Mainflux.mainflux/readers/cassandra/messages.go

//
// Copyright (c) 2018
// Mainflux
//
// SPDX-License-Identifier: Apache-2.0
//

package cassandra

import (
	"github.com/gocql/gocql"
	"github.com/mainflux/mainflux"
	"github.com/mainflux/mainflux/readers"
)

var _ readers.MessageRepository = (*cassandraRepository)(nil)

type cassandraRepository struct {
	session *gocql.Session
}

// New instantiates Cassandra message repository.
func New(session *gocql.Session) readers.MessageRepository {
	return cassandraRepository{session: session}
}

func (cr cassandraRepository) ReadAll(chanID, offset, limit uint64) []mainflux.Message {
	cql := `SELECT channel, publisher, protocol, name, unit,
			value, string_value, bool_value, data_value, value_sum, time,
			update_time, link FROM messages WHERE channel = ? LIMIT ?
			ALLOW FILTERING`

	iter := cr.session.Query(cql, chanID, offset+limit).Iter()
	scanner := iter.Scanner()

	// skip first OFFSET rows
	for i := uint64(0); i < offset; i++ {
		if !scanner.Next() {
			break
		}
	}

	page := []mainflux.Message{}
	for scanner.Next() {
		var msg mainflux.Message
		scanner.Scan(&msg.Channel, &msg.Publisher, &msg.Protocol,
			&msg.Name, &msg.Unit, &msg.Value, &msg.StringValue, &msg.BoolValue,
			&msg.DataValue, &msg.ValueSum, &msg.Time, &msg.UpdateTime, &msg.Link)
		page = append(page, msg)
	}

	if err := iter.Close(); err != nil {
		return []mainflux.Message{}
	}

	return page
}