Use segment ordinals as global ordinals if a segment contains all values for a field on a shard level.

Relates to #5854
Closes #5873

src/main/java/org/elasticsearch/index/fielddata/ordinals/GlobalOrdinalsIndexFieldData.java

@@ -127,8 +127,12 @@ public final class GlobalOrdinalsIndexFieldData extends AbstractIndexComponent i
         public BytesValues.WithOrdinals getBytesValues(boolean needsHashes) {
             BytesValues.WithOrdinals values = afd.getBytesValues(false);
             Ordinals.Docs segmentOrdinals = values.ordinals();
-            Ordinals.Docs globalOrdinals = segmentOrdToGlobalOrdLookup.globalOrdinals(segmentOrdinals);
+            final Ordinals.Docs globalOrdinals;
-
+            if (segmentOrdToGlobalOrdLookup != null) {
+                globalOrdinals = segmentOrdToGlobalOrdLookup.globalOrdinals(segmentOrdinals);
+            } else {
+                globalOrdinals = segmentOrdinals;
+            }
             final BytesValues.WithOrdinals[] bytesValues = new BytesValues.WithOrdinals[atomicReaders.length];
             for (int i = 0; i < bytesValues.length; i++) {
                 bytesValues[i] = atomicReaders[i].afd.getBytesValues(false);

src/main/java/org/elasticsearch/index/fielddata/ordinals/InternalGlobalOrdinalsBuilder.java

@@ -104,7 +104,8 @@ public class InternalGlobalOrdinalsBuilder extends AbstractIndexComponent implem
         breakerService.getBreaker().addWithoutBreaking(memorySizeInBytes);
 
         if (logger.isDebugEnabled()) {
-            String implName = segmentOrdToGlobalOrdLookups[0].getClass().getSimpleName();
+            // this does include the [] from the array in the impl name
+            String implName = segmentOrdToGlobalOrdLookups.getClass().getSimpleName();
             logger.debug(
                     "Global-ordinals[{}][{}][{}] took {} ms",
                     implName,
@@ -225,20 +226,32 @@ public class InternalGlobalOrdinalsBuilder extends AbstractIndexComponent implem
                 PackedIntOrdinalMappingSource[] sources = new PackedIntOrdinalMappingSource[numSegments];
                 for (int i = 0; i < newSegmentOrdToGlobalOrdDeltas.length; i++) {
                     PackedInts.Reader segmentOrdToGlobalOrdDelta = newSegmentOrdToGlobalOrdDeltas[i];
+                    if (segmentOrdToGlobalOrdDelta.size() == maxOrd) {
+                        // This means that a segment contains all the value and in that case segment ordinals
+                        // can be used as global ordinals. This will save an extra lookup per hit.
+                        sources[i] = null;
+                    } else {
                         long ramUsed = segmentOrdToGlobalOrdDelta.ramBytesUsed();
                         sources[i] = new PackedIntOrdinalMappingSource(segmentOrdToGlobalOrdDelta, ramUsed, maxOrd);
                         memorySizeInBytesCounter += ramUsed;
                     }
+
+                }
                 return sources;
             } else {
                 OrdinalMappingSource[] sources = new OrdinalMappingSource[segmentOrdToGlobalOrdDeltas.length];
                 for (int i = 0; i < segmentOrdToGlobalOrdDeltas.length; i++) {
                     MonotonicAppendingLongBuffer segmentOrdToGlobalOrdLookup = segmentOrdToGlobalOrdDeltas[i];
+                    if (segmentOrdToGlobalOrdLookup.size() == maxOrd) {
+                        // idem as above
+                        sources[i] = null;
+                    } else {
                         segmentOrdToGlobalOrdLookup.freeze();
                         long ramUsed = segmentOrdToGlobalOrdLookup.ramBytesUsed();
                         sources[i] = new CompressedOrdinalMappingSource(segmentOrdToGlobalOrdLookup, ramUsed, maxOrd);
                         memorySizeInBytesCounter += ramUsed;
                     }
+                }
                 return sources;
             }
         }

src/main/java/org/elasticsearch/search/aggregations/bucket/BucketsAggregator.java

