dev compression
TRANSCRIPT
Vinod Kumar MTechnology Evangelist – DB and BIMicrosoft Corporationwww.ExtremeExperts.com
Session ObjectivesWhy data compression?
Describe data compression in SQL Server
Describe Space/Performance trade-offs
Key TakeawaysCan reduce size of a database significantly
Easy to enable/disable
No application changes
Performance gains
Session Objectives And Takeaways
Agenda
What is the problem?
Solution
Compression in SQL Server 2008
Problem
Large DatabaseStorage Cost
Workload Performance
Manageability CostBackup/Recovery
Solution
Reduce the size of the databaseReduce the information stored
Compress the dataCompress the data file
No benefit in-memory
Need to compress larger chunks, does not scale for random access
Store data efficiently in the row/page
(+) More data can fit in memory
(+) Better Performance for I/O bound workload
(-) Performance degradation for CPU bound workload
Agenda
What is the problem?
Solution
Compression in SQL Server 2008
Compression in SQL Server
SQL Server 2008 ROW and PAGE compression
Backup Compression
Two key changesEfficient storage of data within row (both for data and index)
Reduce Data Redundancy on the page
Efficient Storage in the ROW
Variable Length Encoding (new row format)
0 0 0 1
4-byte integer
1SQL2008 (compression enabled)
4 bytes
Special Handling of NULL and 0s
CHAR data type storage optimization
SQL2005
Reduce Data Redundancy:Column PrefixFactor out common prefix from the same column across all rows on the page
Store these ‘prefix’ values once and then reference them from respective columns
Example:Student (Name VARCHAR (10),
ID INT,
CODE VARBINARY(3))
Column Prefix
Page Header
0x5B8D80
0x41AABB
0x9A4041
0x112233
0x5CAABB
Lambert 5000000 NULL
4
5 20x41
20x43
20x42
Reduce Data Redundancy: Page Dictionary
Find repeating values across all columns on all the rows on the page
Store these values in a dictionary once and reference them from respective columns
Page Dictionary
Page Header
0x5B8D80
0x41AABB
0x9A4041
0x112233
0x5CAABB
Lambert 5000000 NULL
4
5 20x41
20x43
20x42
Column prefix
Page Dictionary
1
1
0
0
Enabling Compression
Enterprise Edition onlyTypes of data compressions
ROW Stores fixed length values as variable lengthSuperset of vardecimal storage formatRow metadata optimizedBLOB/LOB is not ROW compressed
PAGE (includes ROW)Column PrefixDictionaryOnly in-row BLOB/LOB can potentially benefit from PAGE compression
Enabling Compression Examples
Unpartitioned table
Table
Index
PAGE Compressed
Index
Uncompressed
Table
Index
Enabling Compression ExamplesLatest partition uncompressed
Jan-Mar Apr-June July-Sept Oct-Dec
PAGE Compressed
Uncompressed
ROW Compressed
Data Compression TSQL Example
CREATE TABLE T (c1 int, c2 char(2000) )
WITH (DATA_COMPRESSION = ROW)
CREATE TABLE T_Part (c1 int, c2 char(2000) )
ON somePartScheme (c1)
WITH
(DATA_COMPRESSION = PAGE ON PARTITIONS (1-7),
DATA_COMPRESSION = NONE ON PARTITIONS (8) )
ALTER INDEX CI ON T REBUILD
WITH (DATA_COMPRESSION=PAGE)
ALTER INDEX CI ON T REBUILD PARTITION = 3
WITH (DATA_COMPRESSION=PAGE)
Enabling Compression…
Estimate space savingssp_estimate_data_compression_savings
Space savings depend uponSchema
Data Distribution
DML Operations
INSERT (PAGE Compressed)
Header
CI structure
Header
PAGE Compressed
ROW Compressed
Table And PAGE Compression
PAGE Compressed
Uncompressed
ROW Compressed
Btree And PAGE Compression
ROOT
INTERNALINTERNAL INTERNAL
LEAFLEAFLEAFLEAF
INTERNAL
PAGE Compressed
Uncompressed
ROW Compressed
Impact Of Data Compression
ApplicationNo changes needed in the application
Application throughput increase if I/O bound
UtilitiesAll Database Utilities (e.g. Backup, Index, DBCC) fully supported
Gains if I/O bound
SupportabilityDBCC PAGE enhanced
New Perfmon countersPage Compression attempts/sec
Page Compressed/sec
New columns in DMVssys.db_index_physical_stats
compressed_pages_count
sys.db_index_operational_statsPage_compression_success_count
Page_compression_attempt_count
Summary – Compression
Can reduce size of database significantly
Lower total cost of ownership (TCO)
Easy to enable/disable
No application changes
Performance gains
Related Content
Breakout Sessions (session codes and titles)
Interactive Theater Sessions (session codes and titles)
Hands-on Labs (session codes and titles)
Hands-on Labs (session codes and titles)
Track Resources
Resource 1
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Resource 4
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