Saving Statistics Sample Rates

Pedro Lopes shows off a new feature in the latest SQL Server 2016 CU:

When SQL Server creates or updates statistics and a sampling rate is not manually specified, SQL Server calculates a default sampling rate. Depending on the real distribution of data in the underlying table, the default sampling rate may not accurately represent the data distribution and then cause degradation of query plan efficiency.

To improve this scenario, a database administrator can choose to manually update statistics with a specific sampling rate that can better represent the distribution of data. However, a subsequent automatic update statistics operation will reset back to the default sampling rate, possibly reintroducing degradation of query plan efficiency.

With the most recent SQL Server 2016 SP1 CU4, we released an enhancement for the CREATE and UPDATE STATISTICS command – the ability to persist sampling rates between updates with a PERSIST_SAMPLE_PERCENT keyword.

This seems rather useful.

Related Posts

Troubleshooting Query Performance Changes

Erin Stellato walks us through a troubleshooting guide when users complain about poorly-performing queries: This is tale of troubleshooting… When you unexpectedly or intermittently encounter a change in query performance, it can be extremely frustrating and troublesome for a DBA or developer. If you’re not using Query Store, a third-party application, or your own method […]

Read More

Workarounds for Updating Stats on Secondaries

Niko Neugebauer wants statistics updates on tables running on readable Availability Group secondary nodes: Let’s list the basic known details for the possible solution(for the Enterprise Edition of the Sql Server that is):– We can make the secondary replica readable and read the same data on it. (Not that you should do that by default, […]

Read More

Categories

August 2017
MTWTFSS
« Jul Sep »
 123456
78910111213
14151617181920
21222324252627
28293031