What is a constant scan?

What is a constant scan?

The Constant Scan logical and physical operator introduces a constant row into a query. It will return either zero or one row, which usually contains no columns. A Compute Scalar operator is often used to add columns to the row produced by a Constant Scan.

What is constant scan SQL Server?

A constant scan is a construct within SQL Server that builds a location for storing data, usually a logical location, not a physical one like with a hash or a spool. In your case, the multi-statement function is what the constant scan represents, and it is indicative of poor performance.

Which is better a scan or a seek?

But because Scans have a much higher read rate, they can frequently beat Seeks as long as the ratio of Discarded Rows to Matching Rows is lower than the ratio of Scan rows/sec VS. Seek rows/sec. Questions?

Is it bad to do an index seek?

An index seek operation isn’t necessarily good, nor is an index scan inherently bad. To cast judgment, dig deeper. Its execution plan does a clustered index seek – it’s going to jump to what happens to be the first row in the table (Id -1) and read through all of the rows in the entire table, looking for ones who have a reputation < 0:

Which is more efficient to seek down or seek down the index?

It then decides if it is more efficient to seek down the index, or scan the whole leaf level of the index (in this case, it involves touching every page in the table, because it is a clustered index) It does this by looking at a number of things. Firstly, it guesses how many rows/pages it will need to scan.

What does seek mean in SQL Server logical reads?

It’s technically a “seek” because SQL Server is seeking to a particular value, and then reading out the rows from there. Logical reads shows more proof that it’s reading the entire table: That’s a lot of pages. That’s not what you think of when I say “seek.” Here’s what “seek” and “scan” really mean.