Merge pull request #8558 from vespa-engine/lesters/tensor-partial-update-mixed-tensors-java

Tensor partial update for mixed tensors - Java

20 files changed, 442 insertions, 121 deletions

diff --git a/document/abi-spec.json b/document/abi-spec.json
index 61390af3523..d4db3026b27 100644
--- a/document/abi-spec.json
+++ b/document/abi-spec.json
@@ -5244,7 +5244,7 @@
     ],
     "methods": [
       "public void <init>(com.yahoo.document.update.TensorModifyUpdate$Operation, com.yahoo.document.datatypes.TensorFieldValue)",
-      "public static com.yahoo.tensor.TensorType convertToCompatibleType(com.yahoo.tensor.TensorType)",
+      "public static com.yahoo.tensor.TensorType convertDimensionsToMapped(com.yahoo.tensor.TensorType)",
       "public com.yahoo.document.update.TensorModifyUpdate$Operation getOperation()",
       "public com.yahoo.document.datatypes.TensorFieldValue getValue()",
       "public void setValue(com.yahoo.document.datatypes.TensorFieldValue)",
@@ -5278,6 +5278,7 @@
       "public boolean equals(java.lang.Object)",
       "public int hashCode()",
       "public java.lang.String toString()",
+      "public static com.yahoo.tensor.TensorType extractSparseDimensions(com.yahoo.tensor.TensorType)",
       "public bridge synthetic void setValue(com.yahoo.document.datatypes.FieldValue)",
       "public bridge synthetic com.yahoo.document.datatypes.FieldValue getValue()"
     ],
diff --git a/document/src/main/java/com/yahoo/document/json/readers/TensorAddUpdateReader.java b/document/src/main/java/com/yahoo/document/json/readers/TensorAddUpdateReader.java
index ffbfe49347c..6310fa62d15 100644
--- a/document/src/main/java/com/yahoo/document/json/readers/TensorAddUpdateReader.java
+++ b/document/src/main/java/com/yahoo/document/json/readers/TensorAddUpdateReader.java
@@ -23,22 +23,23 @@ public class TensorAddUpdateReader {
 
     public static TensorAddUpdate createTensorAddUpdate(TokenBuffer buffer, Field field) {
         expectObjectStart(buffer.currentToken());
-        expectTensorTypeIsSparse(field);
+        expectTensorTypeHasSparseDimensions(field);
 
         TensorDataType tensorDataType = (TensorDataType)field.getDataType();
         TensorType tensorType = tensorDataType.getTensorType();
         TensorFieldValue tensorFieldValue = new TensorFieldValue(tensorType);
         fillTensor(buffer, tensorFieldValue);
+
         expectTensorIsNonEmpty(field, tensorFieldValue.getTensor().get());
         return new TensorAddUpdate(tensorFieldValue);
     }
 
-    private static void expectTensorTypeIsSparse(Field field) {
+    private static void expectTensorTypeHasSparseDimensions(Field field) {
         TensorType tensorType = ((TensorDataType)field.getDataType()).getTensorType();
-        if (tensorType.dimensions().stream()
-                .anyMatch(dim -> dim.isIndexed())) {
-            throw new IllegalArgumentException("An add update can only be applied to sparse tensors. "
-                    + "Field '" + field.getName() + "' has unsupported tensor type '" + tensorType + "'");
+        if (tensorType.dimensions().stream().allMatch(TensorType.Dimension::isIndexed)) {
+            throw new IllegalArgumentException("An add update can only be applied to tensors " +
+                    "with at least one sparse dimension. Field '" + field.getName() +
+                    "' has unsupported tensor type '" + tensorType + "'");
         }
     }
 
@@ -48,5 +49,4 @@ public class TensorAddUpdateReader {
         }
     }
 
-
 }
diff --git a/document/src/main/java/com/yahoo/document/json/readers/TensorModifyUpdateReader.java b/document/src/main/java/com/yahoo/document/json/readers/TensorModifyUpdateReader.java
index a9bbba519bd..66588debbca 100644
--- a/document/src/main/java/com/yahoo/document/json/readers/TensorModifyUpdateReader.java
+++ b/document/src/main/java/com/yahoo/document/json/readers/TensorModifyUpdateReader.java
@@ -29,10 +29,8 @@ public class TensorModifyUpdateReader {
     private static final String MODIFY_MULTIPLY = "multiply";
 
     public static TensorModifyUpdate createModifyUpdate(TokenBuffer buffer, Field field) {
-
         expectFieldIsOfTypeTensor(field);
         expectTensorTypeHasNoneIndexedUnboundDimensions(field);
-        expectTensorTypeIsNotMixed(field);
         expectObjectStart(buffer.currentToken());
 
         ModifyUpdateResult result = createModifyUpdateResult(buffer, field);
@@ -58,16 +56,6 @@ public class TensorModifyUpdateReader {
         }
     }
 
-    private static void expectTensorTypeIsNotMixed(Field field) {
-        TensorType tensorType = ((TensorDataType)field.getDataType()).getTensorType();
-        long numMappedDimensions = tensorType.dimensions().stream().filter(dim -> dim.type().equals(TensorType.Dimension.Type.mapped)).count();
-        long numIndexedDimensions = tensorType.dimensions().stream().filter(dim -> dim.isIndexed()).count();
-        if (numMappedDimensions > 0 && numIndexedDimensions > 0) {
-            throw new IllegalArgumentException("A modify update cannot be applied to tensor types with mixed dimensions. "
-                    + "Field '" + field.getName() + "' has mixed tensor type '" + tensorType + "'");
-        }
-    }
-
     private static void expectOperationSpecified(TensorModifyUpdate.Operation operation, String fieldName) {
         if (operation == null) {
             throw new IllegalArgumentException("Modify update for field '" + fieldName + "' does not contain an operation");
@@ -121,7 +109,7 @@ public class TensorModifyUpdateReader {
     private static TensorFieldValue createTensor(TokenBuffer buffer, Field field) {
         TensorDataType tensorDataType = (TensorDataType)field.getDataType();
         TensorType originalType = tensorDataType.getTensorType();
-        TensorType convertedType = TensorModifyUpdate.convertToCompatibleType(originalType);
+        TensorType convertedType = TensorModifyUpdate.convertDimensionsToMapped(originalType);
 
         Tensor.Builder tensorBuilder = Tensor.Builder.of(convertedType);
         readTensorCells(buffer, tensorBuilder);
@@ -129,25 +117,26 @@ public class TensorModifyUpdateReader {
 
         validateBounds(tensor, originalType);
 
-        TensorFieldValue result = new TensorFieldValue(convertedType);
-        result.assign(tensor);
-        return result;
+        return new TensorFieldValue(tensor);
     }
 
