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When AUTO_UPDATE_STATISTICS Doesn’t Happen

Articles tagged Optimiser

When AUTO_UPDATE_STATISTICS Doesn’t Happen

When your SQL Server database is set to have its statistics automatically updated, you will probably conclude that, whenever the distribution statistics are out-of-date, they...

10 min read

Checking the Plan Cache Warnings for a SQL Server Database

How often do you check your query plans during development to see if they contain any warnings? If you're missing them, it means that you're...

10 min read

Join Reordering and Bushy Plans

Normally, the query Optimiser won't consider 'bushy' plans, where both operands to a join operator could be intermediate results from other joins. This means that...

17 min read

Using Optimizer_WhatIF and StatsStream to Simulate a Production Environment

SQL Server's Query optimiser judges the best query plan from the data in the relevant tables and the server's hardware. How, then, can you investigate...

9 min read

Statistics in SQL Server

SQL Server's Query Optimiser relies on statistics for providing a decent query plan. If the statistics are wrong, outdated or missing then you have little...

10 min read

Fixing Gatekeeper Row Cardinality Estimate Issues

The Query Optimiser needs a good estimate of the number of rows likely to be returned by each physical operator in order to select the...

18 min read
Database Administration
in Database Administration

Statistics on Ascending Columns

It comes as rather a shock to find out that one of the commonest circumstances in an OLTP database, an ascending primary key with most...

10 min read

Questions about SQL Server Distribution Statistics

Fabiano was asked a couple of questions about SQL Server Distribution Statistics. Having given an answer based on his current knowledge, he then decided to...

20 min read

Showplan Operator of the Week – Merge Interval

When Fabiano agreed to undertake the epic task of describing each showplan operator, none of us quite predicted the interesting ways that the series helps...

7 min read

ShowPlan Operator of the Week – Merge Join

Did you ever wonder how and why your indexes affect the performance of joins? Once you've read Fabiano's unforgettable explanation, you'll learn to love the...

9 min read

SQL Server Statistics: Problems and Solutions

SQL Server Statistics assist the query optimiser to calculate the best way of running the query. Holger describes every common way that things can go...

39 min read

Showplan Operator of the Week – Stream Aggregate

Fabiano continues his mission to explain the Query Optimiser in practical terms, describing, one week at a time, all the major Showplan Operators used by...

9 min read

Operator of the Week – Spools, Eager Spool

For the fifth part of Fabiano's mission to describe the major Showplan Operators used by SQL Server's Query Optimiser, he introduces the spool operators and...

12 min read

Showplan Operator of the Week – BookMark/Key Lookup

Fabiano continues in his mission to describe the major Showplan Operators used by SQL Server's Query Optimiser. This week he meets a star, the Key...

7 min read

Showplan Operator of the Week – Compute Scalar

The third part of Fabiano's mission to describe the major Showplan Operators used by SQL Server's Query Optimiser continues with the 'Compute Scalar' operator. Fabiano...

6 min read

Showplan Operator of the Week – Concatenation

Fabiano continues in his mission to describe, one week at a time, all the major Showplan Operators used by SQL Server's Query Optimiser to build...

3 min read

Showplan Operator of the week – Assert

As part of his mission to explain the Query Optimiser in practical terms, Fabiano attempts the feat of describing, one week at a time, all...

7 min read

13 Things You Should Know About Statistics and the Query Optimizer

Fabiano launches into a sound technical explanation of the way that the query optimiser works in SQL Server with a mention of Brazilian Soccer stars...

24 min read

Controlling Execution Plans with Hints

The Query Optimizer gets it right most of the time, but occasionally it chooses a plan that isn't the best possible. You can give the...

38 min read