@@ -55,8 +55,6 @@ typedef struct
5555
5656#define DTM_SHMEM_SIZE (1024*1024)
5757#define DTM_HASH_SIZE 1003
58- #define XTM_CONNECT_ATTEMPTS 10
59-
6058
6159void _PG_init (void );
6260void _PG_fini (void );
@@ -79,7 +77,7 @@ static TransactionId DtmGetGlobalTransactionId(void);
7977static bool TransactionIdIsInSnapshot (TransactionId xid ,Snapshot snapshot );
8078static bool TransactionIdIsInDoubt (TransactionId xid );
8179
82- static void dtm_shmem_startup (void );
80+ static void DtmShmemStartup (void );
8381
8482static shmem_startup_hook_type prev_shmem_startup_hook ;
8583static HTAB * xid_in_doubt ;
@@ -121,18 +119,27 @@ static void DumpSnapshot(Snapshot s, char *name)
121119XTM_INFO ("%s\n" ,buf );
122120}
123121
122+ /* In snapshots provided by DTMD xip array is sorted, so we can use bsearch */
124123static bool TransactionIdIsInSnapshot (TransactionId xid ,Snapshot snapshot )
125124{
126125return xid >=snapshot -> xmax
127126|| bsearch (& xid ,snapshot -> xip ,snapshot -> xcnt ,sizeof (TransactionId ),xidComparator )!= NULL ;
128127}
129128
130-
129+ /* Transaction is considered as in-doubt if it is globally committed by DTMD but local commit is not yet completed.
130+ * It can happen because we report DTMD about transaction commit in SetTransactionStatus, which is called inside commit
131+ * after saving transaction state in WAL but before releasing locks. So DTMD can include this transaction in snapshot
132+ * before local commit is completed and transaction is marked as completed in local CLOG.
133+ *
134+ * We use xid_in_doubt hash table to mark transactions which are "precommitted". Entry is inserted in hash table
135+ * before seding status to DTMD and removed after receving response from DTMD and setting transaction status in local CLOG.
136+ * So information about transaction should always present either in xid_in_doubt either in CLOG.
137+ */
131138static bool TransactionIdIsInDoubt (TransactionId xid )
132139{
133140bool inDoubt ;
134141
135- if (!TransactionIdIsInSnapshot (xid ,& DtmSnapshot )) {
142+ if (!TransactionIdIsInSnapshot (xid ,& DtmSnapshot )) {/* transaction is completed according to the snaphot */
136143LWLockAcquire (dtm -> hashLock ,LW_SHARED );
137144inDoubt = hash_search (xid_in_doubt ,& xid ,HASH_FIND ,NULL )!= NULL ;
138145LWLockRelease (dtm -> hashLock );
@@ -740,7 +747,7 @@ _PG_init(void)
740747 * Install hooks.
741748 */
742749prev_shmem_startup_hook = shmem_startup_hook ;
743- shmem_startup_hook = dtm_shmem_startup ;
750+ shmem_startup_hook = DtmShmemStartup ;
744751}
745752
746753/*
@@ -753,7 +760,7 @@ _PG_fini(void)
753760}
754761
755762
756- static void dtm_shmem_startup (void )
763+ static void DtmShmemStartup (void )
757764{
758765if (prev_shmem_startup_hook ) {
759766prev_shmem_startup_hook ();