-    /** Only validate if original type is indexed bound */
-    private static void validateBounds(Tensor convertedTensor, TensorType originalType) {
-        if ( ! originalType.dimensions().stream().allMatch(d -> d instanceof TensorType.IndexedBoundDimension)) {
+    /** Only validate if original type has indexed bound dimensions */
+    static void validateBounds(Tensor convertedTensor, TensorType originalType) {
+        if (originalType.dimensions().stream().noneMatch(d -> d instanceof TensorType.IndexedBoundDimension)) {
             return;
         }
         for (Iterator<Tensor.Cell> iter = convertedTensor.cellIterator(); iter.hasNext(); ) {
             Tensor.Cell cell = iter.next();
             TensorAddress address = cell.getKey();
             for (int i = 0; i < address.size(); ++i) {
-                long label = address.numericLabel(i);
-                long bound = originalType.dimensions().get(i).size().get();  // size is non-optional for indexed bound
-                if (label >= bound) {
-                    throw new IndexOutOfBoundsException("Dimension '" + originalType.dimensions().get(i).name() +
-                            "' has label '" + label + "' but type is " + originalType.toString());
+                TensorType.Dimension dim = originalType.dimensions().get(i);
+                if (dim instanceof TensorType.IndexedBoundDimension) {
+                    long label = address.numericLabel(i);
+                    long bound = dim.size().get();  // size is non-optional for indexed bound
+                    if (label >= bound) {
+                        throw new IndexOutOfBoundsException("Dimension '" + originalType.dimensions().get(i).name() +
+                                "' has label '" + label + "' but type is " + originalType.toString());
+                    }
                 }
             }
         }
diff --git a/document/src/main/java/com/yahoo/document/json/readers/TensorRemoveUpdateReader.java b/document/src/main/java/com/yahoo/document/json/readers/TensorRemoveUpdateReader.java
index 210a6a80ee5..3bb4b2e262f 100644
--- a/document/src/main/java/com/yahoo/document/json/readers/TensorRemoveUpdateReader.java
+++ b/document/src/main/java/com/yahoo/document/json/readers/TensorRemoveUpdateReader.java
@@ -24,23 +24,23 @@ public class TensorRemoveUpdateReader {
 
     static TensorRemoveUpdate createTensorRemoveUpdate(TokenBuffer buffer, Field field) {
         expectObjectStart(buffer.currentToken());
-        expectTensorTypeIsSparse(field);
+        expectTensorTypeHasSparseDimensions(field);
 
         TensorDataType tensorDataType = (TensorDataType)field.getDataType();
-        TensorType tensorType = tensorDataType.getTensorType();
+        TensorType originalType = tensorDataType.getTensorType();
+        TensorType convertedType = TensorRemoveUpdate.extractSparseDimensions(originalType);
+        Tensor tensor = readRemoveUpdateTensor(buffer, convertedType, originalType);
 
-        // TODO: for mixed case extract a new tensor type based only on mapped dimensions
-
-        Tensor tensor = readRemoveUpdateTensor(buffer, tensorType);
         expectAddressesAreNonEmpty(field, tensor);
         return new TensorRemoveUpdate(new TensorFieldValue(tensor));
     }
 
-    private static void expectTensorTypeIsSparse(Field field) {
+    private static void expectTensorTypeHasSparseDimensions(Field field) {
         TensorType tensorType = ((TensorDataType)field.getDataType()).getTensorType();
-        if (tensorType.dimensions().stream().anyMatch(TensorType.Dimension::isIndexed)) {
-            throw new IllegalArgumentException("A remove update can only be applied to sparse tensors. "
-                    + "Field '" + field.getName() + "' has unsupported tensor type '" + tensorType + "'");
+        if (tensorType.dimensions().stream().allMatch(TensorType.Dimension::isIndexed)) {
+            throw new IllegalArgumentException("A remove update can only be applied to tensors " +
+                    "with at least one sparse dimension. Field '" + field.getName() +
+                    "' has unsupported tensor type '" + tensorType + "'");
         }
     }
 
@@ -53,7 +53,7 @@ public class TensorRemoveUpdateReader {
     /**
      * Reads all addresses in buffer and returns a tensor where addresses have cell value 1.0
      */
-    private static Tensor readRemoveUpdateTensor(TokenBuffer buffer, TensorType type) {
+    private static Tensor readRemoveUpdateTensor(TokenBuffer buffer, TensorType type, TensorType originalType) {
         Tensor.Builder builder = Tensor.Builder.of(type);
         expectObjectStart(buffer.currentToken());
         int initNesting = buffer.nesting();
@@ -62,7 +62,7 @@ public class TensorRemoveUpdateReader {
                 expectArrayStart(buffer.currentToken());
                 int nesting = buffer.nesting();
                 for (buffer.next(); buffer.nesting() >= nesting; buffer.next()) {
-                    builder.cell(readTensorAddress(buffer, type), 1.0);
+                    builder.cell(readTensorAddress(buffer, type, originalType), 1.0);
                 }
                 expectCompositeEnd(buffer.currentToken());
             }
@@ -71,12 +71,15 @@ public class TensorRemoveUpdateReader {
         return builder.build();
     }
 
-    private static TensorAddress readTensorAddress(TokenBuffer buffer, TensorType type) {
+    private static TensorAddress readTensorAddress(TokenBuffer buffer, TensorType type, TensorType originalType) {
         TensorAddress.Builder builder = new TensorAddress.Builder(type);
         expectObjectStart(buffer.currentToken());
         int initNesting = buffer.nesting();
         for (buffer.next(); buffer.nesting() >= initNesting; buffer.next()) {
             String dimension = buffer.currentName();
+            if ( ! type.dimension(dimension).isPresent() && originalType.dimension(dimension).isPresent()) {
+                throw new IllegalArgumentException("Indexed dimension address '" + dimension + "' should not be specified in remove update");
+            }
             String label = buffer.currentText();
             builder.add(dimension, label);
         }
diff --git a/document/src/main/java/com/yahoo/document/serialization/VespaDocumentDeserializerHead.java b/document/src/main/java/com/yahoo/document/serialization/VespaDocumentDeserializerHead.java
index 2f22def9aa1..a763db33e7a 100644
--- a/document/src/main/java/com/yahoo/document/serialization/VespaDocumentDeserializerHead.java
+++ b/document/src/main/java/com/yahoo/document/serialization/VespaDocumentDeserializerHead.java
@@ -5,6 +5,7 @@ import com.yahoo.document.DataType;
 import com.yahoo.document.DocumentTypeManager;
 import com.yahoo.document.TensorDataType;
 import com.yahoo.document.datatypes.TensorFieldValue;
+import com.yahoo.document.json.readers.TensorRemoveUpdateReader;
 import com.yahoo.document.update.TensorAddUpdate;
 import com.yahoo.document.update.TensorModifyUpdate;
 import com.yahoo.document.update.TensorRemoveUpdate;
@@ -35,7 +36,10 @@ public class VespaDocumentDeserializerHead extends VespaDocumentDeserializer6 {
             throw new DeserializationException("Expected tensor data type, got " + type);
         }
         TensorDataType tensorDataType = (TensorDataType)type;
-        TensorFieldValue tensor = new TensorFieldValue(TensorModifyUpdate.convertToCompatibleType(tensorDataType.getTensorType()));
+        TensorType tensorType = tensorDataType.getTensorType();
+        TensorType convertedType = TensorModifyUpdate.convertDimensionsToMapped(tensorType);
+
+        TensorFieldValue tensor = new TensorFieldValue(convertedType);
         tensor.deserialize(this);
         return new TensorModifyUpdate(operation, tensor);
     }
@@ -46,7 +50,8 @@ public class VespaDocumentDeserializerHead extends VespaDocumentDeserializer6 {
             throw new DeserializationException("Expected tensor data type, got " + type);
         }
         TensorDataType tensorDataType = (TensorDataType)type;
-        TensorFieldValue tensor = new TensorFieldValue(tensorDataType.getTensorType());
+        TensorType tensorType = tensorDataType.getTensorType();
+        TensorFieldValue tensor = new TensorFieldValue(tensorType);
         tensor.deserialize(this);
         return new TensorAddUpdate(tensor);
     }
@@ -58,10 +63,9 @@ public class VespaDocumentDeserializerHead extends VespaDocumentDeserializer6 {
         }
         TensorDataType tensorDataType = (TensorDataType)type;
         TensorType tensorType = tensorDataType.getTensorType();
+        TensorType convertedType = TensorRemoveUpdate.extractSparseDimensions(tensorType);
 