@@ -65,12 +65,26 @@ public abstract class BucketsAggregator extends Aggregator {
      */
     protected final void collectBucket(int doc, long bucketOrd) throws IOException {
         docCounts = bigArrays.grow(docCounts, bucketOrd + 1);
+        collectExistingBucket(doc, bucketOrd);
+    }
+
+    /**
+     * Same as {@link #collectBucket(int, long)}, but doesn't check if the docCounts needs to be re-sized.
+     */
+    protected final void collectExistingBucket(int doc, long bucketOrd) throws IOException {
         docCounts.increment(bucketOrd, 1);
         for (int i = 0; i < collectableSugAggregators.length; i++) {
             collectableSugAggregators[i].collect(doc, bucketOrd);
         }
     }
 
+    /**
+     * Initializes the docCounts to the specified size.
+     */
+    public void initializeDocCounts(long maxOrd) {
+        docCounts = bigArrays.grow(docCounts, maxOrd);
+    }
+
     /**
      * Utility method to collect the given doc in the given bucket but not to update the doc counts of the bucket
      */

src/main/java/org/elasticsearch/search/aggregations/bucket/terms/GlobalOrdinalsStringTermsAggregator.java

@@ -69,6 +69,7 @@ public class GlobalOrdinalsStringTermsAggregator extends AbstractStringTermsAggr
     public void setNextReader(AtomicReaderContext reader) {
         globalValues = valuesSource.globalBytesValues();
         globalOrdinals = globalValues.ordinals();
+        initializeDocCounts(globalOrdinals.getMaxOrd());
     }
 
     @Override
@@ -76,7 +77,7 @@ public class GlobalOrdinalsStringTermsAggregator extends AbstractStringTermsAggr
         final int numOrds = globalOrdinals.setDocument(doc);
         for (int i = 0; i < numOrds; i++) {
             final long globalOrd = globalOrdinals.nextOrd();
-            collectBucket(doc, createBucketOrd(globalOrd));
+            collectExistingBucket(doc, createBucketOrd(globalOrd));
         }
     }
 

src/test/java/org/elasticsearch/benchmark/search/aggregations/GlobalOrdinalsBenchmark.java

@@ -177,10 +177,11 @@ public class GlobalOrdinalsBenchmark {
         int[] thresholds = new int[]{2048};
         for (int threshold : thresholds) {
             updateThresholdInMapping(threshold);
+            System.out.println("--> Threshold: " + threshold);
 
             for (int fieldSuffix = FIELD_START; fieldSuffix <= FIELD_LIMIT; fieldSuffix <<= 1) {
                 String fieldName = "field_" + fieldSuffix;
-                String name = threshold + "-" + fieldName;
+                String name = "global_ordinals-" + fieldName;
                 if (USE_DOC_VALUES) {
                     fieldName = fieldName + ".doc_values";
                     name = name + "_doc_values"; // can't have . in agg name
@@ -191,7 +192,7 @@ public class GlobalOrdinalsBenchmark {
 
         for (int fieldSuffix = FIELD_START; fieldSuffix <= FIELD_LIMIT; fieldSuffix <<= 1) {
             String fieldName = "field_" + fieldSuffix;
-            String name = "segment-ordinals-" + fieldName;
+            String name = "ordinals-" + fieldName;
             if (USE_DOC_VALUES) {
                 fieldName = fieldName + ".doc_values";
                 name = name + "_doc_values"; // can't have . in agg name
@@ -199,12 +200,12 @@ public class GlobalOrdinalsBenchmark {
             stats.add(terms(name, fieldName, "ordinals"));
         }
 
-        System.out.println("------------------ SUMMARY ----------------------------------------------");
+        System.out.println("------------------ SUMMARY -----------------------------------------");
-        System.out.format(Locale.ENGLISH, "%40s%10s%10s%15s\n", "name", "took", "millis", "fieldata size");
+        System.out.format(Locale.ENGLISH, "%30s%10s%10s%15s\n", "name", "took", "millis", "fieldata size");
         for (StatsResult stat : stats) {
-            System.out.format(Locale.ENGLISH, "%40s%10s%10d%15s\n", stat.name, TimeValue.timeValueMillis(stat.took), (stat.took / QUERY_COUNT), stat.fieldDataMemoryUsed);
+            System.out.format(Locale.ENGLISH, "%30s%10s%10d%15s\n", stat.name, TimeValue.timeValueMillis(stat.took), (stat.took / QUERY_COUNT), stat.fieldDataMemoryUsed);
         }
-        System.out.println("------------------ SUMMARY ----------------------------------------------");
+        System.out.println("------------------ SUMMARY -----------------------------------------");
 
         client.close();
         node.close();