[GitHub] [calcite] Aaaaaaron commented on a change in pull request #2253: [CALCITE-4385] Simplifies AND/OR condition that has common expressions, extract and eliminate/merge them as much as possible (Jiatao Tao)

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Aaaaaaron commented on a change in pull request #2253:
URL: https://github.com/apache/calcite/pull/2253#discussion_r521021422



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File path: core/src/main/java/org/apache/calcite/rex/RexSimplify.java
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@@ -1689,6 +1690,123 @@ RexNode simplifyAnd2ForUnknownAsFalse(List<RexNode> 
terms,
     }
   }
 
+  /**
+   * <p>Simplifies AND/OR condition that has common expressions,
+   * extract and eliminate/merge 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 call) {

Review comment:
       See CALCITE-4375, I split sub-task for this JIRA, you can see the 
comment I reply Julian, "and later we can think to add this logic to 
RexSimplify's main process or just used to simplify the join condition."
   
   IMO, we can first use it to  simplify the join condition, latter we can add 
this to RexSimplify's main process like Spark.




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