Re: Get the offset of a tuple inside a table

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От	Pei He
Тема	Re: Get the offset of a tuple inside a table
Дата	21 сентября 2010 г. 21:56:17
Msg-id	AANLkTinFS1DMFcGBNubD+WcHUDZBepRaFv_==t5oeCFP@mail.gmail.com обсуждение
Ответ на	Re: Get the offset of a tuple inside a table ("Kevin Grittner" <Kevin.Grittner@wicourts.gov>)
Список	pgsql-hackers

Дерево обсуждения

I doesn't realized postgresql can be such clever.

Another problem I just found is after one tuple is deleted, there will be some slots unoccupied. The offset cannot be computed even know how much tuples a page can contain.

I need one hash table.

Thanks
--
Pei

On Tue, Sep 21, 2010 at 8:47 PM, Kevin Grittner <Kevin.Grittner@wicourts.gov> wrote:

Pei He wrote:

> The offset is the order of a tuple in a Sequential Scan.

That's not a safe assumption. Try starting a sequential scan against
a large table on one connection; then before it finishes, start the
same query on another connection. The second query joins the one
already in progress and then starts over, "wrapping around".

-Kevin

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Re: Get the offset of a tuple inside a table