Filter

Link to repository (opens new window)

• Usage
  • Settings
  • Filter
  • Search
  • Fields / Select
  • Sort
  • Join
  • Pagination
• Computed columns
• Security
• Tips
  • Model recommendations
  • Type-safety
  • Static conditions
  • Custom operators
  • Manual joins

goyave.dev/filter allows powerful filtering using query parameters. Inspired by nestjsx/crud (opens new window).

Compatible with Goyave v4 only

Usage

go get goyave.dev/filter

First, apply filters validation to the RuleSet used on the routes you wish the filters on.

import "goyave.dev/filter"

//...


var (
	IndexRequest = validation.RuleSet{}
)

func init() {
	filter.ApplyValidation(IndexRequest)
}

router.Get("/users", user.Index).Validate(user.IndexRequest)

Then implement your controller handler:

import "goyave.dev/filter"

//...

func Index(response *goyave.Response, request *goyave.Request) {
	var users []*model.User
	paginator, tx := filter.Scope(database.GetConnection(), request, &users)
	if response.HandleDatabaseError(tx) {
		response.JSON(http.StatusOK, paginator)
	}
}

And that's it! Now your front-end can add query parameters to filter as it wants.

You can also find records without paginating using ScopeUnpaginated():

var users []*model.User
tx := filter.ScopeUnpaginated(database.GetConnection(), request, &users)
if response.HandleDatabaseError(tx) {
	response.JSON(http.StatusOK, users)
}

Settings

You can disable certain features, or blacklist certain fields using filter.Settings:

settings := &filter.Settings{
	DisableFields: true, // Prevent usage of "fields"
	DisableFilter: true, // Prevent usage of "filter"
	DisableSort:   true, // Prevent usage of "sort"
	DisableJoin:   true, // Prevent usage of "join"

	FieldsSearch:   []string{"a", "b"},      // Optional, the fields used for the search feature
	SearchOperator: filter.Operators["$eq"], // Optional, operator used for the search feature, defaults to "$cont"

	Blacklist: filter.Blacklist{
		// Prevent selecting, sorting and filtering on these fields
		FieldsBlacklist: []string{"a", "b"},

		// Prevent joining these relations
		RelationsBlacklist: []string{"Relation"},

		Relations: map[string]*filter.Blacklist{
			// Blacklist settings to apply to this relation
			"Relation": &filter.Blacklist{
				FieldsBlacklist:    []string{"c", "d"},
				RelationsBlacklist: []string{"Parent"},
				Relations:          map[string]*filter.Blacklist{ /*...*/ },
				IsFinal:            true, // Prevent joining any child relation if true
			},
		},
	},
}
paginator, tx := settings.Scope(database.GetConnection(), request, &results)

Filter

?filter=field||$operator||value

Examples:

?filter=name||$cont||Jack (WHERE name LIKE "%Jack%")

You can add multiple filters. In that case, it is interpreted as an AND condition.

You can use OR conditions using ?or instead, or in combination:

?filter=name||$cont||Jack&or=name||$cont||John (WHERE (name LIKE %Jack% OR name LIKE "%John%"))
?filter=age||$eq||50&filter=name||$cont||Jack&or=name||$cont||John (WHERE ((age = 50 AND name LIKE "%Jack%") OR name LIKE "%John%"))

You can filter using columns from one-to-one relations ("has one" or "belongs to"):

?filter=Relation.name||$cont||Jack

If there is only one "or", it is considered as a regular filter:

?or=name||$cont||John (WHERE name LIKE "%John%")

If both "filter" and "or" are present, then they are interpreted as a combination of two AND groups compared with each other using OR:

?filter=age||$eq||50&filter=name||$cont||Jack&or=name||$cont||John&or=name||$cont||Doe
WHERE ((age = 50 AND name LIKE "%Jack%") OR (name LIKE "%John%" AND name LIKE "%Doe%"))

Note: All the filter conditions added to the SQL query are grouped (surrounded by parenthesis).

Operators

$eq	=, equals
$ne	<>, not equals
$gt	>, greater than
$lt	<, lower than
$gte	>=, greater than or equals
$lte	<=, lower than or equals
$starts	LIKE val%, starts with
$ends	LIKE %val, ends with
$cont	LIKE %val%, contains
$excl	NOT LIKE %val%, not contains
$in	IN (val1, val2,...), in (accepts multiple values)
$notin	NOT IN (val1, val2,...), in (accepts multiple values)
$isnull	IS NULL, is NULL (doesn't accept value)
$notnull	IS NOT NULL, not NULL (doesn't accept value)
$between	BETWEEN val1 AND val2, between (accepts two values)

Search

Search is similar to multiple or=column||$cont||value, but the column and operator are specified by the server instead of the client.

Specify the column using Settings:

settings := &filter.Settings{
	FieldsSearch: []string{"a", "b"},
	SearchOperator: filter.Operators["$eq"], // Optional, defaults to "$cont"
	//...
}

?search=John (WHERE (a LIKE "%John%" OR b LIKE "%John%"))

If you don't specify FieldsSearch, the query will search in all selectable fields.

