1. Hustle and Bustle of SQL Pages
Jacques Mostert
SQLAdventurar

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3. QUERY
Overview
Query -> magic -> results

4. Relational Engine Query Plan Parse Optimize Normalize Buffer Pool
Task
Query Plan
Parse
Task
Task
Optimize
Normalize
Buffer Pool
Storage Engine
Plan Cache
Computer starts query
Query is executed by user
Goes into a task queue
Gets a worker/scheduler
(REMEMBER SQL IS LAZY)
Does a HASH on the query and checks the plan cache
Start language event
Parse
Normalize
Optimize – Engine is MS Holy Grail and closely guarded secret
It has 4 stages
-pre optimization – trivial plan
-transaction processing when cost is < 0.2
-Quick plan when cost is <1
-Full Optimization
Execution plan
Allocate Memory
IO Subsystem

5. Relational Engine Parse Query Plan Optimize Normalize Query Executer
Task
Query Plan
Task
Task
Optimize
Normalize
Query Executer
Buffer Pool
Storage Engine
Plan Cache
Query Executer
Storage engine
Access method manager
Buffer manager
BM checks the data cache and checks for the page it needs
If page is there no need to go to disc if not then it needs to load the page to the buffer pool
Then the request is passed to the IO Manager
IO Manager goes to the disc gets the data and sends it all the way back.
Why does the buffer pool matter? HDD 200MB/s, SDD MB/s DDR6.4GB to 17GB/s
Access Method
Buffer Manager
Data Cache
IO Subsystem
IO Manager

6. What we visualize a SQL page to look like

7. What it actually looks like
Not going to discuss page structures
SQL does not read parts of a page but the whole page
If you set statistics on
128 pages = 1MB
pages = 1GB

8. PAGE (8Kb)

9. EXTEND (64Kb)
Mixed or Uniform

10. Sector Size

11. Select (Read)
Insert (Write)
Delete (Remove)
Update

12. Memory / Buffer

13. TempDB / Workspace
Tempdb is used by the SQL OS for operations, snapshot isolation, always on, index rebuild and so forth
TempDB is SQL Server dumpster or public toilet. Everything or everyone uses it
Sorting is not limited to your memory. Your query is not that important that SQL will give it all to you
Memory is shared and used to cache data, cache execution plans and executing your query

14. Pile Of “HEAP”
Data rows stored random
Pages are everywhere
HEAPS are not bad per-say there could be an advantage to having a HEAP when you insert “random” data and read large chunks without the need for sorting

15. Cluster Confusion
Explain why it is bad to create a clustered index on a column that does not store sequential number like GUID
If a table only has a clustered index it is going to be slow. Because there is then only one copy of the table same as the HEAP

16. Nonclustered Index Nonclustered index – create copies of columns
Clusteres index included

17. This is effectively a covering index for the specific query
This is effectively a covering index for the specific query. In the perfect world there would be an index like this for every query.

18. Table Lock

19. Page Locking

20. Row Locking

21. Sorting
Group By
Create work space
Write down while sql reads

22. Compression

24. THANK YOU!
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