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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"
"os"
"reflect"
"text/tabwriter"
gocql "github.com/gocql/gocql"
)
// Example_dynamicColumns demonstrates how to handle dynamic column list.
func Example_dynamicColumns() {
/* 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.table1(pk text, ck int, value1 text, value2 int, PRIMARY KEY(pk, ck));
insert into example.table1 (pk, ck, value1, value2) values ('a', 1, 'b', 2);
insert into example.table1 (pk, ck, value1, value2) values ('c', 3, 'd', 4);
insert into example.table1 (pk, ck, value1, value2) values ('c', 5, null, null);
create table example.table2(pk int, value1 timestamp, PRIMARY KEY(pk));
insert into example.table2 (pk, value1) values (1, '2020-01-02 03:04:05');
*/
cluster := gocql.NewCluster("localhost:9042")
cluster.Keyspace = "example"
cluster.ProtoVersion = 4
session, err := cluster.CreateSession()
if err != nil {
log.Fatal(err)
}
defer session.Close()
printQuery := func(ctx context.Context, session *gocql.Session, stmt string, values ...interface{}) error {
iter := session.Query(stmt, values...).WithContext(ctx).Iter()
fmt.Println(stmt)
w := tabwriter.NewWriter(os.Stdout, 0, 0, 1, ' ',
0)
for i, columnInfo := range iter.Columns() {
if i > 0 {
fmt.Fprint(w, "\t| ")
}
fmt.Fprintf(w, "%s (%s)", columnInfo.Name, columnInfo.TypeInfo)
}
for {
rd, err := iter.RowData()
if err != nil {
return err
}
if !iter.Scan(rd.Values...) {
break
}
fmt.Fprint(w, "\n")
for i, val := range rd.Values {
if i > 0 {
fmt.Fprint(w, "\t| ")
}
fmt.Fprint(w, reflect.Indirect(reflect.ValueOf(val)).Interface())
}
}
fmt.Fprint(w, "\n")
w.Flush()
fmt.Println()
return iter.Close()
}
ctx := context.Background()
err = printQuery(ctx, session, "SELECT * FROM table1")
if err != nil {
log.Fatal(err)
}
err = printQuery(ctx, session, "SELECT value2, pk, ck FROM table1")
if err != nil {
log.Fatal(err)
}
err = printQuery(ctx, session, "SELECT * FROM table2")
if err != nil {
log.Fatal(err)
}
// SELECT * FROM table1
// pk (varchar) | ck (int) | value1 (varchar) | value2 (int)
// a | 1 | b | 2
// c | 3 | d | 4
// c | 5 | | 0
//
// SELECT value2, pk, ck FROM table1
// value2 (int) | pk (varchar) | ck (int)
// 2 | a | 1
// 4 | c | 3
// 0 | c | 5
//
// SELECT * FROM table2
// pk (int) | value1 (timestamp)
// 1 | 2020-01-02 03:04:05 +0000 UTC
}
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