Well it has been more than 3 years since I used Ingres. At the time this
was a very large problem and from your response it still is (commit quickly
comment). Oracle does not have these limitations and handles concurrency
very nicely without turning anything off.
Jim
"Karl & Betty Schendel" <schendel_at_kbcomputer.com> wrote in message
news:schendel-063B90.12035216052001_at_nnrp05.earthlink.net...
> In article <VsjM6.7768$p33.164070_at_news1.sttls1.wa.home.com>,
> "Jim Kennedy" <kennedy-family_at_home.com> wrote:
>
> > Ingres does have transactions, but it in a way forces you to use auto
> > commit(which means that you aren't using transactions). The concurrency
> > model in Ingres (assuming it hasn't changed since I last used it) is
brain
> > dead. For example, if you insert a row into a table in Ingres with a
> > primary key then most users will not be able to do anything with that
table
> > until you issue a commit! Why? Well Ingres is a page level locking
> > database and so it locks all the pages that the primary key index
traverses
> > to add the row you are inserting. Which is usually about 95% of the
table.
> > Stupid I know, but that is how it works.
>
> This is not true. Ingres does do locking, but it only locks the leaf
> and data pages needed to access the rows you want. (We're assuming
> btree here, Ingres also supports hash-structured tables.)
> This is most certainly NOT 95% of the table.
> There is one situation where the locking is a pain, which is when have
> a monotonic key and a tree-structured table; concurrent inserts will
> tend to hit the same btree leaf and interfere with one another.
> The standard cure is to not use a monotonic key, or to use HASH, or
> to get your transactions over with quickly. (which does not mean
> AUTOCOMMIT!)
>
> Ingres II, which has been out for about 3 years now, allows row level
> locking if you ask for it.
>
> And why does Ingres lock at all, you ask? So that it can implement the
> SERIALIZABLE concurrency condition which the SQL standard says
> should be the default access mode. You can modify the locking scheme,
> or turn it off entirely, depending on your needs. The default is
> SERIALIZABLE since it's the safest and should be used if you don't know
> what you are doing.
>
> Karl
Received on Thu May 17 2001 - 01:48:56 CDT
