englefly commented on code in PR #52742:
URL: https://github.com/apache/doris/pull/52742#discussion_r2183961043
##########
fe/fe-core/src/main/java/org/apache/doris/nereids/rules/rewrite/EliminateEmptyRelation.java:
##########
@@ -102,6 +104,22 @@ public List<Rule> buildRules() {
return new LogicalEmptyRelation(
ConnectContext.get().getStatementContext().getNextRelationId(),
union.getOutput());
+ } else if (union.getConstantExprsList().size() == 1) {
+ List<NamedExpression> constantExprs =
union.getConstantExprsList().get(0);
+ ImmutableList.Builder<NamedExpression>
newOneRowRelationOutput
+ =
ImmutableList.builderWithExpectedSize(constantExprs.size());
+ for (int i = 0; i < constantExprs.size(); i++) {
+ NamedExpression setOutput =
union.getOutput().get(i);
+ NamedExpression constantExpr =
constantExprs.get(i);
+ Expression realConstantExpr = constantExpr
instanceof Alias
+ ? ((Alias) constantExpr).child() :
constantExpr;
+ Alias oneRowRelationOutput = new Alias(
Review Comment:
when constantExpr is alias, why construct an alias again?
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