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-rw-r--r--src/backend/access/heap/heapam.c6
-rw-r--r--src/backend/access/nbtree/nbtinsert.c11
-rw-r--r--src/backend/catalog/catalog.c7
-rw-r--r--src/backend/catalog/index.c7
-rw-r--r--src/backend/executor/execMain.c12
-rw-r--r--src/backend/storage/ipc/procarray.c4
-rw-r--r--src/backend/utils/adt/ri_triggers.c10
-rw-r--r--src/backend/utils/time/tqual.c89
-rw-r--r--src/include/utils/tqual.h117
9 files changed, 145 insertions, 118 deletions
diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index d46308863fe..367831a515a 100644
--- a/src/backend/access/heap/heapam.c
+++ b/src/backend/access/heap/heapam.c
@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/access/heap/heapam.c,v 1.228 2007/02/09 03:35:33 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/access/heap/heapam.c,v 1.229 2007/03/25 19:45:13 tgl Exp $
*
*
* INTERFACE ROUTINES
@@ -1706,7 +1706,7 @@ l1:
if (crosscheck != InvalidSnapshot && result == HeapTupleMayBeUpdated)
{
/* Perform additional check for serializable RI updates */
- if (!HeapTupleSatisfiesSnapshot(tp.t_data, crosscheck, buffer))
+ if (!HeapTupleSatisfiesVisibility(&tp, crosscheck, buffer))
result = HeapTupleUpdated;
}
@@ -2025,7 +2025,7 @@ l2:
if (crosscheck != InvalidSnapshot && result == HeapTupleMayBeUpdated)
{
/* Perform additional check for serializable RI updates */
- if (!HeapTupleSatisfiesSnapshot(oldtup.t_data, crosscheck, buffer))
+ if (!HeapTupleSatisfiesVisibility(&oldtup, crosscheck, buffer))
result = HeapTupleUpdated;
}
diff --git a/src/backend/access/nbtree/nbtinsert.c b/src/backend/access/nbtree/nbtinsert.c
index d2992374e97..c1671ce333c 100644
--- a/src/backend/access/nbtree/nbtinsert.c
+++ b/src/backend/access/nbtree/nbtinsert.c
@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/access/nbtree/nbtinsert.c,v 1.154 2007/03/05 14:13:12 neilc Exp $
+ * $PostgreSQL: pgsql/src/backend/access/nbtree/nbtinsert.c,v 1.155 2007/03/25 19:45:14 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -176,11 +176,14 @@ _bt_check_unique(Relation rel, IndexTuple itup, Relation heapRel,
{
TupleDesc itupdesc = RelationGetDescr(rel);
int natts = rel->rd_rel->relnatts;
+ SnapshotData SnapshotDirty;
OffsetNumber maxoff;
Page page;
BTPageOpaque opaque;
Buffer nbuf = InvalidBuffer;
+ InitDirtySnapshot(SnapshotDirty);
+
page = BufferGetPage(buf);
opaque = (BTPageOpaque) PageGetSpecialPointer(page);
maxoff = PageGetMaxOffsetNumber(page);
@@ -232,13 +235,13 @@ _bt_check_unique(Relation rel, IndexTuple itup, Relation heapRel,
/* okay, we gotta fetch the heap tuple ... */
curitup = (IndexTuple) PageGetItem(page, curitemid);
htup.t_self = curitup->t_tid;
- if (heap_fetch(heapRel, SnapshotDirty, &htup, &hbuffer,
+ if (heap_fetch(heapRel, &SnapshotDirty, &htup, &hbuffer,
true, NULL))
{
/* it is a duplicate */
TransactionId xwait =
- (TransactionIdIsValid(SnapshotDirty->xmin)) ?
- SnapshotDirty->xmin : SnapshotDirty->xmax;
+ (TransactionIdIsValid(SnapshotDirty.xmin)) ?
