Add CESQL SPLIT and ELEMENT_AT functions

[Cali0707]

When working with CE string attributes in a CESQL context, it can be useful to "split" the attribute. We currently support various concatenation operations, but no split function is in the "required functions" section of the spec.

I think having a function along the lines of:

SPLIT(string, separator)

would be very helpful, especially in conjunction with ELEMENT_AT:

ELEMENT_AT(SPLIT(string, separator), index)

Happy to discuss exactly how these function signatures should look, as well as their semantics

[Cali0707]

cc @duglin @jskeet any thoughts here?

[jskeet]

I have no opinions on CESQL I'm afraid. I do worry about feature creep, mind you.

[duglin]

Since there is no ELEMENT_AT function yet, I assume this means also introducing the notion of arrays, right? And then possibly other array related functions/operators?

While I don't have a special use case in mind, I can see the value in a SPLIT type of function, but the did you really want to open the "array can of worms"?

What about simplified functions, like CUT_BEFORE(str, separator) that returns the string before the separator? And CUT_AFTER() for the string after it? Think of go's cut(). Then you can avoid array processing.

[Cali0707]

What about simplified functions, like CUT_BEFORE(str, separator) that returns the string before the separator? And CUT_AFTER() for the string after it? Think of go's cut(). Then you can avoid array processing.

yes that would work great for my use case, and be much simpler.

Thanks for the recommendation @duglin !