Sorry for the late reply.. On Thu, 2005-05-19 at 19:03 +0200, Bram Kuijvenhoven wrote: > After understanding what a VARCHAR is (namely some sort of shortstring > with a fixed maximum length), I wanted first to know whether a newer > MySQL server reports proper field lengths for fields like 'FORMAT > (mydoublefield,3) AS myalias', so I switched to a 4.1 server.
If you store the string 'hello' in a varchar(1000) it only needs 9 bytes of storage-space, while using char(1000) you would need 1000 bytes. In memory, however, fpc indeed uses a shortstring. > However this didn't work, because I needed a newer client also, > because the older client didn't support the newer authentication > protocol requested by the server (according to the error message I > got). > > So I used a newer libMySQL.dll file and adjusted mysql4dyn to > accepting this version. But now I got a authentication error for user > [EMAIL PROTECTED] However I didn't connect as user ODBC?!? That check isn't there for nothing. > The I figured out the TMySQLConnection object connected twice to the > database, once in ConnectToServer and once in PrepareStatement. The > second time it tries to fetch the Host, UserName, Password from the > FMySQL:PMySQL field. But there seem to be nil values in there... and I > guess MySQL somehow tries user ODBC because no username is given. That's because they've changed the PMySQL-type. (Like they change everything, always - just like they want) > I also tried loading the newer dll statically, but then I had to > comment out a lot more functions in mysql4 and mysql4_com than before, > in particular some slave, master and the hash_password functions. > > So my findings are: > - the fpc mysql headers contain way too much function headers, which > causes 'entry point of function blablabla not found' error when > statically loading the library. I think it's better only to try to > import the functions which are also documented as part of the C API at > http://dev.mysql.com/doc/mysql/en/c.html. > - the fpc headers contain declarations of structs (records) that are > not in the MySQL documentation. The only struct described there is the > MYSQL_FIELD struct (or: TMySQL record), besides the other types of > which no members are listed. Perhaps using the other structs isn't > very safe and prone to change. > - mysql4dyn only accepts a 4.0 library and no a 4.1 library; I hope > this can be made more flexible... > I understand the fpc team has become tired of mysql header changes and > incompatibilities, but this problem does not seem to exist with e.g. > the php mysql interface. Maybe the problems can be solved by only > importing and functions that are also in the documentation. (This > would require manual action instead of simply applying h2pas to > mysql.h) > Do you think this is an approach with a chance to success? No. The idea is good though. I think I can use it with the problem of what functions/procedures need to be put into the headers. But, the largest problem is all those things which aren't documented. Example, in http://dev.mysql.com/doc/mysql/en/c-api-datatypes.html you can find that 'field' can be one of the following: FIELD_TYPE_TINY, FIELD_TYPE_SHORT etc.etc. But it could be that for MySQL 4.0 FIELD_TYPE_TINY is defined as 0, while in 4.1 it's defined as 1. So for 4.0 it should be: const FIELD_TYPE_TINY : 0; FIELD_TYPE_SHORT : 1; while for 4.1 it is: const FIELD_TYPE_TINY : 1; FIELD_TYPE_SHORT : 0; And why they keep changing that sort of things, I really don't get. And these differences you can only see in the .h's. (I made this example up, but those differences do exist) > MySQL is widely used and therefore it would be nice if it can be > supported by fpc. (In fact, I've seen people asking things about mysql > on the Lazarus mailing list several times) Me too. > After getting the mysql headers right and 'compatible', I could try to > create a better TMySQLConnection. I'm gonna throw out all non-documented procedures. (Well, they are documented mostly, but elsewhere) And use diff on the .h's -- Met vriendelijke groeten, Joost van der Sluis CNOC Informatiesystemen en Netwerken http://www.cnoc.nl
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