Release Notes
- v3.1
- v3.0
- v2.5
- v2.4
- v2.3
- v2.2
- v2.1
- v2.0
- v1.19

StarRocks
Introduction to StarRocks
Quick Start
Table Design
- Understand StarRocks table design
- Data models
- Data distribution
  - Data distribution
  - Temporary partition
- Sort keys and prefix indexes
Data Loading
Data Unloading
Query Data Sources
- Use catalogs to manage internal and external data
- External tables
Query Acceleration
Administration
- Deployment
- Management
- Data Recovery
  - Data recovery
  - Restore FEs
- User Privilege and Authentication
  - User privilege
  - Authentication
- Performance Tuning
Reference
- SQL Reference
- Function Reference
  - Java UDFs
  - Window functions
  - Aggregate Functions
  - Array Functions
  - Bit Functions
  - Bitmap Functions
  - Conditional Functions
  - Cryptographic Functions
  - Date Functions
  - Geographic Functions
  - JSON Functions
    - Overview of JSON functions and operators
    - JSON operators
    - JSON constructor functions
    - JSON query and processing functions
  - Math Functions
    - abs
    - acos
    - asin
    - atan
    - atan2
    - bin
    - ceil
    - ceiling
    - conv
    - cos
    - cosh
    - cot
    - degrees
    - divide
    - e
    - exp
    - floor
    - fmod
    - greatest
    - least
    - ln
    - log
    - log2
    - log10
    - mod
    - multiply
    - negative
    - pi
    - pmod
    - positive
    - pow
    - radians
    - rand
    - round
    - sign
    - sin
    - sqrt
    - square
    - tan
    - truncate
  - String Functions
  - Pattern Matching Functions
  - Percentile Functions
  - Scalar Functions
    - hll_cardinality
  - Utility Functions
  - cast function
  - hash function
- System variables
- Error code
- System limits
FAQ
- Deploy
- Data Migration
  - Data Loading
  - Data Unloading
- SQL
- Other FAQs
Benchmark
- SSB Benchmark
- TPC-H Benchmark

Developers
- Contribute to StarRocks
- Code Style Guides
  - protobuf style guides
  - thrift style guides
- Use the debuginfo file for debugging
- Development Environment
- Trace Tools
  - Trace

Edit

HLL_HASH

Description

Converts a value to an hll type. Typically used in imports to map a value in the source data to an HLL column type in the Starrocks table.

Syntax

HLL_HASH(column_name)

Parameters

column_name: The new generated hll column name.

Return value

Returns a value of the hll type.

Example

mysql> select hll_cardinality(hll_hash("a"));
+--------------------------------+
| hll_cardinality(hll_hash('a')) |
+--------------------------------+
|                              1 |
+--------------------------------+

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In this article

HLL_HASH