-        // TODO: for mixed case extract a new tensor type based only on mapped dimensions
-
-        TensorFieldValue tensor = new TensorFieldValue(tensorType);
+        TensorFieldValue tensor = new TensorFieldValue(convertedType);
         tensor.deserialize(this);
         return new TensorRemoveUpdate(tensor);
     }
diff --git a/document/src/main/java/com/yahoo/document/update/TensorAddUpdate.java b/document/src/main/java/com/yahoo/document/update/TensorAddUpdate.java
index cfc3ee0c742..f8d2464deb7 100644
--- a/document/src/main/java/com/yahoo/document/update/TensorAddUpdate.java
+++ b/document/src/main/java/com/yahoo/document/update/TensorAddUpdate.java
@@ -7,15 +7,11 @@ import com.yahoo.document.datatypes.FieldValue;
 import com.yahoo.document.datatypes.TensorFieldValue;
 import com.yahoo.document.serialization.DocumentUpdateWriter;
 import com.yahoo.tensor.Tensor;
-import com.yahoo.tensor.TensorAddress;
 
-import java.util.Map;
 import java.util.Objects;
 
 /**
- *  An update used to add cells to a sparse tensor (has only mapped dimensions).
- *
- *  The cells to add are contained in a sparse tensor as well.
+ *  An update used to add cells to a sparse or mixed tensor (has at least one mapped dimension).
  */
 public class TensorAddUpdate extends ValueUpdate<TensorFieldValue> {
 
@@ -50,22 +46,10 @@ public class TensorAddUpdate extends ValueUpdate<TensorFieldValue> {
             return oldValue;
         }
 
-        Tensor oldTensor = ((TensorFieldValue) oldValue).getTensor().get();
-        Map<TensorAddress, Double> oldCells = oldTensor.cells();
-        Map<TensorAddress, Double> addCells = tensor.getTensor().get().cells();
-
-        // currently, underlying implementation disallows multiple entries with the same key
-
-        Tensor.Builder builder = Tensor.Builder.of(oldTensor.type());
-        for (Map.Entry<TensorAddress, Double> oldCell : oldCells.entrySet()) {
-            builder.cell(oldCell.getKey(), addCells.getOrDefault(oldCell.getKey(), oldCell.getValue()));
-        }
-        for (Map.Entry<TensorAddress, Double> addCell : addCells.entrySet()) {
-            if ( ! oldCells.containsKey(addCell.getKey())) {
-                builder.cell(addCell.getKey(), addCell.getValue());
-            }
-        }
-        return new TensorFieldValue(builder.build());
+        Tensor old = ((TensorFieldValue) oldValue).getTensor().get();
+        Tensor update = tensor.getTensor().get();
+        Tensor result = old.merge((left, right) -> right, update.cells());  // note this might be slow for large mixed tensor updates
+        return new TensorFieldValue(result);
     }
 
     @Override
diff --git a/document/src/main/java/com/yahoo/document/update/TensorModifyUpdate.java b/document/src/main/java/com/yahoo/document/update/TensorModifyUpdate.java
index 6111b51ca4e..2773f9d31da 100644
--- a/document/src/main/java/com/yahoo/document/update/TensorModifyUpdate.java
+++ b/document/src/main/java/com/yahoo/document/update/TensorModifyUpdate.java
@@ -37,7 +37,7 @@ public class TensorModifyUpdate extends ValueUpdate<TensorFieldValue> {
     /**
      * Converts the given tensor type to a type that is compatible for being used in this update (has only mapped dimensions).
      */
-    public static TensorType convertToCompatibleType(TensorType type) {
+    public static TensorType convertDimensionsToMapped(TensorType type) {
         TensorType.Builder builder = new TensorType.Builder();
         type.dimensions().stream().forEach(dim -> builder.mapped(dim.name()));
         return builder.build();
diff --git a/document/src/main/java/com/yahoo/document/update/TensorRemoveUpdate.java b/document/src/main/java/com/yahoo/document/update/TensorRemoveUpdate.java
index e9fb1e3efd5..335cda8e133 100644
--- a/document/src/main/java/com/yahoo/document/update/TensorRemoveUpdate.java
+++ b/document/src/main/java/com/yahoo/document/update/TensorRemoveUpdate.java
@@ -7,10 +7,8 @@ import com.yahoo.document.datatypes.FieldValue;
 import com.yahoo.document.datatypes.TensorFieldValue;
 import com.yahoo.document.serialization.DocumentUpdateWriter;
 import com.yahoo.tensor.Tensor;
-import com.yahoo.tensor.TensorAddress;
+import com.yahoo.tensor.TensorType;
 
-import java.util.Iterator;
-import java.util.Map;
 import java.util.Objects;
 
 /**
@@ -25,6 +23,18 @@ public class TensorRemoveUpdate extends ValueUpdate<TensorFieldValue> {
     public TensorRemoveUpdate(TensorFieldValue value) {
         super(ValueUpdateClassID.TENSORREMOVE);
         this.tensor = value;
+        verifyCompatibleType();
+    }
+
+    private void verifyCompatibleType() {
+        if ( ! tensor.getTensor().isPresent()) {
+            throw new IllegalArgumentException("Tensor must be present in remove update");
+        }
+        TensorType tensorType = tensor.getTensor().get().type();
+        TensorType expectedType = extractSparseDimensions(tensor.getDataType().getTensorType());
+        if ( ! tensorType.equals(expectedType)) {
+            throw new IllegalArgumentException("Unexpected type '" + tensorType + "' in remove update. Expected is '" + expectedType + "'");
+        }
     }
 
     @Override
@@ -51,17 +61,10 @@ public class TensorRemoveUpdate extends ValueUpdate<TensorFieldValue> {
             return oldValue;
         }
 
-        Tensor oldTensor = ((TensorFieldValue) oldValue).getTensor().get();
-        Map<TensorAddress, Double> cellsToRemove = tensor.getTensor().get().cells();
-        Tensor.Builder builder = Tensor.Builder.of(oldTensor.type());
-        for (Iterator<Tensor.Cell> i = oldTensor.cellIterator(); i.hasNext(); ) {
-            Tensor.Cell cell = i.next();
-            TensorAddress address = cell.getKey();
-            if ( ! cellsToRemove.containsKey(address)) {
-                builder.cell(address, cell.getValue());
-            }
-        }
-        return new TensorFieldValue(builder.build());
+        Tensor old = ((TensorFieldValue) oldValue).getTensor().get();
+        Tensor update = tensor.getTensor().get();
+        Tensor result = old.remove(update.cells().keySet());
+        return new TensorFieldValue(result);
     }
 
     @Override
@@ -93,4 +96,11 @@ public class TensorRemoveUpdate extends ValueUpdate<TensorFieldValue> {
         return super.toString() + " " + tensor;
     }
 
+    public static TensorType extractSparseDimensions(TensorType type) {
+        TensorType.Builder builder = new TensorType.Builder();
+        type.dimensions().stream().filter(dim -> ! dim.isIndexed()).forEach(dim -> builder.mapped(dim.name()));
+        return builder.build();
+    }
+
+
 }
diff --git a/document/src/test/java/com/yahoo/document/json/DocumentUpdateJsonSerializerTest.java b/document/src/test/java/com/yahoo/document/json/DocumentUpdateJsonSerializerTest.java
index e2736dabd2b..454ad72f344 100644
--- a/document/src/test/java/com/yahoo/document/json/DocumentUpdateJsonSerializerTest.java
+++ b/document/src/test/java/com/yahoo/document/json/DocumentUpdateJsonSerializerTest.java
@@ -40,6 +40,7 @@ public class DocumentUpdateJsonSerializerTest {
 
     final static TensorType sparseTensorType = new TensorType.Builder().mapped("x").mapped("y").build();
     final static TensorType denseTensorType = new TensorType.Builder().indexed("x", 2).indexed("y", 3).build();
+    final static TensorType mixedTensorType = new TensorType.Builder().mapped("x").indexed("y", 3).build();
     final static DocumentTypeManager types = new DocumentTypeManager();
     final static JsonFactory parserFactory = new JsonFactory();
     final static DocumentType docType = new DocumentType("doctype");
@@ -60,6 +61,7 @@ public class DocumentUpdateJsonSerializerTest {
         docType.addField(new Field("byte_field", DataType.BYTE));
         docType.addField(new Field("sparse_tensor", new TensorDataType(sparseTensorType)));
         docType.addField(new Field("dense_tensor", new TensorDataType(denseTensorType)));
+        docType.addField(new Field("mixed_tensor", new TensorDataType(mixedTensorType)));
         docType.addField(new Field("reference_field", new ReferenceDataType(refTargetDocType, 777)));
         docType.addField(new Field("predicate_field", DataType.PREDICATE));
         docType.addField(new Field("raw_field", DataType.RAW));
@@ -336,6 +338,26 @@ public class DocumentUpdateJsonSerializerTest {
     }
 
