public void addKNNBinaryField()

in src/main/java/org/opensearch/knn/index/codec/KNN80Codec/KNN80DocValuesConsumer.java [73:147]
49 lines of code
7 McCabe index (conditional complexity)

    public void addKNNBinaryField(FieldInfo field, DocValuesProducer valuesProducer) throws IOException {
        KNNCounter.GRAPH_INDEX_REQUESTS.increment();
        if (field.attributes().containsKey(KNNVectorFieldMapper.KNN_FIELD)) {

            // Get values to be indexed
            BinaryDocValues values = valuesProducer.getBinary(field);
            KNNCodecUtil.Pair pair = KNNCodecUtil.getFloats(values);
            if (pair.vectors.length == 0 || pair.docs.length == 0) {
                logger.info("Skipping engine index creation as there are no vectors or docs in the documents");
                return;
            }

            // Create library index either from model or from scratch
            String engineFileName;
            String indexPath;
            String tmpEngineFileName;

            if (field.attributes().containsKey(MODEL_ID)) {

                String modelId = field.attributes().get(MODEL_ID);
                Model model = ModelCache.getInstance().get(modelId);

                KNNEngine knnEngine = model.getModelMetadata().getKnnEngine();

                engineFileName = buildEngineFileName(state.segmentInfo.name, knnEngine.getLatestBuildVersion(),
                        field.name, knnEngine.getExtension());
                indexPath = Paths.get(((FSDirectory) (FilterDirectory.unwrap(state.directory))).getDirectory().toString(),
                        engineFileName).toString();
                tmpEngineFileName = engineFileName + TEMP_SUFFIX;
                String tempIndexPath = indexPath + TEMP_SUFFIX;

                if (model.getModelBlob() == null) {
                    throw new RuntimeException("There is no trained model with id \"" + modelId + "\"");
                }

                createKNNIndexFromTemplate(model.getModelBlob(), pair, knnEngine, tempIndexPath);
            } else {

                // Get engine to be used for indexing
                String engineName = field.attributes().getOrDefault(KNNConstants.KNN_ENGINE, KNNEngine.DEFAULT.getName());
                KNNEngine knnEngine = KNNEngine.getEngine(engineName);

                engineFileName = buildEngineFileName(state.segmentInfo.name, knnEngine.getLatestBuildVersion(),
                        field.name, knnEngine.getExtension());
                indexPath = Paths.get(((FSDirectory) (FilterDirectory.unwrap(state.directory))).getDirectory().toString(),
                        engineFileName).toString();
                tmpEngineFileName = engineFileName + TEMP_SUFFIX;
                String tempIndexPath = indexPath + TEMP_SUFFIX;

                createKNNIndexFromScratch(field, pair, knnEngine, tempIndexPath);
            }

            /*
             * Adds Footer to the serialized graph
             * 1. Copies the serialized graph to new file.
             * 2. Adds Footer to the new file.
             *
             * We had to create new file here because adding footer directly to the
             * existing file will miss calculating checksum for the serialized graph
             * bytes and result in index corruption issues.
             */
            //TODO: I think this can be refactored to avoid this copy and then write
            // https://github.com/opendistro-for-elasticsearch/k-NN/issues/330
            try (IndexInput is = state.directory.openInput(tmpEngineFileName, state.context);
                 IndexOutput os = state.directory.createOutput(engineFileName, state.context)) {
                os.copyBytes(is, is.length());
                CodecUtil.writeFooter(os);
            } catch (Exception ex) {
                KNNCounter.GRAPH_INDEX_ERRORS.increment();
                throw new RuntimeException("[KNN] Adding footer to serialized graph failed: " + ex);
            } finally {
                IOUtils.deleteFilesIgnoringExceptions(state.directory, tmpEngineFileName);
            }
        }
    }