[GitHub] [iceberg] rdblue commented on a change in pull request #2062: [CORE] Add in a NOT_STARTS_WITH operator

[GitBox <gi...@apache.org>]

rdblue commented on a change in pull request #2062:
URL: https://github.com/apache/iceberg/pull/2062#discussion_r772652476



##########
File path: api/src/main/java/org/apache/iceberg/expressions/InclusiveMetricsEvaluator.java
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@@ -408,6 +408,54 @@ public Boolean or(Boolean leftResult, Boolean rightResult) {
       return ROWS_MIGHT_MATCH;
     }
 
+    @Override
+    public <T> Boolean notStartsWith(BoundReference<T> ref, Literal<T> lit) {
+      Integer id = ref.fieldId();
+
+      // Iceberg does not implement SQL 3-boolean logic. Return ROWS_MIGHT_MATCH
+      // to allow the query engine to make its own decision regarding NULL values.
+      if (mayContainNull(id)) {
+        return ROWS_MIGHT_MATCH;

Review comment:
       I don't think this is correct. In SQL, `null LIKE 'a%'` should result in `null`, and `null NOT LIKE 'a%'` should also result in `null`. So in both cases, `null` does not match and is ignored.
   
   Here, I think this should use `containsNullsOnly(id)`. In that case, we know that no rows match and can exit before checking bounds.




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