The target is the name of the target index, statistics, or column for which to display statistics information. The table_name is the name of the table that contains the statistics to display. You can view stats that have already been created by running the DBCC SHOW_STATISTICS command:
When automatic statistics are created, they will take the form: WA_Sys_. The creation of stats will be logged in sys.dm_pdw_exec_requests under a different user context. To avoid measurable performance degradation, you should ensure stats have been created first by executing the benchmark workload before profiling the system. The time to create statistics for a single column depends on the size of the table.
EXPLAIN when containing a join or the presence of a predicate is detectedĪutomatic creation of statistics are not created on temporary or external tables.Īutomatic creation of statistics is done synchronously so you may incur slightly degraded query performance if your columns are missing statistics. These statements will trigger automatic creation of statistics: You can check if your dedicated SQL pool has AUTO_CREATE_STATISTICS configured by running the following command:ĪLTER DATABASE SET AUTO_CREATE_STATISTICS ON If statistics are missing, the query optimizer creates statistics on individual columns in the query predicate or join condition to improve cardinality estimates for the query plan.Īutomatic creation of statistics is currently turned on by default. When the database AUTO_CREATE_STATISTICS option is on, dedicated SQL pool analyzes incoming user queries for missing statistics. If it estimates that the selected date will return 1 million rows, it will return a different plan. In most cases, it chooses the plan that will execute the fastest.įor example, if the optimizer estimates that the date your query is filtering on will return one row it will choose one plan. It compares the cost of various query plans, and then chooses the plan with the lowest cost. The dedicated SQL pool query optimizer is a cost-based optimizer. After loading data into dedicated SQL pool, collecting statistics on your data is one of the most important things you can do to optimize your queries. 
The more dedicated SQL pool knows about your data, the faster it can execute queries against it. In this article, you'll find recommendations and examples for creating and updating query-optimization statistics on tables in dedicated SQL pool. Table statistics for dedicated SQL pool in Azure Synapse Analytics
0 kommentar(er)
