Programming language: Go
License: Apache License 2.0
Tags: Query Language    
Latest version: v1.8.1

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Query Parser for REST

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Query Parser is a library for easy building dynamic SQL queries to Database. It provides a simple API for web-applications which needs to do some filtering throught GET queries. It is a connector between the HTTP handler and the DB engine, and manages validations and translations for user inputs.


go get -u github.com/timsolov/rest-query-parser


The idia to write this library comes to me after reading this article: REST API Design: Filtering, Sorting, and Pagination.

And principles enumerated in article I considered very useful and practical to use in our project with amount of listings with different filtering.

Fast start

See cmd/main.go and tests for more examples.

    package main

    import (

        rqp "github.com/timsolov/rest-query-parser"

    func main() {
        url, _ := url.Parse("http://localhost/?sort=+name,-id&limit=10&id=1&i[eq]=5&s[eq]=one&email[like]=*tim*|name[like]=*tim*")
        q, _ := rqp.NewParse(url.Query(), rqp.Validations{
            "limit:required": rqp.MinMax(10, 100),  // limit must present in the Query part and must be between 10 and 100 (default: Min(1))
            "sort":           rqp.In("id", "name"), // sort could be or not in the query but if it is present it must be equal to "in" or "name"
            "s":      rqp.In("one", "two"), // filter: s - string and equal
            "id:int": nil,                  // filter: id is integer without additional validation
            "i:int": func(value interface{}) error { // filter: custom func for validating
                if value.(int) > 1 && value.(int) < 10 {
                    return nil
                return errors.New("i: must be greater then 1 and lower then 10")
            "email": nil,
            "name":  nil,

        fmt.Println(q.SQL("table")) // SELECT * FROM table WHERE id = ? AND i = ? AND s = ? AND (email LIKE ? OR name LIKE ?) ORDER BY name, id DESC LIMIT 10
        fmt.Println(q.Where())      // id = ? AND i = ? AND s = ? AND (email LIKE ? OR name LIKE ?)
        fmt.Println(q.Args())       // [1 5 one %tim% %tim%]

        q.AddValidation("fields", rqp.In("id", "name"))

        fmt.Println(q.SQL("table")) // SELECT id, name FROM table ORDER BY id LIMIT 10
        fmt.Println(q.FieldsSQL())  // id, name
        fmt.Println(q.Args())       // []

Top level fields:

  • fields - fields for SELECT clause separated by comma (",") Eg. &fields=id,name. If nothing provided will use "*" by default. Attention! If you want to use this filter you have to define validation func for it. Use rqp.In("id", "name") func for limit fields for your query.
  • sort - sorting fields list separated by comma (","). Must be validated too. Could include prefix +/- which means ASC/DESC sorting. Eg. &sort=+id,-name will print ORDER BY id, name DESC. You have to filter fields in this parameter by adding rqp.In("id", "name").
  • limit - is limit for LIMIT clause. Should be greater then 0 by default. Definition of the validation for limit is not required. But you may use rqp.Max(100) to limit top threshold.
  • offset - is offset for OFFSET clause. Should be greater then or equal to 0 by default. Definition of the validation for offset is not required.

Validation modificators:

  • :required - parameter is required. Must present in the query string. Raise error if not.
  • :int - parameter must be convertable to int type. Raise error if not.
  • :bool - parameter must be convertable to bool type. Raise error if not.

Supported types

  • string - the default type for all provided filters if not specified another. Could be compared by eq, ne, gt, lt, gte, lte, like, ilike, nlike, nilike, in, nin, is, not methods (nlike, nilike means NOT LIKE, NOT ILIKE respectively, in, nin means IN, NOT IN respectively, is, not for comparison to NULL IS NULL, IS NOT NULL).
  • int - integer type. Must be specified with tag ":int". Could be compared by eq, ne, gt, lt, gte, lte, in, nin methods.
  • bool - boolean type. Must be specified with tag ":bool". Could be compared by eq method.

Date usage

This is simple example to show logic which you can extend.

    import (
        validation "github.com/go-ozzo/ozzo-validation/v4"

    func main() {
        url, _ := url.Parse("http://localhost/?create_at[eq]=2020-10-02")
        q, _ := rqp.NewParse(url.Query(), rqp.Validations{
            "created_at": func(v interface{}) error {
                s, ok := v.(string)
                if !ok {
                    return rqp.ErrBadFormat
                return validation.Validate(s, validation.Date("2006-01-02"))

        q.ReplaceNames(rqp.Replacer{"created_at": "DATE(created_at)"})

        fmt.Println(q.SQL("table")) // SELECT * FROM table WHERE DATE(created_at) = ?