diff options
Diffstat (limited to 'src/backend/access/nbtree/nbtsearch.c')
| -rw-r--r-- | src/backend/access/nbtree/nbtsearch.c | 11 |
1 files changed, 7 insertions, 4 deletions
diff --git a/src/backend/access/nbtree/nbtsearch.c b/src/backend/access/nbtree/nbtsearch.c index 070f14c8b91..36544ecfd58 100644 --- a/src/backend/access/nbtree/nbtsearch.c +++ b/src/backend/access/nbtree/nbtsearch.c @@ -2282,9 +2282,12 @@ _bt_readfirstpage(IndexScanDesc scan, OffsetNumber offnum, ScanDirection dir) * previously-saved right link or left link. lastcurrblkno is the page that * was current at the point where the blkno link was saved, which we use to * reason about concurrent page splits/page deletions during backwards scans. + * In the common case where seized=false, blkno is either so->currPos.nextPage + * or so->currPos.prevPage, and lastcurrblkno is so->currPos.currPage. * - * On entry, caller shouldn't hold any locks or pins on any page (we work - * directly off of blkno and lastcurrblkno instead). Parallel scan callers + * On entry, so->currPos shouldn't be locked by caller. so->currPos.buf must + * be InvalidBuffer/unpinned as needed by caller (note that lastcurrblkno + * won't need to be read again in almost all cases). Parallel scan callers * that seized the scan before calling here should pass seized=true; such a * caller's blkno and lastcurrblkno arguments come from the seized scan. * seized=false callers just pass us the blkno/lastcurrblkno taken from their @@ -2301,8 +2304,8 @@ _bt_readfirstpage(IndexScanDesc scan, OffsetNumber offnum, ScanDirection dir) * success exit (except during so->dropPin index scans, when we drop the pin * eagerly to avoid blocking VACUUM). * - * If there are no more matching records in the given direction, we drop all - * locks and pins, invalidate so->currPos, and return false. + * If there are no more matching records in the given direction, we invalidate + * so->currPos (while ensuring it retains no locks or pins), and return false. * * We always release the scan for a parallel scan caller, regardless of * success or failure; we'll call _bt_parallel_release as soon as possible. |