+ SnapshotDirty.xmin : SnapshotDirty.xmax;
ReleaseBuffer(hbuffer);
diff --git a/src/backend/catalog/catalog.c b/src/backend/catalog/catalog.c
index 4d4a851130b..049d216a787 100644
--- a/src/backend/catalog/catalog.c
+++ b/src/backend/catalog/catalog.c
@@ -10,7 +10,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/catalog/catalog.c,v 1.69 2007/01/05 22:19:24 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/catalog/catalog.c,v 1.70 2007/03/25 19:45:14 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -361,10 +361,13 @@ Oid
GetNewOidWithIndex(Relation relation, Relation indexrel)
{
Oid newOid;
+ SnapshotData SnapshotDirty;
IndexScanDesc scan;
ScanKeyData key;
bool collides;
+ InitDirtySnapshot(SnapshotDirty);
+
/* Generate new OIDs until we find one not in the table */
do
{
@@ -377,7 +380,7 @@ GetNewOidWithIndex(Relation relation, Relation indexrel)
/* see notes above about using SnapshotDirty */
scan = index_beginscan(relation, indexrel,
- SnapshotDirty, 1, &key);
+ &SnapshotDirty, 1, &key);
collides = HeapTupleIsValid(index_getnext(scan, ForwardScanDirection));
diff --git a/src/backend/catalog/index.c b/src/backend/catalog/index.c
index 092a8d8de38..b660a94aabc 100644
--- a/src/backend/catalog/index.c
+++ b/src/backend/catalog/index.c
@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/catalog/index.c,v 1.280 2007/03/03 20:08:41 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/catalog/index.c,v 1.281 2007/03/25 19:45:14 tgl Exp $
*
*
* INTERFACE ROUTINES
@@ -1828,10 +1828,11 @@ validate_index_heapscan(Relation heapRelation,
*/
if (indexInfo->ii_Unique)
{
- /* must hold a buffer lock to call HeapTupleSatisfiesNow */
+ /* must lock buffer to call HeapTupleSatisfiesVisibility */
LockBuffer(scan->rs_cbuf, BUFFER_LOCK_SHARE);
- if (HeapTupleSatisfiesNow(heapTuple->t_data, scan->rs_cbuf))
+ if (HeapTupleSatisfiesVisibility(heapTuple, SnapshotNow,
+ scan->rs_cbuf))
check_unique = true;
else
check_unique = false;
diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index 239656dd06b..b2f7159e8c0 100644
--- a/src/backend/executor/execMain.c
+++ b/src/backend/executor/execMain.c
@@ -26,7 +26,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/executor/execMain.c,v 1.290 2007/03/06 02:06:13 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/executor/execMain.c,v 1.291 2007/03/25 19:45:14 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -1893,6 +1893,7 @@ EvalPlanQual(EState *estate, Index rti,
Relation relation;
HeapTupleData tuple;
HeapTuple copyTuple = NULL;
+ SnapshotData SnapshotDirty;
bool endNode;
Assert(rti != 0);
@@ -1925,12 +1926,13 @@ EvalPlanQual(EState *estate, Index rti,
*
* Loop here to deal with updated or busy tuples
*/
+ InitDirtySnapshot(SnapshotDirty);
tuple.t_self = *tid;
for (;;)
{
Buffer buffer;
- if (heap_fetch(relation, SnapshotDirty, &tuple, &buffer, true, NULL))
+ if (heap_fetch(relation, &SnapshotDirty, &tuple, &buffer, true, NULL))
{
/*
* If xmin isn't what we're expecting, the slot must have been
@@ -1948,17 +1950,17 @@ EvalPlanQual(EState *estate, Index rti,
}
/* otherwise xmin should not be dirty... */
- if (TransactionIdIsValid(SnapshotDirty->xmin))
+ if (TransactionIdIsValid(SnapshotDirty.xmin))
elog(ERROR, "t_xmin is uncommitted in tuple to be updated");
/*
* If tuple is being updated by other transaction then we have to
* wait for its commit/abort.
