[CALCITE-5394] RelToSql converter fails when semi-join is under a join node

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 1.32.0
• Fix Version/s: 1.33.0
• Labels: pull-request-available
• Assignee: Jiajun Xie
• Reporter: Leonid Chistov
• Created: 21/Nov/22 10:16
• Updated: 07/Feb/23 22:33
• Resolved: 12/Dec/22 09:47

Description

The following test case would fail if added to RelToSqlConverterTest.java:

@Test void testSemiJoinUnderJoin() {
  final RelBuilder builder = relBuilder();
  final RelNode base = builder
      .scan("EMP")
      .scan("EMP")
      .join(
          JoinRelType.SEMI, builder.equals(
              builder.field(2, 0, "EMPNO"),
              builder.field(2, 1, "EMPNO")))
      .build();
  final RelNode root = builder
      .scan("DEPT")
      .push(base)
      .join(
          JoinRelType.INNER, builder.equals(
              builder.field(2, 1, "DEPTNO"),
              builder.field(2, 0, "DEPTNO")))
      .project(builder.field("DEPTNO"))
      .build();
  toSql(root);
} 

The exception is:

alias
java.lang.NullPointerException: alias
    at java.base/java.util.Objects.requireNonNull(Objects.java:233)
    at org.apache.calcite.rel.rel2sql.SqlImplementor.collectAliases(SqlImplementor.java:493)
    at org.apache.calcite.rel.rel2sql.SqlImplementor.collectAliases(SqlImplementor.java:491)
    at org.apache.calcite.rel.rel2sql.SqlImplementor.result(SqlImplementor.java:476)
    at org.apache.calcite.rel.rel2sql.RelToSqlConverter.visit(RelToSqlConverter.java:246) 

Cause of failure seems to be that `RelToSqlConverter::visitAntiOrSemiJoin` rewrites semi-join as select with no associated alias.

Issue Links

• links to: GitHub Pull Request #2982