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https://github.com/mainflux/mainflux.git
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117 lines
2.8 KiB
Go
117 lines
2.8 KiB
Go
// Copyright (c) Mainflux
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// SPDX-License-Identifier: Apache-2.0
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package cassandra
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import (
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"fmt"
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"github.com/gocql/gocql"
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"github.com/mainflux/mainflux/pkg/errors"
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"github.com/mainflux/mainflux/pkg/transformers/senml"
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"github.com/mainflux/mainflux/readers"
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)
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var errReadMessages = errors.New("failed to read messages from cassandra database")
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var _ readers.MessageRepository = (*cassandraRepository)(nil)
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type cassandraRepository struct {
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session *gocql.Session
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}
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// New instantiates Cassandra message repository.
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func New(session *gocql.Session) readers.MessageRepository {
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return cassandraRepository{
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session: session,
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}
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}
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func (cr cassandraRepository) ReadAll(chanID string, offset, limit uint64, query map[string]string) (readers.MessagesPage, error) {
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names := []string{}
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vals := []interface{}{chanID}
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for name, val := range query {
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names = append(names, name)
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vals = append(vals, val)
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}
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vals = append(vals, offset+limit)
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selectCQL := buildSelectQuery(chanID, offset, limit, names)
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countCQL := buildCountQuery(chanID, names)
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iter := cr.session.Query(selectCQL, vals...).Iter()
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defer iter.Close()
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scanner := iter.Scanner()
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// skip first OFFSET rows
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for i := uint64(0); i < offset; i++ {
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if !scanner.Next() {
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break
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}
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}
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page := readers.MessagesPage{
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Offset: offset,
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Limit: limit,
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Messages: []senml.Message{},
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}
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for scanner.Next() {
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var msg senml.Message
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err := scanner.Scan(&msg.Channel, &msg.Subtopic, &msg.Publisher, &msg.Protocol,
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&msg.Name, &msg.Unit, &msg.Value, &msg.StringValue, &msg.BoolValue,
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&msg.DataValue, &msg.Sum, &msg.Time, &msg.UpdateTime)
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if err != nil {
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return readers.MessagesPage{}, errors.Wrap(errReadMessages, err)
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}
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page.Messages = append(page.Messages, msg)
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}
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if err := cr.session.Query(countCQL, vals[:len(vals)-1]...).Scan(&page.Total); err != nil {
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return readers.MessagesPage{}, errors.Wrap(errReadMessages, err)
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}
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return page, nil
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}
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func buildSelectQuery(chanID string, offset, limit uint64, names []string) string {
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var condCQL string
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cql := `SELECT channel, subtopic, publisher, protocol, name, unit,
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value, string_value, bool_value, data_value, sum, time,
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update_time FROM messages WHERE channel = ? %s LIMIT ?
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ALLOW FILTERING`
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for _, name := range names {
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switch name {
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case
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"channel",
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"subtopic",
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"publisher",
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"name",
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"protocol":
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condCQL = fmt.Sprintf(`%s AND %s = ?`, condCQL, name)
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}
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}
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return fmt.Sprintf(cql, condCQL)
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}
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func buildCountQuery(chanID string, names []string) string {
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var condCQL string
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cql := `SELECT COUNT(*) FROM messages WHERE channel = ? %s ALLOW FILTERING`
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for _, name := range names {
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switch name {
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case
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"channel",
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"subtopic",
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"publisher",
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"name",
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"protocol":
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condCQL = fmt.Sprintf(`%s AND %s = ?`, condCQL, name)
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}
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}
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return fmt.Sprintf(cql, condCQL)
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}
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