*/
- if (TransactionIdIsValid(SnapshotDirty->xmax))
+ if (TransactionIdIsValid(SnapshotDirty.xmax))
{
ReleaseBuffer(buffer);
- XactLockTableWait(SnapshotDirty->xmax);
+ XactLockTableWait(SnapshotDirty.xmax);
continue; /* loop back to repeat heap_fetch */
}
diff --git a/src/backend/storage/ipc/procarray.c b/src/backend/storage/ipc/procarray.c
index d2d39770c5b..12e61c89263 100644
--- a/src/backend/storage/ipc/procarray.c
+++ b/src/backend/storage/ipc/procarray.c
@@ -23,7 +23,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/storage/ipc/procarray.c,v 1.22 2007/03/23 03:16:39 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/storage/ipc/procarray.c,v 1.23 2007/03/25 19:45:14 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -484,7 +484,7 @@ GetOldestXmin(bool allDbs, bool ignoreVacuum)
* limited cache area for subxact XIDs, full information may not be
* available. If we find any overflowed subxid arrays, we have to mark
* the snapshot's subxid data as overflowed, and extra work will need to
- * be done to determine what's running (see XidInSnapshot() in tqual.c).
+ * be done to determine what's running (see XidInMVCCSnapshot() in tqual.c).
*
* We also update the following backend-global variables:
* TransactionXmin: the oldest xmin of any snapshot in use in the
diff --git a/src/backend/utils/adt/ri_triggers.c b/src/backend/utils/adt/ri_triggers.c
index 72200ced9dc..af363f4acff 100644
--- a/src/backend/utils/adt/ri_triggers.c
+++ b/src/backend/utils/adt/ri_triggers.c
@@ -15,7 +15,7 @@
*
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
*
- * $PostgreSQL: pgsql/src/backend/utils/adt/ri_triggers.c,v 1.92 2007/03/15 23:12:06 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/adt/ri_triggers.c,v 1.93 2007/03/25 19:45:14 tgl Exp $
*
* ----------
*/
@@ -277,11 +277,11 @@ RI_FKey_check(PG_FUNCTION_ARGS)
* We should not even consider checking the row if it is no longer valid,
* since it was either deleted (so the deferred check should be skipped)
* or updated (in which case only the latest version of the row should be
- * checked). Test its liveness with HeapTupleSatisfiesItself.
+ * checked). Test its liveness according to SnapshotSelf.
*
* NOTE: The normal coding rule is that one must acquire the buffer
- * content lock to call HeapTupleSatisfiesFOO. We can skip that here
- * because we know that AfterTriggerExecute just fetched the tuple
+ * content lock to call HeapTupleSatisfiesVisibility. We can skip that
+ * here because we know that AfterTriggerExecute just fetched the tuple
* successfully, so there cannot be a VACUUM compaction in progress on the
* page (either heap_fetch would have waited for the VACUUM, or the
* VACUUM's LockBufferForCleanup would be waiting for us to drop pin).
@@ -289,7 +289,7 @@ RI_FKey_check(PG_FUNCTION_ARGS)
* can be entitled to change its xmin/xmax.
*/
Assert(new_row_buf != InvalidBuffer);
- if (!HeapTupleSatisfiesItself(new_row->t_data, new_row_buf))
+ if (!HeapTupleSatisfiesVisibility(new_row, SnapshotSelf, new_row_buf))
return PointerGetDatum(NULL);
/*
diff --git a/src/backend/utils/time/tqual.c b/src/backend/utils/time/tqual.c
index 13cc211b5db..429005a843a 100644
--- a/src/backend/utils/time/tqual.c
+++ b/src/backend/utils/time/tqual.c
@@ -1,15 +1,14 @@
/*-------------------------------------------------------------------------
*
* tqual.c
- * POSTGRES "time" qualification code, ie, tuple visibility rules.
