Introduce Serialization format for DataInKeySpacePath

fdb-record-layer-core/src/main/java/com/apple/foundationdb/record/provider/foundationdb/keyspace/DataInKeySpacePath.java

@@ -53,6 +53,7 @@ public DataInKeySpacePath(@Nonnull final KeySpacePath path, @Nullable final Tupl
         this.value = value;
     }
 
+    @Nonnull
     public byte[] getValue() {
         return this.value;
     }

fdb-record-layer-core/src/main/java/com/apple/foundationdb/record/provider/foundationdb/keyspace/DirectoryLayerDirectory.java

@@ -30,6 +30,7 @@
 
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
+import java.util.Objects;
 import java.util.Optional;
 import java.util.concurrent.CompletableFuture;
 import java.util.function.Function;
@@ -148,6 +149,18 @@ public DirectoryLayerDirectory(@Nonnull String name, @Nullable Object value,
         this.createHooks = createHooks;
     }
 
+    @Override
+    protected boolean isValueValid(@Nullable Object value) {
+        // DirectoryLayerDirectory accepts both String (logical names) and Long (directory layer values),
+        // but we're making this method stricter, and I hope that using Long is only for a handful of tests,
+        // despite comments saying that the resolved value should be allowed.
+        if (value instanceof String) {
+            // If this directory has a constant value, check that the provided value matches it
+            return Objects.equals(getValue(), KeySpaceDirectory.ANY_VALUE) || Objects.equals(getValue(), value);
+        }
+        return false;
+    }
+
     @Override
     protected void validateConstant(@Nullable Object value) {
         if (!(value instanceof String)) {

fdb-record-layer-core/src/main/java/com/apple/foundationdb/record/provider/foundationdb/keyspace/KeySpaceDirectory.java

@@ -176,6 +176,47 @@ LogMessageKeys.DIR_NAME, getName(),
         }
     }
 
+    /**
+     * Validate that the given value can be used with this directory.
+     * @param value a potential value
+     * @throws RecordCoreArgumentException if the value is not valid
+     */
+    protected void validateValue(@Nullable Object value) {
+        // Validate that the value is valid for this directory
+        if (!isValueValid(value)) {
+            throw new RecordCoreArgumentException("Value does not match directory requirements")
+                .addLogInfo(LogMessageKeys.DIR_NAME, name,
+                    LogMessageKeys.EXPECTED_TYPE, getKeyType(),
+                    LogMessageKeys.ACTUAL, value,
+                    "actual_type", value == null ? "null" : value.getClass().getName(),
+                    "expected_value", getValue());
+        }
+    }
+
+    /**
+     * Checks if the provided value is valid for this directory. This method can be overridden by subclasses
+     * to provide custom validation logic. For example, {@link DirectoryLayerDirectory} accepts both String
+     * (logical names) and Long (directory layer values) even though its key type is LONG.
+     *
+     * @param value the value to validate
+     * @return {@code true} if the value is valid for this directory
+     */
+    protected boolean isValueValid(@Nullable Object value) {
+        // Check if value matches the key type
+        if (!keyType.isMatch(value)) {
+            return false;
+        }
+        // If this directory has a constant value, check that the provided value matches it
+        if (this.value != ANY_VALUE) {
+            if (this.value instanceof byte[] && value instanceof byte[]) {
+                return Arrays.equals((byte[]) this.value, (byte[]) value);
+            } else {
+                return Objects.equals(this.value, value);
+            }
+        }
+        return true;
+    }
+
     /**
      * Given a position in a tuple, checks to see if this directory is compatible with the value at the
      * position, returning either a path indicating that it was compatible or nothing if it was not compatible.

fdb-record-layer-core/src/main/java/com/apple/foundationdb/record/provider/foundationdb/keyspace/KeySpacePath.java

@@ -410,4 +410,13 @@ default RecordCursor<DataInKeySpacePath> exportAllData(@Nonnull FDBRecordContext
                                                            @Nonnull ScanProperties scanProperties) {
         throw new UnsupportedOperationException("exportAllData is not supported");
     }
+
+    /**
+     * Two {@link KeySpacePath}s are equal if they have equal values, the same directory (reference equality) and their
+     * parents are the same.
+     * @param obj another {@link KeySpacePath}
+     * @return {@code true} if this path equals {@code obj}
+     */
+    @Override
+    boolean equals(Object obj);
 }

fdb-record-layer-core/src/main/java/com/apple/foundationdb/record/provider/foundationdb/keyspace/KeySpacePathSerializer.java

