Re: why CTAS faster than Insert select?

From: Dave <x_at_x.com>
Date: Wed, 30 Mar 2005 20:12:36 GMT
Message-ID: <UKD2e.325$G8.84@text.news.blueyonder.co.uk>

"linda" <linglipeng_at_yahoo.com> wrote in message news:1112213165.480529.61710_at_o13g2000cwo.googlegroups.com...
> Connor,
>
> Yes, the Insert is in /*+ APPEND */ mode. When you force session PDML,
> it seems that it does INSERTs in APPEND mode automatically. I did test
> manually putting /*+ APPEND */ as well, it doesn't make a difference in
> terms of timing when comparing to CTAS. I used the runstats_pkg to
> measure the latch difference, it's very comparable (96%), but response
> time almost double. The execution plan also the same (hash joins, index
> FFS). Some how I guess Oracle is executing different code path for CTAS
> and Insert /*+ APPEND */ as select. Even though it's all parallelized
> and nologging, one path is significantly faster than the other. If it's
> really true, then I think Oracle should optimize the path for Insert
> Select as well.
>
> Thanks,
> Linda
>

indexes on the table? Received on Wed Mar 30 2005 - 14:12:36 CST