Run DB migrations on startup

assets/.init.lua

@@ -2,7 +2,11 @@
 
 local migrate = require "migrate"
 
-migrate.migrate()
+local DB_FILENAME = "peachy.db"
+sqlite3 = require "lsqlite3"
+local db = sqlite3.open(DB_FILENAME)
+db:exec("PRAGMA journal_mode=WAL;")
+migrate.migrate(db)
 
 fm = require "fullmoon"
 fm.setTemplate("hello", "Hello, {%& name %}")

assets/.lua/migrate.lua

@@ -3,13 +3,51 @@ local path = require "path"
 
 local filenameRegex = re.compile([=[^([0-9]+).*\.sql$]=])
 
-local function migrate()
+local function throwSqlError(db, prefix)
+	local code = db:errcode()
+	if code ~= sqlite3.OK and code ~= sqlite3.ROW and code ~= sqlite3.DONE then
+		if prefix then
+			error(string.format("%s: %s", prefix, db:errmsg()))
+		else
+			error(db:errmsg())
+		end
+	end
+end
+
+local function transact(db, func, errorPrefix)
+	local name = string.format("savepoint_%d", math.abs(math.random(0)))
+	db:exec(string.format("savepoint "..name))
+	throwSqlError(db, errorPrefix)
+	local success, result = pcall(func)
+	if not success then
+		db:exec("rollback to "..name)
+		error(result, errorPrefix)
+	end
+	db:exec("release "..name)
+	return result
+end
+
+local function getCurrentMigration(db)
+	for seqnum in db:urows("select max(seqnum) from migrations") do return seqnum end
+	throwSqlError(db, "failed to get last migration sequence number", db)
+	return -1
+end
+
+local function recordMigration(db, seqnum)
+	local stmt = db:prepare("insert into migrations (seqnum) values (?)")
+	stmt:bind_values(seqnum)
+	throwSqlError(db, "failed to record migration")
+	stmt:step()
+end
+
+local function migrate(db)
 	local migrations = {}
 	local seqnums = {}
-	local paths = GetZipPaths("/migrations/")
+	local MIGRATION_PATH = "/migrations/"
+	local paths = GetZipPaths(MIGRATION_PATH)
 	for _, p in ipairs(paths) do
-		-- basename -> sequence number
 		-- check that sequence number doesn't already exist
+		if p ~= MIGRATION_PATH then
 			local basename = path.basename(p)
 			local _, seqnum = filenameRegex:search(basename)
 			seqnum = tonumber(seqnum)
@@ -23,10 +61,34 @@ local function migrate()
 				print(string.format("found weird migration name: %s", p))
 			end
 		end
+	end
+
+	db:exec[[
+		create table if not exists migrations (
+			seqnum integer primary key
+		) without rowid
+	]]
+	throwSqlError(db, "failed to create migrations table")
 
 	table.sort(migrations, function(a, b) return a.seqnum < b.seqnum end)
+	local announced
 	for i,mig in ipairs(migrations) do
-		print(string.format("%d: %s", i, mig.filename))
+		local seqnum = mig.seqnum
+		local lastSeqnum = getCurrentMigration(db)
+		if seqnum > lastSeqnum then
+			if not announced then
+				print"Applying migrations:"
+				announced = true
+			end
+			print(mig.filename)
+			local migsql = LoadAsset(mig.filename)
+			transact(db, function()
+				db:exec(migsql)
+				throwSqlError(db, "migration failed")
+				recordMigration(db, seqnum)
+				seqnum = seqnum + 1
+			end)
+		end
 	end
 end
 

assets/migrations/01 create node.sql

@@ -0,0 +1,6 @@
+create table node (
+	id INT PRIMARY KEY,
+	title TEXT NOT NULL,
+	body TEXT NOT NULL
+);
+insert into node(title, body) values ("First post", "This is the beginning of a beautiful relationship.");

assets/migrations/2 create node_type.sql

@@ -0,0 +1,9 @@
+create table node_type (
+	id INT PRIMARY KEY,
+	name TEXT NOT NULL
+);
+
+insert into node_type(id, name) values (0, "Basic post");
+
+alter table node
+add column node_type_id INT NOT NULL references node_type(id) default 0;