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-rw-r--r--src/backend/access/heap/heapam.c42
-rw-r--r--src/backend/access/transam/multixact.c18
-rw-r--r--src/include/access/multixact.h4
3 files changed, 51 insertions, 13 deletions
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 7217e96d6a3..a04763207f0 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -190,9 +190,6 @@ static const int MultiXactStatusLock[MaxMultiXactStatus + 1] =
/* Get the LockTupleMode for a given MultiXactStatus */
#define TUPLOCK_from_mxstatus(status) \
(MultiXactStatusLock[(status)])
-/* Get the is_update bit for a given MultiXactStatus */
-#define ISUPDATE_from_mxstatus(status) \
- ((status) > MultiXactStatusForUpdate)
/* ----------------------------------------------------------------
* heap support routines
@@ -2589,6 +2586,27 @@ compute_infobits(uint16 infomask, uint16 infomask2)
}
/*
+ * Given two versions of the same t_infomask for a tuple, compare them and
+ * return whether the relevant status for a tuple Xmax has changed. This is
+ * used after a buffer lock has been released and reacquired: we want to ensure
+ * that the tuple state continues to be the same it was when we previously
+ * examined it.
+ *
+ * Note the Xmax field itself must be compared separately.
+ */
+static inline bool
+xmax_infomask_changed(uint16 new_infomask, uint16 old_infomask)
+{
+ const uint16 interesting =
+ HEAP_XMAX_IS_MULTI | HEAP_XMAX_LOCK_ONLY | HEAP_LOCK_MASK;
+
+ if ((new_infomask & interesting) != (old_infomask & interesting))
+ return true;
+
+ return false;
+}
+
+/*
* heap_delete - delete a tuple
*
* NB: do not call this directly unless you are prepared to deal with
@@ -2725,7 +2743,7 @@ l1:
* update this tuple before we get to this point. Check for xmax
* change, and start over if so.
*/
- if (!(tp.t_data->t_infomask & HEAP_XMAX_IS_MULTI) ||
+ if (xmax_infomask_changed(tp.t_data->t_infomask, infomask) ||
!TransactionIdEquals(HeapTupleHeaderGetRawXmax(tp.t_data),
xwait))
goto l1;
@@ -2751,7 +2769,7 @@ l1:
* other xact could update this tuple before we get to this point.
* Check for xmax change, and start over if so.
*/
- if ((tp.t_data->t_infomask & HEAP_XMAX_IS_MULTI) ||
+ if (xmax_infomask_changed(tp.t_data->t_infomask, infomask) ||
!TransactionIdEquals(HeapTupleHeaderGetRawXmax(tp.t_data),
xwait))
goto l1;
@@ -3278,7 +3296,7 @@ l2:
* update this tuple before we get to this point. Check for xmax
* change, and start over if so.
*/
- if (!(oldtup.t_data->t_infomask & HEAP_XMAX_IS_MULTI) ||
+ if (xmax_infomask_changed(oldtup.t_data->t_infomask, infomask) ||
!TransactionIdEquals(HeapTupleHeaderGetRawXmax(oldtup.t_data),
xwait))
goto l2;
@@ -3332,7 +3350,7 @@ l2:
* recheck the locker; if someone else changed the tuple while
* we weren't looking, start over.
*/
- if ((oldtup.t_data->t_infomask & HEAP_XMAX_IS_MULTI) ||
+ if (xmax_infomask_changed(oldtup.t_data->t_infomask, infomask) ||
!TransactionIdEquals(
HeapTupleHeaderGetRawXmax(oldtup.t_data),
xwait))
@@ -3353,7 +3371,7 @@ l2:
* some other xact could update this tuple before we get to
* this point. Check for xmax change, and start over if so.
*/
- if ((oldtup.t_data->t_infomask & HEAP_XMAX_IS_MULTI) ||
+ if (xmax_infomask_changed(oldtup.t_data->t_infomask, infomask) ||
!TransactionIdEquals(
HeapTupleHeaderGetRawXmax(oldtup.t_data),
xwait))
@@ -4357,7 +4375,7 @@ l3:
* over.
