In my Windows programs I use this in my generic data capture forms to read nullability, type and data length for presenting the edit window:
select is_nullable as IS_NULLABLE ,data_type as DATA_TYPE ,character_octet_length as CHARACTER_MAXIMUM_LENGTH from VistaDBColumnSchema() where table_name = 'D_ANIMAL' and column_name = 'AN_REG_NAME'
In 5.2.2 and before in Windows it works. Now on Xamarin IOS and 5.7.4, I get this for the identical query:
The given key 'VistaDBColumnSchema' was not present in the dictionary. Error 607 (Provider v. 126.96.36.199): Function does not exist: VistaDBColumnSchema Line #: 1; Column #: 121 Error 607 (Provider v. 188.8.131.52): Function does not exist: VistaDBColumnSchema Line #: 1; Column #: 121
I don't think we changed anything involving that system function, and a quick test in 5.7.4 Data Builder didn't fail for us. It sounds like this is readily reproducible for you, though, so could you try to capture the exception and get the Stack Trace for the exception and any nested inner exceptions (particularly the inner-most)? That would give us a lot more to go on to see why it might be failing.
It could also help if we had your database to try your specific query and hopefully reproduce it for debugging. Could you email firstname.lastname@example.org with the stack trace information and an example database file that reproduces the error? (If it's larger than 20 MB after zipping you will need the instructions here.