elastic · dnhatn · Aug 7, 2025 · Aug 4, 2025 · Aug 5, 2025 · Aug 5, 2025
diff --git a/docs/changelog/132456.yaml b/docs/changelog/132456.yaml
@@ -0,0 +1,5 @@
+pr: 132456
+summary: Some optimizations for constant blocks
+area: ES|QL
+type: enhancement
+issues: []
diff --git a/...main/generated-src/org/elasticsearch/compute/aggregation/blockhash/BytesRefBlockHash.java b/...main/generated-src/org/elasticsearch/compute/aggregation/blockhash/BytesRefBlockHash.java
diff --git a/.../src/main/java/org/elasticsearch/compute/aggregation/CountGroupingAggregatorFunction.java b/.../src/main/java/org/elasticsearch/compute/aggregation/CountGroupingAggregatorFunction.java
@@ -154,9 +154,13 @@ private void addRawInput(int positionOffset, IntBigArrayBlock groups, Block valu
      * This method is called for count all.
      */
     private void addRawInput(IntVector groups) {
-        for (int groupPosition = 0; groupPosition < groups.getPositionCount(); groupPosition++) {
-            int groupId = groups.getInt(groupPosition);
-            state.increment(groupId, 1);
+        if (groups.isConstant()) {
+            state.increment(groups.getInt(0), groups.getPositionCount());
+        } else {
+            for (int groupPosition = 0; groupPosition < groups.getPositionCount(); groupPosition++) {
+                int groupId = groups.getInt(groupPosition);
+                state.increment(groupId, 1);
+            }
         }
     }
 

diff --git a/...ompute/src/main/java/org/elasticsearch/compute/aggregation/ValuesBytesRefAggregators.java b/...ompute/src/main/java/org/elasticsearch/compute/aggregation/ValuesBytesRefAggregators.java
@@ -178,10 +178,21 @@ static void addOrdinalInputVector(
         IntVector ordinalIds,
         IntVector hashIds
     ) {
-        for (int p = 0; p < groupIds.getPositionCount(); p++) {
-            int groupId = groupIds.getInt(p);
-            int ord = ordinalIds.getInt(p + positionOffset);
-            state.addValueOrdinal(groupId, hashIds.getInt(ord));
+        if (groupIds.isConstant() && hashIds.isConstant()) {
+            state.addValueOrdinal(groupIds.getInt(0), hashIds.getInt(0));
+            return;
+        }
+        int lastGroup = groupIds.getInt(0);
+        int lastOrd = ordinalIds.getInt(positionOffset);
+        state.addValueOrdinal(lastGroup, hashIds.getInt(lastOrd));
+        for (int p = 1; p < groupIds.getPositionCount(); p++) {
+            final int nextGroup = groupIds.getInt(p);
+            final int nextOrd = ordinalIds.getInt(p + positionOffset);
+            if (nextGroup != lastGroup || nextOrd != lastOrd) {
+                lastGroup = nextGroup;
+                lastOrd = nextOrd;
+                state.addValueOrdinal(lastGroup, hashIds.getInt(lastOrd));
+            }
         }
     }
 

diff --git a/.../src/main/java/org/elasticsearch/compute/aggregation/blockhash/BytesRefLongBlockHash.java b/.../src/main/java/org/elasticsearch/compute/aggregation/blockhash/BytesRefLongBlockHash.java
@@ -100,10 +100,40 @@ public void add(IntBlock bytesHashes, LongBlock longsBlock, GroupingAggregatorFu
     public IntVector add(IntVector bytesHashes, LongVector longsVector) {
         int positions = bytesHashes.getPositionCount();
         final int[] ords = new int[positions];
-        for (int i = 0; i < positions; i++) {
-            ords[i] = Math.toIntExact(hashOrdToGroup(finalHash.add(bytesHashes.getInt(i), longsVector.getLong(i))));
+        int lastByte = bytesHashes.getInt(0);
+        long lastLong = longsVector.getLong(0);
+        ords[0] = Math.toIntExact(hashOrdToGroup(finalHash.add(lastByte, lastLong)));
+        boolean constant = true;
+        if (bytesHashes.isConstant()) {
+            for (int i = 1; i < positions; i++) {
+                final long nextLong = longsVector.getLong(i);
+                if (nextLong == lastLong) {
+                    ords[i] = ords[i - 1];
+                } else {
+                    ords[i] = Math.toIntExact(hashOrdToGroup(finalHash.add(lastByte, nextLong)));
+                    lastLong = nextLong;
+                    constant = false;
+                }
+            }
+        } else {
+            for (int i = 1; i < positions; i++) {
+                final int nextByte = bytesHashes.getInt(i);
+                final long nextLong = longsVector.getLong(i);
+                if (nextByte == lastByte && nextLong == lastLong) {
+                    ords[i] = ords[i - 1];
+                } else {
+                    ords[i] = Math.toIntExact(hashOrdToGroup(finalHash.add(nextByte, nextLong)));
+                    lastByte = nextByte;
+                    lastLong = nextLong;
+                    constant = false;
+                }
+            }
+        }
+        if (constant) {
+            return blockFactory.newConstantIntVector(ords[0], positions);
+        } else {
+            return blockFactory.newIntArrayVector(ords, positions);
         }
-        return blockFactory.newIntArrayVector(ords, positions);
     }
 
