Geek Sync | Faster Transactions: Query Tuning for Data Manipulation
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You can watch the replay for this Geek Sync webcast, Faster Transactions: Query Tuning for Data Manipulation, in the IDERA Resource Center, http://ow.ly/G4oy50A4qmS. Your server has dozens of CPUs, terabytes of RAM, and solid-state drives, and yet your UPDATE query still takes hours. Why? In this demo-filled session we will discuss common pitfalls for any SQL professional who is manipulating large sets of data with INSERT, UPDATE, and DELETE statements. Not only will you learn about potential issues involving data pages, locks, and the transaction log, but also what techniques you can use to improve performance. Speaker: Jeff Iannucci is a Senior Database Administrator for DriveTime in Tempe, AZ. He has over 20 years of SQL Server experience as both a DBA and Developer in diverse environments such as health care, finance, retail sales, and government. He writes about solving problems for database professionals on both twitter (@DesertDBA) and his blog (desertdba.com), and is a 2020 IDERA ACE.
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Geek Sync | Faster Transactions: Query Tuning for Data Manipulation
- 1. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level Faster Transactions: Query Tuning for Data Manipulation Jeff Iannucci
- 2. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 2 Who in the world is Jeff Iannucci? I live in Arizona, and I sell used cars! Senior Database Administrator at DriveTime SQL Server data professional since 1998
- 3. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 3 Who in the world is Jeff Iannucci? @desertdba jeff@desertdba.com
- 4. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 4 Performance tuning for… UPDATE INSERT DELETE …especially for large amounts of data What is in this session?
- 5. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 5 Show WHAT commands help performance Discuss WHEN to use these commands Explain WHY the performance improves What are the goals of this session?
- 6. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 6 But first…let’s talk about food!
- 7. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 7 The waiter writes down the order… …and orders go in the ticket queue
- 8. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 8 The chef assembles the ingredients… …gets any missing ingredients from pantry
- 9. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 9 The chef holds items while working… …until your order is ready!
- 10. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 10 “Le SQL Server” Your new favorite restaurant…
- 11. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 11 Transaction orders at “Le SQL Server” Log Buffer Cache Transaction Log Buffer Cache Pages Pages on Disk Lock
- 12. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 12 So…how can transactions go faster? Read/write less data pages Create less locks Create less transaction log entries
- 13. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 13 What’s on the menu today? Appetizers: Alter the target table Entrees: Manipulate the transaction Desserts: Modify the database settings
- 14. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 14 Appetizers: altering the target table
- 15. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 15 Let’s start with… An INSERT …into an empty table …of sorted data …that has no indexes …(also known as a heap.)
- 16. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 16 Clustered Index instead of a Heap Ordered data INSERTs faster than random data …if the Clustered Index (CI) matches sort order This works for INSERTs only
- 17. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 17 Clustered Index instead of a Heap
- 18. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 18 Clustered Index instead of a Heap Should every table have a clustered index? ▪ Unsorted INSERTS are slower with a CI ▪ Only faster when CI matches sort order ▪ …but, temporary tables can have a CI
- 19. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 19 Now let’s try a bit of… An UPDATE …that has a clustered index …to every record of a table …and non-clustered indexes.
- 20. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 20 Disabling indexes Reduces data pages manipulated Disable Non-Clustered Indexes (NCIs) only This works for INSERTs, UPDATEs, & DELETEs Disable only NCIs with affected columns
- 21. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 21 Disabling indexes
- 22. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 22 Disabling indexes Yes…but… ▪ REBUILDs take additional time ▪ NCIs are not used until they are rebuilt ▪ Clustered Index scans (temporarily)
- 23. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 23 Entrees: manipulating the transaction
- 24. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 24 Today let’s have… A DELETE …in a table with lots of records …of a majority of data …with lots of user connections …so don’t slow their orders.
- 25. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 25 Batch using WHILE with TOP Separates one transaction to many smaller ones Minimal disruption to concurrent users This works for INSERTs, UPDATEs, & DELETEs Allows other processes to go faster (less slow)
- 26. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 26 Batch using WHILE with TOP
- 27. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 27 Batch using WHILE with TOP What could go wrong? ▪ Could result in a slower query for you ▪ Will result in partial “transaction” if stopped ▪ Lock escalation occurs at 5000 locks
- 28. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 28 For RBAR dieters, try… An UPDATE …in a table with lots of records …of much of the data …but each row is updated …in a separate transaction.
