Remove BTScanOpaqueData.firstPage

It's not necessary to keep the firstPage flag as a field of BTScanOpaqueData.
This commit makes it an argument of the _bt_readpage() function.  We can easily
distinguish first-time and repeated calls (within the scan) of this function.

Reported-by: Peter Geoghegan
Discussion: https://postgr.es/m/CAH2-Wzk4SOsw%2BtHuTFiz8U9Jqj-R77rYPkhWKODCBb1mdHACXA%40mail.gmail.com
Reviewed-by: Pavel Borisov

diff --git a/src/backend/access/nbtree/nbtree.c b/src/backend/access/nbtree/nbtree.c
index 6c8cd93fa0a50fc238a5063128fa4630934a607d..dd6dc0971bcf5e5c7631a781159995298de1786b 100644 (file)
--- a/src/backend/access/nbtree/nbtree.c
+++ b/src/backend/access/nbtree/nbtree.c
@@ -409,7 +409,6 @@ btrescan(IndexScanDesc scan, ScanKey scankey, int nscankeys,
 
    so->markItemIndex = -1;
    so->arrayKeyCount = 0;
-   so->firstPage = false;
    BTScanPosUnpinIfPinned(so->markPos);
    BTScanPosInvalidate(so->markPos);
 

diff --git a/src/backend/access/nbtree/nbtsearch.c b/src/backend/access/nbtree/nbtsearch.c
index be61b3868f42fbe5a87c2f4cbf31f251f812af58..b0c65a42d6d6af9e67174c84c5ed0d178740811c 100644 (file)
--- a/src/backend/access/nbtree/nbtsearch.c
+++ b/src/backend/access/nbtree/nbtsearch.c
@@ -30,7 +30,7 @@ static OffsetNumber _bt_binsrch(Relation rel, BTScanInsert key, Buffer buf);
 static int _bt_binsrch_posting(BTScanInsert key, Page page,
                                OffsetNumber offnum);
 static bool _bt_readpage(IndexScanDesc scan, ScanDirection dir,
-                        OffsetNumber offnum);
+                        OffsetNumber offnum, bool firstPage);
 static void _bt_saveitem(BTScanOpaque so, int itemIndex,
                         OffsetNumber offnum, IndexTuple itup);
 static int _bt_setuppostingitems(BTScanOpaque so, int itemIndex,
@@ -1395,7 +1395,6 @@ _bt_first(IndexScanDesc scan, ScanDirection dir)
    offnum = _bt_binsrch(rel, &inskey, buf);
    Assert(!BTScanPosIsValid(so->currPos));
    so->currPos.buf = buf;
-   so->firstPage = true;
 
    /*
     * Now load data from the first page of the scan.
@@ -1416,7 +1415,7 @@ _bt_first(IndexScanDesc scan, ScanDirection dir)
     * for the page.  For example, when inskey is both < the leaf page's high
     * key and > all of its non-pivot tuples, offnum will be "maxoff + 1".
     */
-   if (!_bt_readpage(scan, dir, offnum))
+   if (!_bt_readpage(scan, dir, offnum, true))
    {
        /*
         * There's no actually-matching data on this page.  Try to advance to
@@ -1520,7 +1519,8 @@ _bt_next(IndexScanDesc scan, ScanDirection dir)
  * Returns true if any matching items found on the page, false if none.
  */
 static bool
-_bt_readpage(IndexScanDesc scan, ScanDirection dir, OffsetNumber offnum)
+_bt_readpage(IndexScanDesc scan, ScanDirection dir, OffsetNumber offnum,
+            bool firstPage)
 {
    BTScanOpaque so = (BTScanOpaque) scan->opaque;
    Page        page;
@@ -1601,7 +1601,7 @@ _bt_readpage(IndexScanDesc scan, ScanDirection dir, OffsetNumber offnum)
     * We skip this for the first page in the scan to evade the possible
     * slowdown of the point queries.
     */
-   if (!so->firstPage && minoff < maxoff)
+   if (!firstPage && minoff < maxoff)
    {
        ItemId      iid;
        IndexTuple  itup;
@@ -1620,7 +1620,6 @@ _bt_readpage(IndexScanDesc scan, ScanDirection dir, OffsetNumber offnum)
    }
    else
    {
-       so->firstPage = false;
        requiredMatchedByPrecheck = false;
    }
 
@@ -2079,7 +2078,7 @@ _bt_readnextpage(IndexScanDesc scan, BlockNumber blkno, ScanDirection dir)
                PredicateLockPage(rel, blkno, scan->xs_snapshot);
                /* see if there are any matches on this page */
                /* note that this will clear moreRight if we can stop */
-               if (_bt_readpage(scan, dir, P_FIRSTDATAKEY(opaque)))
+               if (_bt_readpage(scan, dir, P_FIRSTDATAKEY(opaque), false))
                    break;
            }
            else if (scan->parallel_scan != NULL)
@@ -2170,7 +2169,7 @@ _bt_readnextpage(IndexScanDesc scan, BlockNumber blkno, ScanDirection dir)
                PredicateLockPage(rel, BufferGetBlockNumber(so->currPos.buf), scan->xs_snapshot);
                /* see if there are any matches on this page */
                /* note that this will clear moreLeft if we can stop */
-               if (_bt_readpage(scan, dir, PageGetMaxOffsetNumber(page)))
+               if (_bt_readpage(scan, dir, PageGetMaxOffsetNumber(page), false))
                    break;
            }
            else if (scan->parallel_scan != NULL)
@@ -2487,14 +2486,13 @@ _bt_endpoint(IndexScanDesc scan, ScanDirection dir)
 
    /* remember which buffer we have pinned */
    so->currPos.buf = buf;
-   so->firstPage = true;
 
    _bt_initialize_more_data(so, dir);
 
    /*
     * Now load data from the first page of the scan.
     */
-   if (!_bt_readpage(scan, dir, start))
+   if (!_bt_readpage(scan, dir, start, false))
    {
        /*
         * There's no actually-matching data on this page.  Try to advance to

diff --git a/src/include/access/nbtree.h b/src/include/access/nbtree.h
index 5e083591a62e40cc0602340e545cb1061e4643e8..dab84c90baedc0d8aa4484476a8dadc6136d8206 100644 (file)
--- a/src/include/access/nbtree.h
+++ b/src/include/access/nbtree.h
@@ -1051,9 +1051,6 @@ typedef struct BTScanOpaqueData
    int        *killedItems;    /* currPos.items indexes of killed items */
    int         numKilled;      /* number of currently stored items */
 
-   /* flag indicating the first page in the scan */
-   bool        firstPage;
-
    /*
     * If we are doing an index-only scan, these are the tuple storage
     * workspaces for the currPos and markPos respectively.  Each is of size