     @Override

diff --git a/...compute/src/main/java/org/elasticsearch/compute/aggregation/blockhash/X-BlockHash.java.st b/...compute/src/main/java/org/elasticsearch/compute/aggregation/blockhash/X-BlockHash.java.st
@@ -109,6 +109,11 @@ final class $Type$BlockHash extends BlockHash {
      */
     IntVector add($Type$Vector vector) {
 $if(BytesRef)$
+        if (vector.isConstant()) {
+            BytesRef v = vector.getBytesRef(0, new BytesRef());
+            int groupId = Math.toIntExact(hashOrdToGroupNullReserved(hash.add(v)));
+            return blockFactory.newConstantIntVector(groupId, vector.getPositionCount());
+        }
         var ordinals = vector.asOrdinals();
         if (ordinals != null) {
             return addOrdinalsVector(ordinals);
@@ -168,15 +173,18 @@ $endif$
 $if(BytesRef)$
     private IntVector addOrdinalsVector(OrdinalBytesRefVector inputBlock) {
         IntVector inputOrds = inputBlock.getOrdinalsVector();
-        try (
-            var builder = blockFactory.newIntVectorBuilder(inputOrds.getPositionCount());
-            var hashOrds = add(inputBlock.getDictionaryVector())
-        ) {
-            for (int p = 0; p < inputOrds.getPositionCount(); p++) {
-                int ord = hashOrds.getInt(inputOrds.getInt(p));
-                builder.appendInt(ord);
+        try (var hashOrds = add(inputBlock.getDictionaryVector())) {
+            if (inputOrds.isConstant()) {
+                int ord = hashOrds.getInt(inputOrds.getInt(0));
+                return blockFactory.newConstantIntVector(ord, inputOrds.getPositionCount());
+            }
+            try (var builder = blockFactory.newIntVectorBuilder(inputOrds.getPositionCount())) {
+                for (int p = 0; p < inputOrds.getPositionCount(); p++) {
+                    int ord = hashOrds.getInt(inputOrds.getInt(p));
+                    builder.appendInt(ord);
+                }
+                return builder.build();
             }
-            return builder.build();
         }
     }
 

diff --git a/...compute/src/main/java/org/elasticsearch/compute/lucene/read/SingletonOrdinalsBuilder.java b/...compute/src/main/java/org/elasticsearch/compute/lucene/read/SingletonOrdinalsBuilder.java
@@ -15,6 +15,7 @@
 import org.elasticsearch.compute.data.BytesRefBlock;
 import org.elasticsearch.compute.data.BytesRefVector;
 import org.elasticsearch.compute.data.IntBlock;
+import org.elasticsearch.compute.data.IntVector;
 import org.elasticsearch.compute.data.OrdinalBytesRefBlock;
 import org.elasticsearch.compute.operator.BreakingBytesRefBuilder;
 import org.elasticsearch.core.Releasable;
@@ -64,6 +65,41 @@ public SingletonOrdinalsBuilder endPositionEntry() {
         throw new UnsupportedOperationException("should only have one value per doc");
     }
 
