DB is SQL 2000.
One trigger has the code to begin and commit a named transaction
within it.
Am I right in thinking this is a bad idea?
My understanding is that any commit statement will committ all
transactions regardless of the named transaction, so will this committ
everything done up to that point?
Also I am not sure what will happen if the entire transaction needs to
rollback, bearing in mind the trigger code will have already
committed?
Thanks
Paddy
Paddy,
COMMIT TRAN only backs up one level, so a BEGIN/COMMIT in a trigger should
be fine. A nested commit is not truly and fully committed until the highest
level commits.
It is ROLLBACK that bumps all transactions out and which needs careful
handling.
RLF
"Paddy" <paddymullaney@.btopenworld.com> wrote in message
news:400b44b1-c6f2-4193-b940-d4d4752ad897@.p69g2000hsa.googlegroups.com...
>I am trying to tidy up a bunch of triggers on a legacy database. The
> DB is SQL 2000.
> One trigger has the code to begin and commit a named transaction
> within it.
> Am I right in thinking this is a bad idea?
> My understanding is that any commit statement will committ all
> transactions regardless of the named transaction, so will this committ
> everything done up to that point?
> Also I am not sure what will happen if the entire transaction needs to
> rollback, bearing in mind the trigger code will have already
> committed?
> Thanks
> Paddy
>
>
>
>
|||From locking point of view all the nesting does not do anything. All the
locks belong to the transaction that was open by your connection if there was
one. There is only one transaction no matter how many begin commits are
nested.
So this trigger may control the transactions and can make some sense if and
only if whatever has triggered it was in autocommit. Then your transaction
will be
1) the dml that has caused the trigger to fire
2) whatever is inside the trigger
then it works like so
any rollback in the trigger will rollback 1) and 2) no matter where the
rollback is (in case if there are more then 1 trigger firing, have to watch
how many and how deep do they cascade). Commit in this case will happen when
top level trigger finishes the job and 1) and 2) will be committed. Anything
that has a commit in the cascading triggers etc will not release the locks
according to isolation levels (in this case default one, so yout X locks will
hang out, selects will be released as soon as the next row is
pulled/released, locks escalations will be released when the locked object is
not needed anymore for the query processing).
Thanks, Liliya
|||rollback rolls back no matter if there was a begin tran and the commit.
because there is only one transaction.
Is it working more like a flat transaction with checkpoints of some sort?
not really. Because if there is a chackpoint it matches the beginning of the
very top level transaction... It is ms sql's point of viiew what nested
transactions are and what more important what was possible to implement in
the current engine.
One of the things developers, esp. ones that came from oracle like doing is
trying to implement in a trigger or in an sp an oracle style sequence (sort
of like an identity but they want it to cover several tables, a global
sequence). what bites then is that where they crate a sequence is the table
or/and one row. so they read it, modify id+1 and then go about thier business
and you hope it is only one sequence in their logic and if many they update
those tables in the same order always. If you are not so lucky and your
developers are creative you may find yourself de bugging peculiar kids of
locking and deadlocks and trying to explin to the developed why exactly
commit does not work like any commit supposed to work in your stupid database
. I did see such a then one time with more then one client.if you wounder what happens from transaction point of view if it is not a
trigger but an sp... sane thing pretty much.
here you can see all the locks (will ppublish a sample). in the sp's
provided there is a dbcc call that tells you isolation levels.
|||It does not hurt to check
@.@.trancount in the trigger so you know what kind of transaction context do
you have anyways. if it is 0 you have autocommit and transaction logic in the
trigger may make sense. if @.@.trancount>0, then there is already a transaction
and this trigger becomes a part of it and all the locks it puts in place
belong to the top level transaction and will be released if and only if that
top level transaction commits. rollback will affect the entire transaction,
because there is only one.
Commit in case of the nesting does not even do locks reassigning, because
they always belong to the same top level transaction.
So in case described above 1) becomes your top level transaction where ever
it has started and 2) is as is - everything that the trigger has inside and
all the cascading actions
there will be 3) too. at leases commit/close connection in case if whatever
has triggered your trigger was the last sql in the top level transaction.
