[GitHub] [hbase] openinx commented on a change in pull request #242: HBASE-22422 Retain an ByteBuff with refCnt=0 when getBlock from LRUCache

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openinx commented on a change in pull request #242: HBASE-22422 Retain an ByteBuff with refCnt=0 when getBlock from LRUCache
URL: https://github.com/apache/hbase/pull/242#discussion_r284963100
 
 

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 File path: hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFileReaderImpl.java
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 @@ -1499,15 +1504,14 @@ public HFileBlock readBlock(long dataBlockOffset, long onDiskBlockSize,
         BlockType.BlockCategory category = hfileBlock.getBlockType().getCategory();
 
         // Cache the block if necessary
-        AtomicBoolean cachedRaw = new AtomicBoolean(false);
         cacheConf.getBlockCache().ifPresent(cache -> {
           if (cacheBlock && cacheConf.shouldCacheBlockOnRead(category)) {
-            cachedRaw.set(cacheConf.shouldCacheCompressed(category));
-            cache.cacheBlock(cacheKey, cachedRaw.get() ? hfileBlock : unpacked,
+            cache.cacheBlock(cacheKey,
+              cacheConf.shouldCacheCompressed(category) ? hfileBlock : unpacked,
               cacheConf.isInMemory());
           }
         });
-        if (unpacked != hfileBlock && !cachedRaw.get()) {
+        if (unpacked != hfileBlock) {
 
 Review comment:
   Because no matter we put the compressedBlock or the uncompressedBlock into BlockCache, the BlockCache will retain the cached block (increasing its refCnt).  So here,  we only need to consider whether if the uncompressedBlock is excatly the compressedBlock, if not then just release the compressedBlock because the RPC will reference this uncompressedBlock. 
   It's a bug which was introduced in HBASE-22005. so made a fix here.  
   Will provide a UT for this.
   

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