orm add sqlite3 support, may be support postgres in next commit

orm/db_sqlite.go

@@ -1,9 +1,38 @@
 package orm
 
+var sqliteOperators = map[string]string{
+	"exact":       "= ?",
+	"iexact":      "LIKE ? ESCAPE '\\'",
+	"contains":    "LIKE ? ESCAPE '\\'",
+	"icontains":   "LIKE ? ESCAPE '\\'",
+	"gt":          "> ?",
+	"gte":         ">= ?",
+	"lt":          "< ?",
+	"lte":         "<= ?",
+	"startswith":  "LIKE ? ESCAPE '\\'",
+	"endswith":    "LIKE ? ESCAPE '\\'",
+	"istartswith": "LIKE ? ESCAPE '\\'",
+	"iendswith":   "LIKE ? ESCAPE '\\'",
+}
+
 type dbBaseSqlite struct {
 	dbBase
 }
 
+var _ dbBaser = new(dbBaseSqlite)
+
+func (d *dbBaseSqlite) OperatorSql(operator string) string {
+	return sqliteOperators[operator]
+}
+
+func (d *dbBaseSqlite) SupportUpdateJoin() bool {
+	return false
+}
+
+func (d *dbBaseSqlite) MaxLimit() uint64 {
+	return 9223372036854775807
+}
+
 func newdbBaseSqlite() dbBaser {
 	b := new(dbBaseSqlite)
 	b.ins = b