Github user Ben-Zvi commented on a diff in the pull request:
https://github.com/apache/drill/pull/822#discussion_r119481421
--- 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++;
+ }
+ if ( schema == null ) { estMaxBatchSize = 0; } // incoming was an
empty batch
+ else {
+ // Estimate the max batch size; should use actual data (e.g. lengths
of varchars)
+ updateEstMaxBatchSize(incoming);
+ }
+ long memAvail = memoryLimit - allocator.getAllocatedMemory();
+ if ( !canSpill ) { // single phase, or spill disabled by configuation
+ numPartitions = 1; // single phase should use only a single
partition (to save memory)
+ } else { // two phase
+ // Adjust down the number of partitions if needed - when the memory
available can not hold as
+ // many batches (configurable option), plus overhead (e.g. hash
table, links, hash values))
+ while ( numPartitions * ( estMaxBatchSize * minBatchesPerPartition +
8 * 1024 * 1024) > memAvail ) {
+ numPartitions /= 2;
+ if ( numPartitions < 2) {
+ if ( is2ndPhase ) { canSpill = false; } // 2nd phase needs at
least 2 to make progress
+ break;
+ }
+ }
+ }
+ logger.trace("{} phase. Number of partitions chosen: {}. {} spill",
isTwoPhase?(is2ndPhase?"2nd":"1st"):"Single",
+ numPartitions, canSpill ? "Can" : "Cannot");
+
+ // The following initial safety check should be revisited once we can
lower the number of rows in a batch
+ // In cases of very tight memory -- need at least memory to process
one batch, plus overhead (e.g. hash table)
+ if ( numPartitions == 1 ) {
+ // if too little memory - behave like the old code -- no memory
limit for hash aggregate
+ allocator.setLimit(10_000_000_000L);
+ }
+ // Based on the number of partitions: Set the mask and bit count
+ partitionMask = numPartitions - 1; // e.g. 32 --> 0x1F
+ bitsInMask = Integer.bitCount(partitionMask); // e.g. 0x1F -> 5
+
+ // Create arrays (one entry per partition)
+ htables = new HashTable[numPartitions] ;
+ batchHolders = (ArrayList<BatchHolder>[]) new
ArrayList<?>[numPartitions] ;
+ outBatchIndex = new int[numPartitions] ;
+ outputStream = new OutputStream[numPartitions];
+ spilledBatchesCount = new int[numPartitions];
+ // spilledPaths = new Path[numPartitions];
+ spillFiles = new String[numPartitions];
+ spilledPartitionsList = new ArrayList<SpilledPartition>();
+
+ plannedBatches = numPartitions; // each partition should allocate its
first batch
+
+ // initialize every (per partition) entry in the arrays
+ for (int i = 0; i < numPartitions; i++ ) {
+ try {
+ this.htables[i] =
baseHashTable.createAndSetupHashTable(groupByOutFieldIds, numPartitions);
+ this.htables[i].setMaxVarcharSize(maxColumnWidth);
+ } catch (IllegalStateException ise) {} // ignore
+ catch (Exception e) { throw new DrillRuntimeException(e); }
--- End diff --
Done:
` } catch (ClassTransformationException e) {
throw UserException.unsupportedError(e)
.message("Code generation error - likely an error in the code.")
.build(logger);
} catch (IOException e) {
throw UserException.resourceError(e)
.message("IO Error while creating a hash table.")
.build(logger);
} catch (SchemaChangeException sce) {
throw new IllegalStateException("Unexpected Schema Change while
creating a hash table",sce);
}`
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