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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"
)
// ExampleSession_MapExecuteBatchCAS demonstrates how to execute a batch lightweight transaction.
func ExampleSession_MapExecuteBatchCAS() {
/* 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_batch_table(pk text, ck text, version int, value text, PRIMARY KEY(pk, ck));
*/
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_batch_table (pk, ck, version, value) VALUES (?, ?, ?, ?)",
"pk1", "ck1", 1, "a").WithContext(ctx).Exec()
if err != nil {
log.Fatal(err)
}
err = session.Query("INSERT INTO example.my_lwt_batch_table (pk, ck, version, value) VALUES (?, ?, ?, ?)",
"pk1", "ck2", 1, "A").WithContext(ctx).Exec()
if err != nil {
log.Fatal(err)
}
executeBatch := func(ck2Version int) {
b := session.NewBatch(gocql.LoggedBatch)
b.Entries = append(b.Entries, gocql.BatchEntry{
Stmt: "UPDATE my_lwt_batch_table SET value=? WHERE pk=? AND ck=? IF version=?",
Args: []interface{}{"b", "pk1", "ck1", 1},
})
b.Entries = append(b.Entries, gocql.BatchEntry{
Stmt: "UPDATE my_lwt_batch_table SET value=? WHERE pk=? AND ck=? IF version=?",
Args: []interface{}{"B", "pk1", "ck2", ck2Version},
})
m := make(map[string]interface{})
applied, iter, err := session.MapExecuteBatchCAS(b.WithContext(ctx), m)
if err != nil {
log.Fatal(err)
}
fmt.Println(applied, m)
m = make(map[string]interface{})
for iter.MapScan(m) {
fmt.Println(m)
m = make(map[string]interface{})
}
if err := iter.Close(); err != nil {
log.Fatal(err)
}
}
printState := func() {
scanner := session.Query("SELECT ck, value FROM example.my_lwt_batch_table WHERE pk = ?", "pk1").
WithContext(ctx).Iter().Scanner()
for scanner.Next() {
var ck, value string
err = scanner.Scan(&ck, &value)
if err != nil {
log.Fatal(err)
}
fmt.Println(ck, value)
}
if err := scanner.Err(); err != nil {
log.Fatal(err)
}
}
executeBatch(0)
printState()
executeBatch(1)
printState()
// false map[ck:ck1 pk:pk1 version:1]
// map[[applied]:false ck:ck2 pk:pk1 version:1]
// ck1 a
// ck2 A
// true map[]
// ck1 b
// ck2 B
}
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