nrc commented on issue #12010:
URL: https://github.com/apache/datafusion/issues/12010#issuecomment-2295097808
I'm not sure this will be too useful, but our code for creating a
`ParquetExec` is something like
```
let file_scan_config = FileScanConfig::new(self.object_store_url.clone(),
self.file_schema.clone())
.with_projection(projection.cloned())
.with_limit(limit)
.with_table_partition_cols(partition_fields)
.with_file_groups(file_groups);
let reader_factory =
DefaultParquetFileReaderFactory::new(self.object_store.clone());
let exec = ParquetExecBuilder::new(file_scan_config)
.with_predicate(predicate.clone())
.with_parquet_file_reader_factory(Arc::new(reader_factory))
.build_arc();
```
You can call `ParquetExecBuilder::with_schema_adapter_factory` to supply a
schema adpater indirectly to the `ParqetExec`. However, you can't pass in the
'target' schema to the schema adapter, that happens in `<ParquetExec as
ExecutionPlan>::execute` and is always the file schema from the
`FileScanConfig`. We could pass an adjusted schema to `FileScanConfig::new`,
but I believe the schema is used for other things and so would cause errors
elsewhere. We could write schema adapter factory which makes a custom schema
adapter and in that adapter ignore the passed in schema and target our own, but
that seems like a Bad Idea.
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