@@ -0,0 +1,208 @@
+/*
+ * KeySpacePathSerializer.java
+ *
+ * This source file is part of the FoundationDB open source project
+ *
+ * Copyright 2015-2025 Apple Inc. and the FoundationDB project authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.apple.foundationdb.record.provider.foundationdb.keyspace;
+
+import com.apple.foundationdb.annotation.API;
+import com.apple.foundationdb.record.RecordCoreArgumentException;
+import com.apple.foundationdb.record.logging.LogMessageKeys;
+import com.apple.foundationdb.tuple.Tuple;
+import com.google.protobuf.ByteString;
+
+import javax.annotation.Nonnull;
+import javax.annotation.Nullable;
+import java.util.List;
+import java.util.UUID;
+
+/**
+ * Class for serializing/deserializing between {@link DataInKeySpacePath} and {@link KeySpaceProto.DataInKeySpacePath}.
+ * <p>
+ *     This will serialize relative to a root path, such that the serialized form is relative to that path. This can be
+ *     useful to both:
+ *     <ul>
+ *         <li>Reduce the size of the serialized data, particularly when you have a lot of these.</li>
+ *         <li>Allowing as an intermediate if you have two identical sub-hierarchies in your {@link KeySpace}.</li>
+ *     </ul>
+ * </p>
+ *
+ */
+@API(API.Status.EXPERIMENTAL)
+public class KeySpacePathSerializer {
+
+    @Nonnull
+    private final List<KeySpacePath> root;
+
+    public KeySpacePathSerializer(@Nonnull final KeySpacePath root) {
+        this.root = root.flatten();
+    }
+
+    @Nonnull
+    public ByteString serialize(@Nonnull DataInKeySpacePath data) {
+        final List<KeySpacePath> dataPath = data.getPath().flatten();
+        // two paths are only equal if their parents are equal, so we don't have to validate the whole prefix here
+        if (dataPath.size() < root.size() ||
+                !dataPath.get(root.size() - 1).equals(root.get(root.size() - 1))) {
+            throw new RecordCoreArgumentException("Data is not contained within root path");
+        }
+        KeySpaceProto.DataInKeySpacePath.Builder builder = KeySpaceProto.DataInKeySpacePath.newBuilder();
+        for (int i = root.size(); i < dataPath.size(); i++) {
+            final KeySpacePath keySpacePath = dataPath.get(i);
+            builder.addPath(serialize(keySpacePath));
+        }
+        if (data.getRemainder() != null) {
+            builder.setRemainder(ByteString.copyFrom(data.getRemainder().pack()));
+        }
+        builder.setValue(ByteString.copyFrom(data.getValue()));
+        return builder.build().toByteString();
+    }
+
+    @Nonnull
+    public DataInKeySpacePath deserialize(@Nonnull ByteString bytes) {
+        try {
+            KeySpaceProto.DataInKeySpacePath proto = KeySpaceProto.DataInKeySpacePath.parseFrom(bytes);
+            return deserialize(proto);
+        } catch (com.google.protobuf.InvalidProtocolBufferException e) {
+            throw new RecordCoreArgumentException("Failed to parse serialized DataInKeySpacePath", e);
+        }
+    }
+
+    @Nonnull
+    private DataInKeySpacePath deserialize(@Nonnull KeySpaceProto.DataInKeySpacePath proto) {
+        // Start with the root path
+        KeySpacePath path = root.get(root.size() - 1);
+
+        // Add each path entry from the proto
+        for (KeySpaceProto.KeySpacePathEntry entry : proto.getPathList()) {
+            Object value = deserializeValue(entry);
+            path.getDirectory().getSubdirectory(entry.getName()).validateValue(value);
+            path = path.add(entry.getName(), value);
+        }
+
+        // Extract remainder if present
+        Tuple remainder = null;
+        if (proto.hasRemainder()) {
+            remainder = Tuple.fromBytes(proto.getRemainder().toByteArray());
+        }
+
+        // Extract value
+        if (!proto.hasValue()) {
+            throw new RecordCoreArgumentException("Serialized data must have a value");
+        }
+        byte[] value = proto.getValue().toByteArray();
+
+        return new DataInKeySpacePath(path, remainder, value);
+    }
+
+    @Nullable
+    private static Object deserializeValue(@Nonnull KeySpaceProto.KeySpacePathEntry entry) {
+        // Check which value field is set and return the appropriate value
+        if (entry.hasNullValue()) {
+            return null;
+        } else if (entry.hasBytesValue()) {
+            return entry.getBytesValue().toByteArray();
+        } else if (entry.hasStringValue()) {
+            return entry.getStringValue();
+        } else if (entry.hasLongValue()) {
+            return entry.getLongValue();
+        } else if (entry.hasFloatValue()) {
+            return entry.getFloatValue();
+        } else if (entry.hasDoubleValue()) {
+            return entry.getDoubleValue();
+        } else if (entry.hasBooleanValue()) {
+            return entry.getBooleanValue();
+        } else if (entry.hasUuid()) {
+            KeySpaceProto.KeySpacePathEntry.UUID uuidProto = entry.getUuid();
+            return new UUID(uuidProto.getMostSignificantBits(), uuidProto.getLeastSignificantBits());
+        } else {
+            throw new RecordCoreArgumentException("KeySpacePathEntry has no value set")
+                    .addLogInfo(LogMessageKeys.DIR_NAME, entry.getName());
+        }
+    }
+
+    @Nonnull
+    private static KeySpaceProto.KeySpacePathEntry serialize(@Nonnull final KeySpacePath keySpacePath) {
+        final Object value = keySpacePath.getValue();
+        final KeySpaceDirectory.KeyType keyType = keySpacePath.getDirectory().getKeyType();
+
+        // Validate null handling: NULL type must have null value, all other types must not have null value
+        if (keyType == KeySpaceDirectory.KeyType.NULL) {
+            if (value != null) {
+                throw new RecordCoreArgumentException("NULL key type must have null value")
+                        .addLogInfo(LogMessageKeys.DIR_NAME, keySpacePath.getDirectoryName(),
+                                LogMessageKeys.ACTUAL, value);
+            }
+        } else {
+            if (value == null) {
+                throw new RecordCoreArgumentException("Non-NULL key type cannot have null value")
+                        .addLogInfo(LogMessageKeys.DIR_NAME, keySpacePath.getDirectoryName(),
+                                LogMessageKeys.EXPECTED_TYPE, keyType);
+            }
+        }
+
+        KeySpaceProto.KeySpacePathEntry.Builder builder = KeySpaceProto.KeySpacePathEntry.newBuilder()
+                .setName(keySpacePath.getDirectoryName());
+        try {
+            switch (keyType) {
+                case NULL:
+                    builder.setNullValue(true);
+                    break;
+                case BYTES:
+                    builder.setBytesValue(ByteString.copyFrom((byte[])value));
+                    break;
+                case STRING:
+                    builder.setStringValue((String)value);
+                    break;
+                case LONG:
+                    if (value instanceof Integer) {
+                        builder.setLongValue(((Integer)value).longValue());
+                    } else {
+                        builder.setLongValue((Long)value);
+                    }
+                    break;
+                case FLOAT:
+                    builder.setFloatValue((Float)value);
+                    break;
+                case DOUBLE:
+                    builder.setDoubleValue((Double)value);
+                    break;
+                case BOOLEAN:
+                    builder.setBooleanValue((Boolean)value);
+                    break;
+                case UUID:
+                    final UUID uuid = (UUID)value;
+                    builder.getUuidBuilder()
+                            .setLeastSignificantBits(uuid.getLeastSignificantBits())
+                            .setMostSignificantBits(uuid.getMostSignificantBits());
+                    break;
+                default:
+                    throw new IllegalStateException("Unexpected value: " + keyType);
+            }
+        } catch (ClassCastException e) {
+            throw new RecordCoreArgumentException("KeySpacePath has incorrect value type", e)
+                    .addLogInfo(
+                            LogMessageKeys.DIR_NAME, keySpacePath.getDirectoryName(),
+                            LogMessageKeys.EXPECTED_TYPE, keyType,
+                            LogMessageKeys.ACTUAL, value);
+
+        }
+        return builder.build();
+    }
+
+}

