move db upgrade logic into db crate

This allows shrinking db's API surface.

db/upgrade/mod.rs

@@ -0,0 +1,111 @@
+// This file is part of Moonfire NVR, a security camera digital video recorder.
+// Copyright (C) 2016 Scott Lamb <slamb@slamb.org>
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// In addition, as a special exception, the copyright holders give
+// permission to link the code of portions of this program with the
+// OpenSSL library under certain conditions as described in each
+// individual source file, and distribute linked combinations including
+// the two.
+//
+// You must obey the GNU General Public License in all respects for all
+// of the code used other than OpenSSL. If you modify file(s) with this
+// exception, you may extend this exception to your version of the
+// file(s), but you are not obligated to do so. If you do not wish to do
+// so, delete this exception statement from your version. If you delete
+// this exception statement from all source files in the program, then
+// also delete it here.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+/// Upgrades the database schema.
+///
+/// See `guide/schema.md` for more information.
+
+use db;
+use failure::Error;
+use rusqlite;
+
+mod v0_to_v1;
+mod v1_to_v2;
+mod v2_to_v3;
+
+const UPGRADE_NOTES: &'static str =
+    concat!("upgraded using moonfire-db ", env!("CARGO_PKG_VERSION"));
+
+pub trait Upgrader {
+    fn in_tx(&mut self, &rusqlite::Transaction) -> Result<(), Error> { Ok(()) }
+    fn post_tx(&mut self) -> Result<(), Error> { Ok(()) }
+}
+
+#[derive(Debug)]
+pub struct Args<'a> {
+    pub flag_sample_file_dir: Option<&'a str>,
+    pub flag_preset_journal: &'a str,
+    pub flag_no_vacuum: bool,
+}
+
+fn set_journal_mode(conn: &rusqlite::Connection, requested: &str) -> Result<(), Error> {
+    assert!(!requested.contains(';'));  // quick check for accidental sql injection.
+    let actual = conn.query_row(&format!("pragma journal_mode = {}", requested), &[],
+                                |row| row.get_checked::<_, String>(0))??;
+    info!("...database now in journal_mode {} (requested {}).", actual, requested);
+    Ok(())
+}
+
+pub fn run(args: &Args, conn: &mut rusqlite::Connection) -> Result<(), Error> {
+    let upgraders = [
+        v0_to_v1::new,
+        v1_to_v2::new,
+        v2_to_v3::new,
+    ];
+
+    {
+        assert_eq!(upgraders.len(), db::EXPECTED_VERSION as usize);
+        let old_ver =
+            conn.query_row("select max(id) from version", &[], |row| row.get_checked(0))??;
+        if old_ver > db::EXPECTED_VERSION {
+            bail!("Database is at version {}, later than expected {}",
+                  old_ver, db::EXPECTED_VERSION);
+        } else if old_ver < 0 {
+            bail!("Database is at negative version {}!", old_ver);
+        }
+        info!("Upgrading database from version {} to version {}...", old_ver, db::EXPECTED_VERSION);
+        set_journal_mode(&conn, args.flag_preset_journal).unwrap();
+        for ver in old_ver .. db::EXPECTED_VERSION {
+            info!("...from version {} to version {}", ver, ver + 1);
+            let mut u = upgraders[ver as usize](&args)?;
+            let tx = conn.transaction()?;
+            u.in_tx(&tx)?;
+            tx.execute(r#"
+                insert into version (id, unix_time, notes)
+                             values (?, cast(strftime('%s', 'now') as int32), ?)
+            "#, &[&(ver + 1), &UPGRADE_NOTES])?;
+            tx.commit()?;
+            u.post_tx()?;
+        }
+    }
+
+    // WAL is the preferred journal mode for normal operation; it reduces the number of syncs
+    // without compromising safety.
+    set_journal_mode(&conn, "wal").unwrap();
+    if !args.flag_no_vacuum {
+        info!("...vacuuming database after upgrade.");
+        conn.execute_batch(r#"
+            pragma page_size = 16384;
+            vacuum;
+        "#).unwrap();
+    }
+    info!("...done.");
+    Ok(())
+}