Binary Tables

Binary tables store data in a flat table structure where the table consists of columns and column values. Every field in a binary table is stored as a sequence of bytes.

Binary tables do not store data type information. You manage the encoding for binary tables when storing data and then convert the sequence of bytes into a specific data type using the CAST or CONVERT functions when you run queries against the tables.

For example, if a string is stored in binary format, such as a UTF-8 encoded string, you must use the CAST function for the query to return a string type. If an integer is stored in binary format, such as 4-byte little endian encoding, you must use the CONVERT function for the query to return the integer value instead of the 4-byte sequence.

Querying a Binary Table

The following examples, from the Querying HBase Tutorial, display query results when the binary table “/user/root/binary/students” with two column families, “account” and “address,” is queried without using a conversion function to convert the binary table data into specific data types.

Example 1

SELECT * FROM `/user/root/binary/students`
    students;

+--------------+------------------------------------------------+----------------------------------------------------------------------------+
|   row_key    |                    account                     |                                  address                                   |
+--------------+------------------------------------------------+----------------------------------------------------------------------------+
| [B@78dfa1ed  | {"date":"MjAxNi0wMS0xNQ==","name":"QWxpY2U="}  | {"state":"Q0E=","street":"MTIzIEJhbGxtZXIgQXY=","zipcode":"MTIzNDU="}      |
| [B@22000c9a  | {"date":"MjAxNi0wMy0wOA==","name":"Qm9i"}      | {"state":"Q0E=","street":"MSBJbmZpbml0ZSBMb29w","zipcode":"MTIzNDU="}      |
| [B@313b63e6  | {"date":"MjAxNS0xMi0yMg==","name":"RnJhbms="}  | {"state":"Q0E=","street":"NDM1IFdhbGtlciBDdA==","zipcode":"MTIzNDU="}      |
| [B@321baa4a  | {"date":"MjAxNS0wOS0xNQ==","name":"TWFyeQ=="}  | {"state":"Q0E=","street":"NTYgU291dGhlcm4gUGt3eQ==","zipcode":"MTIzNDU="}  |
+--------------+------------------------------------------------+----------------------------------------------------------------------------+
4 rows selected (0.612 seconds)

In example 2, using the CONVERT_FROM and CAST functions in a query on the same table converts the binary table data to typed data.

Example 2

SELECT CONVERT_FROM(row_key, 'UTF8') AS studentid, CONVERT_FROM(students.account.name,
     'UTF8') AS name, CONVERT_FROM(students.address.state, 'UTF8') AS state,
     CONVERT_FROM(students.address.street, 'UTF8') AS street, CONVERT_FROM(students.address.zipcode,
     'UTF8') AS zipcode, CAST(students.account.`date` as date) AS `date` FROM
     dfs.`/user/root/binary/students`
    students;

+------------+--------+--------+-------------------+----------+-------------+
| studentid  |  name  | state  |      street       | zipcode  |    date     |
+------------+--------+--------+-------------------+----------+-------------+
| student1   | Alice  | CA     | 123 Ballmer Av    | 12345    | 2016-01-15  |
| student2   | Bob    | CA     | 1 Infinite Loop   | 12345    | 2016-03-08  |
| student3   | Frank  | CA     | 435 Walker Ct     | 12345    | 2015-12-22  |
| student4   | Mary   | CA     | 56 Southern Pkwy  | 12345    | 2015-09-15  |
+------------+--------+--------+-------------------+----------+-------------+
4 rows selected (0.702 seconds)