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    • Type: Improvement
    • Status: Open
    • Priority: Major
    • Resolution: Unresolved
    • Affects Version/s: None
    • Fix Version/s: None
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      Description

      @deinspanjer proposed an implementation of the Schema SPI on top of Hazelcast. This will allow metadata to automatically propagate among nodes in a cluster of Optiq instances.

      Similar schemas could be created on top of other data grids (GridGain, JBoss Infinispan).

      The core of Hazelcast is a distributed map that automatically synchronizes among nodes of a cluster. We propose an implementation of `SchemaFactory` that creates a schema that uses such a map. The nodes in the cluster would be able to add sub-schemas, tables and functions (including views and materializations) to a schema and other nodes would see them.

      A schema definition is fairly easily serializable, so it should just work.

      One problem might be to ensure that the contents of tables (in particular large in-memory tables like `ArrayTable`) are not moved between nodes. (It would be great if the data grid makes these accessible, but we need to control the propagation. If a table is large, it is better to send the query to the data, rather than pull the data to the query.)

      The following example creates a schema `hazel` with a sub-schema `foodmart` and a view `female_emps`.

      ```json
      {
      version: '1.0',
      defaultSchema: 'foodmart',
      schemas: [
      {
      type: 'custom',
      name: 'hazel',
      factory: 'net.hydromatic.optiq.impl.hazelcast.HazelcastSchemaFactory',
      operand:

      { configUri: '/my-hazelcast.xml' }

      ,
      schemas: [

      { type: 'jdbc', name: 'foodmart', jdbcUrl: 'jdbc:mysql://db.local/foodmart', jdbcUser: 'foodmart', jdbcPassword: 'foodmart' }

      ],
      tables: [

      { type: 'view' name: 'female_emps', sql: 'select * from "emps" where "gender" = \'F\'' }

      ]
      }
      ]
      }
      ```

      Node1 could add a new view:

      ```java
      Connection connection;
      SchemaPlus rootSchema = ((OptiqConnection) connection).getRootSchema();
      SchemaPlus hazelSchema = rootSchema.getSubSchema("hazel");
      hazelSchema.add("male_emps",
      ViewTable.viewFunction(hazelSchema,
      "select * from \"emps\" where \"gender\" = 'M'", null);
      ```

      and Node2 would see it and be able to use it in its queries.

      ---------------- Imported from GitHub ----------------
      Url: https://github.com/julianhyde/optiq/issues/210
      Created by: julianhyde
      Labels: enhancement,
      Created at: Tue Mar 25 22:45:22 CET 2014
      State: open

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