Re: postgres table have a large number of relpages and occupied a big memory size

I have seen that autovacuum takes long time to process .
please give me the reason ......

On Mon, Aug 8, 2011 at 2:10 PM, Tomas Vondra <tv(at)fuzzy(dot)cz> wrote:
> On 8 Srpen 2011, 8:02, Vivekkumar Pandey wrote:
>> Hi ,
>>
>>       I have version of PostgreSQL as given below:---
>>
>>                                        version
>> -------------------------------------------------------------------------------------
>>  PostgreSQL 8.1.2 on i686-pc-linux-gnu, compiled by GCC gcc (GCC)
>> 3.3.3 (SuSE Linux)
>>
>> And it does't have any n_dead_tup columns in pg_stat_all_tables like this:
>
> That's because this column was added in 8.3.
>
> BTW you're using a way too old version. It's not just that 8.1 is
> unsupported, but the last minor subversion in this branch is 8.1.23. There
> were numerous bugfixes since 8.1.2, so you should upgrade at least to this
> version (and plan to upgrade to something more fresh).
>
>> In what situations table creates a new row instead of using deleted
>> marked tuples that's why size of table increases abnormally.
>
> Whenever a row is modified - that means insert, update or delete. That's
> how PostgreSQL MVCC works. This wasted space needs to be reclaimed, which
> is exactly what (auto)vacuum does.
>
> PS: With HOT this is not exactly true, but HOT is not available in 8.1
> anyway. Another reason to upgrade to a more recent version.
>
> Tomas
>
>
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--
Thanks

VIVEK KUMAR PANDEY