Using TIMESTAMPDIFF() with RelBuilder

[Thomas D'Silva]

Hi,

I get an error while using TIMESTAMPDIFF with RelBuilder. For this example
code

  @Test void testRun2() throws Exception {
    // Equivalent SQL:
    //   SELECT TIMESTAMP(SECOND, HIREDATE, TIMESTAMP'1970-01-01') FROM EMP
    final RelBuilder builder = RelBuilder.create(config().build());
    RelNode root =
        builder.scan("EMP")
            .project(
                builder.getRexBuilder().makeCall(
                    SqlStdOperatorTable.TIMESTAMP_DIFF,
                    builder.getRexBuilder().makeFlag(TimeUnit.SECOND),
                    builder.field("HIREDATE"),

builder.getRexBuilder().makeTimestampLiteral(TimestampString.fromMillisSinceEpoch(0),
0)
                )
            )
            .build();

    try (PreparedStatement preparedStatement = RelRunners.run(root)) {
      String s = CalciteAssert.toString(preparedStatement.executeQuery());
      final String result = "";
      assertThat(s, is(result));
    }
  }

I get an exception

Suppressed: java.lang.RuntimeException: cannot translate call
TIMESTAMPDIFF($t8, $t4, $t9)
at
org.apache.calcite.adapter.enumerable.RexToLixTranslator.visitCall(RexToLixTranslator.java:1157)
at
org.apache.calcite.adapter.enumerable.RexToLixTranslator.visitCall(RexToLixTranslator.java:98)

When a sql string is executed it appears that the TIMESTAMPDIFF function is
converted to a difference of two timestamps (
https://github.com/apache/calcite/blob/a03586c26e1888daebabb271b603fd2871d6a359/core/src/main/java/org/apache/calcite/sql2rel/StandardConvertletTable.java#L1853
).

Is there a way to use the TIMESTAMPDIFF() with RelBuilder or would I have
to do a similar translation as is done in TimestampDiffConvertlet?

Thank you,
Thomas