hsyuan commented on a change in pull request #1286: CALCITE-3155 : Fixing bug
in the unparse of UNION_ALL SqlSetOperator when it has no operands
URL: https://github.com/apache/calcite/pull/1286#discussion_r298811054
##########
File path:
core/src/main/java/org/apache/calcite/rel/rel2sql/RelToSqlConverter.java
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@@ -390,7 +390,22 @@ public Result visit(Values e) {
new SqlIdentifier("DUAL", POS), null, null,
null, null, null, null, null));
}
- if (list.size() == 1) {
+ if (list.isEmpty()) {
+ //In this case we need to construct the following query:
+ // SELECT NULL as C0, NULL as C1, NULL as C2 ... FROM DUAL WHERE FALSE
+ //This would return an empty result set with the same number of
columns as the field names.
Review comment:
Please leave a space after //
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