Othervise 3) is the rest of your toplevel transaction and whatever it
triggeres. The locks produced by your trigger in this case will be hanging (X
ones) much longer then you could have expected - till the end of top level
transaction.
you have 2 big things to watch out for: anything that can be long
transaction. and all the cascades in your triggers in the context of the
transaction the trigger was called from.
If you have no idea what are you dealing with, you still can find out
(unless the triggers do rollback, then all your audit goes good buy).
Create yourself an audit table (id int, trn int, msg varchar(128)) or
whatever you like better
in the triggers put insert in there @.@.trancount and the name of the trigger
and the of the table. at leas you will know this way what kind of
transactions do you have and what does cascade from where. can add some more
info there or maybe if's in case if your triggers do different thing
depending in inserted/updated/deleted values etc.
|||your tables:
CREATE TABLE [dbo].[seq](
[descr] [varchar](128)
[nextval] [int] NULL DEFAULT ((0))
)
CREATE TABLE [dbo].[trnaudit](
[trnout] [int] NULL,
[trnin] [int] NULL,
[descr] [varchar](128)
)
CREATE TRIGGER [dbo].[SeqINSERT]
ON [dbo].[seq]
AFTER INSERT
AS
BEGIN
SET NOCOUNT ON;
begin tran trgseq
declare @.trnin int
select @.trnin=@.@.trancount
insert into trnaudit values(-1, @.trnin, 'transaction test called trigger
SeqINSERT')
commit tran trgseq
END
here is a test for you that has an example and the answer to your question
about the rollback and commit in the trigger
select * from dbo.seq
select * from trnaudit
begin tran
insert into seq values ('transactionrollback', 1)
select * from dbo.seq
select * from trnaudit
rollback
select * from dbo.seq
select * from trnaudit
here is what it returns into text
descr
nextval
------ --
seq1
0
trnout trnin descr
-- --
------
descr
nextval
------ --
seq1
0
transactionrollback
1
trnout trnin descr
-- --
------
-1 2 transaction test called trigger SeqINSERT
descr
nextval
------ --
seq1
0
trnout trnin descr
-- --
------
|||alter proc
_trn_test
as
declare @.trnin int, @.trn int, @.val int
select @.trn=@.@.trancount
if @.trn=0
SET IMPLICIT_TRANSACTIONS ON
else
begin tran
set transaction isolation level read uncommitted
--audit
exec @.val= _nval_test
--insert into trnaudit values(@.trn, @.trnin, '_trn_test updates the sequence')
commit
select 'sp_lock in sp exec @.val= _nval_test call and commit'
select * from master.dbo.syslockinfo
exec sp_lock
-- the first sql statement starts the transaction if begin tran was not
issued earlier
begin tran
select @.trnin=@.@.trancount
insert into trnaudit values(@.trn, @.trnin, '_trn_test in sp begin next tran,
audit')
select 'get in in sp DBCC USEROPTIONS'
DBCC USEROPTIONS
commit
select @.trnin=@.@.trancount
SET IMPLICIT_TRANSACTIONS OFF
insert into trnaudit values(@.trn, @.trnin, '_trn_test in sp after SET
IMPLICIT_TRANSACTIONS OFF')
select 'sp_lock in sp at the end'
select * from master.dbo.syslockinfo
exec sp_lock
return @.val+1
go
alter proc
_nval_test
as
declare @.trnin int, @.trn int, @.val int
select @.trn=@.@.trancount
select @.val=nextval from seq where descr='seq1'
update seq set nextval=@.val+1 where descr='seq1'
--audit
insert into trnaudit values(@.trn, @.trn, '_trn_test in sp _nval_test')
select 'sp_lock in sp after seq update'
exec sp_lock
select * from master.dbo.syslockinfo
return @.val+1
go
|||test and the results:
TEST1
DECLARE @.err INT, @.trn INT, @.trnin int, @.nextval int
set nocount on
SET IMPLICIT_TRANSACTIONS OFF
