GO-RQL-PARSER

Small, simple and lightweight library for Go web applications to translate RQL (Resource Query Language) queries to SQL

Usage

query := `and(eq(foo,3),lt(price,10))&sort(+price)`

p := rqlParser.NewParser() // Instanciate a new parser

// Parse the query and return the root node of the generated tree
rqlRootNode, err := p.Parse(query) 
if err != nil {
	panic("Query is not a valid rql : " + err.Error())
}

// Return the sql string for querying DB
sql, err := rqlParser.NewSqlTranslator(rqlNode).Sql()
if err != nil {
	panic(err)
}

fmt.Println(sql) 
// Print `WHERE ((foo=3) AND (price < 10)) ORDER BY price

Supported operators

The library support by default the following RQL operators :

• AND
  • SQL Operator : AND
• OR
  • SQL Operator : OR
• NE
  • SQL Operator : != (When value is NULL it is translated to the IS NOT SQL operator)
• EQ
  • SQL Operator : = (When value is NULL it is translated to the IS SQL operator)
• LIKE
  • SQL Operator : LIKE
• MATCH
  • SQL Operator : ILIKE
• GT
  • SQL Operator : >
• LT
  • SQL Operator : <
• GE
  • SQL Operator : >=
• LE
  • SQL Operator : <=
• SUM
  • SQL Operator : SUM
• NOT
  • SQL Operator : NOT

Append supported operators

It's easy to handle new operators by simply adding a TranslatorOpFunc to the SQLTranslator :

query := `or(eq(foo,42),between(price,10,100))`
rqlRootNode, err := p.Parse(query) 
if err != nil { 
  panic("Query is not a valid rql : " + err.Error()) 
}

sqlTranslator := rqlParser.NewSqlTranslator(rqlNode)

// Before translating the node, just add the custom operator
// let's define a new function to handle beetween operator
betweenTranslatorFunc := func(n *rqlParser.RqlNode) (s string, err error) {
	var (
		min, max int64
		field    string
	)

	if len(n.Args) != 3 {
		err = fmt.Errorf("between operator require 3 arguments")
		return
	}

	for i, a := range n.Args {
		if v, ok := a.(string); ok {
			switch i {
			case 0:
				if rqlParser.IsValidField(v) {
					field = v
				} else {
					return "", fmt.Errorf("First argument must be a valid field name (arg: %s)", v)
				}
			case 1, 2:
				num, err := strconv.ParseInt(v, 10, 64)
				if err != nil {
					return "", fmt.Errorf("Argument n°%d must be an integer (arg: %s)", i, v)
				}
				if i == 1 {
					min = num
				} else {
					max = num
				}
			}
		} else {
			err = fmt.Errorf("Between example function only support string arguments")
			return
		}
	}

	s = fmt.Sprintf("(%s >= %d) AND (%s <= %d)", field, min, field, max)

	return
}

sqlTranslator.SetOpFunc(`between`, rqlParser.TranslatorOpFunc(betweenTranslatorFunc))
s, err := sqlTranslator.Sql() 
if err != nil { 
  panic(err) 
}
fmt.Println(s) // Will print : "WHERE ((foo=42) OR ((price >= 10) AND (price <= 100)))"

Contributions

Any contribution is welcome.

There is still many improvements that should be added to this library :

• Support type casting (ex: string:42 to force the SQLTranslator to handle 42 as a string)
• Create a per database architecture translator as all databases doesn't support the same operators.