diff --git a/src/backend/access/heap/heapam.c b/src/backend/access/heap/heapam.c
index 6e70ab25c106445374102ccd2188461abe667953..46c7c4da73f7aaf2107e1ddb9be2ef2dd99d288a 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 1.197 2005/08/12 01:35:54 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/access/heap/heapam.c,v 1.198 2005/08/20 00:39:51 tgl Exp $
*
*
* INTERFACE ROUTINES
@@ -22,7 +22,7 @@
* heap_rescan - restart a relation scan
* heap_endscan - end relation scan
* heap_getnext - retrieve next tuple in scan
- * heap_fetch - retrieve tuple with tid
+ * heap_fetch - retrieve tuple with given tid
* heap_insert - insert tuple into a relation
* heap_delete - delete a tuple from a relation
* heap_update - replace a tuple in a relation with another tuple
@@ -152,7 +152,7 @@ heapgettup(Relation relation,
tid = NULL;
}
- tuple->t_tableOid = relation->rd_id;
+ tuple->t_tableOid = RelationGetRelid(relation);
/*
* return null immediately if relation is empty
@@ -800,10 +800,13 @@ heap_getnext(HeapScanDesc scan, ScanDirection direction)
* keep_buf = false, the pin is released and *userbuf is set to InvalidBuffer.
*
* It is somewhat inconsistent that we ereport() on invalid block number but
- * return false on invalid item number. This is historical. The only
- * justification I can see is that the caller can relatively easily check the
- * block number for validity, but cannot check the item number without reading
- * the page himself.
+ * return false on invalid item number. There are a couple of reasons though.
+ * One is that the caller can relatively easily check the block number for
+ * validity, but cannot check the item number without reading the page
+ * himself. Another is that when we are following a t_ctid link, we can be
+ * reasonably confident that the page number is valid (since VACUUM shouldn't
+ * truncate off the destination page without having killed the referencing
+ * tuple first), but the item number might well not be good.
*/
bool
heap_fetch(Relation relation,
@@ -906,7 +909,7 @@ heap_release_fetch(Relation relation,
tuple->t_datamcxt = NULL;
tuple->t_data = (HeapTupleHeader) PageGetItem((Page) dp, lp);
tuple->t_len = ItemIdGetLength(lp);
- tuple->t_tableOid = relation->rd_id;
+ tuple->t_tableOid = RelationGetRelid(relation);
/*
* check time qualification of tuple, then release lock
@@ -950,83 +953,129 @@ heap_release_fetch(Relation relation,
/*
* heap_get_latest_tid - get the latest tid of a specified tuple
+ *
+ * Actually, this gets the latest version that is visible according to
+ * the passed snapshot. You can pass SnapshotDirty to get the very latest,
+ * possibly uncommitted version.
+ *
+ * *tid is both an input and an output parameter: it is updated to
+ * show the latest version of the row. Note that it will not be changed
+ * if no version of the row passes the snapshot test.
*/
-ItemPointer
+void
heap_get_latest_tid(Relation relation,
Snapshot snapshot,
ItemPointer tid)
{
- ItemId lp = NULL;
- Buffer buffer;
- PageHeader dp;
- OffsetNumber offnum;
- HeapTupleData tp;
- HeapTupleHeader t_data;
+ BlockNumber blk;
ItemPointerData ctid;
- bool invalidBlock,
- linkend,
- valid;
+ TransactionId priorXmax;
- /*
- * get the buffer from the relation descriptor Note that this does a
- * buffer pin.
- */
- buffer = ReadBuffer(relation, ItemPointerGetBlockNumber(tid));
- LockBuffer(buffer, BUFFER_LOCK_SHARE);
+ /* this is to avoid Assert failures on bad input */
+ if (!ItemPointerIsValid(tid))
+ return;
/*
- * get the item line pointer corresponding to the requested tid
+ * Since this can be called with user-supplied TID, don't trust the
+ * input too much. (RelationGetNumberOfBlocks is an expensive check,
+ * so we don't check t_ctid links again this way. Note that it would
+ * not do to call it just once and save the result, either.)
*/
- dp = (PageHeader) BufferGetPage(buffer);
- offnum = ItemPointerGetOffsetNumber(tid);
- invalidBlock = true;
- if (!PageIsNew(dp))
- {
- lp = PageGetItemId(dp, offnum);
- if (ItemIdIsUsed(lp))
- invalidBlock = false;
- }
- if (invalidBlock)
- {
- LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
- ReleaseBuffer(buffer);
- return NULL;
- }
+ blk = ItemPointerGetBlockNumber(tid);
+ if (blk >= RelationGetNumberOfBlocks(relation))
+ elog(ERROR, "block number %u is out of range for relation \"%s\"",
+ blk, RelationGetRelationName(relation));
/*
- * more sanity checks
+ * Loop to chase down t_ctid links. At top of loop, ctid is the
+ * tuple we need to examine, and *tid is the TID we will return if
+ * ctid turns out to be bogus.
+ *
+ * Note that we will loop until we reach the end of the t_ctid chain.
+ * Depending on the snapshot passed, there might be at most one visible
+ * version of the row, but we don't try to optimize for that.
