Extend URI loading functionality to other file-loading commands

[apstndb]

Feature Request

Extend URI loading functionality to other commands that load files, such as the \. meta command.

Background

In #470, we implemented URI-based loading functionality that supports multiple schemes:

• gs:// - Google Cloud Storage
• file:// - Local file system
• http:// / https:// - HTTP(S) downloads

This functionality is currently only used for --sample-database flag, but could be valuable for other file-loading operations.

Proposed Enhancement

1. Extend \. Meta Command

The \. command (LOAD) currently only supports local file paths. It could benefit from URI support:

-- Load from Google Cloud Storage
\. gs://my-bucket/scripts/setup.sql

-- Load from HTTP
\. https://raw.githubusercontent.com/example/repo/main/schema.sql

-- Explicit local file
\. file:///home/user/scripts/init.sql

2. Other Potential Applications

• --file / -f flag for batch execution
• --proto-descriptor-file for protobuf descriptors
• Any future features that need to load external resources

Implementation Notes

The core URI loading functions (loadFromURI, loadFromGCS, loadFromHTTP) are already implemented in sample_databases.go. These could be:

1. Moved to a separate package/file (e.g., uri_loader.go)
2. Made more generic and reusable
3. Extended with additional features like:
   • Progress indicators for large files
   • Caching support
   • Authentication for private resources

Benefits

• Consistency: Same URI syntax across all file-loading operations
• Flexibility: Users can load scripts from various sources without manual downloading
• Cloud-native: Direct integration with GCS for Cloud Spanner users
• Convenience: Load scripts directly from GitHub, documentation sites, etc.

Related

• Add --sample-database flag for initializing embedded emulator with official samples #470 - Original implementation for --sample-database