[GitHub] [drill] vvysotskyi commented on a change in pull request #2463: DRILL-8139: Data corruption and occasional segfaults querying Parquet/gzip under the async column reader and sync page reader

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

vvysotskyi commented on a change in pull request #2463:
URL: https://github.com/apache/drill/pull/2463#discussion_r809142708



##########
File path: exec/java-exec/src/main/java/org/apache/drill/exec/store/parquet/compression/DrillCompressionCodecFactory.java
##########
@@ -80,38 +99,56 @@ public DrillCompressionCodecFactory(Configuration config, ByteBufferAllocator al
   }
 
   @Override
-  public BytesInputCompressor getCompressor(CompressionCodecName codecName) {
+  public synchronized BytesInputCompressor getCompressor(CompressionCodecName codecName) {
     if (AIRCOMPRESSOR_CODECS.contains(codecName)) {
       return airCompressors.computeIfAbsent(
           codecName,
           c -> new AirliftBytesInputCompressor(codecName, allocator)
       );
+    } else if (codecName != CompressionCodecName.SNAPPY) {
+      // Work around PARQUET-2126: construct a new codec factory every time to
+      // avoid a concurrrency bug c.f. DRILL-8139. Remove once PARQUET-2126 is
+      // fixed.  Snappy is immune because of the thread safety in the Xerial lib.
+      CompressionCodecFactory ccf = CodecFactory.createDirectCodecFactory(config, allocator, pageSize);
+      // hold onto a reference for later release()
+      singleUseFactories.add(ccf);
+      return ccf.getCompressor(codecName);
     } else {
       return parqCodecFactory.getCompressor(codecName);
     }
   }
 
   @Override
-  public BytesInputDecompressor getDecompressor(CompressionCodecName codecName) {
+  public synchronized BytesInputDecompressor getDecompressor(CompressionCodecName codecName) {
     if (AIRCOMPRESSOR_CODECS.contains(codecName)) {
       return airCompressors.computeIfAbsent(
           codecName,
           c -> new AirliftBytesInputCompressor(codecName, allocator)
       );
+    } else if (codecName != CompressionCodecName.SNAPPY) {

Review comment:
       `AIRCOMPRESSOR_CODECS` contains `CompressionCodecName.SNAPPY`, so this condition will be always `true`.




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