Import wiredtiger: b50d65e8560446e2cd205594e07bbcaa2305b144 from branch mongodb-4.2

ref: d86b3a8a33..b50d65e856
for: 4.3.1

WT-4502       Assertion checking hazard pointers on page discard is too strong
WT-4733       Change test/format to do longer-term repeatable read testing
WT-4743       Fix memory leaks and core dumps in page-split error handling
WT-4786       Coverity: Invalid format specifiers in printf-like invocations
WT-4805       Modify error message verification for test_prepare04.py
WT-4812       Fix the Python distribution script for Python3 changes
WT-4818       Add debugging of bad read file descriptor when files are missing during recovery
WT-4840       WT_CURSOR.modify must require explicit, snapshot-isolation transaction
WT-4864       Coverity: Redundant NULL check
WT-4866       Coverity: WT_SESSION.import can leak memory
WT-4867       Skip assertion when reserved updates are seen
WT-4882       Improve checkpoint performance when there are large metadata pages
WT-4887       Skip read timestamp required assert during recovery
WT-4888       Remove support for Berkeley DB
WT-4891       WT_SESSION.verify memory allocation overrun
WT-4895       Fix debug eviction mode so it chooses skew more randomly
WT-4910       Port Windows SConstruct to Python 3

1 files changed, 8 insertions, 3 deletions

diff --git a/src/third_party/wiredtiger/src/cursor/cur_std.c b/src/third_party/wiredtiger/src/cursor/cur_std.c
index 808780b4675..073df6eaaf6 100644
--- a/src/third_party/wiredtiger/src/cursor/cur_std.c
+++ b/src/third_party/wiredtiger/src/cursor/cur_std.c
@@ -916,11 +916,16 @@ __cursor_modify(WT_CURSOR *cursor, WT_MODIFY *entries, int nentries)
 
 	/*
 	 * The underlying btree code cannot support WT_CURSOR.modify within
-	 * a read-uncommitted transaction. Disallow it here for consistency.
+	 * a read-committed or read-uncommitted transaction, or outside of
+	 * an explicit transaction. Disallow here as well, for consistency.
 	 */
-	if (session->txn.isolation == WT_ISO_READ_UNCOMMITTED)
+	if (session->txn.isolation != WT_ISO_SNAPSHOT)
 		WT_ERR_MSG(session, ENOTSUP,
-		    "not supported in read-uncommitted transactions");
+		    "not supported in read-committed or read-uncommitted "
+		    "transactions");
+	if (F_ISSET(&session->txn, WT_TXN_AUTOCOMMIT))
+		WT_ERR_MSG(session, ENOTSUP,
+		    "not supported in implicit transactions");
 
 	WT_ERR(__cursor_checkkey(cursor));