Re: Concurrent insert question

i) If both A and B run concurrently then either one can
finish before the other. Since the isolation is
serlizable, a transaction can only see rows committed
before its start.
So if they both start at the same time,and A commits
before B. Then B would throw an error at the commit
statement.

ii) If B was "read committed" and A had committed before
B's insert  then B would throw an error during the
"insert" call.

Regards..
Amin




On Mon, 24 Mar 2003 09:38:06 +0100
  u15074 <u15074@hs-harz.de> wrote:
>I have the following table:
>
>create table test(
>key int8,
>length int4,
>level int4,
>pu oid,
>primary key(key));
>
>Now I have two concurrent transactions:
>
>At the time the transactions start, there does't exist a
>row with value 1 for
>the key column.
>
>time transactionA:
>1    begin;
>2    set transaction level serializable;
>3    insert into test(1,..,..,..);
>4
>5    commit;
>
>time transactionB:
>1    begin;
>2    set transaction level serializable;
>3
>4    insert into test(1,..,..,..);
>5
>6    commit;
>
>So my question is, what happens with the insert of
>transactionB?
>Since a row with primary key value 1 doesn't exist within
>transactionB when
>executing the insert-statement, it shouldn't be a problem
>within the
>transaction.
>But if so, how will the constraint be fullfilled? Will
>transactionB be aborted?
>Is there a difference running in transaction level
>serializable or readcommited?
>
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