which: "which" method for CrunchLogicalExpr
Description
NOTE: this isn't correct. Don't use it yet.
Usage
"which"(x, arr.ind = FALSE, useNames = TRUE)
Value
Integer row indices where x is true. Note that this does not
return a Crunch expression. Use this when you need to translate to R values.
For filtering a Crunch expression by x, don't use which.