- *
- * The caller must hold at least a shared buffer context lock on the buffer
- * containing the tuple. (VACUUM FULL assumes it's sufficient to have
- * exclusive lock on the containing relation, instead.)
+ * POSTGRES "time qualification" code, ie, tuple visibility rules.
*
* NOTE: all the HeapTupleSatisfies routines will update the tuple's
* "hint" status bits if we see that the inserting or deleting transaction
- * has now committed or aborted.
+ * has now committed or aborted. If the hint bits are changed,
+ * SetBufferCommitInfoNeedsSave is called on the passed-in buffer.
+ * The caller must hold at least a shared buffer context lock on the buffer
+ * containing the tuple.
*
* NOTE: must check TransactionIdIsInProgress (which looks in PGPROC array)
* before TransactionIdDidCommit/TransactionIdDidAbort (which look in
@@ -32,7 +31,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/utils/time/tqual.c,v 1.101 2007/01/05 22:19:47 momjian Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/time/tqual.c,v 1.102 2007/03/25 19:45:14 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -47,16 +46,21 @@
#include "storage/procarray.h"
#include "utils/tqual.h"
+
+/* Static variables representing various special snapshot semantics */
+SnapshotData SnapshotNowData = {HeapTupleSatisfiesNow};
+SnapshotData SnapshotSelfData = {HeapTupleSatisfiesSelf};
+SnapshotData SnapshotAnyData = {HeapTupleSatisfiesAny};
+SnapshotData SnapshotToastData = {HeapTupleSatisfiesToast};
+
/*
* These SnapshotData structs are static to simplify memory allocation
* (see the hack in GetSnapshotData to avoid repeated malloc/free).
*/
-static SnapshotData SnapshotDirtyData;
-static SnapshotData SerializableSnapshotData;
-static SnapshotData LatestSnapshotData;
+static SnapshotData SerializableSnapshotData = {HeapTupleSatisfiesMVCC};
+static SnapshotData LatestSnapshotData = {HeapTupleSatisfiesMVCC};
/* Externally visible pointers to valid snapshots: */
-Snapshot SnapshotDirty = &SnapshotDirtyData;
Snapshot SerializableSnapshot = NULL;
Snapshot LatestSnapshot = NULL;
@@ -73,11 +77,11 @@ TransactionId RecentXmin = InvalidTransactionId;
TransactionId RecentGlobalXmin = InvalidTransactionId;
/* local functions */
-static bool XidInSnapshot(TransactionId xid, Snapshot snapshot);
+static bool XidInMVCCSnapshot(TransactionId xid, Snapshot snapshot);
/*
- * HeapTupleSatisfiesItself
+ * HeapTupleSatisfiesSelf
* True iff heap tuple is valid "for itself".
*
* Here, we consider the effects of:
@@ -101,7 +105,7 @@ static bool XidInSnapshot(TransactionId xid, Snapshot snapshot);
* Xmax is not committed))) that has not been committed
*/
bool
-HeapTupleSatisfiesItself(HeapTupleHeader tuple, Buffer buffer)
+HeapTupleSatisfiesSelf(HeapTupleHeader tuple, Snapshot snapshot, Buffer buffer)
{
if (!(tuple->t_infomask & HEAP_XMIN_COMMITTED))
{
@@ -278,7 +282,7 @@ HeapTupleSatisfiesItself(HeapTupleHeader tuple, Buffer buffer)
* that do catalog accesses. this is unfortunate, but not critical.
*/
bool
-HeapTupleSatisfiesNow(HeapTupleHeader tuple, Buffer buffer)
+HeapTupleSatisfiesNow(HeapTupleHeader tuple, Snapshot snapshot, Buffer buffer)
{
if (!(tuple->t_infomask & HEAP_XMIN_COMMITTED))
{
@@ -423,6 +427,16 @@ HeapTupleSatisfiesNow(HeapTupleHeader tuple, Buffer buffer)
}
/*
+ * HeapTupleSatisfiesAny
+ * Dummy "satisfies" routine: any tuple satisfies SnapshotAny.
