rubenada commented on a change in pull request #1338: [CALCITE-3210] Fix the
bug that RelToSqlConverter converts "cast(null as $type)" just as null
URL: https://github.com/apache/calcite/pull/1338#discussion_r308153807
##########
File path:
core/src/main/java/org/apache/calcite/rel/rel2sql/RelToSqlConverter.java
##########
@@ -195,15 +198,54 @@ public Result visit(Project e) {
final Builder builder =
x.builder(e, Clause.SELECT);
final List<SqlNode> selectList = new ArrayList<>();
+
+ boolean checkNull = isCastNullNeeded(stack);
for (RexNode ref : e.getChildExps()) {
SqlNode sqlExpr = builder.context.toSql(null, ref);
+ if (checkNull && SqlUtil.isNullLiteral(sqlExpr, false)) {
+ sqlExpr = castNullType(sqlExpr,
e.getRowType().getFieldList().get(selectList.size()));
+ }
addSelect(selectList, sqlExpr, e.getRowType());
}
builder.setSelect(new SqlNodeList(selectList, POS));
return builder.result();
}
+ /**
+ * Check whether null item in select need to be casted
+ * @param stack stack of visit
+ * @return If null need to be casted then return true, otherwise return
false.
+ */
+ private static boolean isCastNullNeeded(Deque<Frame> stack) {
+ final int stackSize = stack.size();
+ for (int i = 1; i < stackSize; i++) {
+ RelNode currentNode = Iterables.get(stack, i).r;
+ if (!(currentNode instanceof SingleRel)) {
Review comment:
The consequence of both conditions is that "null casting is needed". I think
the code will be more concise by combining the conditions, but if you think it
is more clear to have them separate, I'm not against it, let's keep it as it is.
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