[GitHub] [iceberg] rdsr commented on a change in pull request #1169: Reset temporary states inside thread local objects

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

rdsr commented on a change in pull request #1169:
URL: https://github.com/apache/iceberg/pull/1169#discussion_r449850015



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File path: api/src/main/java/org/apache/iceberg/expressions/InclusiveMetricsEvaluator.java
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@@ -102,7 +102,15 @@ private boolean eval(ContentFile<?> file) {
       this.lowerBounds = file.lowerBounds();
       this.upperBounds = file.upperBounds();
 
-      return ExpressionVisitors.visitEvaluator(expr, this);
+      try {
+        return ExpressionVisitors.visitEvaluator(expr, this);
+      } finally {
+        // allow temporary state to be collected because this is in a thread-local
+        this.valueCounts = null;

Review comment:
       I think this is subtle and hard to understand on why this is needed. I prefer the the new visitor approach as you guys discussed in #1139. 




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