NT + deadlock intended behaviour ?

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Hi all,
I'm doing some experiments with NT, I din't expect this behaviuor:

create table test ( a integer );
insert into test values (3);
insert into test values (4);
insert into test values (5);
insert into test values (6);

SESSION 1; SESSION 2;

begin; begin;
update test set a = 300 where a = 3; update test set a = 40 where a = 4;
~ begin;
update test set a = 400 where a = 4;
<BLOCKED>
~ update test set a = 30 where a = 3;
~ <DEAD LOCK DETECTED>
~ commit;
<UNBLOCKED> <-- !?!?!
~ <here I'm able to do another commit>

why SESSION 1 was unblocked ? If I repeat again but I do an abort:

SESSION 1; SESSION 2;

begin; begin;
update test set a = 300 where a = 3; update test set a = 40 where a = 4;
~ begin;
update test set a = 400 where a = 4;
<BLOCKED>
~ update test set a = 30 where a = 3;
~ <DEAD LOCK DETECTED>
~ abort;
<STILL BLOCKED>

Why that commit unblock the SESSION 1?

Regards
Gaetano Mendola

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