diff options
| -rw-r--r-- | src/backend/access/nbtree/nbtsearch.c | 39 |
1 files changed, 26 insertions, 13 deletions
diff --git a/src/backend/access/nbtree/nbtsearch.c b/src/backend/access/nbtree/nbtsearch.c index 7e05e586768..3230b3b8940 100644 --- a/src/backend/access/nbtree/nbtsearch.c +++ b/src/backend/access/nbtree/nbtsearch.c @@ -17,6 +17,7 @@ #include "access/nbtree.h" #include "access/relscan.h" +#include "access/xact.h" #include "miscadmin.h" #include "pgstat.h" #include "storage/predicate.h" @@ -1382,22 +1383,34 @@ _bt_first(IndexScanDesc scan, ScanDirection dir) { /* * We only get here if the index is completely empty. Lock relation - * because nothing finer to lock exists. + * because nothing finer to lock exists. Without a buffer lock, it's + * possible for another transaction to insert data between + * _bt_search() and PredicateLockRelation(). We have to try again + * after taking the relation-level predicate lock, to close a narrow + * window where we wouldn't scan concurrently inserted tuples, but the + * writer wouldn't see our predicate lock. */ - PredicateLockRelation(rel, scan->xs_snapshot); - - /* - * mark parallel scan as done, so that all the workers can finish - * their scan - */ - _bt_parallel_done(scan); - BTScanPosInvalidate(so->currPos); + if (IsolationIsSerializable()) + { + PredicateLockRelation(rel, scan->xs_snapshot); + stack = _bt_search(rel, NULL, &inskey, &buf, BT_READ, + scan->xs_snapshot); + _bt_freestack(stack); + } - return false; + if (!BufferIsValid(buf)) + { + /* + * Mark parallel scan as done, so that all the workers can finish + * their scan. + */ + _bt_parallel_done(scan); + BTScanPosInvalidate(so->currPos); + return false; + } } - else - PredicateLockPage(rel, BufferGetBlockNumber(buf), - scan->xs_snapshot); + + PredicateLockPage(rel, BufferGetBlockNumber(buf), scan->xs_snapshot); _bt_initialize_more_data(so, dir); |