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Subject [GitHub] [flink] danny0405 commented on a change in pull request #14872: [FLINK-21162] [Blink Planner]use "IF(col = '' OR col IS NULL, 'a', 'b')",when co…
Date Tue, 23 Feb 2021 06:44:12 GMT

danny0405 commented on a change in pull request #14872:
URL: https://github.com/apache/flink/pull/14872#discussion_r580799779



##########
File path: flink-table/flink-table-planner-blink/src/main/java/org/apache/calcite/rex/RexSimplify.java
##########
@@ -2670,12 +2670,12 @@ private boolean accept_(RexNode e, List<RexNode> newTerms) {
                             e.getKind(),
                             newTerms);
                 case IS_NULL:
-                    if (negate) {
-                        return false;
-                    }
-                    final RexNode arg = ((RexCall) e).operands.get(0);
-                    return accept1(
-                            arg, e.getKind(), rexBuilder.makeNullLiteral(arg.getType()),
newTerms);
+                    /**
+                     *   when is_null in OR operate ,if change to search('',null) there was
a major mistake,
+                     *   because search has three return values (true,false,null),but OR
Operate only
+                     *   can return true or false,so wo can't change is_null or ... to search('',null);
+                     */
+                    return false;

Review comment:
       The changes forbidden the `is not null` simplification overall, which is beyond the
scope of the case. A better way it to expand the `SEARCH` operator after the `RexSimplify`
invocation, see `FlinkRexUtil.expandSearch`.




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