Github user ashish-m-yh commented on a diff in the pull request:
https://github.com/apache/metamodel/pull/19#discussion_r29445084
--- Diff: solr/src/main/java/org/apache/metamodel/solr/SolrDataContext.java
---
@@ -0,0 +1,403 @@
+/**
+ * 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.metamodel.solr;
+
+import java.io.InputStreamReader;
+import java.io.IOException;
+import java.lang.reflect.Method;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Comparator;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+
+import org.apache.http.HttpResponse;
+import org.apache.http.client.HttpClient;
+import org.apache.http.client.methods.HttpGet;
+import org.apache.http.impl.client.DefaultHttpClient;
+import org.apache.metamodel.DataContext;
+import org.apache.metamodel.MetaModelException;
+import org.apache.metamodel.query.Query;
+import org.apache.metamodel.QueryPostprocessDataContext;
+import org.apache.metamodel.data.DataSet;
+import org.apache.metamodel.data.DataSetHeader;
+import org.apache.metamodel.data.Row;
+import org.apache.metamodel.data.SimpleDataSetHeader;
+import org.apache.metamodel.query.FilterClause;
+import org.apache.metamodel.query.FilterItem;
+import org.apache.metamodel.query.GroupByItem;
+import org.apache.metamodel.query.OrderByItem;
+import org.apache.metamodel.query.SelectItem;
+import org.apache.metamodel.query.LogicalOperator;
+import org.apache.metamodel.query.OperatorType;
+import org.apache.metamodel.query.FunctionType;
+import org.apache.metamodel.schema.Column;
+import org.apache.metamodel.schema.ColumnType;
+import org.apache.metamodel.schema.MutableColumn;
+import org.apache.metamodel.schema.MutableSchema;
+import org.apache.metamodel.schema.MutableTable;
+import org.apache.metamodel.schema.Schema;
+import org.apache.metamodel.schema.Table;
+import org.apache.metamodel.util.SimpleTableDef;
+import org.apache.solr.client.solrj.SolrQuery;
+import org.apache.solr.client.solrj.SolrQuery.ORDER;
+import org.apache.solr.client.solrj.SolrServerException;
+import org.apache.solr.client.solrj.impl.HttpSolrServer;
+import org.apache.solr.client.solrj.response.QueryResponse;
+import org.apache.solr.client.solrj.response.FacetField;
+import org.apache.solr.common.SolrDocumentList;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.ObjectReader;
+
+/**
+ * DataContext implementation for ElasticSearch analytics engine.
+ *
+ * ElasticSearch has a data storage structure hierarchy that briefly goes
like
+ * this:
+ * <ul>
+ * <li>Index</li>
+ * <li>Document type (short: Type) (within an index)</li>
+ * <li>Documents (of a particular type)</li>
+ * </ul>
+ *
+ * When instantiating this DataContext, an index name is provided. Within
this
+ * index, each document type is represented as a table.
+ *
+ * This implementation supports either automatic discovery of a schema or
manual
+ * specification of a schema, through the {@link SimpleTableDef} class.
+ */
+
+public class SolrDataContext extends QueryPostprocessDataContext implements
+ DataContext {
+
+ private static final Logger logger = LoggerFactory
+ .getLogger(SolrDataContext.class);
+
+ public static final String FIELD_ID = "id";
+
+ private final SimpleTableDef tableDef;
+ private final String indexName;
+ private final String url;
+
+ private SolrQuery query = new SolrQuery();
+
+ private static enum queryTypes {
+ ROW, FACET
+ };
+
+ private static final int MAX_RETRIES = 0;
+ private static final int SOCK_TIMEOUT = 1000;
+ private static final int CONN_TIMEOUT = 5000;
+ private static final int DEFAULT_LIMIT = 1000;
+
+ public SolrDataContext(String url, String indexName) {
+ this.url = url;
+ this.indexName = indexName;
+ this.tableDef = detectSchema(url, indexName);
+ }
+
+ private SimpleTableDef detectSchema(String url, String indexName) {
+ SimpleTableDef tableDef = null;
+
+ url += "/schema";
+
+ try {
+ HttpClient httpclient = new DefaultHttpClient();
+ HttpGet request = new HttpGet(url);
+ HttpResponse response = httpclient.execute(request);
+
+ InputStreamReader inputStream = new InputStreamReader(response
+ .getEntity().getContent());
+
+ ObjectReader reader = new ObjectMapper().reader(HashMap.class);
+ Map<String, Object> outerMap = reader.readValue(inputStream);
+
+ Map<String, Object> schemaMap = null;
+
+ if (outerMap != null) {
+ schemaMap = (Map) outerMap.get("schema");
+ }
+
+ if (schemaMap != null) {
+ List<Map<String, String>> fieldMapList = (List) schemaMap
+ .get("fields");
+ List<String> columnNames = new ArrayList<String>();
+ List<ColumnType> columnTypes = new ArrayList<ColumnType>();
+
+ for (int i = 0; i < fieldMapList.size(); i++) {
+ Map<String, String> fieldMap = fieldMapList.get(i);
+
+ columnNames.add(fieldMap.get("name"));
+ columnTypes.add(ColumnType.STRING);
+ }
+
+ String[] columnNamesArr = new String[columnNames.size()];
+ columnNamesArr = columnNames.toArray(columnNamesArr);
+
+ ColumnType[] columnTypesArr = new
ColumnType[columnTypes.size()];
+ columnTypesArr = columnTypes.toArray(columnTypesArr);
+
+ tableDef = new SimpleTableDef(indexName, columnNamesArr,
+ columnTypesArr);
+ }
+ } catch (IOException e) {
+ logger.error("Failed to parse schema", "", e);
+ }
+
+ return tableDef;
+ }
+
+ @Override
+ protected Schema getMainSchema() throws MetaModelException {
+ try {
+ final MutableSchema theSchema = new MutableSchema(
+ getMainSchemaName());
+
+ final MutableTable table =
tableDef.toTable().setSchema(theSchema);
+ final Column idColumn = table.getColumnByName(FIELD_ID);
+ if (idColumn != null && idColumn instanceof MutableColumn) {
+ final MutableColumn mutableColumn = (MutableColumn)
idColumn;
+ mutableColumn.setPrimaryKey(true);
+ }
+ theSchema.addTable(table);
+
+ return theSchema;
+ } catch (Exception e) {
+ throw new MetaModelException("Schema retrieval failed " + e);
+ }
+ }
+
+ @Override
+ protected Number executeCountQuery(Table table,
+ List<FilterItem> whereItems, boolean
functionApproximationAllowed) {
+ String queryStr = "*:*";
+
+ if (whereItems != null) {
+ for (int i = 0; i < whereItems.size(); i++) {
+ FilterItem whereItem = whereItems.get(i);
+ queryStr = whereItem.toString();
+ }
+ }
+
+ QueryResponse response = selectRows(table, null, queryStr, 0, 0);
+ return response.getResults().getNumFound();
+ }
+
+ @Override
+ public DataSet executeQuery(Query q) throws MetaModelException {
--- End diff --
If I do not override executeQuery(...), then the Solr index cannot be
queried by SQL, right? Also, I am calling super.executeQuery(q) at the end, to
handle any other kind of query beyond the specific clauses I am handling. If
the query is totally invalid and goes beyond any query which can be handled,
exception may be thrown or DataSet null returned.
If you feel this approach still has some caveats, what method should be
overridden so that the SQL interface still works?
What's your take?
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