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nbtree: refine _bt_readnextpage contract comments.

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Another minor follow-up commit for commit 1bd4bc85, which changed the
_bt_readnextpage contract.
This commit is contained in:
Peter Geoghegan 2025-03-07 18:35:13 -05:00
parent 088f8e2d56
commit 8e167e6188
1 changed files with 4 additions and 1 deletions
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5
src/backend/access/nbtree/nbtsearch.c
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@ -2183,7 +2183,9 @@ _bt_readfirstpage(IndexScanDesc scan, OffsetNumber offnum, ScanDirection dir)
* scan. A seized=false caller's blkno can never be assumed to be the page * scan. A seized=false caller's blkno can never be assumed to be the page
* that must be read next during a parallel scan, though. We must figure that * that must be read next during a parallel scan, though. We must figure that
* part out for ourselves by seizing the scan (the correct page to read might * part out for ourselves by seizing the scan (the correct page to read might
* already be beyond the seized=false caller's blkno during a parallel scan). * already be beyond the seized=false caller's blkno during a parallel scan,
* unless blkno/so->currPos.nextPage/so->currPos.prevPage is already P_NONE,
* or unless so->currPos.moreRight/so->currPos.moreLeft is already unset).
* *
* On success exit, so->currPos is updated to contain data from the next * On success exit, so->currPos is updated to contain data from the next
* interesting page, and we return true. We hold a pin on the buffer on * interesting page, and we return true. We hold a pin on the buffer on
@ -2204,6 +2206,7 @@ _bt_readnextpage(IndexScanDesc scan, BlockNumber blkno,
BTScanOpaque so = (BTScanOpaque) scan->opaque; BTScanOpaque so = (BTScanOpaque) scan->opaque;
Assert(so->currPos.currPage == lastcurrblkno || seized); Assert(so->currPos.currPage == lastcurrblkno || seized);
Assert(!(blkno == P_NONE && seized));
Assert(!BTScanPosIsPinned(so->currPos)); Assert(!BTScanPosIsPinned(so->currPos));
/* /*