docs/en/administrator-guide/alter-table/alter-table-bitmap-index.md

---
{
    "title": "Bitmap Index",
    "language": "en"
}
---

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# Bitmap Index
Users can speed up queries by creating a bitmap index
This document focuses on how to create an index job, as well as some considerations and frequently asked questions when creating an index.

## Glossary
* bitmap index: a fast data structure that speeds up queries

## Basic Principles
Creating and dropping index is essentially a schema change job. For details, please refer to
[Schema Change](alter-table-schema-change.html).

## Syntax
There are two forms of index creation and modification related syntax, one is integrated with alter table statement, and the other is using separate
create/drop index syntax
1. Create Index

    Please refer to [CREATE INDEX](../../sql-reference/sql-statements/Data%20Definition/CREATE%20INDEX.html) 
    or [ALTER TABLE](../../sql-reference/sql-statements/Data%20Definition/ALTER%20TABLE.html),
    You can also specify a bitmap index when creating a table, Please refer to [CREATE TABLE](../../sql-reference/sql-statements/Data%20Definition/CREATE%20TABLE.html)

2. Show Index

    Please refer to [SHOW INDEX](../../sql-reference/sql-statements/Administration/SHOW%20INDEX.html)

3. Drop Index

    Please refer to [DROP INDEX](../../sql-reference/sql-statements/Data%20Definition/DROP%20INDEX.html) or [ALTER TABLE](../../sql-reference/sql-statements/Data%20Definition/ALTER%20TABLE.html)

## Create Job
Please refer to [Schema Change](alter-table-schema-change.html)
## View Job
Please refer to [Schema Change](alter-table-schema-change.html)

## Cancel Job
Please refer to [Schema Change](alter-table-schema-change.html)

## Notice
* Currently only index of bitmap type is supported.
* The bitmap index is only created on a single column.
* Bitmap indexes can be applied to all columns of the `Duplicate` data model and key columns of the `Aggregate` and `Uniq` models.
* The data types supported by bitmap indexes are as follows:
    * `TINYINT`
    * `SMALLINT`
    * `INT`
    * `UNSIGNEDINT`
    * `BIGINT`
    * `CHAR`
    * `VARCHAR`
    * `DATE`
    * `DATETIME`
    * `LARGEINT`
    * `DECIMAL`
    * `BOOL`
* The bitmap index takes effect only in segmentV2. The table's storage format will be converted to V2 automatically when creating index.