[GitHub] [incubator-iceberg] rdsr commented on a change in pull request #219: Fix concurrent access to lazy PartitionSpec methods

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

rdsr commented on a change in pull request #219: Fix concurrent access to lazy PartitionSpec methods
URL: https://github.com/apache/incubator-iceberg/pull/219#discussion_r294024626
 
 

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 File path: api/src/main/java/org/apache/iceberg/PartitionSpec.java
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 @@ -118,12 +118,18 @@ public int specId() {
 
   public Class<?>[] javaClasses() {
     if (lazyJavaClasses == null) {
-      this.lazyJavaClasses = new Class<?>[fields.length];
-      for (int i = 0; i < fields.length; i += 1) {
-        PartitionField field = fields[i];
-        Type sourceType = schema.findType(field.sourceId());
-        Type result = field.transform().getResultType(sourceType);
-        lazyJavaClasses[i] = result.typeId().javaClass();
+      synchronized (this) {
+        if (lazyJavaClasses == null) {
 
 Review comment:
   I believe  for the double-check idiom to reliably work these fields need to be `volatile`
   http://www.cs.umd.edu/~pugh/java/memoryModel/DoubleCheckedLocking.html

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