Re: Block count usage by a table

Jurij Modic wrote in message <35a32cae.181456931_at_news.siol.net>...
>The question was not how many blocks would the chained row require but
>how many block will the query with SUBSTR's on ROWID report as being
>used. And johnvue_at_gte.net is right about that, it'll count only 1
>block.

It depends on the SUBSTR you use - b.r.f. If you looked on the 'r' portion, then you would get back *all* the blocks for the row. But true, the particular select given might not do this - which was why I recommended ANALYZE.
>
>>>
>>>At least one book mentions that the SELECT query is faster than doing
>>>a ANALYZE TABLE for finding out block count.
>>
>>I have a 100,000,000 row table in my db. That select would take a mightly
>>long time...
>
>True, but analyzing that same table (with COMPUTE STATISTICS) will
>very likely take a much longer time....

But then who would be daft enough to COMPUTE rather than ESTIMATE on such a large table?..

>
>>And remember, the ANALYZE command isn't just for giving *you* data, it's
for
>>giving the *CBO* data.
>
>Could not agree more. In any case, whene there are chained rows in a
>table neither "ANALYZE TABLE" nor the "SELECT COUNT on distinct ROWID
>portions" will give you the correct number of blocks being used by the
>data.
>
>>MotoX.
>
>Regards,
>--
>Jurij Modic <jmodic_at_src.si>
>Certified Oracle7 DBA (OCP)
>================================================
>The above opinions are mine and do not represent
>any official standpoints of my employer
Received on Wed Jul 08 1998 - 09:35:57 CDT