     @Test
+    public void test_tensor_modify_update_on_mixed_tensor() {
+        roundtripSerializeJsonAndMatch(inputJson(
+                "{",
+                "  'update': 'DOCUMENT_ID',",
+                "  'fields': {",
+                "    'mixed_tensor': {",
+                "      'modify': {",
+                "        'operation': 'multiply',",
+                "        'cells': [",
+                "          { 'address': { 'x': 'a', 'y': '0' }, 'value': 2.0 },",
+                "          { 'address': { 'x': 'c', 'y': '1' }, 'value': 3.0 }",
+                "        ]",
+                "      }",
+                "    }",
+                "  }",
+                "}"
+        ));
+    }
+
+    @Test
     public void test_tensor_add_update() {
         roundtripSerializeJsonAndMatch(inputJson(
                 "{",
@@ -355,6 +377,29 @@ public class DocumentUpdateJsonSerializerTest {
     }
 
     @Test
+    public void test_tensor_add_update_mixed() {
+        roundtripSerializeJsonAndMatch(inputJson(
+                "{",
+                "  'update': 'DOCUMENT_ID',",
+                "  'fields': {",
+                "    'mixed_tensor': {",
+                "      'add': {",
+                "        'cells': [",
+                "          { 'address': { 'x': '1', 'y': '0' }, 'value': 2.0 },",
+                "          { 'address': { 'x': '1', 'y': '1' }, 'value': 0.0 },",
+                "          { 'address': { 'x': '1', 'y': '2' }, 'value': 0.0 },",
+                "          { 'address': { 'x': '0', 'y': '0' }, 'value': 0.0 },",
+                "          { 'address': { 'x': '0', 'y': '1' }, 'value': 0.0 },",
+                "          { 'address': { 'x': '0', 'y': '2' }, 'value': 3.0 }",
+                "        ]",
+                "      }",
+                "    }",
+                "  }",
+                "}"
+        ));
+    }
+
+    @Test
     public void test_tensor_remove_update() {
         roundtripSerializeJsonAndMatch(inputJson(
                 "{",
@@ -374,6 +419,24 @@ public class DocumentUpdateJsonSerializerTest {
     }
 
     @Test
+    public void test_tensor_remove_update_mixed() {
+        roundtripSerializeJsonAndMatch(inputJson(
+                "{",
+                "  'update': 'DOCUMENT_ID',",
+                "  'fields': {",
+                "    'mixed_tensor': {",
+                "      'remove': {",
+                "        'addresses': [",
+                "          {'x':'0' }",
+                "        ]",
+                "      }",
+                "    }",
+                "  }",
+                "}"
+        ));
+    }
+
+    @Test
     public void reference_field_id_can_be_update_assigned_non_empty_id() {
         roundtripSerializeJsonAndMatch(inputJson(
                 "{",
diff --git a/document/src/test/java/com/yahoo/document/json/JsonReaderTestCase.java b/document/src/test/java/com/yahoo/document/json/JsonReaderTestCase.java
index e58b26d500d..15d1e859f73 100644
--- a/document/src/test/java/com/yahoo/document/json/JsonReaderTestCase.java
+++ b/document/src/test/java/com/yahoo/document/json/JsonReaderTestCase.java
@@ -1387,12 +1387,30 @@ public class JsonReaderTestCase {
     }
 
     @Test
-    public void tensor_modify_update_on_mixed_tensor_throws() {
-        exception.expect(IllegalArgumentException.class);
-        exception.expectMessage("A modify update cannot be applied to tensor types with mixed dimensions. Field 'mixed_tensor' has mixed tensor type 'tensor(x{},y[3])'");
-        createTensorModifyUpdate(inputJson("{",
-                "  'operation': 'replace',",
-                "  'cells': [] }"), "mixed_tensor");
+    public void tensor_modify_update_with_replace_operation_mixed() {
+        assertTensorModifyUpdate("{{x:a,y:0}:2.0}", TensorModifyUpdate.Operation.REPLACE, "mixed_tensor",
+                inputJson("{",
+                        "  'operation': 'replace',",
+                        "  'cells': [",
+                        "    { 'address': { 'x': 'a', 'y': '0' }, 'value': 2.0 } ]}"));
+    }
+
+    @Test
+    public void tensor_modify_update_with_add_operation_mixed() {
+        assertTensorModifyUpdate("{{x:a,y:0}:2.0}", TensorModifyUpdate.Operation.ADD, "mixed_tensor",
+                inputJson("{",
+                        "  'operation': 'add',",
+                        "  'cells': [",
+                        "    { 'address': { 'x': 'a', 'y': '0' }, 'value': 2.0 } ]}"));
+    }
+
+    @Test
+    public void tensor_modify_update_with_multiply_operation_mixed() {
+        assertTensorModifyUpdate("{{x:a,y:0}:2.0}", TensorModifyUpdate.Operation.MULTIPLY, "mixed_tensor",
+                inputJson("{",
+                        "  'operation': 'multiply',",
+                        "  'cells': [",
+                        "    { 'address': { 'x': 'a', 'y': '0' }, 'value': 2.0 } ]}"));
     }
 
     @Test
@@ -1406,6 +1424,17 @@ public class JsonReaderTestCase {
     }
 
     @Test
+    public void tensor_modify_update_with_out_of_bound_cells_throws_mixed() {
+        exception.expect(IndexOutOfBoundsException.class);
+        exception.expectMessage("Dimension 'y' has label '3' but type is tensor(x{},y[3])");
+        createTensorModifyUpdate(inputJson("{",
+                "  'operation': 'replace',",
+                "  'cells': [",
+                "    { 'address': { 'x': '0', 'y': '3' }, 'value': 2.0 } ]}"), "mixed_tensor");
+    }
+
+
+    @Test
     public void tensor_modify_update_with_unknown_operation_throws() {
         exception.expect(IllegalArgumentException.class);
         exception.expectMessage("Unknown operation 'unknown' in modify update for field 'sparse_tensor'");
@@ -1449,11 +1478,29 @@ public class JsonReaderTestCase {
     }
 
     @Test
-    public void tensor_add_update_on_non_sparse_tensor_throws() {
+    public void tensor_add_update_on_mixed_tensor() {
+        assertTensorAddUpdate("{{x:a,y:0}:2.0, {x:a,y:1}:3.0, {x:a,y:2}:0.0}", "mixed_tensor",
+                inputJson("{",
+                        "  'cells': [",
+                        "    { 'address': { 'x': 'a', 'y': '0' }, 'value': 2.0 },",
+                        "    { 'address': { 'x': 'a', 'y': '1' }, 'value': 3.0 } ]}"));
+    }
+
+    @Test
+    public void tensor_add_update_on_mixed_with_out_of_bound_dense_cells_throws() {
+        exception.expect(IndexOutOfBoundsException.class);
+        exception.expectMessage("Index 3 out of bounds for length 3");
+        createTensorAddUpdate(inputJson("{",
+                "  'cells': [",
+                "    { 'address': { 'x': '0', 'y': '3' }, 'value': 2.0 } ]}"), "mixed_tensor");
+    }
+
+    @Test
+    public void tensor_add_update_on_dense_tensor_throws() {
         exception.expect(IllegalArgumentException.class);
-        exception.expectMessage("An add update can only be applied to sparse tensors. Field 'mixed_tensor' has unsupported tensor type 'tensor(x{},y[3])'");
+        exception.expectMessage("An add update can only be applied to tensors with at least one sparse dimension. Field 'dense_tensor' has unsupported tensor type 'tensor(x[2],y[3])'");
         createTensorAddUpdate(inputJson("{",
-                "  'cells': [] }"), "mixed_tensor");
+                "  'cells': [] }"), "dense_tensor");
     }
 