select @.trn=@.@.trancount, @.trnin=NULL
delete from trnaudit
insert into trnaudit values(@.trn, @.trnin, '_trn_test begin script,
autocommit')
select id, name from sysobjects where name in ('seq', 'trnaudit') or id
=85575343
begin tran
select @.trn=@.@.trancount, @.trnin=NULL
insert into trnaudit values(@.trn, @.trnin, '_trn_test begin script, begin
tran')
set transaction isolation level read committed
select 'get in the script DBCC USEROPTIONS'
DBCC USEROPTIONS
commit
begin tran
exec @.nextval= _nval_test
select @.nextval as NEXTVAL
commit
select 'sp_lock in sp exit and commit'
exec sp_lock
select * from master.dbo.syslockinfo
select @.trn=@.@.trancount, @.trnin=NULL
insert into trnaudit values(@.trn, @.trnin, '_trn_test begin script,after exec
sp')
SET IMPLICIT_TRANSACTIONS OFF
select @.trn=@.@.trancount, @.trnin=NULL
insert into trnaudit values(@.trn, @.trnin, '_trn_test begin script, SET
IMPLICIT_TRANSACTIONS OFF')
select * from trnaudit
--select * from master.dbo.syslockinfo
RESULT:
id name
------
126623494 trnaudit
142623551 seq
85575343 dt_getpropertiesbyid_vcs
get in the script DBCC USEROPTIONS
Set Option
Value
------
textsize
64512
language
us_english
dateformat
mdy
datefirst
7
quoted_identifier
SET
arithabort
SET
nocount
SET
ansi_null_dflt_on
SET
ansi_defaults
SET
ansi_warnings
SET
ansi_padding
SET
ansi_nulls
SET
concat_null_yields_null
SET
isolation level
read committed
(14 row(s) affected)
DBCC execution completed. If DBCC printed error messages, contact your
system administrator.
sp_lock in sp after seq update
spid dbid ObjId IndId Type Resource Mode Status
-- -- -- -- -- -- -- --
51 4 0 0 DB S GRANT
52 4 0 0 DB S GRANT
53 5 0 0 DB S GRANT
53 1 85575343 0 TAB IS GRANT
53 5 126623494 0 RID 1:114074:2 X GRANT
53 5 142623551 0 PAG 1:114070 IX GRANT
53 5 0 0 PAG 1:114074 IX GRANT
53 5 142623551 0 RID 1:114070:0 X GRANT
53 5 142623551 0 TAB IX GRANT
53 5 126623494 0 TAB IX GRANT
54 5 0 0 DB S GRANT
55 5 0 0 DB S GRANT
56 5 0 0 DB S GRANT
57 5 0 0 DB S GRANT
58 5 0 0 DB S GRANT
60 5 0 0 DB S GRANT
rsc_text rsc_bin
rsc_valblk rsc_dbid rsc_indid rsc_objid rsc_type
rsc_flag req_mode req_status req_refcnt req_cryrefcnt req_lifetime req_spid
req_ecid req_ownertype req_transactionID req_transactionUOW
-- --
-- -- -- -- --
-- -- -- -- -- --
-- -- -- --
0x00020400000000000000000000000000
0x00000000000000000000000000000000 4 0 0 2 0
3 1 1 0 0 52 0
3 0
00000000-0000-0000-0000-000000000000
0x00020400000000000000000000000000
0x00000000000000000000000000000000 4 0 0 2 0
3 1 1 0 0 51 0
3 0
00000000-0000-0000-0000-000000000000
0x00020500000000000000000000000000
0x00000000000000000000000000000000 5 0 0 2 0
3 1 1 0 0 55 0
3 0
00000000-0000-0000-0000-000000000000
0x00020500000000000000000000000000
0x00000000000000000000000000000000 5 0 0 2 0
3 1 1 0 0 60 0
3 0
00000000-0000-0000-0000-000000000000
0x00020500000000000000000000000000
0x00000000000000000000000000000000 5 0 0 2 0
3 1 1 0 0 58 0
3 0
00000000-0000-0000-0000-000000000000
0x00020500000000000000000000000000
0x00000000000000000000000000000000 5 0 0 2 0
3 1 1 0 0 56 0
3 0
00000000-0000-0000-0000-000000000000
0x00020500000000000000000000000000
0x00000000000000000000000000000000 5 0 0 2 0
3 1 1 0 0 53 0
3 0
00000000-0000-0000-0000-000000000000
0x00020500000000000000000000000000
0x00000000000000000000000000000000 5 0 0 2 0
3 1 1 0 0 57 0
3 0
00000000-0000-0000-0000-000000000000
0x00020500000000000000000000000000
0x00000000000000000000000000000000 5 0 0 2 0
3 1 1 0 0 54 0
3 0
00000000-0000-0000-0000-000000000000
