[CALCITE-3926] CannotPlanException when an empty LogicalValues requires a certain collation

• Type: Bug
• Status: Closed
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: 1.22.0
• Fix Version/s: 1.23.0
• Component/s: core
• Labels: pull-request-available
• Assignee: Ruben Q L
• Reporter: Ruben Q L
• Created: 15/Apr/20 12:13
• Updated: 24/May/20 12:00
• Resolved: 07/May/20 09:45

Description

The issue can be reproduced with the following test (in RelBuilderTest.java):

  @Test void testEmptyValues() throws Exception {
    final RelBuilder builder = RelBuilder.create(config().build());
    final RelNode root =
        builder
            .scan("DEPT")
            .filter(builder.literal(false)) // generates an empty LogicalValues
            .sort(
                builder.field("DNAME"),
                builder.field("DEPTNO"))
            .build();
    try (PreparedStatement preparedStatement = RelRunners.run(root)) {
      final String s = CalciteAssert.toString(preparedStatement.executeQuery());
      final String result = "";
      assertThat(s, is(result));
    }
  }

The test fails with the following message:

Caused by: org.apache.calcite.plan.RelOptPlanner$CannotPlanException: There are not enough rules to produce a node with desired properties: convention=ENUMERABLE, sort=[1, 0].
Missing conversion is LogicalValues[convention: NONE -> ENUMERABLE, sort: [[0, 1, 2], [1, 2], [2]] -> [1, 0]]
There is 1 empty subset: rel#14:Subset#0.ENUMERABLE.[1, 0], the relevant part of the original plan is as follows
1:LogicalValues(tuples=[[]])

The issue seems to be caused by the empty values: Scan + Filter(false) => LogicalValues(tuples=[[]]).
This empty LogicalValues has as collation (in case of 3 fields): [[0, 1, 2], [1, 2], [2]]; and in the plan we are requesting as sort collation [1, 0].
This could be achieved by: EnumerableSort(sort=[1,0]) + EnumerableValues(tuples=[[]]) ; but for some reason this plan is not generated.

It seems the issue was somehow introduced by CALCITE-3886
https://github.com/apache/calcite/commit/08f4a9889728f94903ff424ed9c20d940b821af5

Issue Links

• is caused by: CALCITE-3886 Execute substitution rule according to the order they get matched
• links to: GitHub Pull Request #1918