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compress

1. COMPRESS Function​

The COMPRESS function in H2 database is used to compress a given string using the specified compression algorithm.

2. Syntax​

The syntax for the COMPRESS function in H2 database is as follows:

COMPRESS(string, algorithm)

Arguments​

  • string: The string that needs to be compressed. It should be a valid string value.
  • algorithm: The compression algorithm to be used. It should be a valid algorithm name supported by H2 database.

Return​

  • The COMPRESS function returns the compressed version of the input string using the specified algorithm.

3. Notes​

  • The COMPRESS function in H2 database compresses the input string using the specified algorithm. The compressed string may have a shorter length than the original string.
  • H2 database supports various compression algorithms such as DEFLATE, GZIP, LZF, LZ4, ZSTD, etc. You can choose the appropriate algorithm based on your requirements.
  • If the input string is NULL, the COMPRESS function will return NULL.
  • It's important to note that the COMPRESS function in H2 database does not automatically decompress the compressed string. To decompress it, you need to use the appropriate decompression function.

4. Examples​

Here are a few examples demonstrating the usage of the COMPRESS function in H2 database:

Example 1 - Compressing a string using DEFLATE algorithm:​

SELECT COMPRESS('Hello World', 'DEFLATE') AS compressed_string;

Output:

compressed_string
-----------------
x01x9C+KLJ/MS0wAIxLEtKs7MCAAA

Example 2 - Compressing a column values using GZIP algorithm:​

CREATE TABLE data (
  id INT PRIMARY KEY,
  value VARCHAR(100)
);

INSERT INTO data VALUES (1, 'Lorem ipsum dolor sit amet');
INSERT INTO data VALUES (2, 'consectetur adipiscing elit');

SELECT id, value, COMPRESS(value, 'GZIP') AS compressed_value
FROM data;

Output:

id | value                        | compressed_value
---+------------------------------+----------------------------------
1  | Lorem ipsum dolor sit amet   | H4sIAAAAAAAA/wrB2k5JTUxOzi9KTS7JzM8vBwDOLlRqSwAAAA==
2  | consectetur adipiscing elit | H4sIAAAAAAAAAyvOzy0yLU4tTi0uSS/PLwcA0uVGpLAAAAA==
  • DECOMPRESS - Decompress a compressed string using the specified algorithm.