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Renumber SnapshotNow and the other special snapshot codes so that

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((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.
This commit is contained in:
Tom Lane 2004-09-11 18:28:34 +00:00
parent 9835944e54
commit 493f72606b
5 changed files with 38 additions and 20 deletions
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20
src/backend/access/heap/heapam.c
View File

@ -8,7 +8,7 @@
* *
* *
* IDENTIFICATION * 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 * INTERFACE ROUTINES
@ -1262,7 +1262,7 @@ simple_heap_insert(Relation relation, HeapTuple tup)
* tid - TID of tuple to be deleted * tid - TID of tuple to be deleted
* ctid - output parameter, used only for failure case (see below) * ctid - output parameter, used only for failure case (see below)
* cid - delete command ID to use in verifying tuple visibility * 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 * wait - true if should wait for any conflicting update to commit/abort
* *
* Normal, successful return value is HeapTupleMayBeUpdated, which * Normal, successful return value is HeapTupleMayBeUpdated, which
@ -1274,7 +1274,8 @@ simple_heap_insert(Relation relation, HeapTuple tup)
*/ */
int int
heap_delete(Relation relation, ItemPointer tid, heap_delete(Relation relation, ItemPointer tid,
ItemPointer ctid, CommandId cid, Snapshot crosscheck, bool wait) ItemPointer ctid, CommandId cid,
Snapshot crosscheck, bool wait)
{ {
ItemId lp; ItemId lp;
HeapTupleData tp; HeapTupleData tp;
@ -1339,7 +1340,7 @@ l1:
result = HeapTupleUpdated; result = HeapTupleUpdated;
} }
if (crosscheck != SnapshotAny && result == HeapTupleMayBeUpdated) if (crosscheck != InvalidSnapshot && result == HeapTupleMayBeUpdated)
{ {
/* Perform additional check for serializable RI updates */ /* Perform additional check for serializable RI updates */
if (!HeapTupleSatisfiesSnapshot(tp.t_data, crosscheck)) if (!HeapTupleSatisfiesSnapshot(tp.t_data, crosscheck))
@ -1443,7 +1444,7 @@ simple_heap_delete(Relation relation, ItemPointer tid)
result = heap_delete(relation, tid, result = heap_delete(relation, tid,
&ctid, &ctid,
GetCurrentCommandId(), SnapshotAny, GetCurrentCommandId(), InvalidSnapshot,
true /* wait for commit */ ); true /* wait for commit */ );
switch (result) switch (result)
{ {
@ -1477,7 +1478,7 @@ simple_heap_delete(Relation relation, ItemPointer tid)
* newtup - newly constructed tuple data to store * newtup - newly constructed tuple data to store
* ctid - output parameter, used only for failure case (see below) * ctid - output parameter, used only for failure case (see below)
* cid - update command ID to use in verifying old tuple visibility * 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 * wait - true if should wait for any conflicting update to commit/abort
* *
* Normal, successful return value is HeapTupleMayBeUpdated, which * Normal, successful return value is HeapTupleMayBeUpdated, which
@ -1491,7 +1492,8 @@ simple_heap_delete(Relation relation, ItemPointer tid)
*/ */
int int
heap_update(Relation relation, ItemPointer otid, HeapTuple newtup, 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; ItemId lp;
HeapTupleData oldtup; HeapTupleData oldtup;
@ -1566,7 +1568,7 @@ l2:
result = HeapTupleUpdated; result = HeapTupleUpdated;
} }
if (crosscheck != SnapshotAny && result == HeapTupleMayBeUpdated) if (crosscheck != InvalidSnapshot && result == HeapTupleMayBeUpdated)
{ {
/* Perform additional check for serializable RI updates */ /* Perform additional check for serializable RI updates */
if (!HeapTupleSatisfiesSnapshot(oldtup.t_data, crosscheck)) 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, result = heap_update(relation, otid, tup,
&ctid, &ctid,
GetCurrentCommandId(), SnapshotAny, GetCurrentCommandId(), InvalidSnapshot,
true /* wait for commit */ ); true /* wait for commit */ );
switch (result) switch (result)
{ {

4
src/backend/commands/async.c
View File

@ -7,7 +7,7 @@
* Portions Copyright (c) 1994, Regents of the University of California * Portions Copyright (c) 1994, Regents of the University of California
* *
* IDENTIFICATION * 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, result = heap_update(lRel, &lTuple->t_self, rTuple,
&ctid, &ctid,
GetCurrentCommandId(), SnapshotAny, GetCurrentCommandId(), InvalidSnapshot,
false /* no wait for commit */ ); false /* no wait for commit */ );
switch (result) switch (result)
{ {

4
src/backend/executor/execMain.c
View File

@ -26,7 +26,7 @@
* *
* *
* IDENTIFICATION * 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 */ /* normal query --- use query snapshot, no crosscheck */
estate->es_snapshot = CopyQuerySnapshot(); estate->es_snapshot = CopyQuerySnapshot();
estate->es_crosscheck_snapshot = SnapshotAny; estate->es_crosscheck_snapshot = InvalidSnapshot;
} }
/* /*

4
src/backend/executor/execUtils.c
View File

@ -8,7 +8,7 @@
* *
* *
* IDENTIFICATION * 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_direction = ForwardScanDirection;
estate->es_snapshot = SnapshotNow; 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_range_table = NIL;
estate->es_result_relations = NULL; estate->es_result_relations = NULL;

26
src/include/utils/tqual.h
View File

@ -8,7 +8,7 @@
* Portions Copyright (c) 1996-2004, PostgreSQL Global Development Group * Portions Copyright (c) 1996-2004, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California * 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" #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 typedef struct SnapshotData
{ {
TransactionId xmin; /* XID < xmin are visible to me */ TransactionId xmin; /* XID < xmin are visible to me */
@ -32,10 +46,12 @@ typedef struct SnapshotData
typedef SnapshotData *Snapshot; typedef SnapshotData *Snapshot;
#define SnapshotNow ((Snapshot) 0x0) /* Special snapshot values: */
#define SnapshotSelf ((Snapshot) 0x1) #define InvalidSnapshot ((Snapshot) 0x0) /* same as NULL */
#define SnapshotAny ((Snapshot) 0x2) #define SnapshotNow ((Snapshot) 0x1)
#define SnapshotToast ((Snapshot) 0x3) #define SnapshotSelf ((Snapshot) 0x2)
#define SnapshotAny ((Snapshot) 0x3)
#define SnapshotToast ((Snapshot) 0x4)
extern DLLIMPORT Snapshot SnapshotDirty; extern DLLIMPORT Snapshot SnapshotDirty;
extern DLLIMPORT Snapshot QuerySnapshot; extern DLLIMPORT Snapshot QuerySnapshot;