MySQL BLOB appears to be unsupported

[Krzmbrzl]

I had a look at https://github.com/SOCI/soci/blob/master/src/backends/mysql/blob.cpp and I noticed that the implementation is essentially just a wrapper around throwing an exception stating that BLOB was not supported.

I am wondering why this is the case? At first I thought that this might be due to MySQL not supporting BLOBs, but this doesn't seem to be the case: https://dev.mysql.com/doc/refman/8.0/en/blob.html

Is this just something that nobody has implemented yet?

[vadz]

Yes, BLOB support is not implemented in all backends. Contributing it for MySQL would be welcome, of course.

[Krzmbrzl]

Alright - Given that I'll need this (unless I am willing to rethink my DB design), chances are that I might give this a shot.

I am wondering though: Why do we even have backend-specific BLOB implementations? My naive assumption was that a BLOB is essentially a wrapper around a std::vector< char > that is used to hold the buffer. But looking at the implementations, this does not seem to be what is done?
Do you happen to know why?

[vadz]

If you look at the existing implementation for e.g. Oracle you can see that using blobs requires using database-specific types. Using vector<byte> or whatever would require copying huge amounts of data, which would rather defeat the purpose of using BLOBs in the first place.

[Krzmbrzl]

Okay, but if I look at e.g. the implementation for sqlite3, this seems like it is essentially a custom implementation of a std::vector (more or less). Thus, I am wondering why there is no "generic" blob implementation that uses an internal buffer to which the data is written and read from and then provide backend-specific implementations where appropriate 🤔

[Krzmbrzl]

After having looked at different implementations, it seems like sqlite3 is essentially the exception here, so that explains why it probably doesn't make a lot of sense to have such a standard implementation...

[vadz]

After having looked at different implementations, it seems like sqlite3 is essentially the exception here

Yes.