@@ -115,13 +115,15 @@ func transfer(id int, cCommits chan int, cAborts chan int, wg *sync.WaitGroup) {
115115 var nCommits = 0
116116 var myCommits = 0
117117
118- conn1 , err := pgx .Connect (cfg1 )
118+ var conn [2 ]* pgx.Conn
119+
120+ conn [0 ], err = pgx .Connect (cfg1 )
119121 checkErr (err )
120- defer conn1 .Close ()
122+ defer conn [ 0 ] .Close ()
121123
122- conn2 , err : =pgx .Connect (cfg2 )
124+ conn [ 1 ] , err = pgx .Connect (cfg2 )
123125 checkErr (err )
124- defer conn2 .Close ()
126+ defer conn [ 1 ] .Close ()
125127
126128 start := time .Now ()
127129 for myCommits < N_ITERATIONS {
@@ -130,23 +132,43 @@ func transfer(id int, cCommits chan int, cAborts chan int, wg *sync.WaitGroup) {
130132 account1 := rand .Intn (N_ACCOUNTS )
131133 account2 := rand .Intn (N_ACCOUNTS )
132134
133- xid = execQuery (conn1 , "select dtm_begin_transaction(2)" )
134- exec (conn2 , "select dtm_join_transaction($1)" , xid )
135-
136- // start transaction
137- exec (conn1 , "begin transaction isolation level " + ISOLATION_LEVEL )
138- exec (conn2 , "begin transaction isolation level " + ISOLATION_LEVEL )
139-
140- ok1 := execUpdate (conn1 , "update t set v = v + $1 where u=$2" , amount , account1 )
141- ok2 := execUpdate (conn2 , "update t set v = v - $1 where u=$2" , amount , account2 )
142- if ! ok1 || ! ok2 {
143- exec (conn1 , "rollback" )
144- exec (conn2 , "rollback" )
145- nAborts += 1
135+ src := conn [rand .Intn (2 )]
136+ dst := conn [rand .Intn (2 )]
137+
138+ if src == dst {
139+ // local transaction
140+ exec (src , "begin transaction isolation level " + ISOLATION_LEVEL )
141+ ok1 := execUpdate (src , "update t set v = v - $1 where u=$2" , amount , account1 )
142+ ok2 := execUpdate (src , "update t set v = v + $1 where u=$2" , amount , account2 )
143+ if ! ok1 || ! ok2 {
144+ exec (src , "rollback" )
145+ nAborts += 1
146+ } else {
147+ exec (src , "commit" )
148+ nCommits += 1
149+ myCommits += 1
150+ }
146151 } else {
147- commit (conn1 , conn2 )
148- nCommits += 1
149- myCommits += 1
152+ // global transaction
153+ xid = execQuery (src , "select dtm_begin_transaction(2)" )
154+ exec (dst , "select dtm_join_transaction($1)" , xid )
155+
156+ // start transaction
157+ exec (src , "begin transaction isolation level " + ISOLATION_LEVEL )
158+ exec (dst , "begin transaction isolation level " + ISOLATION_LEVEL )
159+
160+ ok1 := execUpdate (src , "update t set v = v - $1 where u=$2" , amount , account1 )
161+ ok2 := execUpdate (dst , "update t set v = v + $1 where u=$2" , amount , account2 )
162+
163+ if ! ok1 || ! ok2 {
164+ exec (src , "rollback" )
165+ exec (dst , "rollback" )
166+ nAborts += 1
167+ } else {
168+ commit (src , dst )
169+ nCommits += 1
170+ myCommits += 1
171+ }
150172 }
151173
152174 if time .Since (start ).Seconds () > 1 {
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