| /* |
| // Licensed to Julian Hyde under one or more contributor license |
| // agreements. See the NOTICE file distributed with this work for |
| // additional information regarding copyright ownership. |
| // |
| // Julian Hyde 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 net.hydromatic.linq4j; |
| |
| import net.hydromatic.linq4j.expressions.Expression; |
| |
| import java.lang.reflect.Type; |
| |
| /** |
| * Defines methods to create and execute queries that are described by a |
| * {@link Queryable} object. |
| * |
| * <p>Analogous to LINQ's System.Linq.QueryProvider.</p> |
| * |
| * @author jhyde |
| */ |
| public interface QueryProvider { |
| /** |
| * Constructs a {@link Queryable} object that can evaluate the query |
| * represented by a specified expression tree. |
| * |
| * <p>NOTE: The {@link net.hydromatic.linq4j.Queryable#getExpression()} |
| * property of the returned {@link Queryable} object is equal to |
| * {@code expression}.</p> |
| * |
| * @param expression Expression |
| * @param rowType Row type |
| * @param <T> Row type |
| * |
| * @return Queryable |
| */ |
| <T> Queryable<T> createQuery(Expression expression, Class<T> rowType); |
| |
| /** |
| * Constructs a {@link Queryable} object that can evaluate the query |
| * represented by a specified expression tree. The row type may contain |
| * generic information. |
| * |
| * @param expression Expression |
| * @param rowType Row type |
| * @param <T> Row type |
| * |
| * @return Queryable |
| */ |
| <T> Queryable<T> createQuery(Expression expression, Type rowType); |
| |
| /** |
| * Executes the query represented by a specified expression tree. |
| * |
| * <p>This method executes queries that return a single value |
| * (instead of an enumerable sequence of values). Expression trees that |
| * represent queries that return enumerable results are executed when the |
| * {@link Queryable} object that contains the expression tree is |
| * enumerated.</p> |
| * |
| * <p>The Queryable standard query operator methods that return singleton |
| * results call {@code execute}. They pass it a |
| * {@link net.hydromatic.linq4j.expressions.MethodCallExpression} |
| * that represents a linq4j query. |
| */ |
| <T> T execute(Expression expression, Class<T> type); |
| |
| /** |
| * Executes the query represented by a specified expression tree. |
| * The row type may contain type parameters. |
| */ |
| <T> T execute(Expression expression, Type type); |
| |
| /** |
| * Executes a queryable, and returns an enumerator over the |
| * rows that it yields. |
| * |
| * @param queryable Queryable |
| * |
| * @return Enumerator over rows |
| */ |
| <T> Enumerator<T> executeQuery(Queryable<T> queryable); |
| } |
| |
| // End QueryProvider.java |