[SNMP4J] TableUtils - more efficient fetching of sparse tables

[Michał Steiner]

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