How are indexes implemented in HBase?

In HBase, indexes are implemented in two ways: row-key based indexes and secondary index based indexes.

1. Row key-based indexing: Tables in HBase are stored in order based on their row keys, allowing for index queries to be performed by scanning within a range of row keys. By specifying a range of row keys in Get or Scan operations, the corresponding data can be quickly located for retrieval.
2. Index based on auxiliary index: HBase does not directly support secondary indexes, but they can be implemented by creating additional tables. In the auxiliary index table, the values of the columns that need to be indexed are used as row keys, while the actual data row keys are stored as values in the table. By querying the auxiliary index table to obtain the row keys of the actual data, the corresponding data rows can then be retrieved based on the row keys.

It is important to note that index based on secondary indexes may increase additional storage costs and query expenses, so it is necessary to balance storage space and query performance when designing indexes.