fdb-record-layer-core/src/main/proto/keyspace.proto

@@ -0,0 +1,52 @@
+/*
+  * keyspace.proto
+  *
+  * This source file is part of the FoundationDB open source project
+  *
+  * Copyright 2015-2025 Apple Inc. and the FoundationDB project authors
+  *
+  * Licensed under the Apache License, Version 2.0 (the "License");
+  * you may not use this file except in compliance with the License.
+  * You may obtain a copy of the License at
+  *
+  *     http://www.apache.org/licenses/LICENSE-2.0
+  *
+  * Unless required by applicable law or agreed to in writing, software
+  * distributed under the License is distributed on an "AS IS" BASIS,
+  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+  * See the License for the specific language governing permissions and
+  * limitations under the License.
+  */
+
+syntax = "proto2";
+
+package com.apple.foundationdb.record.provider.foundationdb.keyspace;
+option java_outer_classname = "KeySpaceProto";
+
+message DataInKeySpacePath {
+  repeated KeySpacePathEntry path = 1;
+  optional bytes remainder = 2;
+  optional bytes value = 3;
+}
+
+// Entry representing logical values for a KeySpacePath entry.
+message KeySpacePathEntry {
+  optional string name = 1;
+
+  // specific boolean to indicate this is supposed to be a null
+  optional bool nullValue = 2;
+  optional bytes bytesValue = 3;
+  optional string stringValue = 4;
+  optional int64 longValue = 5;
+  optional float floatValue = 6;
+  optional double doubleValue = 7;
+  optional bool booleanValue = 8;
+  optional UUID uuid = 9;
+
+  message UUID { // TODO find out why we use fixed64 and not just int64
+    // 2 64-bit fields is two tags, the same as 1 bytes field with a length of 16 would be.
+    // fixed64 would be closer to how these are really used, but would fail the unsigned validator.
+    optional sfixed64 most_significant_bits = 1;
+    optional sfixed64 least_significant_bits = 2;
+  }
+}