julianhyde commented on a change in pull request #1959:
URL: https://github.com/apache/calcite/pull/1959#discussion_r422804623
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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:
`NoElementException` is for the case where the source is within the
domain (0 .. sourceCount - 1) but no mapping is present.
If the source is outside the domain - less than 0 or greater than or equal
to sourceCount - then `IndexOutOfBoundsException` would be appropriate.
I don't think `getSourceOpt` or `getTargetOpt` should ever throw
`NoElementException`. They have a different way to communicate no element -
namely by returning -1.
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