MapR 5.1 is at End of Life (EOL) and no longer supported. Please see the latest documentation. This documentation is not being updated.

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.
  - MapR-DB as a Wide-Column Database
    - Logical Model of MapR-DB Binary Tables
    - Filesystem Operations on MapR-DB Tables
    - Migrating Between Apache HBase Tables and MapR-DB Binary Tables
    - Designing Row Keys for MapR-DB Binary Tables
      A row key identifies a row in a MapR-DB binary table.
    - Designing Column Families for MapR-DB Binary Tables
      Scanning an entire table for matches can be very performance-intensive. Column families enable you to group related sets of data and restrict queries to a defined subset, leading to better performance. When you design a column family, think about what kinds of queries are going to be used the most often, and group your columns accordingly.
    - Configuring Maximum Row Sizes for Binary Tables
      The default maximum row size at installation is 32MB. You can configure this maximum by changing the value of the mfs.db.max.rowsize.kb parameter with the maprcli config save command.
    - Enabling Access to MapR Tables via HBase APIs, hbase shell, and MapReduce Jobs
    - Creating MapR-DB Binary Tables
    - Displaying Table Region Information for MapR-DB Tables
    - Creating Applications That Access MapR-DB Binary Tables
      - Mapping Table Namespace Between Apache HBase Tables and MapR-DB Binary Tables
      - Behavior of the MapR dbclient When Connecting to MapR-DB
        Requests from client applications to connect to MapR-DB are handled by the MapR dbclient. This dbclient has the following behaviors when establishing the first connection and when re-establishing connections after the CLDB goes offline.
      - Creating C Applications That Access MapR-DB Binary Tables
        Additional implemented C APIs
        C API for impersonation
        Specifying MapR-DB Binary Tables When Using the C APIs
        Installing the mapr-client Package
        Building and Launching Applications
        Sample Application for Accessing MapR-DB Tables
        Sample Application for Impersonation Support
        Thread-pool Settings for Improving Application Performance
        Support for HBase Java Filters by the MapR-DB C APIs
      - Creating Java Applications That Access MapR-DB Binary Tables
      - Tuning Parameters for Client Applications That Access MapR-DB Binary Tables
        Though tuning client applications is generally not necessary, MapR does offer tuning parameters to change the behavior of client-side caching.
      - Building and Running MapReduce Applications That Access MapR-DB Binary Tables
    - Bulk Loading and MapR-DB Binary Tables
    - Replicating MapR-DB Binary Tables
    - Indexing MapR-DB Binary Tables with Elasticsearch
    - Impersonation via the HBase REST Gateway
- 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.

C API for impersonation

libMapRClient also includes a new function in the connection.h header file: hb_connection_create_as_user(). This function provides support for impersonation, so that you can connect to a MapR cluster and access MapR-DB tables by using a specific username.

/**
 * Creates an hb_connection_t instance for a specific user and initializes its
 * address into the passed pointer.
 */
HBASE_API int32_t
hb_connection_create_as_user(
    const char *zk_quorum,            /* [in] NULL terminated, comma separated
                                       *   string of CLDB servers. e.g.
                                       *   "<server1[:port]>,...". If set to
                                       *   NULL, IP addresses for CLDB nodes will be
                                       *   taken from mapr-clusters.conf */
    const char *zk_root,              /* [in] Ignored for MapR-DB. */
    const char *user,                 /* [in] The user who is being
                                       *   impersonated */
    hb_connection_t *connection_ptr); /* [out] pointer to hb_connection_t */

The user that is passed with the hb_connection_create_as_user() API must have permissions on the tables that the application accesses. For example, to read from a table, the user must have the readperm permission. To write to a table, the user must have the writeperm permission. See Enabling Table Authorizations with Access Control Expressions.

For hb_connection_create() and hb_connection_create_as_user(), the standard C APIs for HBase require a list of ZooKeeper nodes. For MapR-DB, this list is interpreted as a list of CLDB nodes. The zk_root parameter is ignored. If zk_quorum is NULL, then the connection will be created to the default cluster that is listed in the mapr-clusters.conf file.