system table scan
Hi,
I created an additional system table that i need in my system. The table
contains attributes (username, att1, att2, ...)
I need to scan the table for a certain username while retrieving the tupled
ordered by att1.
If i understand correctly, i may use systable_beginscan() and
systable_getnext() to scan a system table while specifying a key (e.g.,
username='user1'). But i know nothing about specifying the order of the
scan.
Should i implement my own table scan functions then? Or there is any
mechanism that i may reuse?
Thanks a lot,
Ehab
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"Ehab Galal" <ehabgalal123@hotmail.com> writes:
If i understand correctly, i may use systable_beginscan() and
systable_getnext() to scan a system table while specifying a key (e.g.,
username='user1'). But i know nothing about specifying the order of the
scan.
The systable_xxx functions allow implementation by either indexscan or
seqscan, therefore they guarantee *nothing* about retrieval order.
If your code does not need to be executed during bootstrap or crash
recovery, you could depend on an indexscan instead. See
toast_fetch_datum() for an example.
regards, tom lane