mysql DBI 事务控制

事务；

事务是任何健壮数据库系统的基本组成,它们 防止错误和数据库腐败通过确保有关数据的改变是原子发生的(不可分割的,要么所有要么什么都不做)


这个章节应用于数据库支持事务和 AutoCommit 是关闭的,查看"AutoCommit" 使用对于各种类型的数据库。


推荐的方式实现健壮的事务在Perl应用是使用RaiseError and eval { ... } 

  $dbh->{AutoCommit} = 0;  # enable transactions, if possible
  $dbh->{RaiseError} = 1;
  eval {
      foo(...)        # do lots of work here
      bar(...)        # including inserts
      baz(...)        # and updates
      $dbh->commit;   # commit the changes if we get this far
  };
  if ($@) {
      warn "Transaction aborted because $@";
      # now rollback to undo the incomplete changes
      # but do it in an eval{} as it may also fail
      eval { $dbh->rollback };
      # add other application on-error-clean-up code here
  }
  
  #!/usr/bin/perl 
use DBI;
$db_name='zjzc';
$ip='127.0.0.1';
$user="root";
$passwd="1234567";
$dbh="";
$dbh = DBI->connect("dbi:mysql:database=$db_name;host=$ip;port=3306",$user,$passwd,{
                          RaiseError => 1,
                          AutoCommit => 0
                        }) or die "can't connect to database ". DBI-errstr;
eval{
$dbh->do("insert into test values('$ARGV[0]')") ;
sleep (100);
$dbh->commit();};
if( $@ ) {
    #warn "Database error: $DBI::errstr
";
    		 $dbh->rollback(); #just die if rollback is failing 
   		 	 };
    		 	 	 $dbh->disconnect; 
					 
					 
如果RaiseError 熟悉没有被设置,DBI 请求需要手动检查错误,像这样:

$h->method(@args) or die $h->errstr;


RaiseError设置后,DBI会自动的die 如果DBI方法调用处理失败,你不需要测试每个方法的返回值


评价方法的主要有点是 事务会正确的回滚 当任何代码(不只是DBI请求) 在内部程序dies 由于任何原因。


使用 $h->{RaiseError} 属性的主要优势是 DBI请求会被自动检查,


[root@wx03 sbin]# cat a1.pl 
use DBI;
use POSIX;
$db_name='scan';
$ip='127.0.0.1';
$user="root";
$passwd="xxx";
$dbh = DBI->connect("dbi:mysql:database=$db_name;host=$ip;port=3306",$user,$passwd,{
                          RaiseError => 1,
                          AutoCommit => 0
                        }) or die "can't connect to database ". DBI-errstr;
eval{
my $XDATE = strftime("%Y%m%d%H%M%S",localtime());
print "$XDATE is $XDATE
";
$dbh->do("update t1 set c1=999 where c1=100") ;
$dbh->commit();};
if( $@ ) {
my $XDATE = strftime("%Y%m%d%H%M%S",localtime());
    #warn "Database error: $DBI::errstr
";
print "$XDATE is $XDATE
";
    		 $dbh->rollback(); #just die if rollback is failing 
   		 	 };
    		$dbh->disconnect; 
[root@wx03 sbin]# perl a1.pl 
$XDATE is 20160823110539
DBD::mysql::db do failed: Lock wait timeout exceeded; try restarting transaction at a1.pl line 14.
$XDATE is 20160823110630

| innodb_lock_wait_timeout                | 50

[root@wx03 sbin]# perl a1.pl 
$XDATE is 20160823110743
DBD::mysql::db do failed: Table 'scan.t19' doesn't exist at a1.pl line 14.
$XDATE is 20160823110743
[root@wx03 sbin]# cat a1.pl 
use DBI;
use POSIX;
$db_name='scan';
$ip='127.0.0.1';
$user="root";
$passwd="xxx";
$dbh = DBI->connect("dbi:mysql:database=$db_name;host=$ip;port=3306",$user,$passwd,{
                          RaiseError => 1,
                          AutoCommit => 0
                        }) or die "can't connect to database ". DBI-errstr;
eval{
my $XDATE = strftime("%Y%m%d%H%M%S",localtime());
print "$XDATE is $XDATE
";
$dbh->do("update t19 set c1=999 where c1=100") ;
$dbh->commit();};
if( $@ ) {
my $XDATE = strftime("%Y%m%d%H%M%S",localtime());
    #warn "Database error: $DBI::errstr
";
print "$XDATE is $XDATE
";
    		 $dbh->rollback(); #just die if rollback is failing 
   		 	 };
    		$dbh->disconnect; 
[root@wx03 sbin]# perl a1.pl 
$XDATE is 20160823110746
DBD::mysql::db do failed: Ta