tidb db 源码
tidb db 代码
文件路径：/br/pkg/utils/db.go
// Copyright 2021 PingCAP, Inc. Licensed under Apache-2.0.
package utils
import (
"context"
"database/sql"
"strings"
"github.com/pingcap/log"
"github.com/pingcap/tidb/kv"
"github.com/pingcap/tidb/sessionctx"
"github.com/pingcap/tidb/util/sqlexec"
"go.uber.org/zap"
)
var (
// check sql.DB and sql.Conn implement QueryExecutor and DBExecutor
_ DBExecutor = &sql.DB{}
_ DBExecutor = &sql.Conn{}
)
// QueryExecutor is a interface for exec query
type QueryExecutor interface {
QueryContext(ctx context.Context, query string, args ...interface{}) (*sql.Rows, error)
QueryRowContext(ctx context.Context, query string, args ...interface{}) *sql.Row
}
// StmtExecutor define both query and exec methods
type StmtExecutor interface {
QueryExecutor
ExecContext(ctx context.Context, query string, args ...interface{}) (sql.Result, error)
}
// DBExecutor is a interface for statements and txn
type DBExecutor interface {
StmtExecutor
BeginTx(ctx context.Context, opts *sql.TxOptions) (*sql.Tx, error)
}
// CheckLogBackupEnabled checks if LogBackup is enabled in cluster.
// this mainly used in three places.
// 1. GC worker resolve locks to scan more locks after safepoint. (every minute)
// 2. Add index skipping use lightning.(every add index ddl)
// 3. Telemetry of log backup feature usage (every 6 hours).
// NOTE: this result shouldn't be cached by caller. because it may change every time in one cluster.
func CheckLogBackupEnabled(ctx sessionctx.Context) bool {
executor, ok := ctx.(sqlexec.RestrictedSQLExecutor)
if !ok {
// shouldn't happen
log.Error("[backup] unable to translate executor from sessionctx")
return false
}
enabled, err := IsLogBackupEnabled(executor)
if err != nil {
// if it failed by any reason. we can simply return true this time.
// for GC worker it will scan more locks in one tick.
// for Add index it will skip using lightning this time.
// for Telemetry it will get a false positive usage count.
log.Warn("[backup] check log backup config failed, ignore it", zap.Error(err))
return true
}
return enabled
}
// IsLogBackupEnabled is used for br to check whether tikv has enabled log backup.
// we use `sqlexec.RestrictedSQLExecutor` as parameter because it's easy to mock.
// it should return error.
func IsLogBackupEnabled(ctx sqlexec.RestrictedSQLExecutor) (bool, error) {
valStr := "show config where name = 'log-backup.enable'"
internalCtx := kv.WithInternalSourceType(context.Background(), kv.InternalTxnBR)
rows, fields, errSQL := ctx.ExecRestrictedSQL(internalCtx, nil, valStr)
if errSQL != nil {
return false, errSQL
}
if len(rows) == 0 {
// no rows mean not support log backup.
return false, nil
}
for _, row := range rows {
d := row.GetDatum(3, &fields[3].Column.FieldType)
value, errField := d.ToString()
if errField != nil {
return false, errField
}
if strings.ToLower(value) == "false" {
return false, nil
}
}
return true, nil
}
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