Add a new WT_SESSION::transaction_range_pin method.

Can be used by applications to identify sessions that are keeping
transaction IDs pinned.

3 files changed, 47 insertions, 1 deletions

diff --git a/src/docs/upgrading.dox b/src/docs/upgrading.dox
index d9346faa170..c3294e34bab 100644
--- a/src/docs/upgrading.dox
+++ b/src/docs/upgrading.dox
@@ -9,6 +9,11 @@ The \c WT_DEADLOCK error return has been deprecated in favor of ::WT_ROLLBACK
 to clarify that WT_SESSION::rollback_transaction should be called; no program
 changes are required.
 </dd>
+<dt>Add a new WT_SESSION::transaction_range_pin method</dt>
+<dd>
+Add a new WT_SESSION::transaction_range_pin method that helps users identify
+when a session is keeping a transaction ID pinned for a long time.
+</dd>
 </dl>
 
 @section version_240 Upgrading to Version 2.4.0
diff --git a/src/include/wiredtiger.in b/src/include/wiredtiger.in
index c033ebc06e7..5b19d63c4a7 100644
--- a/src/include/wiredtiger.in
+++ b/src/include/wiredtiger.in
@@ -1359,6 +1359,22 @@ struct __wt_session {
 	 */
 	int __F(checkpoint)(WT_SESSION *session, const char *config);
 
+	/*!
+	 * Return the transaction ID range pinned by the session handle.
+	 *
+	 * The ID range is approximate and is calculated based on the oldest
+	 * ID needed for the active transaction in this session, compared
+	 * to the newest transaction in the system.
+	 *
+	 * @snippet ex_all.c Transaction range pin
+	 *
+	 * @param session the session handle
+	 * @param range the range of IDs pinned by this session. Zero if
+	 * there is no active transaction.
+	 * @errors
+	 */
+	int __F(transaction_range_pin)(WT_SESSION* session, uint64_t *range);
+
 	/*! @} */
 };
 
diff --git a/src/session/session_api.c b/src/session/session_api.c
index 092bcad3f73..3fb1d444d9d 100644
--- a/src/session/session_api.c
+++ b/src/session/session_api.c
@@ -772,6 +772,30 @@ err:	API_END_RET(session, ret);
 }
 
 /*
+ * __session_transaction_range_pin --
+ *	WT_SESSION->transaction_range_pin method.
+ */
+static int
+__session_transaction_range_pin(WT_SESSION *wt_session, uint64_t *prange)
+{
+	WT_SESSION_IMPL *session;
+	WT_TXN_STATE *txn_state;
+
+	session = (WT_SESSION_IMPL *)wt_session;
+
+	*prange = 0;
+	txn_state = WT_SESSION_TXN_STATE(session);
+	if (txn_state->snap_min == 0 && txn_state->id == 0)
+		return (0);
+
+	*prange = S2C(session)->txn_global.current -
+	    WT_MIN(txn_state->snap_min, txn_state->id);
+
+	return (0);
+
+}
+
+/*
  * __session_checkpoint --
  *	WT_SESSION->checkpoint method.
  */
@@ -916,7 +940,8 @@ __wt_open_session(WT_CONNECTION_IMPL *conn,
 		__session_begin_transaction,
 		__session_commit_transaction,
 		__session_rollback_transaction,
-		__session_checkpoint
+		__session_checkpoint,
+		__session_transaction_range_pin
 	};
 	WT_DECL_RET;
 	WT_SESSION_IMPL *session, *session_ret;