Re: Postgres code for a query intermediate dataset

On 14/09/14 21:18, Rohit Goyal wrote:
> Hi Mark & Atri, :)
>
> Thanks for reply. But, I think i confused you. I am talking about access
> using indexes. So, I assume that B+ tree store key-value pair where
> rohit is the key and all the versions are its value.
>
> Another way to think is I have a secondary index on emp. name and there
> are 4 rohit exist in DB. So, now B+ tree gives me 4 different tuple
> pointer for each Rohit. I want to know the code portion for this where i
> can see all 4 tuple pointer before each one have I/O access to fetch its
> tuple.
>
> Are the suggestions still valid?
>

Visibility rules mentioned earlier apply equally to tables and indexes 
(strictly speaking what happens is index tuples are checked against the 
relevant tables to see if your session can see them), so discussion of 
whether tuples are retrieved via index or table scans is not really 
relevant (i.e query planning/optimization is separate from tuple 
visibility).

Cheers

Mark