Connecting Using Hive HPE Ezmeral Data Fabric Database JSON Connector

This section describes the Hive connector for HPE Ezmeral Data Fabric Database JSON table.

About this task

The Hive connector supports the creation of HPE Ezmeral Data Fabric Database based Hive tables. You can create a JSON table on HPE Ezmeral Data Fabric Database and load CSV data and/or JSON files to HPE Ezmeral Data Fabric Database using the connector. HPE Ezmeral Data Fabric Database based Hive tables can be:

  • Queried just like file system based Hive tables.
  • Combined with file system based Hive tables in joins and sub-queries.
NOTE
If you use Drill to query Hive tables based on MapR Database tables, you can enable the native Drill reader, which can improve query performance.

The following table lists the Hive data type and the corresponding (supported) HPE Ezmeral Data Fabric Database OJAI type:

Hive Type HPE Ezmeral Data Fabric Database OJAI Type
BOOLEAN BOOLEAN
BINARY BINARY
TINYINT BYTE
DATE DATE
DOUBLE DOUBLE
FLOAT FLOAT
INT INT
BIGINT LONG
SMALLINT SHORT
STRING STRING
TIMESTAMP TIMESTAMP
The Hive connector for HPE Ezmeral Data Fabric Database JSON table also supports the use of the following complex data types:
  • map
  • array
  • struct
NOTE
The HPE Ezmeral Data Fabric Database JSON tables do not support ACID transactions, bucketing, and alteration.

Creating a HPE Ezmeral Data Fabric Database JSON Table and Hive Table Using Hive

Procedure

To create a table, run the command similar to the following:
NOTE
The required properties are shown in bold.
CREATE TABLE primitive_types ( 
 id string, 
 bo boolean, 
 d double, 
 da date, 
 f double, 
 i int, 
 s string, 
 ts timestamp) 
STORED BY 'org.apache.hadoop.hive.maprdb.json.MapRDBJsonStorageHandler' 
TBLPROPERTIES("maprdb.table.name" = "/tbl","maprdb.column.id" = "id");
Here:
  • The maprdb.table.name, maprdb.column.id and STORED BY 'org.apache.hadoop.hive.maprdb.json.MapRDBJsonStorageHandler' are mandatory properties.
  • The value for maprdb.column.id column should be of type string or binary.

To create a Hive table that exists on HPE Ezmeral Data Fabric Database, specify EXTERNAL in the table DDL. If the table created is EXTERNAL, when the table is dropped, only its metadata is deleted; the underlying HPE Ezmeral Data Fabric Database data remains intact. On the other hand, if the table is not EXTERNAL, dropping the table deletes both the metadata associated with the table and the underlying HPE Ezmeral Data Fabric Database data.

For example, suppose a JSON table named /apps/my_users with the following values:

{"_id":"001","first_name":"John","last_name":"Doe","age":34} 
{"_id":"002","first_name":"Jack","last_name":"Smith","age":26}
To create a Hive table over existing HPE Ezmeral Data Fabric Database JSON table: 
CREATE EXTERNAL TABLE primitive_types ( 
 user_id string, 
 first_name string, 
 last_name string, 
 age int) 
STORED BY 'org.apache.hadoop.hive.maprdb.json.MapRDBJsonStorageHandler' 
TBLPROPERTIES("maprdb.table.name" = "/apps/my_users","maprdb.column.id" = "user_id");
Now, because table primitive_types points to HPE Ezmeral Data Fabric Database table, you can perform ETL query similar to file system based Hive tables:
SELECT COUNT(*) FROM test_external;
SELECT MAX(age) AS label FROM test_external;
...

Loading CSV Data to HPE Ezmeral Data Fabric Database JSON Table

Procedure

  1. Create intermediate table.
    For example:
    CREATE TABLE stage(id STRING, name STRING, age INT) ROW FORMAT DELIMITED FIELDS TERMINATED BY ',';
  2. Load data to table.
    For example:
    LOAD DATA INPATH '/data' into table stage;
  3. Create HPE Ezmeral Data Fabric Database table in Hive.
    For example:
    CREATE TABLE users(id STRING, name STRING, age INT) 
STORED BY 'org.apache.hadoop.hive.maprdb.json.MapRDBJsonStorageHandler' 
TBLPROPERTIES("maprdb.table.name" = "/users","maprdb.column.id" = "id");
  4. Insert data through stage table.
    For example:
    INSERT INTO TABLE users select id, name, age from stage;

Loading JSON Files to HPE Ezmeral Data Fabric Database JSON Table

Procedure

  1. Add SerDe JAR for JSON.
    For example:
    add jar /opt/mapr/hive/hive-<version>/hcatalog/share/hcatalog/hive-hcatalog-core-<version>-mapr.jar
  2. Create intermediate table.
    For example:
    CREATE EXTERNAL TABLE stage(id string, name string, age int) 
ROW FORMAT SERDE 'org.apache.hive.hcatalog.data.JsonSerDe' 
STORED AS TEXTFILE;
  3. Load data in stage table.
    For example:
    LOAD DATA INPATH '/data' into table stage;
    NOTE
    If there is a key in the JSON file that starts with "_" (for example, "_id"), then treat the names as literals upon creating the schema and query using the same literal syntax. For example, specify `_id` string without any special serde properties. Then in the query, use select `_id` from sometable;. Alternatively, you can use 'org.openx.data.jsonserde.JsonSerDe' and add WITH SERDEPROPERTIES ("mapping.id" = "_id" ) to your table definition.
  4. Create HPE Ezmeral Data Fabric Database table in Hive.
    For example:
    CREATE TABLE users(id STRING, name STRING, age INT) 
STORED BY 'org.apache.hadoop.hive.maprdb.json.MapRDBJsonStorageHandler' 
TBLPROPERTIES("maprdb.table.name" = "/users","maprdb.column.id" = "id");
  5. Insert data through stage table.
    For example:
    INSERT INTO TABLE users select id, name, age from stage;
    If there is a key in your JSON file that starts with "_" (for example, "_id"), treat the names as literals upon creating the schema and also query using the same literal syntax. In the above example, it would look like `_id` string without any special serde properties for it. Then, use again in query as shown below: 
    select `_id`  from sometable;
    Alternatively, use org.openx.data.jsonserde.JsonSerDe and add WITH SERDEPROPERTIES ("mapping.id" = "_id" ) to your table definition.

Example

Refer to Hive MapR Database JSON Connector Tutorial for a connector example.