Re: PostgreSQL+Hibernate Performance

Hi Mark,

Thanks again for the info.
I shall create diff sets of indexes and see the query execution time.
And one of such tables might get around 700,000 records over a period of 4-5
months. So what kind of other measures I need to focus on.
I thought of the following
1) Indexes
2) Better Hardware (RAM & HDD)

And how can i estimate the size of the row? is it like based on the data
types of the columns i have in the table?
Do you have any info to guide me on this?

On Thu, Aug 21, 2008 at 7:32 PM, Mark Lewis <mark(dot)lewis(at)mir3(dot)com> wrote:

> On Thu, 2008-08-21 at 12:33 +0530, Kranti K K Parisa™ wrote:
>
> > On Wed, Aug 20, 2008 at 8:54 PM, Matthew Wakeling
> > <matthew(at)flymine(dot)org> wrote:
> > On Wed, 20 Aug 2008, Kranti K K Parisa™ wrote:
> > creating multiple indexes on same column will effect
> > performance?
> > for example:
> >
> > index1 : column1, column2, column3
> > index2: column1
> > index3: column2,
> > index4: column3
> > index5: column1,column2
> >
> >
> > The sole purpose of indexes is to affect performance.
> >
> > However, if you have index1, there is no point in having
> > index2 or index5.
> >
> > Matthew
> >
> > Thanks Matthew,
> >
> > does that mean i can just have index1, index3, index4?
> >
>
> (trying to get the thread back into newest-comments-last order)
>
> Well, yes you can get away with just index1, index3 and index4, and it
> may well be the optimal solution for you, but it's not entirely
> clear-cut.
>
> It's true that PG can use index1 to satisfy queries of the form "SELECT
> x FROM y WHERE column1=somevalue" or "column1=a AND column2=b". It will
> not be as fast as an index lookup from a single index, but depending on
> the size of the tables/indexes and the selectivity of leading column(s)
> in the index, the difference in speed may be trivial.
>
> On the other hand, if you have individual indexes on column1, column2
> and column3 but no multi-column index, PG can combine the individual
> indexes in memory with a bitmap. This is not as fast as a normal lookup
> in the multi-column index would be, but can still be a big win over not
> having an index at all.
>
> To make an educated decision you might want to read over some of the
> online documentation about indexes, in particular these two sections:
>
> http://www.postgresql.org/docs/8.3/interactive/indexes-multicolumn.html
>
> and
>
> http://www.postgresql.org/docs/8.3/interactive/indexes-bitmap-scans.html
>
> -- Mark
>

--

Best Regards
Kranti Kiran Kumar Parisa
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