RE: ODS Concurrency question
Diane
Absolutely right. I just tried this and look what I got.
create table sltest (
slid serial,
sldesc char(8));
insert into sltest values (0, "AAAAAAAA");
insert into sltest values (0, "BBBBBBBB");
insert into sltest values (4, "CCCCCCCC");
insert into sltest values (10, "DDDDDDDD");
insert into sltest values (4, "EEEEEEEE");
select * from sltest;
slid sldesc
1 AAAAAAAA
2 BBBBBBBB
4 CCCCCCCC
10 DDDDDDDD
4 EEEEEEEE
Also I tried two concurrent processes inserting multiple rows into a =
single table within a transaction and the data from the 2 processes WERE =
interleaved (as seen from the inserted timestamp as well as rowid). The =
lock mode on the table was ROW and I tried with both with and without a =
unique index on the SERIAL column.
My mistake. I guess one keeps learning all the time, huh?
Thanks for your input.
Sujit Pal
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From: Diane Taylor[SMTP:dtaylor@octa.net]
Sent: Thursday, August 28, 1997 9:46 AM
To: 'informix forum'
Subject: <No Subject Supplied>
There is a thread running regarding serial numbers. =20
I believe there is a misconception that serial numbers assume =
uniqueness. Where this is logical, I do not believe it is correct. =
When using serial values you must set a unique index or constraint. For =
instance, I could manually add a duplicate number.
Informix assigns a serial value based upon the highest last value. If =
you have the values 1, 4, 100 the next value Informix assigns will be =
101. By using integer values in a load, I could assign any number. =
Again, Informix would pick up it's assignment based on the highest =
value.
I have a programmer that uses serial values heavily because an Informix =
techy told him they were faster. Personally, I think they are much more =
trouble than any performance you gain. I mean, let's get a little bit =
twiddly......