     @Test
@@ -1470,6 +1517,7 @@ public class JsonReaderTestCase {
         exception.expect(IllegalArgumentException.class);
         exception.expectMessage("Add update for field 'sparse_tensor' does not contain tensor cells");
         createTensorAddUpdate(inputJson("{}"), "sparse_tensor");
+        createTensorAddUpdate(inputJson("{}"), "mixed_tensor");
     }
 
     @Test
@@ -1482,11 +1530,30 @@ public class JsonReaderTestCase {
     }
 
     @Test
-    public void tensor_remove_update_on_non_sparse_tensor_throws() {
+    public void tensor_remove_update_on_mixed_tensor() {
+        assertTensorRemoveUpdate("{{x:1}:1.0,{x:2}:1.0}", "mixed_tensor",
+                inputJson("{",
+                        "  'addresses': [",
+                        "    { 'x': '1' },",
+                        "    { 'x': '2' } ]}"));
+    }
+
+    @Test
+    public void tensor_remove_update_on_mixed_tensor_with_dense_addresses_throws() {
+        exception.expect(IllegalArgumentException.class);
+        exception.expectMessage("Indexed dimension address 'y' should not be specified in remove update");
+        createTensorRemoveUpdate(inputJson("{",
+                        "  'addresses': [",
+                        "    { 'x': '1', 'y': '0' },",
+                        "    { 'x': '2', 'y': '0' } ]}"), "mixed_tensor");
+    }
+
+    @Test
+    public void tensor_remove_update_on_dense_tensor_throws() {
         exception.expect(IllegalArgumentException.class);
-        exception.expectMessage("A remove update can only be applied to sparse tensors. Field 'mixed_tensor' has unsupported tensor type 'tensor(x{},y[3])'");
+        exception.expectMessage("A remove update can only be applied to tensors with at least one sparse dimension. Field 'dense_tensor' has unsupported tensor type 'tensor(x[2],y[3])'");
         createTensorRemoveUpdate(inputJson("{",
-                "  'addresses': [] }"), "mixed_tensor");
+                "  'addresses': [] }"), "dense_tensor");
     }
 
     @Test
@@ -1503,6 +1570,7 @@ public class JsonReaderTestCase {
         exception.expect(IllegalArgumentException.class);
         exception.expectMessage("Remove update for field 'sparse_tensor' does not contain tensor addresses");
         createTensorRemoveUpdate(inputJson("{'addresses': [] }"), "sparse_tensor");
+        createTensorRemoveUpdate(inputJson("{'addresses': [] }"), "mixed_tensor");
     }
 
     @Test
diff --git a/document/src/test/java/com/yahoo/document/update/TensorAddUpdateTest.java b/document/src/test/java/com/yahoo/document/update/TensorAddUpdateTest.java
index eb4001e6415..6935c54ba2a 100644
--- a/document/src/test/java/com/yahoo/document/update/TensorAddUpdateTest.java
+++ b/document/src/test/java/com/yahoo/document/update/TensorAddUpdateTest.java
@@ -12,18 +12,14 @@ public class TensorAddUpdateTest {
     @Test
     public void apply_add_update_operations() {
         assertApplyTo("{{x:0,y:0}:1, {x:0,y:1}:2}", "{{x:0,y:2}:3}", "{{x:0,y:0}:1,{x:0,y:1}:2,{x:0,y:2}:3}");
-        assertApplyTo("{{x:0,y:0}:1, {x:0,y:1}:2}", "{{x:0,y:1}:3}", "{{x:0,y:0}:1,{x:0,y:1}:3}");
-        assertApplyTo("{{x:0,y:0}:1, {x:0,y:1}:2}", "{{x:0,y:1}:3,{x:0,y:2}:4}", "{{x:0,y:0}:1,{x:0,y:1}:3,{x:0,y:2}:4}");
-        assertApplyTo("{}", "{{x:0,y:0}:5}", "{{x:0,y:0}:5}");
-        assertApplyTo("{{x:0,y:0}:1, {x:0,y:1}:2}", "{}", "{{x:0,y:0}:1, {x:0,y:1}:2}");
     }
 
     private void assertApplyTo(String init, String update, String expected) {
         String spec = "tensor(x{},y{})";
         TensorFieldValue initialFieldValue = new TensorFieldValue(Tensor.from(spec, init));
         TensorAddUpdate addUpdate = new TensorAddUpdate(new TensorFieldValue(Tensor.from(spec, update)));
-        TensorFieldValue updatedFieldValue = (TensorFieldValue) addUpdate.applyTo(initialFieldValue);
-        assertEquals(Tensor.from(spec, expected), updatedFieldValue.getTensor().get());
+        Tensor updated = ((TensorFieldValue) addUpdate.applyTo(initialFieldValue)).getTensor().get();
+        assertEquals(Tensor.from(spec, expected), updated);
     }
 
 }
diff --git a/document/src/test/java/com/yahoo/document/update/TensorModifyUpdateTest.java b/document/src/test/java/com/yahoo/document/update/TensorModifyUpdateTest.java
index 6e9444de2be..b885e6ddca0 100644
--- a/document/src/test/java/com/yahoo/document/update/TensorModifyUpdateTest.java
+++ b/document/src/test/java/com/yahoo/document/update/TensorModifyUpdateTest.java
@@ -1,12 +1,6 @@
 // Copyright 2019 Oath Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
 package com.yahoo.document.update;
 
-import com.yahoo.document.Document;
-import com.yahoo.document.DocumentId;
-import com.yahoo.document.DocumentType;
-import com.yahoo.document.DocumentTypeManager;
-import com.yahoo.document.Field;
-import com.yahoo.document.TensorDataType;
 import com.yahoo.document.datatypes.TensorFieldValue;
 import com.yahoo.document.update.TensorModifyUpdate.Operation;
 import com.yahoo.tensor.Tensor;
@@ -28,10 +22,11 @@ public class TensorModifyUpdateTest {
         assertConvertToCompatible("tensor(x{})", "tensor(x[10])");
         assertConvertToCompatible("tensor(x{})", "tensor(x{})");
         assertConvertToCompatible("tensor(x{},y{},z{})", "tensor(x[],y[10],z{})");
+        assertConvertToCompatible("tensor(x{},y{})", "tensor(x{},y[3])");
     }
 
     private static void assertConvertToCompatible(String expectedType, String inputType) {
-        assertEquals(expectedType, TensorModifyUpdate.convertToCompatibleType(TensorType.fromSpec(inputType)).toString());
+        assertEquals(expectedType, TensorModifyUpdate.convertDimensionsToMapped(TensorType.fromSpec(inputType)).toString());
     }
 
