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programs that can quickly read or write to specific subsets of data in an
extremely voluminous data set, without having to search and process
through the entire data set.
Second, it provides a transactional platform for running high-scale,
real-time applications as an ACID-compliant database (meeting stan-
dards for atomicity, consistency, isolation, and durability) while handling
the incredible volume, variety, and complexity of data encountered on
the Hadoop platform. HBase supports the following properties of ACID
compliance:
1.
Atomicity
: All mutations are atomic within a row. For example, a read
or write operation will either succeed or fail.
2.
Consistency
: All rows returned for any execution will consist of a
complete row that existed or exists in the table.
3.
Isolation
: The isolation level is called
read committed
in the traditional
DBMS.
4.
Durability
: All visible data in the system are durable data. For exam-
ple, to phrase durability, a read will never return data that have not
been made durable on disk.
17.3.2.1 HBase Architecture
Data are organized in HBase as rows and columns and tables, very similar to
a database; however, here is where the similarity ends.
HBase architecture is described as follows:
1. Tables
a. Tables are made of rows and columns.
b. Table cells are the intersection of row and column coordinates.
Each cell is versioned by default with a time stamp. The contents
of a cell are treated as an uninterpreted array of bytes.
c. A table row has a sortable row key and an arbitrary number of
columns.
2. Rows
a. Table row keys are also byte arrays. In this configuration, any-
thing can serve as the row key as opposed to strongly typed data
types in the traditional database.
b. Table rows are sorted, byte-ordered, by row key, the table's pri-
mary key, and all table accesses are via the table's primary key.
c. Columns are grouped as families, and a row can have as many
columns as loaded.
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