+    BytesRefBlock tryBuildConstantBlock() {
+        if (minOrd == maxOrd) {
+            boolean seenNulls = false;
+            for (int ord : ords) {
+                if (ord == -1) {
+                    seenNulls = true;
+                    break;
+                }
+            }
+            if (seenNulls == false) {
+                final BytesRef v;
+                try {
+                    v = BytesRef.deepCopyOf(docValues.lookupOrd(minOrd));
+                } catch (IOException e) {
+                    throw new UncheckedIOException("failed to lookup ordinals", e);
+                }
+                BytesRefVector bytes = null;
+                IntVector ordinals = null;
+                boolean success = false;
+                try {
+                    bytes = blockFactory.newConstantBytesRefVector(v, 1);
+                    ordinals = blockFactory.newConstantIntVector(0, ords.length);
+                    final var result = new OrdinalBytesRefBlock(ordinals.asBlock(), bytes);
+                    success = true;
+                    return result;
+                } finally {
+                    if (success == false) {
+                        Releasables.close(bytes, ordinals);
+                    }
+                }
+            }
+        }
+        return null;
+    }
+
     BytesRefBlock buildOrdinal() {
         int valueCount = maxOrd - minOrd + 1;
         long breakerSize = ordsSize(valueCount);
@@ -172,6 +208,10 @@ public long estimatedBytes() {
 
     @Override
     public BytesRefBlock build() {
+        var constantBlock = tryBuildConstantBlock();
+        if (constantBlock != null) {
+            return constantBlock;
+        }
         return shouldBuildOrdinalsBlock() ? buildOrdinal() : buildRegularBlock();
     }
 

diff --git a/...compute/src/test/java/org/elasticsearch/compute/aggregation/blockhash/BlockHashTests.java b/...compute/src/test/java/org/elasticsearch/compute/aggregation/blockhash/BlockHashTests.java
@@ -1715,4 +1715,76 @@ private BlockHash buildBlockHash(int emitBatchSize, Block... values) {
             ? new PackedValuesBlockHash(specs, blockFactory, emitBatchSize)
             : BlockHash.build(specs, blockFactory, emitBatchSize, true);
     }
+
+    public void testConstant() {
+        try (
+            var hash = new BytesRefLongBlockHash(blockFactory, 0, 1, false, randomIntBetween(1, 1000));
+            var bytesHash = new BytesRefBlockHash(0, blockFactory)
+        ) {
+            int iters = between(1, 20);
+            for (int i = 0; i < iters; i++) {
+                final BytesRefBlock bytes;
+                final LongBlock longs;
+                final boolean constantInput = randomBoolean();
+                final int positions = randomIntBetween(1, 100);
+                if (constantInput) {
+                    bytes = blockFactory.newConstantBytesRefBlockWith(new BytesRef(randomAlphaOfLength(10)), positions);
+                    if (randomBoolean()) {
+                        try (IntVector hashIds = bytesHash.add(bytes.asVector())) {
+                            assertTrue(hashIds.isConstant());
+                        }
+                    }
+                    if (randomBoolean()) {
+                        longs = blockFactory.newConstantLongBlockWith(randomNonNegativeLong(), positions);
+                    } else {
+                        long value = randomNonNegativeLong();
+                        try (var builder = blockFactory.newLongVectorFixedBuilder(positions)) {
+                            for (int p = 0; p < positions; p++) {
+                                builder.appendLong(value);
+                            }
+                            longs = builder.build().asBlock();
+                        }
+                    }
+                } else {
+                    try (var builder = blockFactory.newBytesRefBlockBuilder(positions)) {
+                        for (int p = 0; p < positions; p++) {
+                            builder.appendBytesRef(new BytesRef(randomAlphaOfLength(10)));
+                        }
+                        bytes = builder.build();
+                    }
+                    try (var builder = blockFactory.newLongVectorFixedBuilder(positions)) {
+                        for (int p = 0; p < positions; p++) {
+                            builder.appendLong(randomNonNegativeLong());
+                        }
+                        longs = builder.build().asBlock();
+                    }
+                }
+                try (Page page = new Page(bytes, longs)) {
+                    hash.add(page, new GroupingAggregatorFunction.AddInput() {
+                        @Override
+                        public void add(int positionOffset, IntArrayBlock groupIds) {
+                            fail("should not call IntArrayBlock");
+                        }
+
+                        @Override
+                        public void add(int positionOffset, IntBigArrayBlock groupIds) {
+                            fail("should not call IntBigArrayBlock");
+                        }
+
+                        @Override
+                        public void add(int positionOffset, IntVector groupIds) {
+                            if (constantInput) {
+                                assertTrue(groupIds.isConstant());
+                            }
+                        }
+
+                        @Override
+                        public void close() {
+
+                        }
+                    });
+                }
+            }
+        }
+    }
 }