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Top 5 Things You Didn't Know About
InMemory OLTP
Your
company
logo here
Vinod Kumar M
@vinodk_sql
http://blogs.ExtremeExperts.com
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 DDL
CREATE 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);
Hash Index
Secondary
Indexes are
specified inline
This table is memory
optimized
This table is durable
Memory Optimized Table Creation
Create Table
DDL
Code generation
and compilation
Table DLL
produced
Table DLL loaded
UNDERSTANDING HASH INDEXES
Hash Indexes
Hash function f:
Hash index with (bucket_count=8):
Hash mapping:
Array of
8-byte
Memory
pointers
f(Pinal) f(Vinod)
f(Lakhani)
0
1
2
3
4
5
6
7
f(MP)
f(KAR)
f(CHENNAI)
• Maps values to buckets
• Built into the system
Hash
Collisions
Memory Optimized Tables and
Indexes
Timestamps Chain ptrs
Hash index
on Name
f(Pinal)
50, ∞
Name
City
Hash index
on City
Pinal
BLR
f(BLR)
f(Vinod)
f(Chennai)
90, ∞
Vinod
Chennai
Memory Optimized Tables and
Indexes
Timestamps Chain ptrs
Hash index
on Name
f(Balu)
50, ∞
Name
City
Hash index
on City
Pinal
BLR
f(BLR)
100, ∞
Balu
BLR
90, ∞
Vinod
Chennai
T100: INSERT (Balu, BLR)
Memory Optimized Tables and
Indexes
Timestamps Chain ptrs
Hash index
on Name
50, ∞
Name
City
Hash index
on City
Pinal
BLR
100, ∞
Balu
BLR
90, 150
Vinod
Chennai
T150:
DELETE (Vinod, Chennai)
Memory Optimized Tables and
Indexes
Timestamps Chain ptrs
Hash index
on Name
f(Balu)
50, ∞
100,200
∞
100,
Name
City
Hash index
on City
Pinal
Balu
BLR
BLR
f(Chennai)
200, ∞
90, 150
Balu
Vinod
Chennai
Chennai
T200: UPDATE
(Balu, BLR) to
(Balu, Chennai)
Memory Optimized Tables and
Indexes
Timestamps Chain ptrs
Hash index
on Name
f(Pinal)
50, ∞
Name
City
Hash index
on City
Pinal
BLR
f(BLR)
f(Balu)
100, 200
Balu
BLR
f(Chennnai)
200, ∞
90, 150
Balu
Vinod
Chennai
Chennai
T250: Garbage collection
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 memoryoptimized log records transparently
• Not supported
– Differential backup
QUESTION