Function insertValKeyOrIdx

postgres/parser/json/json.go:1256–1300

(j JSON, key string, newVal JSON, insertAfter bool)

var errCannotReplaceExistingKey = pgerror.WithCandidateCode(errors.New("cannot replace existing key"), pgcode.InvalidParameterValue)

func insertValKeyOrIdx(j JSON, key string, newVal JSON, insertAfter bool) (JSON, error) {
	switch v := j.(type) {
	case *jsonEncoded:
		n, err := v.shallowDecode()
		if err != nil {
			return nil, err
		}
		return insertValKeyOrIdx(n, key, newVal, insertAfter)
	case jsonObject:
		result, err := v.SetKey(key, newVal, true)
		if err != nil {
			return nil, err
		}
		if len(result) == len(v) {
			return nil, errCannotReplaceExistingKey
		}
		return result, nil
	case jsonArray:
		idx, err := strconv.Atoi(key)
		if err != nil {
			return nil, err
		}
		if idx < 0 {
			idx = len(v) + idx
		}
		if insertAfter {
			idx++
		}

		var result = make(jsonArray, len(v)+1)
		if idx <= 0 {
			copy(result[1:], v)
			result[0] = newVal
		} else if idx >= len(v) {
			copy(result, v)
			result[len(result)-1] = newVal
		} else {
			copy(result[:idx], v[:idx])
			copy(result[idx+1:], v[idx:])
			result[idx] = newVal
		}
		return result, nil
	}
	return j, nil
}

// DeepInsert inserts a value at a path in a JSON document.
// Implements the jsonb_insert builtin.