1:114074:2 0x000905009ABD01000100020000000000
0x00000000000000000000000000000000 5 0 126623494 9 0
5 1 0 0 33554432 53 0
1 593838
00000000-0000-0000-0000-000000000000
1:114070 0x0006050096BD01000100000000000000
0x00000000000000000000000000000000 5 0 142623551 6 0
8 1 1 0 33554432 53 0
1 593838
00000000-0000-0000-0000-000000000000
1:114074 0x000605009ABD01000100000000000000
0x00000000000000000000000000000000 5 0 0 6 0
8 1 0 0 33554432 53 0
1 593838
00000000-0000-0000-0000-000000000000
1:114070:0 0x0009050096BD01000100000000000000
0x00000000000000000000000000000000 5 0 142623551 9 0
5 1 0 0 33554432 53 0
1 593838
00000000-0000-0000-0000-000000000000
0x000505003F4380080000000000000000
0x00000000000000000000000000000000 5 0 142623551 5 0
8 1 1 0 33554432 53 0
1 593838
00000000-0000-0000-0000-000000000000
0x00050500061F8C070000000000000000
0x00000000000000000000000000000000 5 0 126623494 5 0
8 1 1 0 33554432 53 0
1 593838
00000000-0000-0000-0000-000000000000
NEXTVAL
4
sp_lock in sp exit and commit
spid dbid ObjId IndId Type Resource Mode Status
-- -- -- -- -- -- -- --
51 4 0 0 DB S GRANT
52 4 0 0 DB S GRANT
53 5 0 0 DB S GRANT
53 1 85575343 0 TAB IS GRANT
54 5 0 0 DB S GRANT
55 5 0 0 DB S GRANT
56 5 0 0 DB S GRANT
57 5 0 0 DB S GRANT
58 5 0 0 DB S GRANT
60 5 0 0 DB S GRANT
rsc_text rsc_bin
rsc_valblk rsc_dbid rsc_indid rsc_objid rsc_type
rsc_flag req_mode req_status req_refcnt req_cryrefcnt req_lifetime req_spid
req_ecid req_ownertype req_transactionID req_transactionUOW
-- --
-- -- -- -- --
-- -- -- -- -- --
-- -- -- --
0x00020400000000000000000000000000
0x00000000000000000000000000000000 4 0 0 2 0
3 1 1 0 0 52 0
3 0
00000000-0000-0000-0000-000000000000
0x00020400000000000000000000000000
0x00000000000000000000000000000000 4 0 0 2 0
3 1 1 0 0 51 0
3 0
00000000-0000-0000-0000-000000000000
0x00020500000000000000000000000000
0x00000000000000000000000000000000 5 0 0 2 0
3 1 1 0 0 55 0
3 0
00000000-0000-0000-0000-000000000000
0x00020500000000000000000000000000
0x00000000000000000000000000000000 5 0 0 2 0
3 1 1 0 0 60 0
3 0
00000000-0000-0000-0000-000000000000
0x00020500000000000000000000000000
0x00000000000000000000000000000000 5 0 0 2 0
3 1 1 0 0 58 0
3 0
00000000-0000-0000-0000-000000000000
0x00020500000000000000000000000000
0x00000000000000000000000000000000 5 0 0 2 0
3 1 1 0 0 56 0
3 0
00000000-0000-0000-0000-000000000000
0x00020500000000000000000000000000
0x00000000000000000000000000000000 5 0 0 2 0
3 1 1 0 0 53 0
3 0
00000000-0000-0000-0000-000000000000
0x00020500000000000000000000000000
0x00000000000000000000000000000000 5 0 0 2 0
3 1 1 0 0 57 0
3 0
00000000-0000-0000-0000-000000000000
0x00020500000000000000000000000000
0x00000000000000000000000000000000 5 0 0 2 0
3 1 1 0 0 54 0
3 0
00000000-0000-0000-0000-000000000000
trnout trnin descr
-- --
------
0 NULL _trn_test begin script, autocommit
1 NULL _trn_test begin script, begin tran
1 1 _trn_test in sp _nval_test
0 NULL _trn_test begin script,after exec sp
0 NULL _trn_test begin script, SET IMPLICIT_TRANSACTIONS OFF
|||RESULT:
id name
------
126623494 trnaudit
142623551 seq
85575343 dt_getpropertiesbyid_vcs
get in the script DBCC USEROPTIONS
Set Option
Value
------
textsize
64512
language
us_english
dateformat
mdy
datefirst
7
quoted_identifier
SET
arithabort
SET
nocount
SET
ansi_null_dflt_on
SET
ansi_defaults
SET
ansi_warnings
SET
ansi_padding
SET
ansi_nulls
SET
concat_null_yields_null
SET
isolation level
read committed
(14 row(s) affected)
DBCC execution completed. If DBCC printed error messages, contact your
system administrator.
