Re: What is Parallel DML?

"Galen Boyer" <galenboyer_at_hotpop.com> wrote

> This would fail if I tried to do it myself. A BETWEEN is
> effectively < x and > y and the > y for rowid will fail to find
> rows. But I'm sure Oracle knows how to do it.

Are you not thinking about rownum Galen? I know that does not like a BETWEEN clause or a GREATER THAN, but I'm sure that rowid can be treated like that without any problems in plain SQL.

BTW, Oracle also adds hints such as ROWID(A1), PIV_SSF to PQ SQL - and one I think called GIV_GB or something which I used to see often when using PQ on 7.x.

> How could we mimic PQ by splitting up the query ourselves into 50
> different queries and then running them all at the same time?

Why would you want to when Oracle PQ can do it for you?

> Could this be done and get the pretty much the same result that
> Oracle does (Disregarding the final count, just get fifty
> answers)?

You mean perform an independant summarisation of a million rows at a time of a 50 million row table, resulting in 50 answers? Not sure what you want to achieve by this...

I think that you can emulate this when dealing with a table where you have some control over physical storage of data - partitioning for example. But when you deal with raw rowid's, it is likely going to be very difficult. You can use something like DBA_EXTENTS to get file id's and block numbers for the table in question. But I'm not sure how you would go about converting that into rowid ranges for multiple queries (never have dug that deep into rowid's myself).

--
Billy