SQL Server Deep Dive Denis Reznik Data Architect at Intapp

About me  Kiev, Ukraine  Data Architect at Intapp Inc.  Microsoft MVP  Leader of Kyiv SQL Server User Group  Co-author of “SQL Server MVP Deep Dives vol. 2”  SoftServe IT-Awards judge 2 |

SQL Server Network Interface

SQL Server Protocols  Shared Memory  TCP/IP  Named Pipes  VIA (Deprecated)

TDS Endpoints TCP/IP Shared Memory Named Pipes VIA DAC TCP/IP Note: TDS – Tabular Data Stream

Query Processing

Parser  Parse Query Text  Check base SQL syntax  Check if plan is already in cache  Returns ParseTree

Algebrizer  Check that objects are exist and available in current execution context  Define types for every node in ParseTree  Returns QueryTree (Logical representation of the query)

Optimizer  Goal – get the optimal execution plan Optimizer Query Tree Pre-Optimization Search for trivial plan Load statistics (optional) Simplification – syntax transformation

Optimizer Phase 0 Exploration – plan alternatives Return Transaction Processing plan Load statistics

Optimizer Phase 1 Next set of query rules Returns Quick Plan Estimate parallel plan (executed twice)

Optimizer Phase 2 Full optimization Returns Full Plan Indexed views

Index (B-Tree) - Seek … … 1.. 1M 1.. 2K 2K+1.. 4K 1M-2K.. 1M ,5K 1,5K+1..2K SELECT * FROM Users WHERE Id = 523

Index (B-Tree) - Scan … … 1.. 1M 1.. 2K 2K+1.. 4K 1M-2K.. 1M ,5K 1,5K+1..2K SELECT * FROM Users

Index (B-Tree) – Range Scan … … 1.. 1M 1.. 2K 2K+1.. 4K 1M-2K.. 1M ,5K 1,5K+1..2K SELECT * FROM Users WHERE Id BETWEEN 700 AND 1700

Statistics SELECT * FROM Users WHERE Id BETWEEN 2100 AND 2500

Executor  Execute query using its Query Plan  Ask Storage Engine for data

Demo SQL Server, are you kidding me?

Storage Engine

Buffer Pool Data Cache Database File Access Methods Buffer Manager Select Data

Modify Data Buffer Pool Data Cache Database File Access Methods Buffer Manager Transaction Log Log Manager Log Buffer

Lock Types - Shared S S S S X X

Lock Types - Exclusive X X X X S S

Lock Types - Update U U U U S S S S X X

Lock Types – Intent locks S S IS

S S S S S S … S S n n = 5000 Table S S if lock can’t be put on table, process will try this every n rows 12 Buffer Pool Memory for locks S S > 24% Lock Escalation

Demo Use NOLOCK carefully

SQL OS

Execution model Session Thread Pool Running Suspended Runnable Task(s) SchedulerLogical CPU

Demo Worker Threads Starvation

@denisreznik Thank You!