1. Additional fix against ERROR: Child itemid marked as unused

   in CommitTransaction().
2. Changes in GetSnapshotData().

diff --git a/src/backend/access/transam/xact.c b/src/backend/access/transam/xact.c
index 6884e635904fce8e6d174c7797d476763e321b72..6bde05733ac829b51776bfc4cc8ca09a4f4f7f41 100644 (file)
--- a/src/backend/access/transam/xact.c
+++ b/src/backend/access/transam/xact.c
@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *       $Header: /cvsroot/pgsql/src/backend/access/transam/xact.c,v 1.38 1999/06/03 04:41:41 vadim Exp $
+ *       $Header: /cvsroot/pgsql/src/backend/access/transam/xact.c,v 1.39 1999/06/03 13:33:12 vadim Exp $
  *
  * NOTES
  *             Transaction aborts can now occur two ways:
@@ -646,18 +646,6 @@ RecordTransactionCommit()
        FlushBufferPool(!TransactionFlushEnabled());
        if (leak)
                ResetBufferPool();
-
-       /*
-        * Let others know about no transaction in progress.
-        * Note that this must be done _before_ releasing locks
-        * we hold or bad (too high) XmaxRecent value might be
-        * used by vacuum.
-        */
-       if (MyProc != (PROC *) NULL)
-       {
-               MyProc->xid = InvalidTransactionId;
-               MyProc->xmin = InvalidTransactionId;
-       }
 }
 
 
@@ -950,6 +938,28 @@ CommitTransaction()
        DestroyNoNameRels();
        AtEOXact_portals();
        RecordTransactionCommit();
+
+       /*
+        * Let others know about no transaction in progress by me.
+        * Note that this must be done _before_ releasing locks we hold 
+        * and SpinAcquire(ShmemIndexLock) is required - or bad (too high) 
+        * XmaxRecent value might be used by vacuum: UPDATE with xid 0 is 
+        * blocked by xid 1' UPDATE, xid 1 is doing commit while xid 2 
+        * gets snapshot - if xid 2' GetSnapshotData sees xid 1 as running
+        * then it must see xid 0 as running as well or XmaxRecent = 1
+        * might be used by concurrent vacuum causing
+        *         ERROR:  Child itemid marked as unused
+        * This bug was reported by Hiroshi Inoue and I was able to reproduce
+        * it with 3 sessions and gdb.  - vadim 06/03/99
+        */
+       if (MyProc != (PROC *) NULL)
+       {
+               SpinAcquire(ShmemIndexLock);
+               MyProc->xid = InvalidTransactionId;
+               MyProc->xmin = InvalidTransactionId;
+               SpinRelease(ShmemIndexLock);
+       }
+
        RelationPurgeLocalRelation(true);
        AtCommit_Cache();
        AtCommit_Locks();

diff --git a/src/backend/storage/ipc/shmem.c b/src/backend/storage/ipc/shmem.c
index eafe53b0bb13de4cfd788f113cfecb36b6acf085..04cfa1a812eaa49c9e9ecf95f2c707fab0e35431 100644 (file)
--- a/src/backend/storage/ipc/shmem.c
+++ b/src/backend/storage/ipc/shmem.c
@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *       $Header: /cvsroot/pgsql/src/backend/storage/ipc/shmem.c,v 1.40 1999/05/25 16:11:11 momjian Exp $
+ *       $Header: /cvsroot/pgsql/src/backend/storage/ipc/shmem.c,v 1.41 1999/06/03 13:33:13 vadim Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -593,6 +593,10 @@ ShmemInitStruct(char *name, unsigned long size, bool *foundPtr)
  *
  * Strange place for this func, but we have to lookup process data structures
  * for all running backends. - vadim 11/26/96
+ *
+ * We should keep all PROC structs not in ShmemIndex - this is too
+ * general hash table...
+ *
  */
 bool
 TransactionIdIsInProgress(TransactionId xid)
@@ -648,10 +652,7 @@ GetSnapshotData(bool serializable)
 
        snapshot->xip = (TransactionId *) malloc(have * sizeof(TransactionId));
        snapshot->xmin = cid;
-       if (serializable)
-               snapshot->xmax = cid;
-       else
-               ReadNewTransactionId(&(snapshot->xmax));
+       ReadNewTransactionId(&(snapshot->xmax));
 
        SpinAcquire(ShmemIndexLock);
 
@@ -660,8 +661,10 @@ GetSnapshotData(bool serializable)
        {
                if (result == (ShmemIndexEnt *) TRUE)
                {
-                       if (MyProc->xmin == InvalidTransactionId)
+                       if (serializable)
                                MyProc->xmin = snapshot->xmin;
+                       /* Serializable snapshot must be computed before any other... */
+                       Assert(MyProc->xmin != InvalidTransactionId);
                        SpinRelease(ShmemIndexLock);
                        snapshot->xcnt = count;
                        return snapshot;
@@ -670,13 +673,24 @@ GetSnapshotData(bool serializable)
                        strncmp(result->key, "PID ", 4) != 0)
                        continue;
                proc = (PROC *) MAKE_PTR(result->location);
-               xid = proc->xid;                /* we don't use spin-locking in xact.c ! */
-               if (proc == MyProc || xid < FirstTransactionId)
+               /* 
+                * We don't use spin-locking when changing proc->xid 
+                * in GetNewTransactionId() and in AbortTransaction() !..
+                */
+               xid = proc->xid;
+               if (proc == MyProc || 
+                       xid < FirstTransactionId || xid >= snapshot->xmax)
+               {
+                       /*
+                        * Seems that there is no sense to store xid >= snapshot->xmax
+                        * (what we got from ReadNewTransactionId above) in snapshot->xip 
+                        * - we just assume that all xacts with such xid-s are running 
+                        * and may be ignored.
+                        */
                        continue;
+               }
                if (xid < snapshot->xmin)
                        snapshot->xmin = xid;
-               else if (xid > snapshot->xmax)
-                       snapshot->xmax = xid;
                if (have == 0)
                {
                        snapshot->xip = (TransactionId *) realloc(snapshot->xip,
@@ -712,7 +726,7 @@ GetXmaxRecent(TransactionId *XmaxRecent)
 
        Assert(ShmemIndex);
 
-       ReadNewTransactionId(XmaxRecent);
+       *XmaxRecent = GetCurrentTransactionId();
 
        SpinAcquire(ShmemIndexLock);
 
@@ -728,7 +742,7 @@ GetXmaxRecent(TransactionId *XmaxRecent)
                        strncmp(result->key, "PID ", 4) != 0)
                        continue;
                proc = (PROC *) MAKE_PTR(result->location);
-               xmin = proc->xmin;              /* we don't use spin-locking in xact.c ! */
+               xmin = proc->xmin;      /* we don't use spin-locking in AbortTransaction() ! */
                if (proc == MyProc || xmin < FirstTransactionId)
                        continue;
                if (xmin < *XmaxRecent)