     @Test
@@ -46,15 +41,9 @@ public class TensorModifyUpdateTest {
     public void apply_modify_update_operations() {
         assertApplyTo("tensor(x{},y{})", Operation.REPLACE,
                 "{{x:0,y:0}:1, {x:0,y:1}:2}", "{{x:0,y:1}:0}", "{{x:0,y:0}:1,{x:0,y:1}:0}");
-        assertApplyTo("tensor(x{},y{})", Operation.ADD,
-                "{{x:0,y:0}:1, {x:0,y:1}:2}", "{{x:0,y:1}:3}", "{{x:0,y:0}:1,{x:0,y:1}:5}");
-        assertApplyTo("tensor(x{},y{})", Operation.MULTIPLY,
-                "{{x:0,y:0}:3, {x:0,y:1}:2}", "{{x:0,y:1}:3}", "{{x:0,y:0}:3,{x:0,y:1}:6}");
-        assertApplyTo("tensor(x[1],y[2])", Operation.REPLACE,
-                "{{x:0,y:0}:1, {x:0,y:1}:2}", "{{x:0,y:1}:0}", "{{x:0,y:0}:1,{x:0,y:1}:0}");
         assertApplyTo("tensor(x[1],y[2])", Operation.ADD,
                 "{{x:0,y:0}:1, {x:0,y:1}:2}", "{{x:0,y:1}:3}", "{{x:0,y:0}:1,{x:0,y:1}:5}");
-        assertApplyTo("tensor(x[1],y[2])", Operation.MULTIPLY,
+        assertApplyTo("tensor(x{},y[2])", Operation.MULTIPLY,
                 "{{x:0,y:0}:3, {x:0,y:1}:2}", "{{x:0,y:1}:3}", "{{x:0,y:0}:3,{x:0,y:1}:6}");
     }
 
diff --git a/document/src/test/java/com/yahoo/document/update/TensorRemoveUpdateTest.java b/document/src/test/java/com/yahoo/document/update/TensorRemoveUpdateTest.java
index 40ab00facdb..3a005e858c8 100644
--- a/document/src/test/java/com/yahoo/document/update/TensorRemoveUpdateTest.java
+++ b/document/src/test/java/com/yahoo/document/update/TensorRemoveUpdateTest.java
@@ -12,9 +12,6 @@ public class TensorRemoveUpdateTest {
     @Test
     public void apply_remove_update_operations() {
         assertApplyTo("{{x:0,y:0}:2, {x:0,y:1}:3}", "{{x:0,y:1}:1}", "{{x:0,y:0}:2}");
-        assertApplyTo("{{x:0,y:0}:1, {x:0,y:1}:2}", "{{x:0,y:0}:1,{x:0,y:1}:1}", "{}");
-        assertApplyTo("{}", "{{x:0,y:0}:1}", "{}");
-        assertApplyTo("{{x:0,y:0}:2, {x:0,y:1}:3}", "{}", "{{x:0,y:0}:2, {x:0,y:1}:3}");
     }
 
     private void assertApplyTo(String init, String update, String expected) {
diff --git a/vespa-hadoop/abi-spec.json b/vespa-hadoop/abi-spec.json
index 5bbac15f0e5..e3f4dcf272a 100644
--- a/vespa-hadoop/abi-spec.json
+++ b/vespa-hadoop/abi-spec.json
@@ -1201,6 +1201,8 @@
       "public com.yahoo.tensor.IndexedTensor withType(com.yahoo.tensor.TensorType)",
       "public com.yahoo.tensor.DimensionSizes dimensionSizes()",
       "public java.util.Map cells()",
+      "public com.yahoo.tensor.Tensor merge(java.util.function.DoubleBinaryOperator, java.util.Map)",
+      "public com.yahoo.tensor.Tensor remove(java.util.Set)",
       "public int hashCode()",
       "public java.lang.String toString()",
       "public boolean equals(java.lang.Object)",
@@ -1245,6 +1247,8 @@
       "public java.util.Iterator valueIterator()",
       "public java.util.Map cells()",
       "public com.yahoo.tensor.Tensor withType(com.yahoo.tensor.TensorType)",
+      "public com.yahoo.tensor.Tensor merge(java.util.function.DoubleBinaryOperator, java.util.Map)",
+      "public com.yahoo.tensor.Tensor remove(java.util.Set)",
       "public int hashCode()",
       "public java.lang.String toString()",
       "public boolean equals(java.lang.Object)"
@@ -1330,6 +1334,8 @@
       "public java.util.Iterator valueIterator()",
       "public java.util.Map cells()",
       "public com.yahoo.tensor.Tensor withType(com.yahoo.tensor.TensorType)",
+      "public com.yahoo.tensor.Tensor merge(java.util.function.DoubleBinaryOperator, java.util.Map)",
+      "public com.yahoo.tensor.Tensor remove(java.util.Set)",
       "public int hashCode()",
       "public java.lang.String toString()",
       "public boolean equals(java.lang.Object)",
@@ -1432,6 +1438,8 @@
       "public double asDouble()",
       "public abstract com.yahoo.tensor.Tensor withType(com.yahoo.tensor.TensorType)",
       "public com.yahoo.tensor.Tensor modify(java.util.function.DoubleBinaryOperator, java.util.Map)",
+      "public abstract com.yahoo.tensor.Tensor merge(java.util.function.DoubleBinaryOperator, java.util.Map)",
+      "public abstract com.yahoo.tensor.Tensor remove(java.util.Set)",
       "public com.yahoo.tensor.Tensor map(java.util.function.DoubleUnaryOperator)",
       "public varargs com.yahoo.tensor.Tensor reduce(com.yahoo.tensor.functions.Reduce$Aggregator, java.lang.String[])",
       "public com.yahoo.tensor.Tensor reduce(com.yahoo.tensor.functions.Reduce$Aggregator, java.util.List)",
diff --git a/vespajlib/abi-spec.json b/vespajlib/abi-spec.json
index 932513f8a57..c3fe8c5c7ad 100644
--- a/vespajlib/abi-spec.json
+++ b/vespajlib/abi-spec.json
@@ -808,6 +808,8 @@
       "public com.yahoo.tensor.IndexedTensor withType(com.yahoo.tensor.TensorType)",
       "public com.yahoo.tensor.DimensionSizes dimensionSizes()",
       "public java.util.Map cells()",
+      "public com.yahoo.tensor.Tensor merge(java.util.function.DoubleBinaryOperator, java.util.Map)",
+      "public com.yahoo.tensor.Tensor remove(java.util.Set)",
       "public int hashCode()",
       "public java.lang.String toString()",
       "public boolean equals(java.lang.Object)",
@@ -852,6 +854,8 @@
       "public java.util.Iterator valueIterator()",
       "public java.util.Map cells()",
       "public com.yahoo.tensor.Tensor withType(com.yahoo.tensor.TensorType)",
+      "public com.yahoo.tensor.Tensor merge(java.util.function.DoubleBinaryOperator, java.util.Map)",
+      "public com.yahoo.tensor.Tensor remove(java.util.Set)",
       "public int hashCode()",
       "public java.lang.String toString()",
       "public boolean equals(java.lang.Object)"
@@ -937,6 +941,8 @@
       "public java.util.Iterator valueIterator()",
       "public java.util.Map cells()",
       "public com.yahoo.tensor.Tensor withType(com.yahoo.tensor.TensorType)",
+      "public com.yahoo.tensor.Tensor merge(java.util.function.DoubleBinaryOperator, java.util.Map)",
+      "public com.yahoo.tensor.Tensor remove(java.util.Set)",
       "public int hashCode()",
       "public java.lang.String toString()",
       "public boolean equals(java.lang.Object)",
@@ -1039,6 +1045,8 @@
       "public double asDouble()",
       "public abstract com.yahoo.tensor.Tensor withType(com.yahoo.tensor.TensorType)",
       "public com.yahoo.tensor.Tensor modify(java.util.function.DoubleBinaryOperator, java.util.Map)",
+      "public abstract com.yahoo.tensor.Tensor merge(java.util.function.DoubleBinaryOperator, java.util.Map)",
+      "public abstract com.yahoo.tensor.Tensor remove(java.util.Set)",
       "public com.yahoo.tensor.Tensor map(java.util.function.DoubleUnaryOperator)",
       "public varargs com.yahoo.tensor.Tensor reduce(com.yahoo.tensor.functions.Reduce$Aggregator, java.lang.String[])",
       "public com.yahoo.tensor.Tensor reduce(com.yahoo.tensor.functions.Reduce$Aggregator, java.util.List)",
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/IndexedTensor.java b/vespajlib/src/main/java/com/yahoo/tensor/IndexedTensor.java
index fb55b2d5014..38d832d01c2 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/IndexedTensor.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/IndexedTensor.java
@@ -13,6 +13,7 @@ import java.util.Map;
 import java.util.NoSuchElementException;
 import java.util.Optional;
 import java.util.Set;
+import java.util.function.DoubleBinaryOperator;
 
