stjordanis / goven

Goven (go-oven) is a go library that allows you to have a drop-in query language for your database schema.

Goven 🧑‍🍳

Goven (go-oven) is a go library that allows you to have a drop-in query language for your database schema.

• Take any gorm database object and with a few lines of code you can make it searchable.
• Safe query language not exposing SQL to your users.
• Easily extensible to support more advanced queries for your own schema.
• Basic grammar that allows for powerful queries.

Like a real life oven, it takes something raw (your database struct + a query input) and produces something specific (the schema specific parser + SQL output). We call the adaptors "recipes" that Goven can make. Currently Goven only supports a SQL adaptor, but the AST produced by the lexer/parser can easily be extended to other query languages.

Recipes

Basic Example

You can make a basic query using gorm against your database, something like this:

reflection := reflect.ValueOf(&User{})
queryAdaptor, err := sql_adaptor.NewDefaultAdaptorFromStruct(reflection)
if err != nil {
    return nil, err
}

dbQuery := db.WithContext(ctx)
parsedQuery, err := queryAdaptor.Parse("(name=james AND age > 11) OR [email protected]")
if err != nil {
	return nil, err
}
dbQuery = query.Model(User{}).Where(parsedQuery.Raw, sql_adaptor.StringSliceToInterfaceSlice(parsedQuery.Values)...)
err = dbQuery.Find(&users).Error

The values are interpolated to prevent injection attacks.

Extension Example

You can also extend the basic query language with regex matchers. An example would be having a Tag struct on your User schema.

type User struct {
	gorm.Model
	name string
	tags []Tag
}

type Tag struct {
	gorm.Model
	Key string
	Value string
}

You can make this searchable my defining a regex and a custom matcher.

e.g if we want tags[key]=value to work then we can add the following matcher when creating the adaptor.

KeyValueRegex = `(tags)\[(.+)\]`

// keyValueMatcher is a custom matcher for and tags[y].
func keyValueMatcher(ex *goven_parser.Expression) (*goven_sql.SqlResponse, error) {
	reg, err := regexp.Compile(KeyValueRegex)
	if err != nil {
		return nil, err
	}
	slice := reg.FindStringSubmatch(ex.Field)
	if slice == nil {
		return nil, errors.New("didn't match regex expression")
	}
	if len(slice) < 3 {
		return nil, errors.New("regex match slice is too short")
	}
	sq := goven_sql.SqlResponse{
		Raw:    fmt.Sprintf("id IN (SELECT user_id FROM %s WHERE key=? AND value%s?)", slice[1], ex.Comparator),
		Values: []string{slice[2], ex.Value},
	}
	return &sq, nil
}

Protecting Fields

Sometimes we may not want particular fields to be searchable by end users. You can protect them by removing them from the fields mapping when creating your adaptor.

defaultFields := goven_sql.FieldParseValidatorFromStruct(gorm)
delete(defaultFields, "fieldname")

Grammar

Goven has a simple syntax that allows for powerful queries.

Fields can be compared using the following operators:

=, !=, >=, <=, <, >, %

The % operator allows you to do partial string matching using LIKE.

Multiple queries can be combined using AND, OR.

Together this means you can build up a query like this:

model_name=iris AND version>=2.0

More advanced queries can be built up using bracketed expressions:

(model_name=iris AND version>=2.0) OR artifact_type=TENSORFLOW