The columnstore index is the standard for storing and querying large data warehousing fact tables. It uses column-based data storage and query processing to achieve up to 10x query performance gains in your data warehouse over traditional row-oriented storage, and up to 10x data compression over the uncompressed data size. Beginning with SQL Server 2016, columnstore indexes enable operational analytics, the ability to run performant real-time analytics on a transactional workload.
These are key terms and concepts are associated with columnstore indexes.
columnstore
A columnstore is data that is logically organized as a table with rows and columns, and physically stored in a column-wise data format.
rowstore
A rowstore is data that is logically organized as a table with rows and columns, and then physically stored in a row-wise data format. This has been the traditional way to store relational table data. In SQL Server, rowstore refers to table where the underlying data storage format is a heap, a clustered index, or a memory-optimized table.
column segment
A column segment is a column of data from within the rowgroup.
Delete bitmap:
cancellations are logical, are erased when you recalculate
Delta rowgroups:
inserted rows that have yet to be compressed
They can even be created on tables in memory that does not. it’s handled as all other indices. Through the Delay feature is possible to force the delay after a certain time instead of reaching the number of rows. You can also Filter data and exclude certain indices values (eg the deleted parts)
How to write it:
— Create a clustered columnstore index on disk-based table.
CREATE CLUSTERED COLUMNSTORE INDEX index_name
ON [database_name. [schema_name ] . | schema_name . ] table_name
[ WITH ( < with_option> [ ,…n ] ) ]
[ ON <on_option> ]
[ ; ]— create a durable (data will be persisted) memory-optimized table
— two of the columns are indexed
CREATE TABLE dbo.ShoppingCart (
ShoppingCartId INT IDENTITY(1,1) PRIMARY KEY NONCLUSTERED,
UserId INT NOT NULL INDEX ix_UserId NONCLUSTERED HASH WITH (BUCKET_COUNT=1000000),
CreatedDate DATETIME2 NOT NULL,
TotalPrice MONEYINDEX ShoppingCartId CLUSTERED COLUMNSTORE
) WITH (MEMORY_OPTIMIZED=ON)
GO
Here there are the principal differences between sql 2014 and sql 2016 :
| Columnstore Index Feature | SQL Server 2014 | SQL Server 2016 |
| Batch execution for multi-threaded queries | yes | yes |
| Batch execution for single-threaded queries | yes | |
| Archival compression option. | yes | yes |
| Snapshot isolation and read-committed snapshot isolation | yes | |
| Specify columnstore index when creating a table. | yes | |
| AlwaysOn supports columnstore indexes. | yes | yes |
| AlwaysOn readable secondary supports read-only nonclustered columnstore index | yes | yes |
| AlwaysOn readable secondary supports updateable columnstore indexes. | yes | |
| Read-only nonclustered columnstore index on heap or btree. | yes | yes* |
| Updateable nonclustered columnstore index on heap or btree | yes | |
| Additional btree indexes allowed on a heap or btree that has a nonclustered columnstore index. | yes | yes |
| Updateable clustered columnstore index. | yes | yes |
| Btree index on a clustered columnstore index. | yes | |
| Columnstore index on a memory-optimized table. | yes | |
| Nonclustered columnstore index definition supports using a filtered condition. | yes | |
| Compression delay option for columnstore indexes in CREATE TABLE and ALTER TABLE. | yes |