 /**
  * An indexed (dense) tensor backed by a double array.
@@ -190,6 +191,16 @@ public class IndexedTensor implements Tensor {
     }
 
     @Override
+    public Tensor merge(DoubleBinaryOperator op, Map<TensorAddress, Double> cells) {
+        throw new IllegalArgumentException("Merge is not supported for indexed tensors");
+    }
+
+    @Override
+    public Tensor remove(Set<TensorAddress> addresses) {
+        throw new IllegalArgumentException("Remove is not supported for indexed tensors");
+    }
+
+    @Override
     public int hashCode() { return Arrays.hashCode(values); }
 
     @Override
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/MappedTensor.java b/vespajlib/src/main/java/com/yahoo/tensor/MappedTensor.java
index ec3020a1a4e..22ceed22d3e 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/MappedTensor.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/MappedTensor.java
@@ -5,6 +5,8 @@ import com.google.common.collect.ImmutableMap;
 
 import java.util.Iterator;
 import java.util.Map;
+import java.util.Set;
+import java.util.function.DoubleBinaryOperator;
 
 /**
  * A sparse implementation of a tensor backed by a Map of cells to values.
@@ -51,6 +53,38 @@ public class MappedTensor implements Tensor {
     }
 
     @Override
+    public Tensor merge(DoubleBinaryOperator op, Map<TensorAddress, Double> addCells) {
+
+        // currently, underlying implementation disallows multiple entries with the same key
+
+        Tensor.Builder builder = Tensor.Builder.of(type());
+        for (Map.Entry<TensorAddress, Double> cell  : cells.entrySet()) {
+            TensorAddress address = cell.getKey();
+            double value = cell.getValue();
+            builder.cell(address, addCells.containsKey(address) ? op.applyAsDouble(value, addCells.get(address)) : value);
+        }
+        for (Map.Entry<TensorAddress, Double> addCell : addCells.entrySet()) {
+            if ( ! cells.containsKey(addCell.getKey())) {
+                builder.cell(addCell.getKey(), addCell.getValue());
+            }
+        }
+        return builder.build();
+    }
+
+    @Override
+    public Tensor remove(Set<TensorAddress> addresses) {
+        Tensor.Builder builder = Tensor.Builder.of(type());
+        for (Iterator<Tensor.Cell> i = cellIterator(); i.hasNext(); ) {
+            Tensor.Cell cell = i.next();
+            TensorAddress address = cell.getKey();
+            if ( ! addresses.contains(address)) {
+                builder.cell(address, cell.getValue());
+            }
+        }
+        return builder.build();
+    }
+
+    @Override
     public int hashCode() { return cells.hashCode(); }
 
     @Override
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/MixedTensor.java b/vespajlib/src/main/java/com/yahoo/tensor/MixedTensor.java
index 17e33c58a13..08878edeb83 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/MixedTensor.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/MixedTensor.java
@@ -9,6 +9,8 @@ import java.util.HashMap;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
+import java.util.Set;
+import java.util.function.DoubleBinaryOperator;
 import java.util.stream.Collectors;
 
 /**
@@ -70,13 +72,17 @@ public class MixedTensor implements Tensor {
         return cells.iterator();
     }
 
+    private Iterable<Cell> cellIterable() {
+        return this::cellIterator;
+    }
+
     /**
      * Returns an iterator over the values of this tensor.
      * The iteration order is the same as for cellIterator.
      */
     @Override
     public Iterator<Double> valueIterator() {
-        return new Iterator<Double>() {
+        return new Iterator<>() {
             Iterator<Cell> cellIterator = cellIterator();
             @Override
             public boolean hasNext() {
@@ -108,6 +114,38 @@ public class MixedTensor implements Tensor {
     }
 
     @Override
+    public Tensor merge(DoubleBinaryOperator op, Map<TensorAddress, Double> addCells) {
+        Tensor.Builder builder = Tensor.Builder.of(type());
+        for (Cell cell  : cellIterable()) {
+            TensorAddress address = cell.getKey();
+            double value = cell.getValue();
+            builder.cell(address, addCells.containsKey(address) ? op.applyAsDouble(value, addCells.get(address)) : value);
+        }
+        for (Map.Entry<TensorAddress, Double> addCell : addCells.entrySet()) {
+            builder.cell(addCell.getKey(), addCell.getValue());
+        }
+        return builder.build();
+    }
+
+    @Override
+    public Tensor remove(Set<TensorAddress> addresses) {
+        Tensor.Builder builder = Tensor.Builder.of(type());
+
+        // iterate through all sparse addresses referencing a dense subspace
+        for (Map.Entry<TensorAddress, Long> entry : index.sparseMap.entrySet()) {
+            TensorAddress sparsePartialAddress = entry.getKey();
+            if ( ! addresses.contains(sparsePartialAddress)) {  // assumption: addresses only contain the sparse part
+                long offset = entry.getValue();
+                for (int i = 0; i < index.denseSubspaceSize; ++i) {
+                    Cell cell = cells.get((int)offset + i);
+                    builder.cell(cell.getKey(), cell.getValue());
+                }
+            }
+        }
+        return builder.build();
+    }
+
+    @Override
     public int hashCode() { return cells.hashCode(); }
 
     @Override
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/Tensor.java b/vespajlib/src/main/java/com/yahoo/tensor/Tensor.java
index 8002990e5c6..eb16801c306 100644
--- a/vespajlib/src/main/java/com/yahoo/tensor/Tensor.java
+++ b/vespajlib/src/main/java/com/yahoo/tensor/Tensor.java
@@ -25,6 +25,7 @@ import java.util.Iterator;
 import java.util.List;
 import java.util.Map;
 import java.util.Optional;
+import java.util.Set;
 import java.util.function.DoubleBinaryOperator;
 import java.util.function.DoubleUnaryOperator;
 import java.util.function.Function;
@@ -113,6 +114,29 @@ public interface Tensor {
         return builder.build();
     }
 
+    /**
+     * Returns a new tensor where existing cells in this tensor have been
+     * modified according to the given operation and cells in the given map.
+     * In contrast to {@link #modify}, previously non-existing cells are added
+     * to this tensor. Only valid for sparse or mixed tensors.
+     *
+     * @param op how to update overlapping cells
+     * @param cells cells to merge with this tensor
+     * @return a new tensor where this tensor is merged with the other
+     */
+    Tensor merge(DoubleBinaryOperator op, Map<TensorAddress, Double> cells);
+
+    /**
+     * Returns a new tensor where existing cells in this tensor have been
+     * removed according to the given set of addresses. Only valid for sparse
+     * or mixed tensors. For mixed tensors, addresses are assumed to only
+     * contain the sparse dimensions, as the entire dense subspace is removed.
+     *
+     * @param addresses list of addresses to remove
+     * @return a new tensor where cells have been removed
+     */
+    Tensor remove(Set<TensorAddress> addresses);
+
     // ----------------- Primitive tensor functions
 
