Make rs_cindex and rs_ntuples unsigned

HeapScanDescData.rs_cindex and rs_ntuples can't be less than 0. All scan
types using the heap scan descriptor expect these values to be >= 0.
Make that expectation clear by making rs_cindex and rs_ntuples unsigned.

Also remove the test in heapam_scan_bitmap_next_tuple() that checks if
rs_cindex < 0. This was never true, but now that rs_cindex is unsigned,
it makes even less sense.

While we are at it, initialize both rs_cindex and rs_ntuples to 0 in
initscan().

Author: Melanie Plageman
Reviewed-by: Dilip Kumar
Discussion: https://postgr.es/m/CAAKRu_ZxF8cDCM_BFi_L-t%3DRjdCZYP1usd1Gd45mjHfZxm0nZw%40mail.gmail.com

diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index d00300c5dcbcba170e83dd6e52bcd637e782fe82..6cdc68d981a47927156ec72c18eeee3bfab85c93 100644 (file)
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -378,6 +378,8 @@ initscan(HeapScanDesc scan, ScanKey key, bool keep_startblock)
    ItemPointerSetInvalid(&scan->rs_ctup.t_self);
    scan->rs_cbuf = InvalidBuffer;
    scan->rs_cblock = InvalidBlockNumber;
+   scan->rs_ntuples = 0;
+   scan->rs_cindex = 0;
 
    /*
     * Initialize to ForwardScanDirection because it is most common and
@@ -943,8 +945,8 @@ heapgettup_pagemode(HeapScanDesc scan,
 {
    HeapTuple   tuple = &(scan->rs_ctup);
    Page        page;
-   int         lineindex;
-   int         linesleft;
+   uint32      lineindex;
+   uint32      linesleft;
 
    if (likely(scan->rs_inited))
    {
@@ -989,6 +991,7 @@ continue_page:
            ItemId      lpp;
            OffsetNumber lineoff;
 
+           Assert(lineindex <= scan->rs_ntuples);
            lineoff = scan->rs_vistuples[lineindex];
            lpp = PageGetItemId(page, lineoff);
            Assert(ItemIdIsNormal(lpp));

diff --git a/src/backend/access/heap/heapam_handler.c b/src/backend/access/heap/heapam_handler.c
index a8d95e0f1c1a0a7c3f220e08103eeb870b4abbc2..d0e5922eed78acacd93628c9d37c1802f6d53927 100644 (file)
--- a/src/backend/access/heap/heapam_handler.c
+++ b/src/backend/access/heap/heapam_handler.c
@@ -2303,7 +2303,7 @@ heapam_scan_bitmap_next_tuple(TableScanDesc scan,
    /*
     * Out of range?  If so, nothing more to look at on this page
     */
-   if (hscan->rs_cindex < 0 || hscan->rs_cindex >= hscan->rs_ntuples)
+   if (hscan->rs_cindex >= hscan->rs_ntuples)
        return false;
 
    targoffset = hscan->rs_vistuples[hscan->rs_cindex];

diff --git a/src/include/access/heapam.h b/src/include/access/heapam.h
index 96cf82f97b754bffb9128942e3e8fd313238f96c..04afb1a6a66d71f24ee2b3d874de559467027a9b 100644 (file)
--- a/src/include/access/heapam.h
+++ b/src/include/access/heapam.h
@@ -103,8 +103,8 @@ typedef struct HeapScanDescData
    int         rs_empty_tuples_pending;
 
    /* these fields only used in page-at-a-time mode and for bitmap scans */
-   int         rs_cindex;      /* current tuple's index in vistuples */
-   int         rs_ntuples;     /* number of visible tuples on page */
+   uint32      rs_cindex;      /* current tuple's index in vistuples */
+   uint32      rs_ntuples;     /* number of visible tuples on page */
    OffsetNumber rs_vistuples[MaxHeapTuplesPerPage];    /* their offsets */
 }          HeapScanDescData;
 typedef struct HeapScanDescData *HeapScanDesc;