| // 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. |
| = Working with SQL |
| |
| Ignite comes with ANSI-99 compliant, horizontally scalable and fault-tolerant distributed SQL database. The distribution is provided either by partitioning the data across cluster nodes or by full replication, depending on the use case. |
| |
| As a SQL database, Ignite supports all DML commands including SELECT, UPDATE, INSERT, and DELETE queries and also implements a subset of DDL commands relevant for distributed systems. |
| |
| You can interact with Ignite as you would with any other SQL enabled storage by connecting with link:SQL/JDBC/jdbc-driver/[JDBC] or link:SQL/ODBC/odbc-driver[ODBC] drivers from both external tools and applications. Java, .NET and C++ developers can leverage native link:SQL/sql-api[SQL APIs]. |
| |
| Internally, SQL tables have the same data structure as link:data-modeling/data-modeling#key-value-cache-vs-sql-table[key-value caches]. It means that you can change partition distribution of your data and leverage link:data-modeling/affinity-collocation[affinity colocation techniques] for better performance. |
| |
| Ignite's default SQL engine uses H2 Database to parse and optimize queries and generate execution plans, but also the Apache Calcite-based SQL engine can be enabled to execute queries. |
| |
| WARNING: Apache Calcite-based SQL engine is an experimental feature. For more information, see the link:SQL/sql-calcite[Calcite-based SQL engine, window=_blank] section. |
| |
| == Distributed Queries |
| |
| Queries against link:data-modeling/data-partitioning#partitioned[partitioned] tables are executed in a distributed manner: |
| |
| - The query is parsed and split into multiple “map” queries and a single “reduce” query. |
| - All the map queries are executed on all the nodes where required data resides. |
| - All the nodes provide result sets of local execution to the query initiator that, in turn, will merge provided result sets into the final results. |
| |
| You can force a query to be processed locally, i.e. on the subset of data that is stored on the node where the query is executed. |
| |
| == Local Queries |
| |
| If a query is executed over a link:data-modeling/data-partitioning#replicated[replicated] table, it will be run against the local data. |
| |
| Queries over partitioned tables are executed in a distributed manner. |
| However, you can force local execution of a query over a partitioned table. |
| See link:SQL/sql-api#local-execution[Local Execution] for details. |
| |
| |
| //// |
| == Known Limitations |
| TODO |
| |
| https://apacheignite-sql.readme.io/docs/how-ignite-sql-works#section-known-limitations |
| |
| https://issues.apache.org/jira/browse/IGNITE-7822 - describe this if not fixed |
| //// |