     default Tensor map(DoubleUnaryOperator mapper) {
diff --git a/vespajlib/src/test/java/com/yahoo/tensor/TensorTestCase.java b/vespajlib/src/test/java/com/yahoo/tensor/TensorTestCase.java
index 2c9eefbd130..02d16e6f3e4 100644
--- a/vespajlib/src/test/java/com/yahoo/tensor/TensorTestCase.java
+++ b/vespajlib/src/test/java/com/yahoo/tensor/TensorTestCase.java
@@ -151,12 +151,106 @@ public class TensorTestCase {
                 Tensor.from("tensor(x[1],y[2])", "{{x:0,y:0}:1, {x:0,y:1}:2}"),
                 Tensor.from("tensor(x[1],y[3])", "{}"),
                 Tensor.from("tensor(x[1],y[2])", "{{x:0,y:0}:0,{x:0,y:1}:0}"));
+        assertTensorModify((left, right) -> left * right,
+                Tensor.from("tensor(x{},y[3])", "{{x:0,y:0}:1, {x:0,y:1}:2}"),
+                Tensor.from("tensor(x{},y{})", "{{x:0,y:1}:3}"),
+                Tensor.from("tensor(x{},y[3])", "{{x:0,y:0}:1,{x:0,y:1}:6}"));
+    }
+
+    @Test
+    public void testTensorMerge() {
+        assertTensorMerge(
+                Tensor.from("tensor(x{},y{})", "{{x:0,y:0}:1,{x:0,y:1}:2}"),
+                Tensor.from("tensor(x{},y{})", "{{x:0,y:2}:3}"),
+                Tensor.from("tensor(x{},y{})", "{{x:0,y:0}:1,{x:0,y:1}:2,{x:0,y:2}:3}"));
+        assertTensorMerge(
+                Tensor.from("tensor(x{},y{})", "{{x:0,y:0}:1,{x:0,y:1}:2}"),
+                Tensor.from("tensor(x{},y{})", "{{x:0,y:1}:3}"),
+                Tensor.from("tensor(x{},y{})", "{{x:0,y:0}:1,{x:0,y:1}:3}"));
+        assertTensorMerge(
+                Tensor.from("tensor(x{},y{})", "{{x:0,y:0}:1,{x:0,y:1}:2}"),
+                Tensor.from("tensor(x{},y{})", "{{x:0,y:1}:3,{x:0,y:2}:4}"),
+                Tensor.from("tensor(x{},y{})", "{{x:0,y:0}:1,{x:0,y:1}:3,{x:0,y:2}:4}"));
+        assertTensorMerge(
+                Tensor.from("tensor(x{},y{})", "{}"),
+                Tensor.from("tensor(x{},y{})", "{{x:0,y:0}:5}"),
+                Tensor.from("tensor(x{},y{})", "{{x:0,y:0}:5}"));
+        assertTensorMerge(
+                Tensor.from("tensor(x{},y{})", "{{x:0,y:0}:1,{x:0,y:1}:2}"),
+                Tensor.from("tensor(x{},y{})", "{}"),
+                Tensor.from("tensor(x{},y{})", "{{x:0,y:0}:1,{x:0,y:1}:2}"));
+        assertTensorMerge(
+                Tensor.from("tensor(x{},y[3])", "{{x:0,y:0}:1,{x:0,y:1}:2}"),
+                Tensor.from("tensor(x{},y[3])", "{{x:0,y:2}:3}"),
+                Tensor.from("tensor(x{},y[3])", "{{x:0,y:0}:0,{x:0,y:1}:0,{x:0,y:2}:3}"));  // notice difference with sparse case - y is dense dimension here with default value 0.0
+        assertTensorMerge(
+                Tensor.from("tensor(x{},y[3])", "{{x:0,y:0}:1,{x:0,y:1}:2}"),
+                Tensor.from("tensor(x{},y[3])", "{{x:0,y:1}:3}"),
+                Tensor.from("tensor(x{},y[3])", "{{x:0,y:0}:0,{x:0,y:1}:3,{x:0,y:2}:0}"));
+        assertTensorMerge(
+                Tensor.from("tensor(x{},y[3])", "{{x:0,y:0}:1,{x:0,y:1}:2}"),
+                Tensor.from("tensor(x{},y[3])", "{{x:0,y:1}:3,{x:0,y:2}:4}"),
+                Tensor.from("tensor(x{},y[3])", "{{x:0,y:0}:0,{x:0,y:1}:3,{x:0,y:2}:4}"));
+        assertTensorMerge(
+                Tensor.from("tensor(x{},y[3])", "{}"),
+                Tensor.from("tensor(x{},y[3])", "{{x:0,y:0}:5}"),
+                Tensor.from("tensor(x{},y[3])", "{{x:0,y:0}:5}"));
+        assertTensorMerge(
+                Tensor.from("tensor(x{},y[3])", "{{x:0,y:0}:1,{x:0,y:1}:2}"),
+                Tensor.from("tensor(x{},y[3])", "{}"),
+                Tensor.from("tensor(x{},y[3])", "{{x:0,y:0}:1,{x:0,y:1}:2}"));
+    }
+
+    @Test
+    public void testTensorRemove() {
+        assertTensorRemove(
+                Tensor.from("tensor(x{},y{})", "{{x:0,y:0}:2,{x:0,y:1}:3}"),
+                Tensor.from("tensor(x{},y{})", "{{x:0,y:1}:1}"),
+                Tensor.from("tensor(x{},y{})", "{{x:0,y:0}:2}"));
+        assertTensorRemove(
+                Tensor.from("tensor(x{},y{})", "{{x:0,y:0}:1,{x:0,y:1}:2}"),
+                Tensor.from("tensor(x{},y{})", "{{x:0,y:0}:1,{x:0,y:1}:1}"),
+                Tensor.from("tensor(x{},y{})", "{}"));
+        assertTensorRemove(
+                Tensor.from("tensor(x{},y{})", "{}"),
+                Tensor.from("tensor(x{},y{})", "{{x:0,y:0}:1}"),
+                Tensor.from("tensor(x{},y{})", "{}"));
+        assertTensorRemove(
+                Tensor.from("tensor(x{},y{})", "{{x:0,y:0}:2,{x:0,y:1}:3}"),
+                Tensor.from("tensor(x{},y{})", "{}"),
+                Tensor.from("tensor(x{},y{})", "{{x:0,y:0}:2,{x:0,y:1}:3}"));
+        assertTensorRemove(
+                Tensor.from("tensor(x{},y[3])", "{{x:0,y:0}:2, {x:0,y:1}:3}"),
+                Tensor.from("tensor(x{})", "{{x:0}:1}"),  // notice update is without dense dimension
+                Tensor.from("tensor(x{},y[3])", "{}"));
+        assertTensorRemove(
+                Tensor.from("tensor(x{},y[3])", "{{x:0,y:0}:1,{x:1,y:0}:2}"),
+                Tensor.from("tensor(x{})", "{{x:0}:1}"),
+                Tensor.from("tensor(x{},y[3])", "{{x:1,y:0}:2,{x:1,y:1}:0,{x:1,y:2}:0}"));
+        assertTensorRemove(
+                Tensor.from("tensor(x{},y[3])", "{}"),
+                Tensor.from("tensor(x{})", "{{x:0}:1}"),
+                Tensor.from("tensor(x{},y[3])", "{}"));
+        assertTensorRemove(
+                Tensor.from("tensor(x{},y[3])", "{{x:0,y:0}:2,{x:0,y:1}:3}"),
+                Tensor.from("tensor(x{})", "{}"),
+                Tensor.from("tensor(x{},y[3])", "{{x:0,y:0}:2,{x:0,y:1}:3}"));
     }
 
     private void assertTensorModify(DoubleBinaryOperator op, Tensor init, Tensor update, Tensor expected) {
         assertEquals(expected, init.modify(op, update.cells()));
     }
 
+    private void assertTensorMerge(Tensor init, Tensor update, Tensor expected) {
+        DoubleBinaryOperator op = (left, right) -> right;
+        assertEquals(expected, init.merge(op, update.cells()));
+    }
+
+    private void assertTensorRemove(Tensor init, Tensor update, Tensor expected) {
+        assertEquals(expected, init.remove(update.cells().keySet()));
+    }
+
+
     private double dotProduct(Tensor tensor, List<Tensor> tensors) {
         double sum = 0;
         TensorFunction dotProductFunction = new Reduce(new Join(new ConstantTensor(tensor),