[GitHub] [incubator-hudi] bvaradar commented on a change in pull request #972: [HUDI-313] Fix select count star error when querying a realtime table

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bvaradar commented on a change in pull request #972: [HUDI-313] Fix select count star error when querying a realtime table
URL: https://github.com/apache/incubator-hudi/pull/972#discussion_r340751698
 
 

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 File path: hudi-hadoop-mr/src/main/java/org/apache/hudi/hadoop/realtime/HoodieParquetRealtimeInputFormat.java
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 @@ -197,10 +197,27 @@ private static synchronized Configuration addRequiredProjectionFields(Configurat
     return configuration;
   }
 
+  /**
+   * Hive will append read columns' ids to old columns' ids during getRecordReader. In some cases, e.g. SELECT COUNT(*),
+   * the read columns' id is an empty string and Hive will combine it with Hoodie required projection ids and becomes
+   * e.g. ",2,0,3" and will cause an error. This method is used to avoid this situation.
+   */
+  private static synchronized Configuration cleanProjectionColumnIds(Configuration conf) {
 
 Review comment:
   @zhedoubushishi : You can synchronize on the passed conf object instead of static synchronization which becomes a global lock at the JVM level. 
   
   You can do something like 
   synchronized(conf) {
    ....
   }
   inside your cleanProjectionColumnIds. 

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