) CREATE INDEX tbl_idx ON tbl (date_col, state); SELECT id, date_col, state FROM tbl WHERE date_col = CURRENT_DATE - INTERVAL '5' YEAR AND state = 'X';
- 45. 3-Minute Quiz: Indexing Skills Q5: Good or Bad? (equality vs. ranges) CREATE INDEX tbl_idx ON tbl (date_col, state); SELECT id, date_col, state FROM tbl WHERE date_col = CURRENT_DATE - INTERVAL '5' YEAR AND state = 'X';
- 46. Indexes: The Neglected All-Rounder Everybody knows indexing is important for performance, yet nobody takes the time to learn and apply is properly.
- 47. Indexes: The Neglected All-Rounder Index details are hardly known. ! “Details” like column-order or equality vs. range conditions must be learned and understood. Only one index capability is used: finding data quickly ! Indexes have three capabilities (powers): finding data, clustering data, and sorting data. Indexing is done from single query perspective. ! Should be done from application perspective (considering all queries). It’s a design task!
- 48. Indexes: The Neglected All-Rounder Are you just adding indexes or are you designing indexes?
- 49. About Markus Winand Tuning developers for high SQL performance Training co (one-man show): winand.at Geeky blog: use-the-index-luke.com Author of: SQL Performance Explained