如何在delphi中解压缩mysql字符串

Question

I want to compress MySQL result or string inside MySQL query and the result will send to delphi application. I use this to speed up connectivity. The problem is how to uncompress string from MySQL result inside delphi.

Here is my sample query

Select Compress(AColumn), Compress(BColumn) from ATable

Answer 1

Compress is for storage
The compress keyword in MySQL is not meant to reduce network traffic, but rather to reduce storage requirements.
The details of the compression are not documented and may vary from server to server.

COMPRESS(string_to_compress)

Compresses a string and returns the result as a binary string. This function requires MySQL to have been compiled with a compression library such as zlib. Otherwise, the return value is always NULL. The compressed string can be uncompressed with UNCOMPRESS() .

Note that the ability to uncompress depends on the compression library that your MySQL version was compiled with.

Modify the connection string if you want network compression
If you want to compress the network data you specify this in the connection settings: Add the following string to the Properties property.
UseCompression = true;

A list of all connection properties can be found here:
https://www.connectionstrings.com/mysql/

More info can be found here: http://dev.mysql.com/doc/refman/5.0/es/connector-net-examples-mysqlconnection.html#connector-net-examples-mysqlconnection-connectionstring
(note that this info is quite old, but I'm tweaking the url for the newer versions results in a 404 page not found error).

Note that in Delphi the connectionstring is largly filed in by the properties:
- Database
- Port
- Password
etc
In the Properties property you only supply those ConnectionString options that Delphi does not already cover in its other properties. Multiple arguments are separated by a ; .

Further complications
Different component packs use different names for the extra data you can put into the ConnectionString.
ZEOS calls it properties
Other people call it other things.