chunweilei commented on a change in pull request #1611: [CALCITE-3355] Deduce
whether CASE and COALESCE may produce NULL values
URL: https://github.com/apache/calcite/pull/1611#discussion_r352398475
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File path: core/src/main/java/org/apache/calcite/sql/fun/SqlCaseOperator.java
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@@ -230,14 +232,29 @@ private RelDataType inferTypeFromValidator(
SqlNodeList thenList = caseCall.getThenOperands();
ArrayList<SqlNode> nullList = new ArrayList<>();
List<RelDataType> argTypes = new ArrayList<>();
- for (SqlNode node : thenList) {
- argTypes.add(
- callBinding.getValidator().deriveType(
- callBinding.getScope(), node));
+
+ final SqlNodeList whenOperands = caseCall.getWhenOperands();
+ final RelDataTypeFactory typeFactory = callBinding.getTypeFactory();
+
+ final int size = thenList.getList().size();
+ for (int i = 0; i < size; i++) {
+ SqlNode node = thenList.get(i);
+ RelDataType type = callBinding.getValidator().deriveType(
+ callBinding.getScope(), node);
+ SqlNode operand = whenOperands.get(i);
+ if (operand.getKind() == SqlKind.IS_NOT_NULL && type.isNullable()) {
+ SqlBasicCall call = (SqlBasicCall) operand;
+ if (call.getOperandList().get(0).equalsDeep(node, Litmus.IGNORE)) {
+ // We're sure that the type is not nullable if the kind is IS NOT
NULL.
+ type = typeFactory.createTypeWithNullability(type, false);
+ }
+ }
Review comment:
IMO, it won't lose nullable information if there is IS_NULL expression. For
instance,
The type of `CASE WHEN name is null then name else 'NO' end` is:
1) nullable if `name` is nullable
2) not nullable if `name` is not nullable
Am I right?
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