@@ -2036,8 +2036,8 @@ _bt_steppage(IndexScanDesc scan, ScanDirection dir)
20362036 *_bt_readnextpage() -- Read next page containing valid data for scan
20372037 *
20382038 * On success exit, so->currPos is updated to contain data from the next
2039- * interesting page. Caller is responsible to release lock and pin on
2040- *buffer on success. We return true to indicate success.
2039+ * interesting page, and we return true. Caller must releasethe lock( and
2040+ *maybe the pin) on the buffer on success exit .
20412041 *
20422042 * If there are no more matching records in the given direction, we drop all
20432043 * locks and pins, set so->currPos.buf to InvalidBuffer, and return false.
@@ -2127,18 +2127,9 @@ _bt_readnextpage(IndexScanDesc scan, BlockNumber blkno, ScanDirection dir)
21272127 *
21282128 * It might be possible to rearrange this code to have less overhead
21292129 * in pinning and locking, but that would require capturing the left
2130- * pointer when the page is initially read, and using it here, along
2131- * with big changes to _bt_walk_left() and the code below. It is not
2132- * clear whether this would be a win, since if the page immediately to
2133- * the left splits after we read this page and before we step left, we
2134- * would need to visit more pages than with the current code.
2135- *
2136- * Note that if we change the code so that we drop the pin for a scan
2137- * which uses a non-MVCC snapshot, we will need to modify the code for
2138- * walking left, to allow for the possibility that a referenced page
2139- * has been deleted. As long as the buffer is pinned or the snapshot
2140- * is MVCC the page cannot move past the half-dead state to fully
2141- * deleted.
2130+ * sibling block number when the page is initially read, and then
2131+ * optimistically starting there (rather than pinning the page twice).
2132+ * It is not clear that this would be worth the complexity.
21422133 */
21432134if (BTScanPosIsPinned (so -> currPos ))
21442135_bt_lockbuf (rel ,so -> currPos .buf ,BT_READ );
@@ -2243,9 +2234,8 @@ _bt_parallel_readpage(IndexScanDesc scan, BlockNumber blkno, ScanDirection dir)
22432234 * Returns InvalidBuffer if there is no page to the left (no lock is held
22442235 * in that case).
22452236 *
2246- * When working on a non-leaf level, it is possible for the returned page
2247- * to be half-dead; the caller should check that condition and step left
2248- * again if it's important.
2237+ * It is possible for the returned leaf page to be half-dead; caller must
2238+ * check that condition and step left again when required.
22492239 */
22502240static Buffer
22512241_bt_walk_left (Relation rel ,Buffer buf )
@@ -2288,8 +2278,7 @@ _bt_walk_left(Relation rel, Buffer buf)
22882278 * anymore, not that its left sibling got split more than four times.
22892279 *
22902280 * Note that it is correct to test P_ISDELETED not P_IGNORE here,
2291- * because half-dead pages are still in the sibling chain. Caller
2292- * must reject half-dead pages if wanted.
2281+ * because half-dead pages are still in the sibling chain.
22932282 */
22942283tries = 0 ;
22952284for (;;)