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/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
/*
* Content before git sha 34fdeebefcbf183ed7f916f931aa0586fdaa1b40
* Copyright (c) 2016, The Gocql authors,
* provided under the BSD-3-Clause License.
* See the NOTICE file distributed with this work for additional information.
*/
package gocql_test
import (
"context"
"fmt"
"log"
gocql "github.com/gocql/gocql"
)
// ExampleQuery_MapScanCAS demonstrates how to execute a single-statement lightweight transaction.
func ExampleQuery_MapScanCAS() {
/* The example assumes the following CQL was used to setup the keyspace:
create keyspace example with replication = { 'class' : 'SimpleStrategy', 'replication_factor' : 1 };
create table example.my_lwt_table(pk int, version int, value text, PRIMARY KEY(pk));
*/
cluster := gocql.NewCluster("localhost:9042")
cluster.Keyspace = "example"
cluster.ProtoVersion = 4
session, err := cluster.CreateSession()
if err != nil {
log.Fatal(err)
}
defer session.Close()
ctx := context.Background()
err = session.Query("INSERT INTO example.my_lwt_table (pk, version, value) VALUES (?, ?, ?)",
1, 1, "a").WithContext(ctx).Exec()
if err != nil {
log.Fatal(err)
}
m := make(map[string]interface{})
applied, err := session.Query("UPDATE example.my_lwt_table SET value = ? WHERE pk = ? IF version = ?",
"b", 1, 0).WithContext(ctx).MapScanCAS(m)
if err != nil {
log.Fatal(err)
}
fmt.Println(applied, m)
var value string
err = session.Query("SELECT value FROM example.my_lwt_table WHERE pk = ?", 1).WithContext(ctx).
Scan(&value)
if err != nil {
log.Fatal(err)
}
fmt.Println(value)
m = make(map[string]interface{})
applied, err = session.Query("UPDATE example.my_lwt_table SET value = ? WHERE pk = ? IF version = ?",
"b", 1, 1).WithContext(ctx).MapScanCAS(m)
if err != nil {
log.Fatal(err)
}
fmt.Println(applied, m)
var value2 string
err = session.Query("SELECT value FROM example.my_lwt_table WHERE pk = ?", 1).WithContext(ctx).
Scan(&value2)
if err != nil {
log.Fatal(err)
}
fmt.Println(value2)
// false map[version:1]
// a
// true map[]
// b
}
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