Re: Doubt in IndexScanDescData

On Feb 17, 2008, at 4:33 PM, Suresh wrote:

> [ "include/access/relscan.h" ]
>
> In IndexScanDescData, whats the purpose of having two Relation
> variables.
>
> typedef struct IndexScanDescData
> {
> Relation heapRelation; /* heap relation
> descriptor, or NULL */
> Relation indexRelation; /* index relation
> descriptor */
> ....
> ...
> }IndexScanDescData;

The index does not contain the entire tuple. If you index column A
the index will not contain values in column B of the same table.
Thus, if you find a record in the index one of the things which have
to be done is to get the record from disk to check visibility and
other columns.

best regards,

hans-juergen schoenig

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