Fairly good idea IMHO, especially considering Christopher's point
about the unlikeliness of needing an exact count anyway.
Regards, Christoph
>
> How about:
>
> Implement a function "estimated_count" that can be used instead of
> "count". It could use something like the algorithm in
> src/backend/commands/analyze.c to get a reasonably accurate psuedo count
> quickly.
>
> The advantage of this approach is that "count" still means (exact)count
> (for your xact snapshot anyway). Then the situation becomes:
>
> Want a fast count? - use estimated_count(*)
> Want an exact count - use count(*)
>
> regards
>
> Mark
>
> Christopher Browne wrote:
>
> >For a small table, it will be cheaper to walk through and calculate
> >count(*) directly from the tuples themselves.
> >
> >The situation where it may be worthwhile to do this is a table which
> >is rather large (thus count(*) is expensive) where there is some
> >special reason to truly care how many rows there are in the table.
> >For _most_ tables, it seems unlikely that this will be true. For
> >_most_ tables, it is absolutely not worth the cost of tracking the
> >information.
> >
> >