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context.go
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context.go
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// Licensed to ClickHouse, Inc. under one or more contributor
// license agreements. See the NOTICE file distributed with
// this work for additional information regarding copyright
// ownership. ClickHouse, Inc. 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.
package clickhouse_api
import (
"context"
"fmt"
"github.com/google/uuid"
"github.com/xiaoxiaolai/clickhouse-go"
clickhouse_tests "github.com/xiaoxiaolai/clickhouse-go/tests"
"net"
"time"
)
func UseContext() error {
env, err := GetNativeTestEnvironment()
if err != nil {
return err
}
dialCount := 0
conn, err := clickhouse.Open(&clickhouse.Options{
Addr: []string{fmt.Sprintf("%s:%d", env.Host, env.Port)},
Auth: clickhouse.Auth{
Database: env.Database,
Username: env.Username,
Password: env.Password,
},
DialContext: func(ctx context.Context, addr string) (net.Conn, error) {
dialCount++
var d net.Dialer
return d.DialContext(ctx, "tcp", addr)
},
})
if err != nil {
return err
}
if !clickhouse_tests.CheckMinServerServerVersion(conn, 22, 6, 1) {
return nil
}
// we can use context to pass settings to a specific API call
ctx := clickhouse.Context(context.Background(), clickhouse.WithSettings(clickhouse.Settings{
"allow_experimental_object_type": "1",
}))
conn.Exec(ctx, "DROP TABLE IF EXISTS example")
// to create a JSON column we need allow_experimental_object_type=1
if err = conn.Exec(ctx, `
CREATE TABLE example (
Col1 JSON
)
Engine Memory
`); err != nil {
return err
}
// queries can be cancelled using the context
ctx, cancel := context.WithCancel(context.Background())
go func() {
cancel()
}()
if err = conn.QueryRow(ctx, "SELECT sleep(3)").Scan(); err == nil {
return fmt.Errorf("expected cancel")
}
// set a deadline for a query - this will cancel the query after the absolute time is reached.
// queries will continue to completion in ClickHouse
ctx, cancel = context.WithDeadline(context.Background(), time.Now().Add(-time.Second))
defer cancel()
if err := conn.Ping(ctx); err == nil {
return fmt.Errorf("expected deadline exceeeded")
}
// set a query id to assist tracing queries in logs e.g. see system.query_log
var one uint8
queryId, _ := uuid.NewUUID()
ctx = clickhouse.Context(context.Background(), clickhouse.WithQueryID(queryId.String()))
if err = conn.QueryRow(ctx, "SELECT 1").Scan(&one); err != nil {
return err
}
conn.Exec(context.Background(), "DROP QUOTA IF EXISTS foobar")
defer func() {
conn.Exec(context.Background(), "DROP QUOTA IF EXISTS foobar")
}()
ctx = clickhouse.Context(context.Background(), clickhouse.WithQuotaKey("abcde"), clickhouse.WithBlockBufferSize(100))
// set a quota key - first create the quota
if err = conn.Exec(ctx, "CREATE QUOTA IF NOT EXISTS foobar KEYED BY client_key FOR INTERVAL 1 minute MAX queries = 5 TO default"); err != nil {
return err
}
type Number struct {
Number uint64 `ch:"number"`
}
for i := 1; i <= 6; i++ {
var result []Number
if err = conn.Select(ctx, &result, "SELECT number FROM numbers(10)"); err != nil {
return err
}
}
return nil
}