xwkuang5 commented on a change in pull request #2312:
URL: https://github.com/apache/calcite/pull/2312#discussion_r552327648
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File path: core/src/main/java/org/apache/calcite/sql/fun/SqlCastFunction.java
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@@ -93,6 +95,29 @@ public SqlCastFunction() {
//~ Methods ----------------------------------------------------------------
+ @Override public void validateCall(final SqlCall call, final SqlValidator
validator,
+ final SqlValidatorScope scope,
+ final SqlValidatorScope operandScope) {
+ try {
+ super.validateCall(call, validator, scope, operandScope);
+ } catch (UnsupportedOperationException ex) {
+ assert call.operandCount() == 2;
+ throw validator.newValidationError(call,
+ RESOURCE.cannotCastToType(call.operand(1).toString()));
+ }
+ }
+
+ @Override public RelDataType deriveType(final SqlValidator validator,
+ final SqlValidatorScope scope, final SqlCall call) {
+ try {
+ return super.deriveType(validator, scope, call);
+ } catch (UnsupportedOperationException ex) {
+ assert call.operandCount() == 2;
+ throw validator.newValidationError(call,
+ RESOURCE.cannotCastToType(call.operand(1).toString()));
Review comment:
You are right, I think it should.
However, I found that incorporating the cause will make this a much larger
change than it is right now. Currently, `SqlValidator` interface only has a
`newValidationError` method that takes an `ExInst`, which represents an
exception without cause. We can add a new method `newValidationErrorWithCause`
to the `SqlValidator` interface. There will need to be some refactoring for
`SqlUtil.newContextException` as well. Note that hacking this by adding
`initCause` to the resulting exception returned from `newValidationError` does
not work because the exception has already been initialized with a cause during
construction.
Overall, I think this can be split into a refactoring commit + this commit.
I think the combined LOC will be >100. Not sure if the extra code added and
refactoring is worth the benefit: on one hand, having the cause provides better
context. On the other hand, the cast function is not that complicated
`CAST(value as type)` and the current exception message might be enough for
debugging.
What do you think?
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