In Memory OLTP

SQL server 2014 Hekaton Engine

Frederik Bogaerts

Give me more

NSLOOKUP 127.0.0.0

Hekaton in a nutshell

Please ExplainWhy Demo

So long …

Hekaton – In Memory OLTPHash

Indexes

Memory Optimiz

ed Tables

Range Indexe

s

Latch-free

Hekaton Engine

Source: Microsoft.com

Prepare your databaseCreate Database Add memory optimized filegroup Add file to filegroup

Memory Optimized TablesCREATE TABLE [Customer]( [CustomerID] INT NOT NULL

PRIMARY KEY NONCLUSTERED HASH WITH (BUCKET_COUNT = 1000000),

[Name] NVARCHAR(250) NOT NULL, [CustomerSince] DATETIME NULL

INDEX [ICustomerSince] NONCLUSTERED)WITH (MEMORY_OPTIMIZED = ON, DURABILITY = SCHEMA_AND_DATA);

Limitations No DML

no LOBs, no XML and no CLR data types

No Foreign Key or Check constraints

No UNIQUE indexes other than PK

Max 8 indexes

Data Structures

New Row Format

Versioning : Timestamps

No data page

containers

Row header Payload (table columns)

Begin Ts End Ts StmtId IdxLinkCount

8 bytes 8 bytes 4 bytes 2 + 2 (padding) bytes

8 bytes * (IdxLinkCount)

Source: Microsoft.com

Indexes

Buckets

Point Lookups

HashRange Scanning

BW-Tree

Non Clustered

Hash Indexes

Source: Microsoft.com

Range Indexes

Source: Microsoft.com

Natively Compiled Procs CREATE PROCEDURE [dbo].[InsertOrder] @id INT, @date DATETIME WITH NATIVE_COMPILATION, SCHEMABINDING, EXECUTE AS OWNERAS BEGIN ATOMIC WITH (TRANSACTION ISOLATION LEVEL = SNAPSHOT, LANGUAGE = N'us_english')

-- insert T-SQL hereEND

LimitationsOnly In MEM tables

No OUTER JOIN, no DISTINCT no OR, no subqueries, no CASE

Limited built-in functions

BUT: Fastest way!

Good news : Interface will be expanded in next version

T-SQL (Not) Supported

INTEROP

Truncate

Dynamic en keyset cursors

Cross database

Linked servers

Locking Hints – Isolation Levels

Merge

Garbage Collection

Multi Versioning Stale Rows Scans slow Bloathing memory

DiagnosticsAll starting with sys.dm_db_xtpDMO

• sys.dm_db_xtp_checkpoint_files• sys.dm_db_xtp_table_memory_stats• Sys.dm_db_xtp_index_stats

XEvents• From SYS.dm_xe_objects O JOIN SYS.dm.xe_packages P on O.package_guid = P.guid where P.name = ‘XtpEngine’

Perfomance Counters• From sys.dm_os_performance_counters where object_name like ‘XTP%’

Keep In MindData in memory at all times

Still using log files

Do not exceed 256 GB of InMem table

Going For Gold

Please ExplainWhy Demo

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A SQL query walks into a bar and sees two tables. He walks up to them and says 'Can I join you?

The SQL query found the table by doing a full scan of the other tables…

In the meanwhile, the waitress arrived at the table. Woohoow what a nice view…

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