*/
LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE);
- if (!(tuple->t_data->t_infomask & HEAP_XMAX_IS_MULTI) ||
+ if (xmax_infomask_changed(tuple->t_data->t_infomask, infomask) ||
!TransactionIdEquals(HeapTupleHeaderGetRawXmax(tuple->t_data),
xwait))
{
@@ -4376,7 +4394,7 @@ l3:
LockBuffer(*buffer, BUFFER_LOCK_EXCLUSIVE);
/* if the xmax changed in the meantime, start over */
- if ((tuple->t_data->t_infomask & HEAP_XMAX_IS_MULTI) ||
+ if (xmax_infomask_changed(tuple->t_data->t_infomask, infomask) ||
!TransactionIdEquals(
HeapTupleHeaderGetRawXmax(tuple->t_data),
xwait))
@@ -4444,7 +4462,7 @@ l3:
* could update this tuple before we get to this point. Check
* for xmax change, and start over if so.
*/
- if (!(tuple->t_data->t_infomask & HEAP_XMAX_IS_MULTI) ||
+ if (xmax_infomask_changed(tuple->t_data->t_infomask, infomask) ||
!TransactionIdEquals(
HeapTupleHeaderGetRawXmax(tuple->t_data),
xwait))
@@ -4500,7 +4518,7 @@ l3:
* some other xact could update this tuple before we get to
* this point. Check for xmax change, and start over if so.
*/
- if ((tuple->t_data->t_infomask & HEAP_XMAX_IS_MULTI) ||
+ if (xmax_infomask_changed(tuple->t_data->t_infomask, infomask) ||
!TransactionIdEquals(
HeapTupleHeaderGetRawXmax(tuple->t_data),
xwait))
diff --git a/src/backend/access/transam/multixact.c b/src/backend/access/transam/multixact.c
index d4ad6787a59..459f59cb4e0 100644
--- a/src/backend/access/transam/multixact.c
+++ b/src/backend/access/transam/multixact.c
@@ -457,7 +457,7 @@ MultiXactIdExpand(MultiXactId multi, TransactionId xid, MultiXactStatus status)
for (i = 0, j = 0; i < nmembers; i++)
{
if (TransactionIdIsInProgress(members[i].xid) ||
- ((members[i].status > MultiXactStatusForUpdate) &&
+ (ISUPDATE_from_mxstatus(members[i].status) &&
TransactionIdDidCommit(members[i].xid)))
{
newMembers[j].xid = members[i].xid;
@@ -713,6 +713,22 @@ MultiXactIdCreateFromMembers(int nmembers, MultiXactMember *members)
return multi;
}
+ /* Verify that there is a single update Xid among the given members. */
+ {
+ int i;
+ bool has_update = false;
+
+ for (i = 0; i < nmembers; i++)
+ {
+ if (ISUPDATE_from_mxstatus(members[i].status))
+ {
+ if (has_update)
+ elog(ERROR, "new multixact has more than one updating member");
+ has_update = true;
+ }
+ }
+ }
+
/*
* Assign the MXID and offsets range to use, and make sure there is space
* in the OFFSETs and MEMBERs files. NB: this routine does
diff --git a/src/include/access/multixact.h b/src/include/access/multixact.h
index 9729f275089..1f048e8ed5d 100644
--- a/src/include/access/multixact.h
+++ b/src/include/access/multixact.h
@@ -48,6 +48,10 @@ typedef enum
#define MaxMultiXactStatus MultiXactStatusUpdate
+/* does a status value correspond to a tuple update? */
+#define ISUPDATE_from_mxstatus(status) \
+ ((status) > MultiXactStatusForUpdate)
+
typedef struct MultiXactMember
{
generated by cgit v1.2.3 (git 2.25.1) at 2025-06-02 07:54:52 +0000