Re: What's the XID?

how do u know this theory ? 1 + (2 * number of columns in the SELECT)
just try & test? or have any document?

Guillaume Lelarge-3 wrote:
>
> Tom Lane wrote:
>> "ivan.hou" <ivan(dot)hou(at)msa(dot)hinet(dot)net> writes:
>>> step 1. SELECT datname, age(datfrozenxid) FROM pg_database;
>>> --> mydb age:33183
>>> step 2. SELECT datname, age(datfrozenxid) FROM pg_database;
>>> --> mydb age:33188
>>
>>> why always increased by 5?
>>
>> If you do it directly in psql, it increases by 1.
>>
>>> Postgresql Ver:8.1.3
>>> using pgAdminIII Query window
>>
>> Perhaps you should ask the pgAdmin people what they're doing behind your
>> back ...
>
> We first send the query to the database. For each returned column, we
> send two queries. The first one gives us the type's name of the column
> and the second one gives us the OID of the base type. So, each query
> executed with pgAdmin's query tool should increase age(datfrozenxid) by :
> 1 + (2 * number of columns in the SELECT)
>
> Regards.
>
>
> --
> Guillaume.
> http://www.postgresqlfr.org
> http://dalibo.com
>
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>

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