Support row order independent checking in check_column

[filipsch]

When checking columns, there should be an option to compare the columns without accounting for the order of the rows. This can be done brutally, by simply ordering the column and seeing what happens, or ordering by a certain column, and keeping the permutation to order other columns accordingly (which is more correct I think). As this can raise the number of steps in checking quite a bit, I think you should make this opt-in to start with.

[machow]

in production, using a special function sort_rows inside check_result. How about seeing how things go for the intro to sql course, and then making if opt-in if there's trouble? My feelings toward sorting have softened :p

[filipsch]

@machow The intro courses will not pose any difficulties performance-wise I think, so good idea! Glad to hear about the softening!

[machow]

@filipsch given that one of the intro-sql exercises was timing out, due to trying to COUNT and GROUP BY a table with 9 million rows. I think I might be a bit leery again...!

[machow]

This is currently possible through sort_rows, it just needs to be exposed to SCT creators.