- 29. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 29 Explicit transaction Reduces the pain of Row By Agonizing Row Consolidates many transaction into one This works for INSERTs, UPDATEs, & DELETEs Use when concurrency is not a factor
- 30. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 30 Explicit transaction
- 31. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 31 Explicit transaction The fine print: ▪ Locked resources during transaction ▪ Concurrent users wait for resources ▪ A bit like TABLOCK
- 32. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 32 What you really want is… An INSERT …into an empty table …of sorted or unsorted data …and make it fast as you can!
- 33. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 33 Minimally logged INSERT Less records in the Transaction Log Logging of page allocations, not record inserts …because this locks the entire INSERT table Use when no concurrent usage
- 34. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 34 What do you mean by “table lock”? RECORD LOCK PAGE LOCK TABLE LOCK
- 35. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 35 What do you mean by “page allocation”? RECORD logging (default) PAGE allocation logging
- 36. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 36 Some minimally-logged transaction rules Database NOT in FULL recovery model Table is not replicated Table is not memory-optimized
- 37. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 37 Some minimally-logged transaction rules Table has no indexes (is a heap), or… …if the table has indexes then it must be empty May require Trace Flag 610 https://docs.microsoft.com/en-us/sql/relational-databases/import- export/prerequisites-for-minimal-logging-in-bulk-import?view=sql-server-ver15
- 38. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 38 Minimally logged INSERT
- 39. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 39 Minimally logged INSERT The bad news: ▪ Concurrent users wait for resources ▪ Only uncommitted (“dirty”) reads ▪ Only works for INSERT, although…
- 40. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 40 Next you might enjoy… A DELETE …in a table with lots of records …of a majority of data …and make it fast …like minimal logging!
- 41. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 41 Minimally logged DELETE Wait…what?!? Utilize minimally logged INSERTs - Twice! (Not simultaneously, though) Let’s lock TWO tables
- 42. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 42 Minimally logged DELETE
- 43. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 43 Minimally logged DELETE So what’s the catch? ▪ Best for removing a majority of the data ▪ DISABLE/re-ENABLE constraints ▪ All the rules for minimal logging apply
- 44. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 44 Desserts: modifying database settings
- 45. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 45 What sounds good is… An INSERT …into an empty table …of sorted or unsorted data …in a database with FULL recovery model …and gimme minimal logging!
- 46. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 46 Bulk Logged Recovery Model Change recovery model to BULK_LOGGED Utilize minimally-logged transactions This works for INSERTs (and savvy DELETEs) Does NOT break the backup chain!
- 47. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 47 Bulk Logged Recovery Model
- 48. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 48 Bulk Logged Recovery Model Warning: ▪ ALL database transactions affected ▪ No Point-In-Time recovery ▪ Consult with your Database Administrator
- 49. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 49 Let’s boldly finish with… A DELETE …in a table with lots of records …of a bunch of data …for those on a RBAR diet.
- 50. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 50 Delayed Durability Delays the hardening of transactions to log Log Buffer Cache Work with data Then write to T-Log
- 51. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 51 Use with lots of small transactions Delayed Durability This works for INSERTs, UPDATEs, & DELETEs
- 52. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 52 Delayed Durability
- 53. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 53 Delayed Durability Why isn’t everyone using this? ▪ Lost transactions if SQL Server stops ▪ Works best for lots of small transactions ▪ Consult with your Database Administrator
- 54. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 54 Let’s review the menu
- 55. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 55 Appetizers: Alter the target table Query options INSERT UPDATE DELETE Clustered index on a heap Disable indexes
- 56. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 56 Entrees: Transaction manipulation Query options INSERT UPDATE DELETE Batching (WHILE with TOP) Explicit transactions Minimally logged INSERT Minimally logged DELETE
- 57. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 57 Desserts: Database settings Query options INSERT UPDATE DELETE Bulk Logged recovery model Delayed durability
- 58. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 58 And NOW… Here is IDERA’s Rey Rios with a demo of SQL Diagnostic Manager…
- 59. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 59 What questions do you have?
- 60. Topics ▪ Click to edit Master text styles • Second level • Third level − Fourth level • Fifth level 60 That’s the end. Thank you! jeff@desertdba.com @desertdba