contributing functions

[gavinking]

So far the most common migration question that has come up on stackoverflow is how to register SQL functions from a MetadataBuilderContributor.

This is possible, you can instantiate a NamedFunctionDescriptor or PatternFunctionDescriptor.

But, in our own code, we don't actually do it this way: we use PatternFunctionDescriptorBuilder and NamedFunctionDescriptorBuilder, which currently depend on the SqmFunctionRegistry, which is not available in the MetadataBuilderContributor. Perhaps we should let users do it this way too.

Or perhaps it's not necessary. I'm not sure.

[gavinking]

On the other hand, perhaps this was a misuse of MetadataBuilderContributor. Perhaps the correct answer is to use FunctionContributor in 6.

@sebersole, is that right?

[gavinking]

Probably an issue here is that there is no hibernate.function_contributors property for JPA bootstrap like there is hibernate.type_contributors for TypeContributors. We might need to fix that I guess.

[gavinking]

https://hibernate.atlassian.net/browse/HHH-15952

[gavinking]

Also, we can't apply a FunctionContributor via the bootstrap APIs like we can with TypeContributor.

[gavinking]

Also, we can't apply a FunctionContributor via the bootstrap APIs like we can with TypeContributor.

This is now solved. FunctionContributor was the right way to handle this.