mergermarket/queryparser

Package queryparser parses a Google-like search string to return a Query object.

The resulting Query object can be used as an interim representation between user input and something like ElasticSearch's Query DSL.

Usage

A simple example:

package main
import (
    "fmt"
    "github.com/mergermarket/queryparser"
    "strings"
)

func main() {
	query, _ := queryparser.NewParser(strings.NewReader(`(apple OR pear) AND (pie OR crumble)`)).Parse()
	fmt.Println(query)
}

output:

{Occur:MUST, SubQueries:[{Occur:SHOULD, Terms:["apple","pear"]},{Occur:SHOULD, Terms:["pie","crumble"]}]}

What is Query?

Query is a simple but hopefully useful model of the intention behind the parsed string.

1. Occur: how to determine whether a document matches the query.
   1. MUST = all query components must match.
   2. SHOULD = at least one query component must match.
2. Terms: zero or more words or phrases
3. SubQueries: zero or more Query objects. So yeah wow like recursive, man.

Syntax

The parser can handle arbitrary combinations of:

• single word
• phrase surrounded by quotes
• any of the above combined with boolean operators "OR" and "AND"
• any of the above grouped with parentheses

Query component	Example	Intention
single word	kayak	Match documents containing the word kayak
multiple words	kayak hammer	Match documents containing both kayak and hammer, in any order, not necessarily together.
" "	"roof slate"	Match documents containing the exact phrase roof slate.
( )	(baboon OR warthog) snake	Match documents containing at least one of baboon or warthog, and also snake.
AND	book AND pdf	Match both query components. Equivalent to book pdf
OR	tree OR shrub	Match either query component.

Look at the parser tests for more examples.

Operator precedence

Operators have the following precedence, in descending order:

Operator
( )
AND
OR

For example, because AND has higher precedence than OR, the following queries:

apple AND pear OR rhubarb

apple OR pear AND rhubarb

evaluate as if written as follows:

(apple AND pear) OR rhubarb

apple OR (pear AND rhubarb)

TODO

Not yet supported:

• "foo NOT bar" match only documents that contain "foo" but not "bar"
• "-bar" match only documents that do not contain "bar"