sp_lock in sp after seq update
spid dbid ObjId IndId Type Resource Mode Status
-- -- -- -- -- -- -- --
51 4 0 0 DB S GRANT
52 4 0 0 DB S GRANT
53 5 0 0 DB S GRANT
53 1 85575343 0 TAB IS GRANT
53 5 126623494 0 RID 1:114074:2 X GRANT
53 5 142623551 0 PAG 1:114070 IX GRANT
53 5 0 0 PAG 1:114074 IX GRANT
53 5 142623551 0 RID 1:114070:0 X GRANT
53 5 142623551 0 TAB IX GRANT
53 5 126623494 0 TAB IX GRANT
54 5 0 0 DB S GRANT
55 5 0 0 DB S GRANT
56 5 0 0 DB S GRANT
57 5 0 0 DB S GRANT
58 5 0 0 DB S GRANT
60 5 0 0 DB S GRANT
|||rsc_text rsc_bin
rsc_valblk rsc_dbid rsc_indid rsc_objid rsc_type
rsc_flag req_mode req_status req_refcnt req_cryrefcnt req_lifetime req_spid
req_ecid req_ownertype req_transactionID req_transactionUOW
-- --
-- -- -- -- --
-- -- -- -- -- --
-- -- -- --
0x00020400000000000000000000000000
0x00000000000000000000000000000000 4 0 0 2 0
3 1 1 0 0 52 0
3 0
00000000-0000-0000-0000-000000000000
0x00020400000000000000000000000000
0x00000000000000000000000000000000 4 0 0 2 0
3 1 1 0 0 51 0
3 0
00000000-0000-0000-0000-000000000000
0x00020500000000000000000000000000
0x00000000000000000000000000000000 5 0 0 2 0
3 1 1 0 0 55 0
3 0
00000000-0000-0000-0000-000000000000
0x00020500000000000000000000000000
0x00000000000000000000000000000000 5 0 0 2 0
3 1 1 0 0 60 0
3 0
00000000-0000-0000-0000-000000000000
0x00020500000000000000000000000000
0x00000000000000000000000000000000 5 0 0 2 0
3 1 1 0 0 58 0
3 0
00000000-0000-0000-0000-000000000000
0x00020500000000000000000000000000
0x00000000000000000000000000000000 5 0 0 2 0
3 1 1 0 0 56 0
3 0
00000000-0000-0000-0000-000000000000
0x00020500000000000000000000000000
0x00000000000000000000000000000000 5 0 0 2 0
3 1 1 0 0 53 0
3 0
00000000-0000-0000-0000-000000000000
0x00020500000000000000000000000000
0x00000000000000000000000000000000 5 0 0 2 0
3 1 1 0 0 57 0
3 0
00000000-0000-0000-0000-000000000000
0x00020500000000000000000000000000
0x00000000000000000000000000000000 5 0 0 2 0
3 1 1 0 0 54 0
3 0
00000000-0000-0000-0000-000000000000
1:114074:2 0x000905009ABD01000100020000000000
0x00000000000000000000000000000000 5 0 126623494 9 0
5 1 0 0 33554432 53 0
1 593838
00000000-0000-0000-0000-000000000000
1:114070 0x0006050096BD01000100000000000000
0x00000000000000000000000000000000 5 0 142623551 6 0
8 1 1 0 33554432 53 0
1 593838
00000000-0000-0000-0000-000000000000
1:114074 0x000605009ABD01000100000000000000
0x00000000000000000000000000000000 5 0 0 6 0
8 1 0 0 33554432 53 0
1 593838
00000000-0000-0000-0000-000000000000
1:114070:0 0x0009050096BD01000100000000000000
