The blog has a typo. The first line needs to have the text in uppercase: > query WHERE name = ‘ABC’ > create an indexed UPPER(name) column The point is that

The blog has a typo. The first line needs to have the text in uppercase: > query WHERE name = ‘ABC’ > create an indexed UPPER(name) column The point is that the index itself is already on the data with the function applied. So it's not a full scan, the way the original query was. Of course, in this particular example you just want to use a case-insensitive collation to begin with. But the general concept is valid.