1. Sunil Agarwal | Principal Program Manager
03 | Materialized Views and Concurrency
Sunil Agarwal | Principal Program Manager

2. Clustered Columnstore Index: Materialized View
Enforcing Uniqueness
Create a materialized view
create view dbo.myview_t_account with schemabinding as
select accountkey,accounttype, accountcodealternatekey
from dbo.T_ACCOUNT
-- create a materialized view
create unique clustered index clix_my_t_account on myview_t_account (accountkey)
Avoiding Scan of Clustered Columnstore Index
Create nonclustered index on MV with included column(s)
Pros – good for equality and short-range scans
Cons – Storage overhead and expensive DML operations
Columnstore technology was first introduced in SQL Server 2012 and has been significantly enhanced for SQL Server Columnstore indexes can not only accelerate data warehouse workloads by an order of magnitude but also reduce storage requirements by an order of magnitude. Columnstore indexes are a hybrid technology leveraging the best of disk & in-memory capabilities. In this session we cover how to take advantage of columnstore capabilities in your applications and dive into the internals of how columnstore works.

3. Clustered Columnstore Index: Concurrency
Querying
Higher Granularity Locks for efficiency: ROWGROUP granularity
Will cause blocking with concurrent DMLs.
No support of RCSI or SI
Recommendation: use Read Uncommitted Isolation level with concurrent DML
Insert
Optimized for DW load: Concurrent Inserts are allowed into same ROWGROUP
DELETE
Takes X lock on the ROWGROUP
Does not block INSERT as they go into a new ROWGROUP
UPDATE
Done as DELETE followed by INSERT

4. Columnstore Index: Catalog Views
sys.column_store_row_groups
Visibility into all columnstore row groups (in columnar + delta store)
Use this DMV to determine number of delta stores
Every partition has at least one delta store
Each partition can have multiple delta stores
Use this DMV to determine quality of clustered columnstore index:
If rowgroup contains <1M rows, investigate why
sys.column_store_segments
Find ranges of column value for segment elimination
Dictionary usage
Segment size
sys.column_store_dictionaries
number of entries in primary and secondary
Size

5. Materialized Views and Concurrency [Sunil Agarwal]