0x00000000000000000000000000000000 5 0 142623551 9 0
5 1 0 0 33554432 53 0
1 593838
00000000-0000-0000-0000-000000000000
0x000505003F4380080000000000000000
0x00000000000000000000000000000000 5 0 142623551 5 0
8 1 1 0 33554432 53 0
1 593838
00000000-0000-0000-0000-000000000000
0x00050500061F8C070000000000000000
0x00000000000000000000000000000000 5 0 126623494 5 0
8 1 1 0 33554432 53 0
1 593838
00000000-0000-0000-0000-000000000000
NEXTVAL
4
sp_lock in sp exit and commit
spid dbid ObjId IndId Type Resource Mode Status
-- -- -- -- -- -- -- --
51 4 0 0 DB S GRANT
52 4 0 0 DB S GRANT
53 5 0 0 DB S GRANT
53 1 85575343 0 TAB IS GRANT
54 5 0 0 DB S GRANT
55 5 0 0 DB S GRANT
56 5 0 0 DB S GRANT
57 5 0 0 DB S GRANT
58 5 0 0 DB S GRANT
60 5 0 0 DB S GRANT
rsc_text rsc_bin
rsc_valblk rsc_dbid rsc_indid rsc_objid rsc_type
rsc_flag req_mode req_status req_refcnt req_cryrefcnt req_lifetime req_spid
req_ecid req_ownertype req_transactionID req_transactionUOW
-- --
-- -- -- -- --
-- -- -- -- -- --
-- -- -- --
0x00020400000000000000000000000000
0x00000000000000000000000000000000 4 0 0 2 0
3 1 1 0 0 52 0
3 0
00000000-0000-0000-0000-000000000000
0x00020400000000000000000000000000
0x00000000000000000000000000000000 4 0 0 2 0
3 1 1 0 0 51 0
3 0
00000000-0000-0000-0000-000000000000
0x00020500000000000000000000000000
0x00000000000000000000000000000000 5 0 0 2 0
3 1 1 0 0 55 0
3 0
00000000-0000-0000-0000-000000000000
0x00020500000000000000000000000000
0x00000000000000000000000000000000 5 0 0 2 0
3 1 1 0 0 60 0
3 0
00000000-0000-0000-0000-000000000000
0x00020500000000000000000000000000
0x00000000000000000000000000000000 5 0 0 2 0
3 1 1 0 0 58 0
3 0
00000000-0000-0000-0000-000000000000
0x00020500000000000000000000000000
0x00000000000000000000000000000000 5 0 0 2 0
3 1 1 0 0 56 0
3 0
00000000-0000-0000-0000-000000000000
0x00020500000000000000000000000000
0x00000000000000000000000000000000 5 0 0 2 0
3 1 1 0 0 53 0
3 0
00000000-0000-0000-0000-000000000000
0x00020500000000000000000000000000
0x00000000000000000000000000000000 5 0 0 2 0
3 1 1 0 0 57 0
3 0
00000000-0000-0000-0000-000000000000
0x00020500000000000000000000000000
0x00000000000000000000000000000000 5 0 0 2 0
3 1 1 0 0 54 0
3 0
00000000-0000-0000-0000-000000000000
trnout trnin descr
-- --
------
0 NULL _trn_test begin script, autocommit
1 NULL _trn_test begin script, begin tran
1 1 _trn_test in sp _nval_test
0 NULL _trn_test begin script,after exec sp
0 NULL _trn_test begin script, SET IMPLICIT_TRANSACTIONS OFF
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