+ */
+bool
+HeapTupleSatisfiesAny(HeapTupleHeader tuple, Snapshot snapshot, Buffer buffer)
+{
+ return true;
+}
+
+/*
* HeapTupleSatisfiesToast
* True iff heap tuple is valid as a TOAST row.
*
@@ -437,7 +451,8 @@ HeapTupleSatisfiesNow(HeapTupleHeader tuple, Buffer buffer)
* table.
*/
bool
-HeapTupleSatisfiesToast(HeapTupleHeader tuple, Buffer buffer)
+HeapTupleSatisfiesToast(HeapTupleHeader tuple, Snapshot snapshot,
+ Buffer buffer)
{
if (!(tuple->t_infomask & HEAP_XMIN_COMMITTED))
{
@@ -676,20 +691,22 @@ HeapTupleSatisfiesUpdate(HeapTupleHeader tuple, CommandId curcid,
* previous commands of this transaction
* changes made by the current command
*
- * This is essentially like HeapTupleSatisfiesItself as far as effects of
+ * This is essentially like HeapTupleSatisfiesSelf as far as effects of
* the current transaction and committed/aborted xacts are concerned.
* However, we also include the effects of other xacts still in progress.
*
- * Returns extra information in the global variable SnapshotDirty, namely
- * xids of concurrent xacts that affected the tuple. SnapshotDirty->xmin
- * is set to InvalidTransactionId if xmin is either committed good or
- * committed dead; or to xmin if that transaction is still in progress.
- * Similarly for SnapshotDirty->xmax.
+ * A special hack is that the passed-in snapshot struct is used as an
+ * output argument to return the xids of concurrent xacts that affected the
+ * tuple. snapshot->xmin is set to the tuple's xmin if that is another
+ * transaction that's still in progress; or to InvalidTransactionId if the
+ * tuple's xmin is committed good, committed dead, or my own xact. Similarly
+ * for snapshot->xmax and the tuple's xmax.
*/
bool
-HeapTupleSatisfiesDirty(HeapTupleHeader tuple, Buffer buffer)
+HeapTupleSatisfiesDirty(HeapTupleHeader tuple, Snapshot snapshot,
+ Buffer buffer)
{
- SnapshotDirty->xmin = SnapshotDirty->xmax = InvalidTransactionId;
+ snapshot->xmin = snapshot->xmax = InvalidTransactionId;
if (!(tuple->t_infomask & HEAP_XMIN_COMMITTED))
{
@@ -759,7 +776,7 @@ HeapTupleSatisfiesDirty(HeapTupleHeader tuple, Buffer buffer)
}
else if (TransactionIdIsInProgress(HeapTupleHeaderGetXmin(tuple)))
{
- SnapshotDirty->xmin = HeapTupleHeaderGetXmin(tuple);
+ snapshot->xmin = HeapTupleHeaderGetXmin(tuple);
/* XXX shouldn't we fall through to look at xmax? */
return true; /* in insertion by other */
}
@@ -805,7 +822,7 @@ HeapTupleSatisfiesDirty(HeapTupleHeader tuple, Buffer buffer)
if (TransactionIdIsInProgress(HeapTupleHeaderGetXmax(tuple)))
{
- SnapshotDirty->xmax = HeapTupleHeaderGetXmax(tuple);
+ snapshot->xmax = HeapTupleHeaderGetXmax(tuple);
return true;
}
@@ -832,8 +849,8 @@ HeapTupleSatisfiesDirty(HeapTupleHeader tuple, Buffer buffer)
}
/*
- * HeapTupleSatisfiesSnapshot
- * True iff heap tuple is valid for the given snapshot.
+ * HeapTupleSatisfiesMVCC
+ * True iff heap tuple is valid for the given MVCC snapshot.
