[GitHub] [solr] noblepaul commented on a change in pull request #476: SOLR-15880

[GitBox <gi...@apache.org>]

noblepaul commented on a change in pull request #476:
URL: https://github.com/apache/solr/pull/476#discussion_r780884950



##########
File path: solr/core/src/java/org/apache/solr/search/neural/KnnQParser.java
##########
@@ -0,0 +1,100 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.solr.search.neural;
+
+import org.apache.lucene.search.Query;
+import org.apache.solr.common.SolrException;
+import org.apache.solr.common.params.SolrParams;
+import org.apache.solr.request.SolrQueryRequest;
+import org.apache.solr.schema.DenseVectorField;
+import org.apache.solr.schema.FieldType;
+import org.apache.solr.schema.SchemaField;
+import org.apache.solr.search.QParser;
+import org.apache.solr.search.QueryParsing;
+
+public class KnnQParser extends QParser {
+
+    static final String TOP_K = "topK";// retrieve the top K results based on the distance similarity function 
+    static final int DEFAULT_TOP_K = 10;
+
+    /**
+     * Constructor for the QParser
+     *
+     * @param qstr        The part of the query string specific to this parser
+     * @param localParams The set of parameters that are specific to this QParser.  See https://solr.apache.org/guide/local-parameters-in-queries.html
+     * @param params      The rest of the {@link SolrParams}
+     * @param req         The original {@link SolrQueryRequest}.
+     */
+    public KnnQParser(String qstr, SolrParams localParams, SolrParams params, SolrQueryRequest req) {
+        super(qstr, localParams, params, req);
+    }
+
+    @Override
+    public Query parse() {
+        String denseVectorField = localParams.get(QueryParsing.F);
+        String vectorToSearch = localParams.get(QueryParsing.V);
+        int topK = localParams.getInt(TOP_K, DEFAULT_TOP_K);
+
+        if (denseVectorField == null || denseVectorField.isEmpty()) {
+            throw new SolrException(SolrException.ErrorCode.BAD_REQUEST, "the Dense Vector field 'f' is missing");
+        }
+
+        if (vectorToSearch == null || vectorToSearch.isEmpty()) {
+            throw new SolrException(SolrException.ErrorCode.BAD_REQUEST, "the Dense Vector to search is missing");
+        }
+
+        SchemaField schemaField = req.getCore().getLatestSchema().getField(denseVectorField);
+        FieldType fieldType = schemaField.getType();
+        if (!(fieldType instanceof DenseVectorField)) {
+            throw new SolrException(SolrException.ErrorCode.BAD_REQUEST, "only DenseVectorField is compatible with Knn Query Parser");
+        }
+
+        DenseVectorField denseVectorType = (DenseVectorField) fieldType;
+        float[] parsedVectorToSearch = parseVector(vectorToSearch, denseVectorType.getDimension());
+        return denseVectorType.getKnnVectorQuery(schemaField, parsedVectorToSearch, topK);
+    }
+
+    /**
+     * Parses a String vector.
+     *
+     * @param value with format: [f1, f2, f3, f4...fn]
+     * @return a float array
+     */
+    private float[] parseVector(String value, int dimension) {
+        if (!value.startsWith("[") || !value.endsWith("]")) {
+            throw new SolrException(SolrException.ErrorCode.BAD_REQUEST, "incorrect vector format." +
+                    " The expected format is:'[f1,f2..f3]' where each element f is a float");
+        }
+
+        String[] elements = value.substring(1, value.length() - 1).split(",");

Review comment:
       Please use `org.apache.commons.lang.Stringutils.split(String str, char separatorChar)`




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