Re: Doubt in index scan code

On 8-Mar-08, at 11:06 AM, Suresh wrote:

> Hello all,
>
> I have a custom code written inside postgres in an application we use.
> The snippet is as below :
> Here inner plan is an index scan.
>
> scandesc = ((IndexScanState *)innerPlan)->iss_ScanDesc;
>
> flag=index_getmulti(scandesc, &tidelm->tid, 1, &ret_tids);
>
> Now consider a query like
>
> explain select * from dept,manager where did=id ;
> QUERY PLAN
> ---------------------------------------------------------------------------
> Nested Loop (cost=0.00..269.09 rows=45 width=72)
> -> seq scan on manager (cost=0.00..6.50 rows=45 width=36)
> -> Index Scan using id1 on dept (cost=0.00..5.82 rows=1 width=36)
> Index Cond: ("outer".did = dept.id)
>
> Say seq scan retrieves did in the order 30,10, 20.. My doubt is in
> what order
> will index_getmulti return tids. How does the scandesc work ?
>
> Will it return the tids as firstly macthing inners for dept=30, then
> dept=10 ?
>
since you have no order by clause in the query rows will be returned
in the order they are found on the disc.

Dave
> Please help me with this.
>
> Thanks and regards,
> Suresh
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