Decide how we want to throw/capture error during execution

[zyang-tudb]

There could be error during execution, either because internal problem or invalid query (for example skip with expression evaluated to zero or negative int). We need to think about how we want to throw and capture execution errors. Exception is one way, but I'm not sure whether it's the best.

[LianxinGao]

neo4j will give a exception:

match (n:Person) return n skip -1

Invalid input '-1' is not a valid value, must be a positive integer (line 1, column 32 (offset: 31))
"match (n:Person) return n skip -1"

[zyang-tudb]

There are two options:

• try-catch-finally This looks similar to Java's. However, Scala has no CheckedException, meaning we cannot declare types of Exception that might be thrown from a function or have the guarantee that all thrown Exceptions will be handled.
• Try-Success-Failure This requires a function that might generate error to return a Try object. Try object can be Success or Failure. Caller have to match Try to either Success or Failure. This guarantees all possible Exceptions can be handled as long as we don' convert Try to Success by force.

IMO we should take the second approach.