[GitHub] [calcite] Aaaaaaron commented on a change in pull request #2253: [CALCITE-4385] Extracts and eliminates/merges the condition that has common expressions (Jiatao Tao)

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Aaaaaaron commented on a change in pull request #2253:
URL: https://github.com/apache/calcite/pull/2253#discussion_r535269911



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File path: core/src/main/java/org/apache/calcite/rex/RexSimplify.java
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@@ -1698,6 +1699,113 @@ RexNode simplifyAnd2ForUnknownAsFalse(List<RexNode> 
terms,
     }
   }
 
+  /**
+   * <p>Simplifies AND/OR condition that has common expressions,
+   * extracts and eliminates/merges them as much as possible.</p>
+   * <ul>
+   * <li>(a OR b) AND (a OR b OR c OR d) =&gt; (a OR b)
+   * <li>(a OR b OR c OR d) AND (a OR b OR e OR f) =&gt; (a OR b) OR ((c OR d) 
AND (e OR f))
+
+   * <li>(a AND b) OR (a AND b AND c) =&gt; (a AND b)
+   * <li>(a AND b AND c AND d) OR (a AND b AND e AND f) =&gt;
+   * (a AND b) AND ((c AND d) OR (e AND f))
+   * </ul>
+   * <p> The difference between {@link #simplifyAnd} is that {@link 
#simplifyAnd} mainly
+   * simplifies expressions whose answer can be determined without evaluating 
both sides,
+   * like: FALSE AND (xxx) =&gt; FALSE</p>
+   */
+  public RexNode eliminateCommonExprInCondition(RexNode node) {
+    if (!(node instanceof RexCall)) {
+      return node;
+    }
+    // Simplify children recursively
+    // so that when we simplify parent node
+    // the child node should be simplified
+    List<RexNode> operands = ((RexCall) node).getOperands();
+    List<RexNode> simplifiedChildren = operands.stream()
+        .map(this::eliminateCommonExprInCondition)
+        .collect(Collectors.toList());

Review comment:
       You are right, I'll add a condition, if node.kind is neither AND nor OR, 
just return the node, not into this recursion.




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