rkondakov commented on a change in pull request #1959:
URL: https://github.com/apache/calcite/pull/1959#discussion_r422699962
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File path: core/src/main/java/org/apache/calcite/util/mapping/Mappings.java
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@@ -1245,12 +1271,30 @@ public void set(int source, int target) {
assert isValid();
}
+ /**
+ * Returns the source that a target maps to, or -1 if it is not mapped.
+ *
+ * @throws NoElementException if target is out of sources range.
+ */
public int getSourceOpt(int target) {
- return sources[target];
+ try {
+ return sources[target];
+ } catch (ArrayIndexOutOfBoundsException e) {
+ throw new Mappings.NoElementException("invalid target " + target);
Review comment:
Hmm.. it is also said in javadoc that `FunctionMapping#getTarget` throws
`NoElementException if source is not mapped`. Which is closer to the truth. In
this case `NoElementException` is valid move.
I also noticed that for some mappings it was an original behavior, i.e.
`Permutation#getTarget()`. I just made the fix by analogy with this legacy
behavior.
I agree that it is far from perfect. May be `IllegalArgumentException` is
more suitable here. But I think that `ArrayIndexOutOfBoundsException` is not
the best choice.
What if I just change the javadoc of `NoElementException` to `Should be
thrown when source or target is not mapped`?
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