1. Dual Partitioning for improved performance in VLDBs Ashwin Rao Karavadi, Rakesh Parida Microsoft IT

2. Data Partitioning Why? Split a table into manageable partitions Improve data access performance Simplify maintenance

3. Partitioned Views Available since SQL Server 7.0 A partitioned view is a view defined by a UNION ALL of member tables structured in the same way, but stored separately as multiple tables in either the same instance of SQL Server or in a group of autonomous instances of SQL Server servers Query optimizer utilizes constraints to perform partition elimination Partition elimination occurs for SELECT and for DML statements Only one column can be used for partitioning With only one constraint on the partitioning column

4. Partitioned Tables Available SQL Server 2005 onwards Data is partitioned horizontally so that groups of rows are mapped into individual partitions, based on a specified column. The partitions can be put on one or more filegroups in the database. The table or index is treated as a single logical entity when queries or updates are performed on the data Static and dynamic partition elimination Only one partition column can be used for partitioning

5. Dual partitioning using partitioned views and partitioned tables Partition data using partitioned views over partitioned tables Why dual partitioning: – Support for scenarios where there is a need to partition on two columns – Optimized access when filtering on both columns – Can spread data across multiple DBs/servers

6. Dual partitioning – application specific scenario Very large table with data related to FiscalYear and FiscalMonth Need to archive data into a different database based on FiscalYear Optimized data access for queries based on FiscalYear and FiscalMonth Simplified data loading from source and data extraction to archive

7. Dual partitioning – sample execution plans

9. Partition-aligned indexed views Available SQL Server 2008 onwards Can create indexed views over the data in partitioned tables to improve query performance – In order for a view to be indexed and automatically maintained during partition switching, the base table and the view must share equivalent partitioning schemes. That means that if the base table and the view use different partition schemes, the two partition schemes must be based on the same, or equivalent, partition functions Can be (judiciously) used to improve performance

10. Partition-aligned indexed views – sample execution plans

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