Renumber SnapshotNow and the other special snapshot codes so that

((Snapshot) NULL) can no longer be confused with a valid snapshot,
as per my recent suggestion.  Define a macro InvalidSnapshot for 0.
Use InvalidSnapshot instead of SnapshotAny as the do-nothing special
case for heap_update and heap_delete crosschecks; this seems a little
cleaner even though the behavior is really the same.

diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 6dd0c357fbb14f8c8e4cea3873dca38910da3e62..e5284d0b8c11a9f252ba0d1ede0e51cfa6e2efe8 100644 (file)
--- 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 1.173 2004/08/29 05:06:40 momjian Exp $
+ *       $PostgreSQL: pgsql/src/backend/access/heap/heapam.c,v 1.174 2004/09/11 18:28:32 tgl Exp $
  *
  *
  * INTERFACE ROUTINES
@@ -1262,7 +1262,7 @@ simple_heap_insert(Relation relation, HeapTuple tup)
  *     tid - TID of tuple to be deleted
  *     ctid - output parameter, used only for failure case (see below)
  *     cid - delete command ID to use in verifying tuple visibility
- *     crosscheck - if not SnapshotAny, also check tuple against this
+ *     crosscheck - if not InvalidSnapshot, also check tuple against this
  *     wait - true if should wait for any conflicting update to commit/abort
  *
  * Normal, successful return value is HeapTupleMayBeUpdated, which
@@ -1274,7 +1274,8 @@ simple_heap_insert(Relation relation, HeapTuple tup)
  */
 int
 heap_delete(Relation relation, ItemPointer tid,
-                ItemPointer ctid, CommandId cid, Snapshot crosscheck, bool wait)
+                       ItemPointer ctid, CommandId cid,
+                       Snapshot crosscheck, bool wait)
 {
        ItemId          lp;
        HeapTupleData tp;
@@ -1339,7 +1340,7 @@ l1:
                        result = HeapTupleUpdated;
        }
 
-       if (crosscheck != SnapshotAny && result == HeapTupleMayBeUpdated)
+       if (crosscheck != InvalidSnapshot && result == HeapTupleMayBeUpdated)
        {
                /* Perform additional check for serializable RI updates */
                if (!HeapTupleSatisfiesSnapshot(tp.t_data, crosscheck))
@@ -1443,7 +1444,7 @@ simple_heap_delete(Relation relation, ItemPointer tid)
 
        result = heap_delete(relation, tid,
                                                 &ctid,
-                                                GetCurrentCommandId(), SnapshotAny,
+                                                GetCurrentCommandId(), InvalidSnapshot,
                                                 true /* wait for commit */ );
        switch (result)
        {
@@ -1477,7 +1478,7 @@ simple_heap_delete(Relation relation, ItemPointer tid)
  *     newtup - newly constructed tuple data to store
  *     ctid - output parameter, used only for failure case (see below)
  *     cid - update command ID to use in verifying old tuple visibility
- *     crosscheck - if not SnapshotAny, also check old tuple against this
+ *     crosscheck - if not InvalidSnapshot, also check old tuple against this
  *     wait - true if should wait for any conflicting update to commit/abort
  *
  * Normal, successful return value is HeapTupleMayBeUpdated, which
@@ -1491,7 +1492,8 @@ simple_heap_delete(Relation relation, ItemPointer tid)
  */
 int
 heap_update(Relation relation, ItemPointer otid, HeapTuple newtup,
-                ItemPointer ctid, CommandId cid, Snapshot crosscheck, bool wait)
+                       ItemPointer ctid, CommandId cid,
+                       Snapshot crosscheck, bool wait)
 {
        ItemId          lp;
        HeapTupleData oldtup;
@@ -1566,7 +1568,7 @@ l2:
                        result = HeapTupleUpdated;
        }
 
