Function column_changes 

pub fn column_changes(change: Option<Option<&Attachment>>) -> [Param; 5]

Builds the parameters of an UPDATE of one attachment’s columns: a change flag, then the four columns.

None keeps the stored file (flag false, four NULLs that the SQL ignores), Some(None) clears the columns (flag true, four NULLs), Some(Some(file)) points them to file. The generated SQL reads avatar_key = CASE WHEN ?1 THEN ?2 ELSE avatar_key END, ..., so one statement handles “unchanged”, “removed” and “replaced” without building SQL at runtime. Deleting the replaced object is up to the caller (delete_attachments, after the write succeeds).

Examples

use ocre::{params, storage::{self, Attachment}};

let photo = Attachment { key: "k".into(), filename: "a.png".into(), content_type: "image/png".into(), size: 3 };
assert_eq!(storage::column_changes(Some(Some(&photo))), params![true, "k", "a.png", "image/png", 3_i64][..]);
let null = None::<i64>;
assert_eq!(storage::column_changes(Some(None))[..], params![true, null, null, null, null]);
assert_eq!(storage::column_changes(None)[0], params![false][0]);