*
* Here, we consider the effects of:
* all transactions committed as of the time of the given snapshot
@@ -853,8 +870,8 @@ HeapTupleSatisfiesDirty(HeapTupleHeader tuple, Buffer buffer)
* can't see it.)
*/
bool
-HeapTupleSatisfiesSnapshot(HeapTupleHeader tuple, Snapshot snapshot,
- Buffer buffer)
+HeapTupleSatisfiesMVCC(HeapTupleHeader tuple, Snapshot snapshot,
+ Buffer buffer)
{
if (!(tuple->t_infomask & HEAP_XMIN_COMMITTED))
{
@@ -949,7 +966,7 @@ HeapTupleSatisfiesSnapshot(HeapTupleHeader tuple, Snapshot snapshot,
* By here, the inserting transaction has committed - have to check
* when...
*/
- if (XidInSnapshot(HeapTupleHeaderGetXmin(tuple), snapshot))
+ if (XidInMVCCSnapshot(HeapTupleHeaderGetXmin(tuple), snapshot))
return false; /* treat as still in progress */
if (tuple->t_infomask & HEAP_XMAX_INVALID) /* xid invalid or aborted */
@@ -994,7 +1011,7 @@ HeapTupleSatisfiesSnapshot(HeapTupleHeader tuple, Snapshot snapshot,
/*
* OK, the deleting transaction committed too ... but when?
*/
- if (XidInSnapshot(HeapTupleHeaderGetXmax(tuple), snapshot))
+ if (XidInMVCCSnapshot(HeapTupleHeaderGetXmax(tuple), snapshot))
return true; /* treat as still in progress */
return false;
@@ -1241,8 +1258,6 @@ GetLatestSnapshot(void)
* Copy the given snapshot.
*
* The copy is palloc'd in the current memory context.
- *
- * Note that this will not work on "special" snapshots.
*/
Snapshot
CopySnapshot(Snapshot snapshot)
@@ -1290,7 +1305,7 @@ CopySnapshot(Snapshot snapshot)
* This is currently identical to pfree, but is provided for cleanliness.
*
* Do *not* apply this to the results of GetTransactionSnapshot or
- * GetLatestSnapshot.
+ * GetLatestSnapshot, since those are just static structs.
*/
void
FreeSnapshot(Snapshot snapshot)
@@ -1316,7 +1331,7 @@ FreeXactSnapshot(void)
}
/*
- * XidInSnapshot
+ * XidInMVCCSnapshot
* Is the given XID still-in-progress according to the snapshot?
*
* Note: GetSnapshotData never stores either top xid or subxids of our own
@@ -1325,7 +1340,7 @@ FreeXactSnapshot(void)
* apply this for known-committed XIDs.
*/
static bool
-XidInSnapshot(TransactionId xid, Snapshot snapshot)
+XidInMVCCSnapshot(TransactionId xid, Snapshot snapshot)
{
uint32 i;
diff --git a/src/include/utils/tqual.h b/src/include/utils/tqual.h
index 0b3ef50ac34..e3596e2d507 100644
--- a/src/include/utils/tqual.h
+++ b/src/include/utils/tqual.h
@@ -8,7 +8,7 @@
* Portions Copyright (c) 1996-2007, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/utils/tqual.h,v 1.65 2007/01/05 22:19:59 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/utils/tqual.h,v 1.66 2007/03/25 19:45:14 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -20,23 +20,31 @@
/*
- * "Regular" snapshots are pointers to a SnapshotData structure.
- *
- * We also have some "special" snapshot values that have fixed meanings
- * and don't need any backing SnapshotData. These are encoded by small
- * integer values, which of course is a gross violation of ANSI C, but
- * it works fine on all known platforms.
- *
- * SnapshotDirty is an even more special case: its semantics are fixed,
- * but there is a backing SnapshotData struct for it. That struct is
- * actually used as *output* data from tqual.c, not input into it.
- * (But hey, SnapshotDirty ought to have a dirty implementation, no? ;-))
+ * We use SnapshotData structures to represent both "regular" (MVCC)
+ * snapshots and "special" snapshots that have non-MVCC semantics.
