[SNMP4J] TableUtils - more efficient fetching of sparse tables

[Michał Steiner]

Great! I can be first to test it.

I agree that improvement will be visible only in specific cases.  We have a
tables  with  almost 200 columns where some of them are full, some are
empty or have just couple of cells with value. So in our case  it could be
huge improvement.

-- 
Michal

2015-12-07 12:35 GMT+01:00 Frank Fock <fock at agentpp.com>:

> Hi Michal,
> The proposed improvement can be indeed applied to any column,
> but will have an effect only if the a lot of cells are missing and the
> distribution is asymmetric.
> I will try to implement the improvement for SNMP4J 2.4.0
>
> Best regards
> Frank
>
> > Am 02.12.2015 um 09:19 schrieb Michał Steiner <mist at mist.pl>:
> >
> > Hi,
> >
> > I've noticed that getTable method in org.snmp4j.util.TableUtils could be
> > more efficient for sparse tables.
> >
> > Consider table with 3 columns and 3 rows, but in first column there is a
> > lot of empty cells:
> >
> > Column1           Column2        Column3
> > value-1-1         value-2-1     value-3-1
> > <empty>           value-2-2     value-3-2
> > <empty>           value-2-3     value-3-3
> >
> > Today implementation works more or less like this:
> >
> > get-next   Column1      Column2       Column3
> > response   value-1-1    value-2-1     value-3-1
> >
> > get-next   value-1-1      value-2-1     value-3-1
> > response   value-2-1      value-2-2     value-3-2
> >
> > get-next   value-1-1       value-2-2     value-3-2
> > response   value-2-1       value-2-3     value-3-3
> >
> > get-next   value-1-1      value-2-3     value-3-3
> > response   value-2-1      value-3-3     value from next table
> >
> >
> > As you can see  request for    value-1-1  is done 3 times and only first
> > one makes sense.
> > This is  an issue for large tables (lot of columns and rows) with many
> > empty cells.
> > This algorithm can be improved. After first response from other column we
> > can just stop asking about it. Conversation will look like this:
> >
> >
> > get-next    Column1    Column2        Column3
> > response   value-1-1   value-2-1      value-3-1
> >
> > get-next   value-1-1    value-2-1     value-3-1
> > response   value-2-1    value-2-2     value-3-2    <-- value-2-1  is from
> > different column
> >
> > get-next               value-2-2      value-3-2 <-- in next requests we
> > skip  first column
> > response               value-2-3      value-3-3
> >
> > get-next               value-2-3      value-3-3
> > response               value-3-3      value from next table
> >
> > I guess that bulk request are handled in the similar way, aren't they ?
> >
> > Are my observations correct ?
> > What do you think about such improvement?
> >
> >
> > Regards
> >
> > Michal
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