update

src-tauri/src/localdb.rs

@@ -4,7 +4,7 @@
 //! snapshot is restored in the order proven on the Data PC's dumps: pre-data,
 //! every table's data (in parallel), sequences, post-data.
 
-use std::collections::VecDeque;
+use std::collections::{BTreeSet, VecDeque};
 use std::path::{Path, PathBuf};
 use std::process::{Command, Stdio};
 use std::sync::atomic::{AtomicU64, AtomicUsize, Ordering};
@@ -420,6 +420,18 @@ const ADDING_MARKER: &str = "adding-tables.txt";
 /// copy would make this PC's Engine API skip migrations its schema never had.
 const OWN_DATABASE_ONLY: [&str; 1] = ["public.odian_schema_migrations"];
 
+/// The files of a snapshot a database lacking only `missing` needs: the schema and sequence
+/// dumps (small, and adding tables reads them) and the data of the missing tables. The rest
+/// is data the database already holds. A data dump with no plain table name is kept, the
+/// safe side of not knowing.
+pub fn files_needed(files: &[DbFile], missing: &[String]) -> BTreeSet<String> {
+  files
+    .iter()
+    .filter(|f| f.section != "data" || table_of(f).is_none_or(|table| missing.contains(&table)))
+    .map(|f| f.path.clone())
+    .collect()
+}
+
 /// The snapshot's data tables an existing database may lack and be given.
 fn candidate_tables(files: &[DbFile]) -> Vec<String> {
   files
@@ -565,6 +577,37 @@ CREATE FUNCTION public.hospital_count() RETURNS bigint AS $$ SELECT count(*) FRO
                ("postgis_hospital", "TABLE", "public.postgis_hospital".to_string()));
   }
 
+  #[test]
+  fn a_database_keeping_its_data_needs_only_the_schema_and_the_tables_it_lacks() {
+    let file = |section: &str, table: Option<&str>, path: &str| DbFile {
+      section: section.to_string(),
+      table: table.map(str::to_string),
+      path: path.to_string(),
+      size: 1,
+    };
+    let files = [
+      file("pre-data", None, "db/S/pre-data.dump"),
+      file("data", Some("public.odb_note"), "db/S/data/public.odb_note.dump"),
+      file("data", Some("public.postgis_hospital"), "db/S/data/public.postgis_hospital.dump"),
+      file("data", None, "db/S/data/Weird Name.dump"),
+      file("data", Some("public.odian_schema_migrations"), "db/S/data/public.odian_schema_migrations.dump"),
+      file("sequences", None, "db/S/sequences.dump"),
+      file("post-data", None, "db/S/post-data.dump"),
+    ];
+    let needed = files_needed(&files, &["public.postgis_hospital".to_string()]);
+    assert_eq!(
+      needed.into_iter().collect::<Vec<_>>(),
+      [
+        "db/S/data/Weird Name.dump",
+        "db/S/data/public.postgis_hospital.dump",
+        "db/S/post-data.dump",
+        "db/S/pre-data.dump",
+        "db/S/sequences.dump",
+      ]
+    );
+    assert_eq!(files_needed(&files, &[]).len(), 4, "nothing missing: the schema dumps and the unnamed one");
+  }
+
   #[test]
   fn a_table_is_referenced_whole_never_as_a_prefix() {
     assert!(references("CREATE INDEX i ON public.postgis_hospital USING gist (geom);", "public.postgis_hospital"));