NobiGo commented on code in PR #4403:
URL: https://github.com/apache/calcite/pull/4403#discussion_r2123413147
##########
core/src/main/java/org/apache/calcite/sql/fun/SqlInternalOperators.java:
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@@ -224,6 +224,40 @@ private SqlInternalOperators() {
public static final SqlAggFunction LITERAL_AGG =
SqlLiteralAggFunction.INSTANCE;
+ /** CAST NOT NULL operator used for cast expression to make it non-nullable
in SqlNode.
+ *
+ * <p>For example:
+ * <pre>{@code COALESCE(a,b)
+ * }</pre>
+ *
+ * <p>is converted to
+ *
+ * <pre>{@code CASE WHEN a is not null THEN a ELSE b
+ * }</pre>
+ * by {@code SqlCoalesceFunction#rewriteCall}.
+ *
+ * <p>When a is nullable and b is non-nullable, the {@code COALESCE(a,b)}
data type will be
+ * non-nullable and {@code CASE WHEN a is not null THEN a ELSE b} data type
will be nullable.
Review Comment:
CALCITE-3675 can't resolve this issue.
```
@Test void testCoalesceSubquery() {
final String sql = "SELECT"
+ " deptno, "
+ " coalesce((select sum(empno) from emp "
+ " where deptno = emp.deptno limit 1), 0) as w "
+ "FROM dept";
sql(sql).ok();
}
```
This SQL generates RelNode is:
```
LogicalProject(DEPTNO=[$0], W=[CASE(IS NOT NULL($2), $3, 0)])
LogicalJoin(condition=[true], joinType=[left])
LogicalJoin(condition=[true], joinType=[left])
LogicalTableScan(table=[[CATALOG, SALES, DEPT]])
LogicalSort(fetch=[1])
LogicalAggregate(group=[{}], EXPR$0=[SUM($0)])
LogicalProject(EMPNO=[$0])
LogicalFilter(condition=[=($7, $7)])
LogicalTableScan(table=[[CATALOG, SALES, EMP]])
LogicalSort(fetch=[1])
LogicalAggregate(group=[{}], EXPR$0=[SUM($0)])
LogicalProject(EMPNO=[$0])
LogicalFilter(condition=[=($7, $7)])
LogicalTableScan(table=[[CATALOG, SALES, EMP]])
```
When use the condition
`isNotNullCall.getOperands().get(0).equals(thenNode)`, it is failed(`$2 != $3`).
This PR will make CALCITE-3675 unnecessary.
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