[GitHub] [incubator-iotdb] jt2594838 commented on a change in pull request #430: [IOTDB-193]Create schema automatically

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jt2594838 commented on a change in pull request #430: [IOTDB-193]Create schema automatically
URL: https://github.com/apache/incubator-iotdb/pull/430#discussion_r334353560
 
 

 ##########
 File path: server/src/main/java/org/apache/iotdb/db/utils/DeviceIdCache.java
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 @@ -0,0 +1,53 @@
+package org.apache.iotdb.db.utils;
+
+import org.apache.iotdb.db.exception.PathErrorException;
+import org.apache.iotdb.db.exception.StorageGroupException;
+import org.apache.iotdb.tsfile.exception.cache.CacheException;
+
+import java.util.List;
+import java.util.concurrent.CopyOnWriteArrayList;
+
+public abstract class DeviceIdCache {
 
 Review comment:
   The number of devices in a system is rather limited and holding all in memory is not a burden, so I do not suggest making it an LRU cache for meaningless overhead. 
   Nevertheless, I seriously doubt the performance of using a List, as the `contains()` method can be extremely slow even when there are only thousands of devices (not to mention you are using a COWList). I strongly recommend using a HashSet.

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