Обсуждение: RelFileNode to Relation
Hi
I need to get a Relation instance but I have only a RelFileNode!
I see the relcache.h, only the following function seems helpful
extern Relation RelationIdGetRelation(Oid relationId);
However, there is another problem, In the RelFileNode, only relNode exist and as comment said this is equivalent to pg_class.relfilenode and in some situation relation oid (pg_class.oid) and relation file node are not the same.
So i cant use above function!
Any idea?
Regards,
Soroosh Sardari
Sharif University of Tech.
Soroosh Sardari <soroosh.sardari@gmail.com> writes:
> I need to get a Relation instance but I have only a RelFileNode!
Why do you think you need to do that? Such a lookup is inherently the
wrong thing, because relations' relfilenode values are not fixed (unless
you have a lock on the relation, which presumably you don't).
regards, tom lane
On Sat, Oct 19, 2013 at 11:53 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
Soroosh Sardari <soroosh.sardari@gmail.com> writes:Why do you think you need to do that? Such a lookup is inherently the
> I need to get a Relation instance but I have only a RelFileNode!
wrong thing, because relations' relfilenode values are not fixed (unless
you have a lock on the relation, which presumably you don't).
regards, tom lane
I know, it's against PG abstraction.
In PG we don't need to know anything about relation in the smgr level. but in my project i want to encrypt
all pages of a particular relation and decrypt it when those pages are fetching back to buffer.
This behavior depends on some relation properties. So in smgropen I must get some knowledge about the relation and all of i have is RelFileNode.
I can not see the pg_class for the relation oid, because smgropen may called before insertion in pg_class.
Soroosh