RE: Hash Table Probe

[Greg Wilburn <gwilburn@xxxxxxxxxxxxxxxxxxxxxxx>]

Sorry... I should have mentioned that I've already been through some of these explanations.

It's returning a count of 20-40 (that's how many rows meet the criteria)...  The Select is using 
OPTIMIZE FOR 250 ROWS (as suggested by the IBM DB group)

The SQL statements are executing within a CGI application... so I can only really control the source (view) and the indexes.

-----Original Message-----
From: MIDRANGE-L [mailto:midrange-l-bounces@xxxxxxxxxxxxxxxxxx] On Behalf Of Charles Wilt
Sent: Wednesday, June 17, 2020 1:12 PM
To: Midrange Systems Technical Discussion <midrange-l@xxxxxxxxxxxxxxxxxx>
Subject: Re: Hash Table Probe

Greg,

When running a statement from STRSQL or Run SQL Scripts, the default is
optimize=*FIRSTIO

Which means, give me back the first set of rows as quickly as possible,
even if it means getting the full set will take longer.

Try setting optimize=*ALLIO

That should get you closer, however you're likely to still see a difference
since the Db (and Run SQL Scripts in particular) pages back the results set
if you're returning more than a few hundred rows..

Charles


On Wed, Jun 17, 2020 at 9:09 AM Greg Wilburn <
gwilburn@xxxxxxxxxxxxxxxxxxxxxxx> wrote:

> I have and SQL COUNT statement running over a complex SQL View...  The
> SELECT statement of the same rows takes 1-2 seconds.  The COUNT(*) takes
> 6-8 seconds.
>
> When I ran this through RUN SQL SCRIPTS using run & explain, I see:
> Hash Probe <- Temporary Hash Table <- Table Probe
>
> The Table Probe is 90% of the time used.  I'm just not sure how to
> eliminate or reduce the amount of CPU time this takes.
> I already have quite a few indexes over the DB2 table... I can see that in
> the              "List of Indexes Optimized"
>
> Anyone point me in the right direction?
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