silundong commented on code in PR #4400:
URL: https://github.com/apache/calcite/pull/4400#discussion_r2107006293
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core/src/main/java/org/apache/calcite/rex/RexSimplify.java:
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@@ -2364,6 +2366,37 @@ private RexNode simplifyCeilFloor(RexCall e) {
ImmutableList.of(operand, e.getOperands().get(1)));
}
+ /** Simplify TRIM function by eliminating nested duplication.
+ *
+ * <p>Examples:
+ * <ul>
+ *
+ * <li>{@code trim(trim(' aa '))} returns {@code trim(' aa ')}
+ *
+ * <li>{@code trim(BOTH ' ' from trim(BOTH ' ' from ' aa '))}
+ * returns {@code trim(BOTH ' ' from ' aa ')}
+ *
+ * <li>{@code trim(LEADING 'a' from trim(BOTH ' ' from ' aa '))} does not
change
+ *
+ * </ul>
+ */
+ private RexNode simplifyTrim(RexCall e) {
+ if (e.getOperands().size() != 3) {
+ return e;
+ }
+
+ if (e.getOperands().get(2) instanceof RexCall) {
Review Comment:
I think the simplification of idempotency alone is not sufficient. It should
be combined with general simplification. For example, if the third (and maybe
the second too) operand is not trim but another `RexCall`, there is a lack of
simplification for it.
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