Top 5 Things You Didn't Know About InMemory OLTP

Vinod Kumar M

@vinodk_sql

http://blogs.ExtremeExperts.com

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Myths about In-Memory OLTP

• SQL Server In-Memory OLTP is a recent

response to competitors’ offerings

• In-Memory OLTP is like DBCC PINTABLE

• In-Memory Databases are new separate products

• You can use In-Memory OLTP in an existing SQL

Server app with NO changes whatsoever

• Since tables are in memory, the data is not

Durable or Highly Available – I will lose it after

server crash

What is In-Memory OLTP?• SQL Server 2014 adds in-memory technology to boost performance of OLTP workloads

Create Table DDLCREATE TABLE [Customer](

[CustomerID] INT NOT NULL

PRIMARY KEY NONCLUSTERED HASH WITH (BUCKET_COUNT = 1000000),

[Name] NVARCHAR(250) NOT NULL

INDEX [IName] HASH WITH (BUCKET_COUNT = 1000000),

[CustomerSince] DATETIME NULL

)

WITH (MEMORY_OPTIMIZED = ON, DURABILITY = SCHEMA_AND_DATA);

This table is memory optimized This table is durable

Secondary Indexes are

specified inline

Hash Index

Memory Optimized Table Creation

Create Table DDL

Code generation and compilation

Table DLL produced

Table DLL loaded

UNDERSTANDING HASH INDEXES

Hash Indexes

4567

0123

Array of

8-byte

Memory

pointers

Hash index with (bucket_count=8): Hash function f:• Maps values to buckets

• Built into the systemHash mapping:

f(Lakhani)

f(Vinod)f(Pinal)

f(MP)

f(CHENNAI)

Hash

Collisionsf(KAR)

Memory Optimized Tables and Indexes

50, ∞ Pinal BLR

Timestamps NameChain ptrs City

Hash index

on CityHash index

on Name

90, ∞ Vinod Chennai

f(Pinal)

f(Vinod)

f(BLR)

f(Chennai)

Memory Optimized Tables and Indexes

50, ∞ Pinal BLR

Timestamps NameChain ptrs City

Hash index

on CityHash index

on Name

T100: INSERT (Balu, BLR)

100, ∞ Balu BLR

90, ∞ Vinod Chennai

f(Balu) f(BLR)

90, 150 Vinod Chennai

Memory Optimized Tables and Indexes

50, ∞ Pinal BLR

Timestamps NameChain ptrs City

Hash index

on CityHash index

on Name

T150: DELETE (Vinod, Chennai)

100, ∞ Balu BLR

Memory Optimized Tables and Indexes

90, 150 Vinod Chennai

50, ∞ Pinal BLR

Timestamps NameChain ptrs City

Hash index

on CityHash index

on Name

T200: UPDATE

(Balu, BLR) to

(Balu, Chennai)

100, ∞ Balu BLR

200, ∞ Balu Chennai

100, 200

f(Chennai)

f(Balu)

Memory Optimized Tables and Indexes

90, 150 Vinod Chennai

50, ∞ Pinal BLR

Timestamps NameChain ptrs City

Hash index

on CityHash index

on Name

T250: Garbage collection

100, 200 Balu BLR

200, ∞ Balu Chennai

f(Balu)

f(Pinal)

f(Chennnai)

f(BLR)

HOW INMEMORY PROCEDURES ARE CREATED !!!

Procedure Creation

CREATE PROC DDL

Query optimization

Code generation and compilation

Procedure DLL produced

Procedure DLL loaded

Backup for Memory-Optimized Tables

• Integrated with SQL Database Backup

– Memory-Optimized file group is backed up

as part SQL database backup

• Existing backup scripts work with minimal or

no changes

• Transaction log backup includes memory-

optimized log records transparently

• Not supported

– Differential backup

QUESTION