FUSE_ENCODING

返回应用于表中特定列的编码类型。它可帮助你了解数据在表中如何以原生格式被压缩和存储。

语法

FUSE_ENCODING('<database_name>', '<table_name>', '<column_name>')

该函数返回一个包含以下列的结果集：

示例

-- Create a table with an integer column 'c' and apply 'Lz4' compression
CREATE TABLE t(c INT) STORAGE_FORMAT = 'native' COMPRESSION = 'lz4';

-- Insert data into the table.
INSERT INTO t SELECT number FROM numbers(2048);

-- Analyze the encoding for column 'c' in table 't'
SELECT LEVEL_ONE, LEVEL_TWO, COUNT(*)
FROM FUSE_ENCODING('default', 't', 'c')
GROUP BY LEVEL_ONE, LEVEL_TWO;

level_one   |level_two|count(*)|
------------+---------+--------+
DeltaBitpack|         |       1|

--  Insert 2,048 rows with the value 1 into the table 't'
INSERT INTO t (c)
SELECT 1
FROM numbers(2048);

SELECT LEVEL_ONE, LEVEL_TWO, COUNT(*)
FROM FUSE_ENCODING('default', 't', 'c')
GROUP BY LEVEL_ONE, LEVEL_TWO;

level_one   |level_two|count(*)|
------------+---------+--------+
OneValue    |         |       1|
DeltaBitpack|         |       1|