Support Type Coercion in Parquet Reader

[tustvold]

Is your feature request related to a problem or challenge?

#6404 by @e1ijah1 added support for type coercion within SchemaAdapter, we should hook up ParquetExec to make use of this to allow for mixed schema within a single ParquetExec

Describe the solution you'd like

I would like to be able to read a set of parquet files with different schema and have them coerced to the same schema

Describe alternatives you've considered

No response

Additional context

No response

[e1ijah1]

I'm interested and can complete this new issue too, but I'm uncertain on how to integrate SchemaAdapter into ParquetExec for mixed schemas. Could you please provide me with a little guidance or a high-level overview of how this might be done? Thank you

[tustvold]

I think a first step would be switching ParquetOpener::open from using map_projections to the new API. I'm not sure what work might be required to make predicate pushdown work correctly, but I think this would be a good first step

[e1ijah1]

@tustvold
I have implemented this feature in my latest commit. Could you please review it when you are available? Thank you.