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

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

RussellSpitzer commented on a change in pull request #2062:
URL: https://github.com/apache/iceberg/pull/2062#discussion_r770852322



##########
File path: api/src/main/java/org/apache/iceberg/expressions/InclusiveMetricsEvaluator.java
##########
@@ -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;
+      }
+
+      ByteBuffer prefixAsBytes = lit.toByteBuffer();
+
+      Comparator<ByteBuffer> comparator = Comparators.unsignedBytes();
+
+      // notStartsWith will match unless all values must start with the prefix. This happens when the lower and upper
+      // bounds both start with the prefix.
+      if (lowerBounds != null && upperBounds != null &&
+          lowerBounds.containsKey(id) && upperBounds.containsKey(id)) {
+        ByteBuffer lower = lowerBounds.get(id);
+        // if lower is shorter than the prefix, it can't start with the prefix

Review comment:
       I think let's try to keep pronouns out of this since I have difficulty parsing this statement. I'm always confused though.
   
   // if lower is shorter than the prefix then lower doesn't start with the prefix




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