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This article is about what the basic concepts in HBase are. The editor thinks it is very practical, so share it with you as a reference and follow the editor to have a look.

HBase is an open source implementation of Google Bigtable. HBase is an open source, distributed, multi-version, column-oriented storage model. HBase uses HDFS as its file system (or local), and it can also use the MapReduce computing model to process big data in parallel.

Basic concepts in HBase:

Row Key

1) Row key is the primary key for retrieving records.

2) the Row key line key (Row key) can be any string (the maximum length is 64KB, which is usually 10-100bytes in practical applications). Inside hbase, row key is saved as a byte array.

3) data is sorted and stored according to the byte order of Row key. When designing a key, you should fully sort the storage feature and put together the row stores that are often read together. (location correlation)

4) the reading and writing of rows is an atomic operation.

Column family (column family)

1) each column in the HBase table belongs to a column family, which must be given in advance as part of the table schema (schema) definition and must be defined before using the table. Column names are prefixed with the column family, separated by a colon (:), such as courses:math.

2) access control, disk and memory usage statistics are all carried out at the column family level. In practical applications, control permissions on column families can help us manage different types of applications: we allow some applications to add new basic data, some applications can read basic data and create inherited column families, and some applications are only allowed to browse data (or even not all data for privacy reasons).

Cell (memory unit)

The unit uniquely determined by {row key, column (= +), version}. The data in cell is typeless and is all stored in bytecode form.

Timestamp (timestamp)

1) each cell holds multiple versions of the same data, which are indexed by timestamps.

2) the timestamp is 64-bit integer.

3) it can be assigned automatically (current system time) or specified by the user.

4) different versions of data are sorted in reverse order according to timestamp.

5) HBase provides two data version recovery mechanisms: a. Save the last n versions of the data; b. Save the version in the latest period of time. You can set it for each column family.

Thank you for reading! This is the end of this article on "what are the basic concepts in HBase". I hope the above content can be of some help to you, so that you can learn more knowledge. if you think the article is good, you can share it for more people to see!

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