fixup: Add comments to MIGRATIONS list

Author: tankyleo

rust/impls/src/postgres_store.rs

@@ -41,12 +41,18 @@ const LOG_MIGRATION_STMT: &str = "INSERT INTO vss_db_upgrades VALUES($1);";
 #[cfg(test)]
 const GET_MIGRATION_LOG_STMT: &str = "SELECT upgrade_from FROM vss_db_upgrades;";
 
+// APPEND-ONLY list of migration statements
+//
+// Each statement MUST be applied in-order, and only once per database.
+//
+// We make an exception for the vss_db table creation statement, as users of VSS could have initialized the table
+// themselves.
 const MIGRATIONS: &[&str] = &[
 	"CREATE TABLE vss_db_version (db_version INTEGER);",
 	"INSERT INTO vss_db_version VALUES(1);",
+	// A write-only log of all the migrations performed on this database, useful for debugging and testing
 	"CREATE TABLE vss_db_upgrades (upgrade_from INTEGER);",
-	// We do not complain if the table already exists, as a previous version of VSS could have already created
-	// this table
+	// We do not complain if the table already exists, as users of VSS could have already created this table
 	"CREATE TABLE IF NOT EXISTS vss_db (
 	    user_token character varying(120) NOT NULL CHECK (user_token <> ''),
 	    store_id character varying(120) NOT NULL CHECK (store_id <> ''),
@@ -100,7 +106,7 @@ async fn initialize_vss_database(postgres_endpoint: &str, db_name: &str) -> Resu
 	})?;
 
 	if num_rows == 0 {
-		let stmt = format!("{} {}", INIT_DB_CMD, db_name);
+		let stmt = format!("{} {};", INIT_DB_CMD, db_name);
 		client.execute(&stmt, &[]).await.map_err(|e| {
 			Error::new(ErrorKind::Other, format!("Failed to create database {}: {}", db_name, e))
 		})?;