[BEAM-12853] VALUES produces a UNION, window can't be set afterwards

[apilloud]

This mitigates a bug in the PubSubTableProvider exposed by the calcite upgrade.

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Java
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[apilloud]

R: @ibzib

[ibzib]

Any idea why this test passed before?

[apilloud]

Before the calcite upgrade this plan was produced:

    BeamIOSinkRel(table=[[beam, message]], operation=[INSERT], flattened=[true])
      LogicalValues(tuples=[[{ 1970-01-01 00:00:00.001, 'person1', 80, true }, { 1970-01-01 00:00:00.002, 'person2', 70, false }]])

After the calcite upgrade this plan was produced:

    BeamIOSinkRel(table=[[beam, message]], operation=[INSERT], flattened=[true])
      LogicalUnion(all=[true])
        LogicalProject(EXPR$0=[1970-01-01 00:00:00.001:TIMESTAMP(6)], EXPR$1=['person1'], EXPR$2=[80], EXPR$3=[true])
          LogicalValues(tuples=[[{ 0 }]])
        LogicalProject(EXPR$0=[1970-01-01 00:00:00.002:TIMESTAMP(6)], EXPR$1=['person2'], EXPR$2=[70], EXPR$3=[false])
          LogicalValues(tuples=[[{ 0 }]])

The LogicalUnion gets turned into BeamUnionRel, which eventually becomes a CoGroup. Calcite could probably produce a simpler plan (we'd need to write or enable some more optimizer rules) but PubSubTableProvider is also broken here (it shouldn't depend on the pipeline not containing a CoGroup).

[ibzib]

LGTM