Updating statistics sql 2016 r2
Statistics are small, lightweight objects that describe the distribution of data in a SQL Server table. First Name By Year and you run this query: SQL Server needs to estimate how many rows will come back for First Name Id=74846. Statistics are lightweight little pieces of information that SQL Server keeps on tables and indexes to help the optimizer do a good job. First Name By Year table was freshly created when we ran our query, it would have no column statistics.The SQL Server query optimizer uses statistics to estimate how many rows will be returned by parts of your query. By default, the SQL Server optimizer will see that no statistics exists, and wait while two column statistics are created on the First Name Id and Gender columns.The thresholds for when auto-update statistics kicks in are a little complicated.For SQL Server 2005 – SQL Server 2014 (with no trace flags) to make an optimization decision that the update is kicked off. Trace Flag 2371 makes the formula for large tables more dynamic.Trace Flag 7471 is a global trace flag released in SQL Server 2014 SP1 Cumulative Update 6.This trace flag changes the locking behavior associated with updating statistics.
But in general it does NOT pay off to enable trace flags “just in case” for most people.(I think we know which team really felt some pain and wanted this trace flag to exist, because the trace flag was announced on their blog! So if you’re using SQL Server 2016, you don’t need to decide.) Trace flag 2371 is available in SQL Server 2008R2 SP1-SQL Server 2014. Erik Darling tested out the behavior in 2016 and wrote about it here.With the trace flag on, if you set up jobs to concurrently update statistics on the same table, they won’t block each other on metadata related to statistics updates.Jonathan Kehayias has a great post on TF 7471 on SQL