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Hi Tom, I've been asked to review performance on one of our databases, and one of the issues I found was the statistics have been locked since 2011 and are considered stale. Marc You collect stats in pending mode, so nothing "sees" them, and then run selected key queries from the application against the pending stats, using: optimizer_use_pending_statistics = true at session level, or by login trigger etc.
Each histogram step includes a range of column values followed by an upper bound column value, which includes all possible column values between boundary values (excluding the boundary values themselves).
Updating Statistics is critical for the SQL Server optimizer to have the latest information about the database to select the best query plan.
Unfortunately, I am hesitant to enable AUTO UPDATE STATISTICS at a database level or for specific tables.
He reports that he has observed the AUTO_UPDATE_STATISTICS_ASYNC configuration cause major issues in two data warehouse systems that involved near-real time loads.
In both cases, a similar pattern occurred: queries against a recent time frame hit just after the load, did not trigger a synchronous update and the query optimizer chose a seek where a scan would have been more appropriate.