+ * The specific semantics of a snapshot are encoded by the "satisfies"
+ * function.
*/
+typedef struct SnapshotData *Snapshot;
+
+typedef bool (*SnapshotSatisfiesFunc) (HeapTupleHeader tuple,
+ Snapshot snapshot, Buffer buffer);
typedef struct SnapshotData
{
- TransactionId xmin; /* XID < xmin are visible to me */
- TransactionId xmax; /* XID >= xmax are invisible to me */
+ SnapshotSatisfiesFunc satisfies; /* tuple test function */
+ /*
+ * The remaining fields are used only for MVCC snapshots, and are
+ * normally just zeroes in special snapshots. (But xmin and xmax
+ * are used specially by HeapTupleSatisfiesDirty.)
+ *
+ * An MVCC snapshot can never see the effects of XIDs >= xmax.
+ * It can see the effects of all older XIDs except those listed in
+ * the snapshot. xmin is stored as an optimization to avoid needing
+ * to search the XID arrays for most tuples.
+ */
+ TransactionId xmin; /* all XID < xmin are visible to me */
+ TransactionId xmax; /* all XID >= xmax are invisible to me */
uint32 xcnt; /* # of xact ids in xip[] */
TransactionId *xip; /* array of xact IDs in progress */
/* note: all ids in xip[] satisfy xmin <= xip[i] < xmax */
@@ -50,24 +58,30 @@ typedef struct SnapshotData
CommandId curcid; /* in my xact, CID < curcid are visible */
} SnapshotData;
-typedef SnapshotData *Snapshot;
+#define InvalidSnapshot ((Snapshot) NULL)
-/* Special snapshot values: */
-#define InvalidSnapshot ((Snapshot) 0x0) /* same as NULL */
-#define SnapshotNow ((Snapshot) 0x1)
-#define SnapshotSelf ((Snapshot) 0x2)
-#define SnapshotAny ((Snapshot) 0x3)
-#define SnapshotToast ((Snapshot) 0x4)
+/* Static variables representing various special snapshot semantics */
+extern DLLIMPORT SnapshotData SnapshotNowData;
+extern DLLIMPORT SnapshotData SnapshotSelfData;
+extern DLLIMPORT SnapshotData SnapshotAnyData;
+extern DLLIMPORT SnapshotData SnapshotToastData;
-extern DLLIMPORT Snapshot SnapshotDirty;
+#define SnapshotNow (&SnapshotNowData)
+#define SnapshotSelf (&SnapshotSelfData)
+#define SnapshotAny (&SnapshotAnyData)
+#define SnapshotToast (&SnapshotToastData)
+
+/*
+ * We don't provide a static SnapshotDirty variable because it would be
+ * non-reentrant. Instead, users of that snapshot type should declare a
+ * local variable of type SnapshotData, and initialize it with this macro.
+ */
+#define InitDirtySnapshot(snapshotdata) \
+ ((snapshotdata).satisfies = HeapTupleSatisfiesDirty)
/* This macro encodes the knowledge of which snapshots are MVCC-safe */
#define IsMVCCSnapshot(snapshot) \
- ((snapshot) != SnapshotNow && \
- (snapshot) != SnapshotSelf && \
- (snapshot) != SnapshotAny && \
- (snapshot) != SnapshotToast && \
- (snapshot) != SnapshotDirty)
+ ((snapshot)->satisfies == HeapTupleSatisfiesMVCC)
extern DLLIMPORT Snapshot SerializableSnapshot;
@@ -78,7 +92,6 @@ extern TransactionId TransactionXmin;
extern TransactionId RecentXmin;
extern TransactionId RecentGlobalXmin;
-
/*
* HeapTupleSatisfiesVisibility
* True iff heap tuple satisfies a time qual.
