Estimated Number Of Rows To Be Read

Rob Farley discusses a successful Connect item’s implementation:

I opened it up, and sure enough, no sign of that 7,276 value. It looks just the same as the estimated plan I just showed.

Getting plans out of the cache is where the estimated values come into their own. It’s not just that I’d prefer to not actually run potentially-expensive queries on customer databases. Querying the plan cache is one thing, but running queries to get the actuals – that’s a lot harder.

With SQL 2016 SP1 installed, thanks to that Connect item, I can now see the Estimated Number of Rows to be Read property in estimated plans, and in the plan cache. The operator tooltip shown here is taken from the cache, and I can easily see that Estimated property showing 7,276. This is shown from Management Studio because Plan Explorer doesn’t yet call out this property explicitly:

If you’re looking to use SQL Server 2016 SP1, read the whole thing; this will make query tuning without running those horribly expensive queries a bit easier.

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