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5.1 DB & Streams
This section covers the MapR-DB, MapR-Streams, and MapR-Gateways features. Each feature may contain both administrator and developer topics.
MapR-DB
MapR-DB as a Document Database
MapR-DB supports OJAI documents as a native data store. OJAI documents are stored in a compact binary format, not as plain ASCII text.
Granting or Denying Access to Fields with Access-Control Expressions
By using access-control expressions (ACEs), you can grant or deny access to fields and column families that are in JSON tables.
Default Permissions for JSON Tables
The following table summarizes the default access-control expressions for the supported ways of setting the read, traverse, and write permissions.

MapR 5.1 Documentation

5.1 DB & Streams
This section covers the MapR-DB, MapR-Streams, and MapR-Gateways features. Each feature may contain both administrator and developer topics.
- MapR-DB
  - Architecture of MapR-DB
    MapR-DB's architecture gives it a large of advantages over other NoSQL databases.
  - Performance Enhancements for SSD Based MapR-DB Deployments
  - MapR-DB as a Document Database
    MapR-DB supports OJAI documents as a native data store. OJAI documents are stored in a compact binary format, not as plain ASCII text.
    - OJAI Documents
      An OJAI document is a tree of fields. Each field has a type and a value, and also has either a name or an array index. Field names are strings. The root of each document is a map.
    - JSON Tables
      Documents are stored in JSON tables, which are tables in which every row is an OJAI document.
    - Creating, Reading, Updating, and Deleting Documents and Tables with the MapR-DB JSON Java API Library
      The basic tasks that you can perform with the API library involve the Admin, Document, DocumentMutation, QueryCondition, Table, and TableDescriptor interfaces.
    - Listing Tables with the MapR-DB JSON Java API Library
      List the JSON tables that are in a folder by calling an Admin object's listTables() method, passing as an argument the path of the folder.
    - Altering JSON Tables with the MapR-DB OJAI Java API Library
      Change the values of table attributes by using a TableDescriptor object and then passing that object to the Admin interface's altertable() method.
    - Deleting JSON Tables with the MapR-DB OJAI Java API Library
      Delete a JSON table by calling an Admin object's deleteTable() method, passing as an argument the path of the table to delete.
    - Compiling and Running Applications that Access JSON Tables and Documents
      You can compile applications that use the MapR-DB JSON API by using the required JAR file from the MapR Maven repository or from the MapR installation. Run applications with the mapr command.
    - Tuning Parameters for Client Applications That Access MapR-DB JSON Tables
      Though tuning client applications is generally not necessary, MapR does offer tuning parameters to change the behavior of client-side caching.
    - Loading Documents into JSON Tables
      There are three command-line utilities for loading documents into JSON tables: mapr copytable, mapr importtable (which works in conjunction with the mapr exporttable utility), and mapr importJSON
    - MapR-DB JSON MapReduce API Library
      This API library extends the Apache Hadoop MapReduce framework, so that you can write your own MapReduce applications to write data from one JSON table to another.
    - Column Families in JSON Tables
      JSON tables store data in column families, which are collections of fields that are stored together on disk.
    - Granting or Denying Access to Fields with Access-Control Expressions
      By using access-control expressions (ACEs), you can grant or deny access to fields and column families that are in JSON tables.
      - How to Obtain readperm and writeperm on a Field
        In this scenario, you want to perform an operation on a field, and the operation requires that you have readperm and writeperm on that field. How you obtain these permissions depends on whether the field is in the default column family or a non-default column family.
      - How to Obtain readperm or writeperm on a Field
        In this scenario, you want to perform an operation on a field, and the operation requires that you have readperm or writeperm on that field. How you obtain either permission depends on whether the field is in the default column family or a non-default column family.
      - Setting Permissions on Arrays
        Permissions apply to an entire array, not to individual elements in an array. However, it is possible to set permissions on fields within documents or maps that are stored in an array.
      - Default Permissions for JSON Tables
        The following table summarizes the default access-control expressions for the supported ways of setting the read, traverse, and write permissions.
    - Getting Started with MapR-DB JSON and OJAI
  - MapR-DB as a Wide-Column Database
- MapR Streams
  MapR Streams brings integrated publish/subscribe messaging to the MapR Converged Data Platform.
- MapR Gateways
  A MapR gateway mediates one-way communication between a source MapR cluster and a destination cluster. MapR-DB binary tables and MapR Streams streams can be replicated.

Default Permissions for JSON Tables

The following table summarizes the default access-control expressions for the supported ways of setting the read, traverse, and write permissions.

Action	Method	Permissions	Default Access-Control Expressions
Set default permissions on new column families when creating a JSON table	Java API	`-defaultreadperm -defaulttraverseperm -defaultwriteperm`	`u:<ID of the process>`
	`maprcli table create`		`u:<user ID of table creator>`
	mapr dbshell
	MCS
Set default permissions on new column families when editing a JSON table	`maprcli table edit`		Current ACEs
	MCS		Current ACEs
Set permissions on a column family when creating the column family	`maprcli table cf create`	`-readperm -traverseperm -writeperm`	ACEs for `–defaultreadperm`, `-defaulttraverseperm`, and `-defaultwriteperm`
	MCS
Set permissions on a column family when editing the column family	`maprcli table cf edit`		Current ACEs
	MCS		Current ACEs
Seting permissions on individual fields	`maprcli table cf colperm set`		Inherited from column family or parent field
Seting permissions on individual fields	MCS		Inherited from column family or parent field

The default permissions for column families are determined when tables are created. The default permissions for fields are inherited from the column families in which the columns are located.