Sql server updating large databases
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.When tables have more than 25,000 rows, the threshold for automatic statistics update becomes more dynamic, and this adjusts as the rowcount goes up.Jonathan Kehayias has a great post on TF 7471 on SQL He demos the trace flag in a video for the SQL Skills Insider Newsletter where he shows the changes in locking behavior this flag introduces.If you’re managing lots of SQL Server instances and want ultimate customization, there is a free version of Minion Reindex. The answers to both of these questions impact what it does to GROUP those rows and SUM the Name Count column.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.I’m also not talking about statistics for memory optimized tables in this article. Back when I read philosophy, I found Aristotle a bit annoying because he talked so much about “moderation”. You shouldn’t run statistics maintenance against a database at the same time you’re checking for corruption, rebuilding indexes, or running other IO intensive processes.
Statistics are small, and are created super fast– my query isn’t measurably any faster when I run it a second time.
See a graph of the adjusting threshold in this post from the SAP team.