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From: paul-rogers <git@git.apache.org>
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Subject: [GitHub] drill pull request #822: DRILL-5457: Spill implementation for Hash Aggregate
Content-Type: text/plain
Message-Id: <20170527053812.D2E9BE04F2@git1-us-west.apache.org>
Date: Sat, 27 May 2017 05:38:12 +0000 (UTC)
archived-at: Sat, 27 May 2017 05:38:22 -0000

Github user paul-rogers commented on a diff in the pull request:

    https://github.com/apache/drill/pull/822#discussion_r118812251
  
    --- Diff: exec/java-exec/src/main/java/org/apache/drill/exec/physical/impl/aggregate/HashAggTemplate.java ---
    @@ -266,17 +508,138 @@ public void setup(HashAggregate hashAggrConfig, HashTableConfig htConfig, Fragme
           }
         }
     
    -    ChainedHashTable ht =
    +    spillSet = new SpillSet(context,hashAggrConfig, UserBitShared.CoreOperatorType.HASH_AGGREGATE);
    +    baseHashTable =
             new ChainedHashTable(htConfig, context, allocator, incoming, null /* no incoming probe */, outgoing);
    -    this.htable = ht.createAndSetupHashTable(groupByOutFieldIds);
    -
    +    this.groupByOutFieldIds = groupByOutFieldIds; // retain these for delayedSetup, and to allow recreating hash tables (after a spill)
         numGroupByOutFields = groupByOutFieldIds.length;
    -    batchHolders = new ArrayList<BatchHolder>();
    -    // First BatchHolder is created when the first put request is received.
     
         doSetup(incoming);
       }
     
    +  /**
    +   *  Delayed setup are the parts from setup() that can only be set after actual data arrives in incoming
    +   *  This data is used to compute the number of partitions.
    +   */
    +  private void delayedSetup() {
    +
    +    // Set the number of partitions from the configuration (raise to a power of two, if needed)
    +    numPartitions = context.getConfig().getInt(ExecConstants.HASHAGG_NUM_PARTITIONS_KEY);
    +    if ( numPartitions == 1 ) {
    +      canSpill = false;
    +      logger.warn("Spilling was disabled");
    +    }
    +    while (Integer.bitCount(numPartitions) > 1) { // in case not a power of 2
    +      numPartitions++;
    +    }
    --- End diff --
    
    `BaseAllocator.nextPowerOfTwo()`. I've seen other implementations as well. Maybe pick one and put it in a utilities class somewhere so we don't have to reinvent it multiple times?


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