Row count comparison partitions

[vijaykiran]

See docs/soda_checks_yaml.md. L69 find the TODO

Consider if we should push it to the user to define the right variables and avoid clashes between the variable names when comparing?

So will we map the variables of 1 table to the other as the user makes the reference in the check? Or do we force the user to submit the right variables in the scan as input.