Fields / Select

?fields=field1,field2

A comma-separated list of fields to select. If this field isn't provided, uses SELECT *.

Sort

?sort=column,ASC|DESC

Examples:

?sort=name,ASC
?sort=age,DESC

You can also sort by multiple fields.

?sort=age,DESC&sort=name,ASC

Join

?join=relation

Preload a relation. You can also only select the columns you need:

?join=relation||field1,field2

You can join multiple relations:

?join=profile||firstName,email&join=notifications||content&join=tasks

Pagination

Internally, goyave.dev/filter uses Goyave's Paginator (opens new window).

?page=1&per_page=10

• If page isn't given, the first page will be returned.
• If per_page isn't given, the default page size will be used. This default value can be overridden by changing filter.DefaultPageSize.
• Either way, the result is always paginated, even if those two parameters are missing.

Computed columns

Sometimes you need to work with a "virtual" column that is not stored in your database, but is computed using an SQL expression. A dynamic status depending on a date for example. In order to support the features of this library properly, you will have to add the expression to your model using the computed struct tag:

type MyModel struct {
	ID uint
	// ...
	StartDate time.Time
	Status    string `gorm:"->;-:migration" computed:"CASE WHEN ~~~ct~~~.start_date < NOW() THEN 'pending' ELSE 'started' END"`
}

Note: the ~~~ct~~~ is an indicator for the current table. It will be replaced by the correct table or relation name automatically. This allows the usage of computed fields in relations too, where joins are needed.

Tip: you can also use composition to avoid including the virtual column into your model:

type MyModel struct{
	ID uint
	// ...
	StartDate time.Time
}

type MyModelWithStatus struct{
	MyModel
	Status string `gorm:"->;-:migration" computed:"CASE WHEN ~~~ct~~~.start_date < NOW() THEN 'pending' ELSE 'started' END"` 
}

When using JSON columns, you can support filters on nested fields inside that JSON column using a computed column:

// This example is compatible with PostgreSQL.
// JSON processing may be different if you are using another database engine. 
type MyModel struct {
	ID            uint
	JSONColumn    datatypes.JSON
	SomeJSONField null.Int `gorm:"->;-:migration" computed:"(~~~ct~~~.json_column->>'fieldName')::int"`
}

It is important to make sure your JSON expression returns a value that has a type that matches the struct field to avoid DB errors. Database engines usually only return text types from JSON. If your field is a number, you'll have to cast it or you will get database errors when filtering on this field.

Security

• Inputs are escaped to prevent SQL injections.
• Fields are pre-processed and clients cannot request fields that don't exist. This prevents database errors. If a non-existing field is required, it is simply ignored. The same goes for sorts and joins. It is not possible to request a relation that doesn't exist.
• Type-safety: in the same field pre-processing, the broad type of the field is checked against the database type (based on the model definition). This prevents database errors if the input cannot be converted to the column's type.
• Foreign keys are always selected in joins to ensure associations can be assigned to parent model.
• Be careful with bidirectional relations (for example an article is written by a user, and a user can have many articles). If you enabled both your models to preload these relations, the client can request them with an infinite depth (Articles.User.Articles.User...). To prevent this, it is advised to use the relation blacklist or IsFinal on the deepest requestable models. See the settings section for more details.

Tips

Model recommendations

• Use json:",omitempty" on all model fields.
  • Note: using omitempty on slices will remove them from the json result if they are not nil and empty. There is currently no solution to this problem using the standard json package.
• Use json:"-" on foreign keys.
• Use *null.Time from the gopkg.in/guregu/null.v4 (opens new window) library instead of sql.NullTime.
• Always specify gorm:"foreignKey", otherwise falls back to "ID".
• Don't use gorm.Model and add the necessary fields manually. You get better control over json struct tags this way.
• Use pointers for nullable relations and nullable fields that implement sql.Scanner (such as null.Time).

Type-safety

For non-native types that don't implement the driver.Valuer interface, you should always use the filterType struct tag. This struct tag enforces the field's recognized broad type for the type-safety conversion. It is also recommended to always add this tag when working with arrays. This tag is effective for the filter and search features.

Available broad types are:

• text / text[]
• enum / enum[]: use this with custom enum types to prevent "invalid input value" or "invalid operator" errors
• bool / bool[]
• int8 / int8[], int16 / int16[], int32 / int32[], int64 / int64[]
• uint / uint[], uint16 / uint16[], uint32 / uint32[], uint64 / uint64[]
• float32 / float32[], float64 / float64[]
• time / time[]
• -: unsupported data type. Fields tagged with - will be ignored in filters and search: no condition will be added to the WHERE clause.

If not provided, the type will be determined from GORM's data type. If GORM's data type is a custom type that is not directly supported by this library, the type will fall back to - (unsupported) and the field will be ignored in the filters.

If the type is supported but the user input cannot be used with the requested column, the built-in operators will generate a FALSE condition.

