xiedeyantu commented on code in PR #4400:
URL: https://github.com/apache/calcite/pull/4400#discussion_r2122468746
##########
core/src/test/java/org/apache/calcite/test/RexImplicationCheckerTest.java:
##########
@@ -360,6 +361,97 @@ public class RexImplicationCheckerTest {
hasToString("2014"));
}
+ /** Test case for
+ * <a
href="https://issues.apache.org/jira/browse/CALCITE-7042";>[CALCITE-7042]
+ * Eliminate nested TRIM calls, exploiting the fact that TRIM is
idempotent</a>. */
+ @Test void testSimplifyIdempotentFunctions() {
Review Comment:
I think we should pass a test case like the following, even if the third
parameter in trim is not a trim expression, we should continue to recursively
simplify. The floor I used may not be very appropriate, but I just want to
express this idea.
```
@Test void testSimplifyIdempotentFunctions() {
final Fixture f = new Fixture();
RexLiteral trimBoth = f.rexBuilder.makeLiteral("BOTH");
RexLiteral trimed = f.rexBuilder.makeLiteral("a");
final RexNode literalTs =
f.timestampLiteral(new TimestampString("2010-10-10 00:00:00"));
final RexNode innerFloorCall =
f.rexBuilder.makeCall(SqlStdOperatorTable.FLOOR, literalTs,
f.rexBuilder.makeFlag(TimeUnitRange.YEAR));
final RexNode outerFloorCall =
f.rexBuilder.makeCall(SqlStdOperatorTable.FLOOR, innerFloorCall,
f.rexBuilder.makeFlag(TimeUnitRange.YEAR));
RexCall floorSimplifiedExpr =
(RexCall) f.simplify.simplifyPreservingType(outerFloorCall,
RexUnknownAs.UNKNOWN, true);
assertThat(floorSimplifiedExpr,
hasToString("FLOOR(2010-10-10 00:00:00, FLAG(YEAR))"));
RelDataType varcharType =
f.typeFactory.createSqlType(SqlTypeName.VARCHAR);
RexCall floorSimplifiedExpr2 =
(RexCall)
f.simplify.simplifyPreservingType(f.rexBuilder.makeCast(varcharType,
outerFloorCall),
RexUnknownAs.UNKNOWN, true);
assertThat(floorSimplifiedExpr2,
hasToString("CAST(FLOOR(2010-10-10 00:00:00, FLAG(YEAR))):VARCHAR
NOT NULL"));
RexCall innerTrimCall =
(RexCall) f.rexBuilder.makeCall(SqlStdOperatorTable.TRIM, trimBoth,
trimed,
f.rexBuilder.makeCast(varcharType, outerFloorCall));
RexCall outerTrimCall =
(RexCall) f.rexBuilder.makeCall(SqlStdOperatorTable.TRIM, trimBoth,
trimed, innerTrimCall);
RexCall trimSimplifiedCall =
(RexCall) f.simplify.simplifyPreservingType(outerTrimCall,
RexUnknownAs.UNKNOWN, true);
// We will get this Currently
// assertThat(trimSimplifiedCall,
hasToString("TRIM('BOTH', 'a', CAST(FLOOR(FLOOR(2010-10-10 00:00:00,
"
+ "FLAG(YEAR)), FLAG(YEAR))):VARCHAR NOT NULL)"));
// I think We hope to get like this
assertThat(trimSimplifiedCall,
hasToString("TRIM('BOTH', 'a', CAST(FLOOR(2010-10-10 00:00:00, "
+ "FLAG(YEAR))):VARCHAR NOT NULL)"));
}
```
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