Обсуждение: Query tuning

<div class="Section1"><p class="MsoNormal"><font face="Comic Sans MS" size="2"><span style="font-size:
10.0pt;font-family:"Comic Sans MS"">Hi,</span></font><p class="MsoNormal"><font face="Comic Sans MS" size="2"><span
style="font-size:
10.0pt;font-family:"Comic Sans MS""> </span></font><p class="MsoNormal"><font face="Comic Sans MS" size="2"><span
style="font-size:
10.0pt;font-family:"Comic Sans MS""> </span></font><p class="MsoNormal"><font face="Comic Sans MS" size="2"><span
style="font-size:
10.0pt;font-family:"Comic Sans MS"">I have a query which is run across 3 tables JOB_TYPE_FIRST, JOB_TYPE_SECOND and
JOB_ALLOCATION_WORKLIST.</span></font><pclass="MsoNormal"><font face="Comic Sans MS" size="2"><span style="font-size: 
10.0pt;font-family:"Comic Sans MS""> </span></font><p class="MsoNormal"><font face="Comic Sans MS" size="2"><span
style="font-size:
10.0pt;font-family:"Comic Sans MS"">The column JOBID is referenced in JOB_ALLOCATION_WORKLIST table and primary key in
bothJOB_TYPE_FIRST, JOB_TYPE_SECOND tables.</span></font><p class="MsoNormal"><font face="Comic Sans MS" size="2"><span
style="font-size:
10.0pt;font-family:"Comic Sans MS""> </span></font><p class="MsoNormal"><font face="Comic Sans MS" size="2"><span
style="font-size:
10.0pt;font-family:"Comic Sans MS"">There is one more column BOOK_ID which is supplied as the binding parameter to the
query.The query looks like:</span></font><p class="MsoNormal"><font face="Comic Sans MS" size="2"><span
style="font-size:
10.0pt;font-family:"Comic Sans MS""> </span></font><p class="MsoNormal"><font face="Comic Sans MS" size="2"><span
style="font-size:
10.0pt;font-family:"Comic Sans MS"">select count(distinct(j.JOBID)) as jobCount </span></font><p
class="MsoNormal"><fontface="Comic Sans MS" size="2"><span style="font-size: 
10.0pt;font-family:"Comic Sans MS"">from  JOB_TYPE_FIRST a, JOB_TYPE_SECOND b, JOB_ALLOCATION_WORKLIST j
</span></font><pclass="MsoNormal"><font face="Comic Sans MS" size="2"><span style="font-size: 
10.0pt;font-family:"Comic Sans MS"">where (( a.JOBID = j.JOBID) </span></font><p class="MsoNormal"><font face="Comic
SansMS" size="2"><span style="font-size: 
10.0pt;font-family:"Comic Sans MS"">and (a.BOOK_ID = :bookId)) </span></font><p class="MsoNormal"><font face="Comic
SansMS" size="2"><span style="font-size: 
10.0pt;font-family:"Comic Sans MS"">or ((b.JOBID = j.JOBID) </span></font><p class="MsoNormal"><font face="Comic Sans
MS"size="2"><span style="font-size: 
10.0pt;font-family:"Comic Sans MS"">and (b.BOOK_ID = :bookId));</span></font><p class="MsoNormal"><font face="Comic
SansMS" size="2"><span style="font-size: 
10.0pt;font-family:"Comic Sans MS""> </span></font><p class="MsoNormal"><font face="Comic Sans MS" size="2"><span
style="font-size:
10.0pt;font-family:"Comic Sans MS"">As the records in the database are too large it is having huge cost and stalling
theserver and takes lot of time. </span></font><p class="MsoNormal"><font face="Comic Sans MS" size="2"><span
style="font-size:
10.0pt;font-family:"Comic Sans MS""> </span></font><p class="MsoNormal"><font face="Comic Sans MS" size="2"><span
style="font-size:
10.0pt;font-family:"Comic Sans MS"">Can anyone suggest a better way to fetch the results for the query or tune it? Any
helpwould be highly appreciated.</span></font><p class="MsoNormal"><font face="Comic Sans MS" size="2"><span
style="font-size:
10.0pt;font-family:"Comic Sans MS""> </span></font><p class="MsoNormal"><font face="Comic Sans MS" size="2"><span
style="font-size:
10.0pt;font-family:"Comic Sans MS""> </span></font><p class="MsoNormal"><font face="Comic Sans MS" size="2"><span
style="font-size:
10.0pt;font-family:"Comic Sans MS"">Thanks & Regards,</span></font><p class="MsoNormal"><font face="Comic Sans MS"
size="2"><spanstyle="font-size: 
10.0pt;font-family:"Comic Sans MS"">Kapil</span></font></div><p><strong><span style="font-size:10.0pt;font-family:
"Palatino Linotype","serif";color:green"> Please do not print this email unless it is absolutely necessary.
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Hi kapil,

Here you have specified 3 tables, does JOB_TYPE_FIRST and JOB_TYPE_SECOND both contain all the JOBID in the third table?

Maybe i can help you if you elaborate your problem a bit more.

Regards,
Moiz Kothari




--
Hobby Site : http://dailyhealthtips.blogspot.com

On Thu, May 15, 2008 at 12:00 AM,  <kapil.munish@wipro.com> wrote:
> Hi,
>
> select count(distinct(j.JOBID)) as jobCount
> from  JOB_TYPE_FIRST a, JOB_TYPE_SECOND b, JOB_ALLOCATION_WORKLIST j
> where (( a.JOBID = j.JOBID)
> and (a.BOOK_ID = :bookId))
> or ((b.JOBID = j.JOBID)
> and (b.BOOK_ID = :bookId));

Have you tried joining a with j and b with j separately, and then
doing a union on those two sets?

On Fri, 2008-05-16 at 09:21 -0600, Scott Marlowe wrote:
> On Thu, May 15, 2008 at 12:00 AM,  <kapil.munish@wipro.com> wrote:
> > Hi,
> >
> > select count(distinct(j.JOBID)) as jobCount
> > from  JOB_TYPE_FIRST a, JOB_TYPE_SECOND b, JOB_ALLOCATION_WORKLIST j
> > where (( a.JOBID = j.JOBID)
> > and (a.BOOK_ID = :bookId))
> > or ((b.JOBID = j.JOBID)
> > and (b.BOOK_ID = :bookId));
> 
> Have you tried joining a with j and b with j separately, and then
> doing a union on those two sets?

That seems the only way to get a sane answer to this query, which is
otherwise an unconstrained join on both sides of the OR. Great example
of a query which runs slow because the question is phrased incorrectly.
Count(distinct) is pretty much the only function that will give the same
answer as a correctly phrased query.

-- Simon Riggs           www.2ndQuadrant.comPostgreSQL Training, Services and Support