Example

type MyModel struct{
	ID uint
	// ...
	StartDate null.Time `filterType:"time"`
}

Static conditions

If you want to add static conditions (not automatically defined by the library), it is advised to group them like so:

users := []model.User{}
db := database.GetConnection()
db = db.Where(db.Session(&gorm.Session{NewDB: true}).Where("username LIKE ?", "%Miss%").Or("username LIKE ?", "%Ms.%"))
paginator, tx := filter.Scope(db, request, &users)
if response.HandleDatabaseError(tx) {
	response.JSON(http.StatusOK, paginator)
}

Custom operators

You can add custom operators (or override existing ones) by modifying the filter.Operators map:

import (
	"gorm.io/gorm"
	"gorm.io/gorm/schema"
	"goyave.dev/filter"
	"goyave.dev/goyave/v4/util/sqlutil"
)

// ...

filter.Operators["$cont"] = &filter.Operator{
	Function: func(tx *gorm.DB, f *filter.Filter, column string, dataType filter.DataType) *gorm.DB {
		if dataType != filter.DataTypeString {
			return f.Where("FALSE")
		}
		query := column + " LIKE ?"
		value := "%" + sqlutil.EscapeLike(f.Args[0]) + "%"
		return f.Where(tx, query, value)
	},
	RequiredArguments: 1,
}

filter.Operators["$eq"] = &filter.Operator{
	Function: func(tx *gorm.DB, f *filter.Filter, column string, dataType filter.DataType) *gorm.DB {
		if dataType.IsArray() {
			return f.Where("FALSE")
		}
		arg, ok := filter.ConvertToSafeType(f.Args[0], dataType)
		if !ok {
			return f.Where("FALSE")
		}
		query := fmt.Sprintf("%s = ?", column, op)
		return f.Where(tx, query, arg)
	},
	RequiredArguments: 1,
}

Array operators

Some database engines such as PostgreSQL provide operators for array operations (@>, &&, ...). You may encounter issue implementing these operators in your project because of GORM converting slices into records (("a", "b") instead of {"a", "b"}).

To fix this issue, you will have to implement your own variant of ConvertArgsToSafeType so it returns a pointer to a slice with a concrete type instead of []interface{}. By sending a pointer to GORM, it won't try to render the slice itself and pass it directly to the underlying driver, which usually knows how to handle slices for the native types.

Example (using generics with go 1.18+):

type argType interface {
	string | int64 | uint64 | float64 | bool
}

func init() {
	filter.Operators["$arrayin"] = &filter.Operator{
		Function: func (tx *gorm.DB, f *filter.Filter, column string, dataType filter.DataType) *gorm.DB {
			if !dataType.IsArray() {
				return f.Where("FALSE")
			}

			if dataType == filter.DataTypeEnumArray {
				column = fmt.Sprintf("CAST(%s as TEXT[])", column)
			}
		
			query := fmt.Sprintf("%s @> ?", column)
			switch dataType {
			case filter.DataTypeTextArray, filter.DataTypeEnumArray, filter.DataTypeTimeArray:
				return bindArrayArg[string](tx, query, f, dataType)
			case filter.DataTypeFloat32Array, filter.DataTypeFloat64Array:
				return bindArrayArg[float64](tx, query, f, dataType)
			case filter.DataTypeUint8Array, filter.DataTypeUint16Array, filter.DataTypeUint32Array, filter.DataTypeUint64Array:
				return bindArrayArg[uint64](tx, query, f, dataType)
			case filter.DataTypeInt8Array, filter.DataTypeInt16Array, filter.DataTypeInt32Array, filter.DataTypeInt64Array:
				return bindArrayArg[int64](tx, query, f, dataType)
			}
		
			// If you need to handle DataTypeBoolArray, use pgtype.BoolArray
			return f.Where("FALSE")
		},
		RequiredArguments: 1,
	}
}

func bindArrayArg[T argType](tx *gorm.DB, query string, f *filter.Filter, dataType filter.DataType) *gorm.DB {
	args, ok := convertArgsToSafeTypeArray[T](f.Args, dataType)
	if !ok {
		return f.Where("FALSE")
	}
	return f.Where(tx, query, args)
}

func convertArgsToSafeTypeArray[T argType](args []string, dataType filter.DataType) (*[]T, bool) {
	result := make([]T, 0, len(args))
	for _, arg := range args {
		a, ok := filter.ConvertToSafeType(arg, dataType)
		if !ok {
			return nil, false
		}
		result = append(result, a.(T))
	}

	return &result, true
}

Manual joins

Manual joins are supported and won't clash with joins that are automatically generated by the library. That means that if needed, you can write something like described in the following piece of code.

func Index(response *goyave.Response, request *goyave.Request) {
	var users []*model.User

	db := database.GetConnection().Joins("Relation")

	paginator, tx := filter.Scope(db, request, &users)
	if response.HandleDatabaseError(tx) {
		response.JSON(http.StatusOK, paginator)
	}
}