[]string in, string out

[porjo]

I have a situation where if I store a []string with a single element I get back a value of type string, whereas if I store a []string with 2 or more elements, I get back a value of type []interface{}

Is this a property of Go language, or something about Bleve implementation?

This example code below demonstrates the issue. It should produce output:

abc result type string
xyz result type []interface {}

package main

import (
	"fmt"
	"log"
	"reflect"

	"github.com/blevesearch/bleve"
)

type doc struct {
	Name       string
	Recipients []string
}

func main() {
	mapping := bleve.NewIndexMapping()
	index, err := bleve.NewMemOnly(mapping)

	// single string
	id := "1234"
	d1 := doc{Name: "abc", Recipients: []string{"a@example.com"}}
	err = index.Index(id, d1)
	if err != nil {
		log.Fatal(err)
	}

	query := bleve.NewMatchQuery("abc")
	search := bleve.NewSearchRequest(query)
	search.Fields = []string{"Name", "Recipients"}
	searchResults, err := index.Search(search)
	if err != nil {
		log.Fatal(err)
	}

	hit := searchResults.Hits[0]
	fmt.Printf("abc result type %s\n", reflect.TypeOf(hit.Fields["Recipients"]))

	// multi strings
	id = "5678"
	d2 := doc{Name: "xyz", Recipients: []string{"a@example.com", "b@example.com"}}
	err = index.Index(id, d2)
	if err != nil {
		log.Fatal(err)
	}

	query = bleve.NewMatchQuery("xyz")
	search = bleve.NewSearchRequest(query)
	search.Fields = []string{"Name", "Recipients"}
	searchResults, err = index.Search(search)
	if err != nil {
		log.Fatal(err)
	}

	hit = searchResults.Hits[0]
	fmt.Printf("xyz result type %s\n", reflect.TypeOf(hit.Fields["Recipients"]))
}

[mschoch]

The problem is that stored fields in bleve are kind of broken. The implementation cannot always return to you the exact original value (which is what users want). On top of that, support for arrays was added later, and as you found, an array with one element is confused with there being no array at all.

I'm fine with leaving this issue open to track it, but it's going to take a bleve2 type overhaul of stored fields to address this properly.

[pbnsilva]

What is the best way to get an array back in the current version?

[mschoch]

As the code sample above illustrates, if you index an array of strings, you will get back a []interface{} containing strings. There is no other way in Bleve.