-       if (crosscheck != SnapshotAny && result == HeapTupleMayBeUpdated)
+       if (crosscheck != InvalidSnapshot && result == HeapTupleMayBeUpdated)
        {
                /* Perform additional check for serializable RI updates */
                if (!HeapTupleSatisfiesSnapshot(oldtup.t_data, crosscheck))
@@ -1804,7 +1806,7 @@ simple_heap_update(Relation relation, ItemPointer otid, HeapTuple tup)
 
        result = heap_update(relation, otid, tup,
                                                 &ctid,
-                                                GetCurrentCommandId(), SnapshotAny,
+                                                GetCurrentCommandId(), InvalidSnapshot,
                                                 true /* wait for commit */ );
        switch (result)
        {

diff --git a/src/backend/commands/async.c b/src/backend/commands/async.c
index f25b8570455004ba2b9fefdabe9a07b88cc573fb..c964f8d9fa789c71fad9fe43b41ec379d5d78355 100644 (file)
--- a/src/backend/commands/async.c
+++ b/src/backend/commands/async.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/commands/async.c,v 1.116 2004/09/06 23:32:54 tgl Exp $
+ *       $PostgreSQL: pgsql/src/backend/commands/async.c,v 1.117 2004/09/11 18:28:33 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -544,7 +544,7 @@ AtCommit_Notify(void)
                                 */
                                result = heap_update(lRel, &lTuple->t_self, rTuple,
                                                                         &ctid,
-                                                                        GetCurrentCommandId(), SnapshotAny,
+                                                                        GetCurrentCommandId(), InvalidSnapshot,
                                                                         false /* no wait for commit */ );
                                switch (result)
                                {

diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index d77bc7054a31455ce42de96eb038cc2532d6545f..b009e73e105d282afb8faa9d8312ac2341bfd3a3 100644 (file)
--- 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 1.236 2004/08/29 05:06:42 momjian Exp $
+ *       $PostgreSQL: pgsql/src/backend/executor/execMain.c,v 1.237 2004/09/11 18:28:34 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -176,7 +176,7 @@ ExecutorStart(QueryDesc *queryDesc, bool useCurrentSnapshot, bool explainOnly)
        {
                /* normal query --- use query snapshot, no crosscheck */
                estate->es_snapshot = CopyQuerySnapshot();
-               estate->es_crosscheck_snapshot = SnapshotAny;
+               estate->es_crosscheck_snapshot = InvalidSnapshot;
        }
 
        /*

diff --git a/src/backend/executor/execUtils.c b/src/backend/executor/execUtils.c
index 79ab787b07a0fcdeddf316d5a4000cb9a7902d49..a1736766b2675eabe43e2032c06fff9248c63a91 100644 (file)
--- a/src/backend/executor/execUtils.c
+++ b/src/backend/executor/execUtils.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *       $PostgreSQL: pgsql/src/backend/executor/execUtils.c,v 1.114 2004/08/29 05:06:42 momjian Exp $
+ *       $PostgreSQL: pgsql/src/backend/executor/execUtils.c,v 1.115 2004/09/11 18:28:34 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -179,7 +179,7 @@ CreateExecutorState(void)
         */
        estate->es_direction = ForwardScanDirection;
        estate->es_snapshot = SnapshotNow;
-       estate->es_crosscheck_snapshot = SnapshotAny;           /* means no crosscheck */
+       estate->es_crosscheck_snapshot = InvalidSnapshot;       /* no crosscheck */
        estate->es_range_table = NIL;
 
        estate->es_result_relations = NULL;

diff --git a/src/include/utils/tqual.h b/src/include/utils/tqual.h
index e378e444da1be2a2fce399d2095b410671be3ea2..627bcaf75a12f8f59c96b79d2b9bab1ae422c878 100644 (file)
--- a/src/include/utils/tqual.h
+++ b/src/include/utils/tqual.h
@@ -8,7 +8,7 @@
  * Portions Copyright (c) 1996-2004, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/utils/tqual.h,v 1.50 2004/08/29 04:13:11 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/utils/tqual.h,v 1.51 2004/09/11 18:28:34 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -19,6 +19,20 @@
 #include "access/xact.h"
 
 
+/*
+ * "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? ;-))
+ */
+
 typedef struct SnapshotData
 {
        TransactionId xmin;                     /* XID < xmin are visible to me */
@@ -32,10 +46,12 @@ typedef struct SnapshotData
 
 typedef SnapshotData *Snapshot;
 
-#define SnapshotNow                                    ((Snapshot) 0x0)
-#define SnapshotSelf                           ((Snapshot) 0x1)
-#define SnapshotAny                                    ((Snapshot) 0x2)
-#define SnapshotToast                          ((Snapshot) 0x3)
+/* 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)
 
 extern DLLIMPORT Snapshot SnapshotDirty;
 extern DLLIMPORT Snapshot QuerySnapshot;