Thread: hi,is it dangerous to only use tuple pointer through heap_getnext()?

hi,i use these codes to store only pointer of tuple :
HeapTuple *tuple;
    tuple = heap_getnext(pHeapScanDesc,ForwardScanDirection);
    while(tuple){
        //[1#]here i only store the pointer of tuple in an array for later using,that means i don't retrive attribute data from this tuple ,is this ok?
        myArray[i++]=tuple;
        //then next tuple
        tuple = heap_getnext(pHeapScanDesc,ForwardScanDirection);
    }
at place [1#],i only store the pointer of current tuple in an array for later using,that means i don't retrieve attribute data from this tuple ,is this ok?
could these tuple pointers be invalid sometimes later if myArray still reference these tuples? i know these tuples have been read into buffers in shared memory, yet I am not sure wether these buffers be replaced or marked invalid when myArray still points to these tuples in according buffers.
thanks a lot!

peng

Excerpts from sunpeng's message of vie may 14 19:15:47 -0400 2010:
> hi,i use these codes to store only pointer of tuple :
> HeapTuple *tuple;
>     tuple = heap_getnext(pHeapScanDesc,ForwardScanDirection);
>     while(tuple){
>         //[1#]here i only store the pointer of tuple in an array for later
> using,that means i don't retrive attribute data from this tuple ,is this ok?

No, this is not safe.  The buffer is unpinned after heap_getnext walks
to the next buffer, and thus could be used for a different page.

--