Github user kaspersorensen commented on a diff in the pull request:
https://github.com/apache/metamodel/pull/19#discussion_r29112631
--- 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 --
Overriding the executeQuery(...) method is a source of many painful things
because the query object can represent _any_ query. That means you need to be
very very careful with safe-guarding your code against unexpected scenarios. To
give an example of just one thing that will go very wrong here: What if the
query has multiple FROM items - or even a JOIN in it? Or what if there are
aliases shared between the clauses. As a subclass of
QueryPostprocessDataContext we try to liberate you from the responsibility of
having to consider all such scenarios. There are a bunch of other methods
available that are a lot easier to implement. And if you really want to
override executeQuery(...) then add a lot of safe-guarding so that you ensure
you only handle specifically the type of query that you have in mind.
---
If your project is set up for it, you can reply to this email and have your
reply appear on GitHub as well. If your project does not have this feature
enabled and wishes so, or if the feature is enabled but not working, please
contact infrastructure at infrastruct...@apache.org or file a JIRA ticket
with INFRA.
---
