Re: Can rs_cindex be < 0 for bitmap heap scans?

On Fri, Oct 25, 2024 at 10:07 PM Melanie Plageman <melanieplageman(at)gmail(dot)com>
wrote:

> On Fri, Oct 25, 2024 at 10:29 AM Melanie Plageman
> <melanieplageman(at)gmail(dot)com> wrote:
> >
> > Tom suggested off-list that if rs_cindex can't be zero, then it should
> > be unsigned. I checked the other scan types using the
> > HeapScanDescData, and it seems none of them use values of rs_cindex or
> > rs_ntuples < 0. As such, here is a patch making both rs_ntuples and
> > rs_cindex unsigned.
>
>
@@ -943,8 +945,8 @@ heapgettup_pagemode(HeapScanDesc scan,
{
HeapTuple tuple = &(scan->rs_ctup);
Page page;
- int lineindex;
- int linesleft;
+ uint32 lineindex;
+ uint32 linesleft;

IMHO we can't make "lineindex" as uint32, because just see the first code
block[1] of heapgettup_pagemode(), we use this index as +ve (Forward scan
)as well as -ve (Backward scan).

[1]
if (likely(scan->rs_inited))
{
/* continue from previously returned page/tuple */
page = BufferGetPage(scan->rs_cbuf);

lineindex = scan->rs_cindex + dir;
if (ScanDirectionIsForward(dir))

--Refer definition of ScanDirection
typedef enum ScanDirection
{
BackwardScanDirection = -1,
NoMovementScanDirection = 0,
ForwardScanDirection = 1
} ScanDirection;

--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com