[Tarantool-patches] [PATCH v4 03/12] txm: save does_require_old_tuple flag in txn_stmt

[Aleksandr Lyapunov <alyapunov@tarantool.org>]

That flag is needed for transactional conflict manager - if any
other transaction commits a replacement of old_tuple before
current one and the flag is set - the current transaction will
be aborted.
For example REPLACE just replaces a key, no matter what tuple
lays in the index and thus does_require_old_tuple = false.
In contrast, UPDATE makes new tuple using old_tuple and thus
the statement will require old_tuple (does_require_old_tuple = true).
INSERT also does_require_old_tuple = true because it requires
old_tuple to be NULL.

Part of #4897
---
 src/box/memtx_space.c | 17 +++++++++++++++++
 src/box/txn.c         | 53 ++++++++++++++++++++++++++++++++++-----------------
 src/box/txn.h         | 13 +++++++++++++
 3 files changed, 65 insertions(+), 18 deletions(-)

diff --git a/src/box/memtx_space.c b/src/box/memtx_space.c
index d30ce44..7624130 100644
--- a/src/box/memtx_space.c
+++ b/src/box/memtx_space.c
@@ -316,6 +316,10 @@ memtx_space_execute_replace(struct space *space, struct txn *txn,
 	if (stmt->new_tuple == NULL)
 		return -1;
 	tuple_ref(stmt->new_tuple);
+
+	if (mode == DUP_INSERT)
+		stmt->does_require_old_tuple = true;
+
 	if (memtx_space->replace(space, NULL, stmt->new_tuple,
 				 mode, &stmt->old_tuple) != 0)
 		return -1;
@@ -342,6 +346,13 @@ memtx_space_execute_delete(struct space *space, struct txn *txn,
 	struct tuple *old_tuple;
 	if (index_get(pk, key, part_count, &old_tuple) != 0)
 		return -1;
+
+	/*
+	 * We have to delete exactly old_tuple just because we return it as
+	 * a result.
+	 */
+	stmt->does_require_old_tuple = true;
+
 	if (old_tuple != NULL &&
 	    memtx_space->replace(space, old_tuple, NULL,
 				 DUP_REPLACE_OR_INSERT, &stmt->old_tuple) != 0)
@@ -390,6 +401,9 @@ memtx_space_execute_update(struct space *space, struct txn *txn,
 	if (stmt->new_tuple == NULL)
 		return -1;
 	tuple_ref(stmt->new_tuple);
+
+	stmt->does_require_old_tuple = true;
+
 	if (memtx_space->replace(space, old_tuple, stmt->new_tuple,
 				 DUP_REPLACE, &stmt->old_tuple) != 0)
 		return -1;
@@ -496,6 +510,9 @@ memtx_space_execute_upsert(struct space *space, struct txn *txn,
 			stmt->new_tuple = NULL;
 		}
 	}
+
+	stmt->does_require_old_tuple = true;
+
 	/*
 	 * It's OK to use DUP_REPLACE_OR_INSERT: we don't risk
 	 * inserting a new tuple if the old one exists, since
diff --git a/src/box/txn.c b/src/box/txn.c
index 093808a..d9fbb51 100644
--- a/src/box/txn.c
+++ b/src/box/txn.c
@@ -109,6 +109,7 @@ txn_stmt_new(struct region *region)
 	stmt->engine_savepoint = NULL;
 	stmt->row = NULL;
 	stmt->has_triggers = false;
+	stmt->does_require_old_tuple = false;
 	return stmt;
 }
 
@@ -351,27 +352,43 @@ txn_commit_stmt(struct txn *txn, struct request *request)
 	 * - perhaps we should run triggers even for deletes which
 	 *   doesn't find any rows
 	 */
-	if (stmt->space != NULL && !rlist_empty(&stmt->space->on_replace) &&
-	    stmt->space->run_triggers && (stmt->old_tuple || stmt->new_tuple)) {
-		int rc = 0;
-		if(!space_is_temporary(stmt->space)) {
-			rc = trigger_run(&stmt->space->on_replace, txn);
-		} else {
+	if (stmt->space != NULL && stmt->space->run_triggers &&
+	    (stmt->old_tuple || stmt->new_tuple)) {
+		if (!rlist_empty(&stmt->space->before_replace)) {
 			/*
-			 * There is no row attached to txn_stmt for
-			 * temporary spaces, since DML operations on them
-			 * are not written to WAL. Fake a row to pass operation
-			 * type to lua on_replace triggers.
+			 * Triggers see old_tuple and that tuple
+			 * must remain the same
 			 */
-			assert(stmt->row == NULL);
-			struct xrow_header temp_header;
-			temp_header.type = request->type;
-			stmt->row = &temp_header;
-			rc = trigger_run(&stmt->space->on_replace, txn);
-			stmt->row = NULL;
+			stmt->does_require_old_tuple = true;
+		}
+		if (!rlist_empty(&stmt->space->on_replace)) {
+			/*
+			 * Triggers see old_tuple and that tuple
+			 * must remain the same
+			 */
+			stmt->does_require_old_tuple = true;
+
+			int rc = 0;
+			if(!space_is_temporary(stmt->space)) {
+				rc = trigger_run(&stmt->space->on_replace, txn);
+			} else {
+				/*
+				 * There is no row attached to txn_stmt for
+				 * temporary spaces, since DML operations on
+				 * them are not written to WAL.
+				 * Fake a row to pass operation type to lua
+				 * on_replace triggers.
+				 */
+				assert(stmt->row == NULL);
+				struct xrow_header temp_header;
+				temp_header.type = request->type;
+				stmt->row = &temp_header;
+				rc = trigger_run(&stmt->space->on_replace, txn);
+				stmt->row = NULL;
+			}
+			if (rc != 0)
+				goto fail;
 		}
-		if (rc != 0)
-			goto fail;
 	}
 	--txn->in_sub_stmt;
 	return 0;
diff --git a/src/box/txn.h b/src/box/txn.h
index 35e1ab9..007284f 100644
--- a/src/box/txn.h
+++ b/src/box/txn.h
@@ -175,6 +175,19 @@ struct txn_stmt {
 	struct xrow_header *row;
 	/** on_commit and/or on_rollback list is not empty. */
 	bool has_triggers;
+	/**
+	 * Whether the stmt requires to replace exactly old_tuple (member).
+	 * That flag is needed for transactional conflict manager - if any
+	 * other transaction commits a replacement of old_tuple before current
+	 * one and the flag is set - the current transaction will be aborted.
+	 * For example REPLACE just replaces a key, no matter what tuple
+	 * lays in the index and thus does_require_old_tuple = false.
+	 * In contrast, UPDATE makes new tuple using old_tuple and thus
+	 * the statement will require old_tuple (does_require_old_tuple = true).
+	 * INSERT also does_require_old_tuple = true because it requires
+	 * old_tuple to be NULL.
+	 */
+	bool does_require_old_tuple;
 	/** Commit/rollback triggers associated with this statement. */
 	struct rlist on_commit;
 	struct rlist on_rollback;
-- 
2.7.4