[GitHub] [doris] morrySnow commented on a diff in pull request #18975: [opt](Nereids) simplify decimalv3 comparison predicate

["morrySnow (via GitHub)" <gi...@apache.org>]

morrySnow commented on code in PR #18975:
URL: https://github.com/apache/doris/pull/18975#discussion_r1177384207


##########
fe/fe-core/src/main/java/org/apache/doris/nereids/rules/expression/rules/SimplifyDecimalV3Comparison.java:
##########
@@ -0,0 +1,77 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License.  You may obtain a copy of the License at
+//
+//   http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied.  See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+package org.apache.doris.nereids.rules.expression.rules;
+
+import org.apache.doris.nereids.rules.expression.AbstractExpressionRewriteRule;
+import org.apache.doris.nereids.rules.expression.ExpressionRewriteContext;
+import org.apache.doris.nereids.trees.expressions.Cast;
+import org.apache.doris.nereids.trees.expressions.ComparisonPredicate;
+import org.apache.doris.nereids.trees.expressions.Expression;
+import org.apache.doris.nereids.trees.expressions.literal.DecimalV3Literal;
+import org.apache.doris.nereids.types.DecimalV3Type;
+
+import com.google.common.base.Preconditions;
+
+import java.math.BigDecimal;
+
+/**
+ * if we have a column with decimalv3 type and set enable_decimal_conversion = false.
+ * we have a column named col1 with type decimalv3(15, 2)
+ * and we have a comparison like col1 > 0.5 + 0.1
+ * then the result type of 0.5 + 0.1 is decimalv2(27, 9)
+ * and the col1 need to convert to decimalv3(27, 9) to match the precision of right hand
+ * this rule simplify it from cast(col1 as decimalv3(27, 9)) > 0.6 to col1 > 0.6
+ */
+public class SimplifyDecimalV3Comparison extends AbstractExpressionRewriteRule {
+
+    public static SimplifyDecimalV3Comparison INSTANCE = new SimplifyDecimalV3Comparison();
+
+    @Override
+    public Expression visitComparisonPredicate(ComparisonPredicate cp, ExpressionRewriteContext context) {
+        Expression left = rewrite(cp.left(), context);
+        Expression right = rewrite(cp.right(), context);
+
+        if (left.getDataType() instanceof DecimalV3Type
+                && left instanceof Cast
+                && ((Cast) left).child().getDataType() instanceof DecimalV3Type
+                && right instanceof DecimalV3Literal) {
+            return doProcess(cp, (Cast) left, (DecimalV3Literal) right);
+        }
+
+        if (left != cp.left() || right != cp.right()) {
+            return cp.withChildren(left, right);
+        } else {
+            return cp;
+        }
+    }
+
+    private Expression doProcess(ComparisonPredicate cp, Cast left, DecimalV3Literal right) {
+        BigDecimal trailingZerosValue = right.getValue().stripTrailingZeros();
+        int scale = trailingZerosValue.scale();
+        int precision = Math.max(scale, trailingZerosValue.precision());
+        Expression castChild = left.child();
+        Preconditions.checkState(castChild.getDataType() instanceof DecimalV3Type);
+        DecimalV3Type leftType = (DecimalV3Type) castChild.getDataType();
+        if (leftType.getPrecision() < precision || leftType.getScale() < scale) {
+            return cp.withChildren(left, right);

Review Comment:
   good idea~



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