[GitHub] [hadoop-ozone] avijayanhwx commented on a change in pull request #654: HDDS-3150. Implement getIfExist in Table and use it in CreateKey/File

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avijayanhwx commented on a change in pull request #654: HDDS-3150. Implement getIfExist in Table and use it in CreateKey/File
URL: https://github.com/apache/hadoop-ozone/pull/654#discussion_r390664487
 
 

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 File path: hadoop-hdds/framework/src/main/java/org/apache/hadoop/hdds/utils/db/RDBTable.java
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 @@ -155,6 +155,32 @@ public boolean isExist(byte[] key) throws IOException {
     }
   }
 
+  @Override
+  public byte[] getIfExist(byte[] key) throws IOException {
+    try {
+      // RocksDB#keyMayExist
+      // If the key definitely does not exist in the database, then this
+      // method returns false, else true.
+      rdbMetrics.incNumDBKeyGetIfExistChecks();
+      StringBuilder outValue = new StringBuilder();
+      boolean keyMayExist = db.keyMayExist(handle, key, outValue);
+      if (keyMayExist) {
+        // Not using out value from string builder, as that is causing
+        // IllegalArgumentException during protobuf parsing.
 
 Review comment:
   Does this mean we cannot use the outValue that we pass in? If 'keyMayExist' returns true, and the value is indeed present in the block cache, I believe the outValue will have the data.  

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