@@ -86,30 +99,11 @@ extern TransactionId RecentGlobalXmin;
* Notes:
* Assumes heap tuple is valid.
* Beware of multiple evaluations of snapshot argument.
- * Hint bits in the HeapTuple's t_infomask may be updated as a side effect.
+ * Hint bits in the HeapTuple's t_infomask may be updated as a side effect;
+ * if so, the indicated buffer is marked dirty.
*/
#define HeapTupleSatisfiesVisibility(tuple, snapshot, buffer) \
-((snapshot) == SnapshotNow ? \
- HeapTupleSatisfiesNow((tuple)->t_data, buffer) \
-: \
- ((snapshot) == SnapshotSelf ? \
- HeapTupleSatisfiesItself((tuple)->t_data, buffer) \
- : \
- ((snapshot) == SnapshotAny ? \
- true \
- : \
- ((snapshot) == SnapshotToast ? \
- HeapTupleSatisfiesToast((tuple)->t_data, buffer) \
- : \
- ((snapshot) == SnapshotDirty ? \
- HeapTupleSatisfiesDirty((tuple)->t_data, buffer) \
- : \
- HeapTupleSatisfiesSnapshot((tuple)->t_data, snapshot, buffer) \
- ) \
- ) \
- ) \
- ) \
-)
+ ((*(snapshot)->satisfies) ((tuple)->t_data, snapshot, buffer))
/* Result codes for HeapTupleSatisfiesUpdate */
typedef enum
@@ -127,16 +121,25 @@ typedef enum
HEAPTUPLE_DEAD, /* tuple is dead and deletable */
HEAPTUPLE_LIVE, /* tuple is live (committed, no deleter) */
HEAPTUPLE_RECENTLY_DEAD, /* tuple is dead, but not deletable yet */
- HEAPTUPLE_INSERT_IN_PROGRESS, /* inserting xact is still in progress */
+ HEAPTUPLE_INSERT_IN_PROGRESS, /* inserting xact is still in progress */
HEAPTUPLE_DELETE_IN_PROGRESS /* deleting xact is still in progress */
} HTSV_Result;
-extern bool HeapTupleSatisfiesItself(HeapTupleHeader tuple, Buffer buffer);
-extern bool HeapTupleSatisfiesNow(HeapTupleHeader tuple, Buffer buffer);
-extern bool HeapTupleSatisfiesDirty(HeapTupleHeader tuple, Buffer buffer);
-extern bool HeapTupleSatisfiesToast(HeapTupleHeader tuple, Buffer buffer);
-extern bool HeapTupleSatisfiesSnapshot(HeapTupleHeader tuple,
- Snapshot snapshot, Buffer buffer);
+/* These are the "satisfies" test routines for the various snapshot types */
+extern bool HeapTupleSatisfiesMVCC(HeapTupleHeader tuple,
+ Snapshot snapshot, Buffer buffer);
+extern bool HeapTupleSatisfiesNow(HeapTupleHeader tuple,
+ Snapshot snapshot, Buffer buffer);
+extern bool HeapTupleSatisfiesSelf(HeapTupleHeader tuple,
+ Snapshot snapshot, Buffer buffer);
+extern bool HeapTupleSatisfiesAny(HeapTupleHeader tuple,
+ Snapshot snapshot, Buffer buffer);
+extern bool HeapTupleSatisfiesToast(HeapTupleHeader tuple,
+ Snapshot snapshot, Buffer buffer);
+extern bool HeapTupleSatisfiesDirty(HeapTupleHeader tuple,
+ Snapshot snapshot, Buffer buffer);
+
+/* Special "satisfies" routines with different APIs */
extern HTSU_Result HeapTupleSatisfiesUpdate(HeapTupleHeader tuple,
CommandId curcid, Buffer buffer);
extern HTSV_Result HeapTupleSatisfiesVacuum(HeapTupleHeader tuple,
generated by cgit v1.2.3 (git 2.25.1) at 2025-06-17 12:52:20 +0000