This topic describes the behaviour associated with promoting entities such as files and folders.
[info] Not Supported
Promoting folders with non-homogenous file types is not supported.
When you issue queries against files or folders, the default behavior is to not auto-promote files/folders to datasets.
For example, given a MAPRFS source with a Root: [folder | file] structure,
if you executed
select * from MAPRFS.folder.file, the query fails.
[info] Previous Auto-Promote Behaviour
Prior to Dremio version 3.0, Dremio's default behavior for filesystem-based sources (HDFS, S3, NAS, etc) was to automatically auto-promote a folder or file to a dataset when you run a query on a file or folder.
For example, given a MAPRFS source with a Root: [folder | file] structure, if you executed select * from MAPRFS.folder.file, the file would automatically be promoted to a dataset.
If you want to automatically promote files when queries are issued against the file or folder,
- Edit your source.
- Navigate to Edit Source > Metadata > Dataset Handling.
- Select "Automatically format files into physical datasets when users issue queries.".