How to maintain Azure SQL Indexes and Statistics


There are a lot of work that Azure SQL saves from you, and most of the users we meet seems to believe that maintain the database indexes and statistics is one the missions you can forget when you migrate to Azure SQL.

Statistics objects, like in the box version of SQL have by default “Auto update” set to ON.

the condition to run the auto update is update for at least 20% + 500 rows in the table. if the condition is met, the update will occur when the optimizer need to generate execution plan against that table. so except that the update will take some time and use IO resources (which is very important information if you are on the cloud PAAS database) the update will read only 30% of the rows to generate the updated statistics therefore the statistic might not be 100% accurate.

  • You can use QDS to force the best plan for the statistics, but this is your responsibility to keep it up to date.

so, this maintenance still need to be done by the DBA, and if this has not been done, your database can suffer from poor performance just because of that.

I created a maintenance solution (Yes, I was inspired by Ola Hallengren’s solution) just that this one is lighter and suitable with Azure SQL DB (V12)

Now, all you have to do is download the T-SQL script, execute it on your Azure SQL DB and execute the maintenance procedure.

Quick remark about the options you have:

exec  AzureSQLMaintenance @operation,@mode

@operation: {all, index, statistics} (no default)

statistics: will run only statistics update

index: will run only index maintenance

@mode: {smart, dummy} (Default: smart)

smart: will touch only modified statistics and choose index maintenance by % of fragmentation

dummy: will run through all statistics or indexes.

 

Procedure Code:

AzureSQLMaintenance

 

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