*/
+ ctid = *tid;
+ priorXmax = InvalidTransactionId; /* cannot check first XMIN */
+ for (;;)
+ {
+ Buffer buffer;
+ PageHeader dp;
+ OffsetNumber offnum;
+ ItemId lp;
+ HeapTupleData tp;
+ bool valid;
- tp.t_datamcxt = NULL;
- t_data = tp.t_data = (HeapTupleHeader) PageGetItem((Page) dp, lp);
- tp.t_len = ItemIdGetLength(lp);
- tp.t_self = *tid;
- ctid = tp.t_data->t_ctid;
+ /*
+ * Read, pin, and lock the page.
+ */
+ buffer = ReadBuffer(relation, ItemPointerGetBlockNumber(&ctid));
+ LockBuffer(buffer, BUFFER_LOCK_SHARE);
+ dp = (PageHeader) BufferGetPage(buffer);
- /*
- * check time qualification of tid
- */
+ /*
+ * Check for bogus item number. This is not treated as an error
+ * condition because it can happen while following a t_ctid link.
+ * We just assume that the prior tid is OK and return it unchanged.
+ */
+ offnum = ItemPointerGetOffsetNumber(&ctid);
+ if (offnum < FirstOffsetNumber || offnum > PageGetMaxOffsetNumber(dp))
+ {
+ LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
+ ReleaseBuffer(buffer);
+ break;
+ }
+ lp = PageGetItemId(dp, offnum);
+ if (!ItemIdIsUsed(lp))
+ {
+ LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
+ ReleaseBuffer(buffer);
+ break;
+ }
- HeapTupleSatisfies(&tp, relation, buffer, dp,
- snapshot, 0, NULL, valid);
+ /* OK to access the tuple */
+ tp.t_self = ctid;
+ tp.t_datamcxt = NULL;
+ tp.t_data = (HeapTupleHeader) PageGetItem(dp, lp);
+ tp.t_len = ItemIdGetLength(lp);
- linkend = true;
- if ((t_data->t_infomask & HEAP_XMIN_COMMITTED) != 0 &&
- !ItemPointerEquals(tid, &ctid))
- linkend = false;
+ /*
+ * After following a t_ctid link, we might arrive at an unrelated
+ * tuple. Check for XMIN match.
+ */
+ if (TransactionIdIsValid(priorXmax) &&
+ !TransactionIdEquals(priorXmax, HeapTupleHeaderGetXmin(tp.t_data)))
+ {
+ LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
+ ReleaseBuffer(buffer);
+ break;
+ }
- LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
- ReleaseBuffer(buffer);
+ /*
+ * Check time qualification of tuple; if visible, set it as the new
+ * result candidate.
+ */
+ HeapTupleSatisfies(&tp, relation, buffer, dp,
+ snapshot, 0, NULL, valid);
+ if (valid)
+ *tid = ctid;
- if (!valid)
- {
- if (linkend)
- return NULL;
- heap_get_latest_tid(relation, snapshot, &ctid);
- *tid = ctid;
- }
+ /*
+ * If there's a valid t_ctid link, follow it, else we're done.
+ */
+ if ((tp.t_data->t_infomask & (HEAP_XMAX_INVALID | HEAP_IS_LOCKED)) ||
+ ItemPointerEquals(&tp.t_self, &tp.t_data->t_ctid))
+ {
+ LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
+ ReleaseBuffer(buffer);
+ break;
+ }
- return tid;
+ ctid = tp.t_data->t_ctid;
+ priorXmax = HeapTupleHeaderGetXmax(tp.t_data);
+ LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
+ ReleaseBuffer(buffer);
+ } /* end of loop */
}
/*
@@ -1083,7 +1132,7 @@ heap_insert(Relation relation, HeapTuple tup, CommandId cid,
HeapTupleHeaderSetCmin(tup->t_data, cid);
HeapTupleHeaderSetXmax(tup->t_data, 0); /* zero out Datum fields */
HeapTupleHeaderSetCmax(tup->t_data, 0); /* for cleanliness */
- tup->t_tableOid = relation->rd_id;
+ tup->t_tableOid = RelationGetRelid(relation);
/*
* If the new tuple is too big for storage or contains already toasted
@@ -1197,29 +1246,34 @@ simple_heap_insert(Relation relation, HeapTuple tup)
}
/*
- * heap_delete - delete a tuple
+ * heap_delete - delete a tuple
*
* NB: do not call this directly unless you are prepared to deal with
* concurrent-update conditions. Use simple_heap_delete instead.
*
- * relation - table to be modified
+ * relation - table to be modified (caller must hold suitable lock)
* 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
+ * update_xmax - output parameter, used only for failure case (see below)
+ * cid - delete command ID (used for visibility test, and stored into
+ * cmax if successful)
* 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
* actually means we did delete it. Failure return codes are
* HeapTupleSelfUpdated, HeapTupleUpdated, or HeapTupleBeingUpdated
- * (the last only possible if wait == false). On a failure return,
- * *ctid is set to the ctid link of the target tuple (possibly a later
- * version of the row).
+ * (the last only possible if wait == false).
+ *
+ * In the failure cases, the routine returns the tuple's t_ctid and t_xmax.
+ * If t_ctid is the same as tid, the tuple was deleted; if different, the
+ * tuple was updated, and t_ctid is the location of the replacement tuple.
+ * (t_xmax is needed to verify that the replacement tuple matches.)
*/
HTSU_Result
heap_delete(Relation relation, ItemPointer tid,
- ItemPointer ctid, CommandId cid,
- Snapshot crosscheck, bool wait)
+ ItemPointer ctid, TransactionId *update_xmax,
+ CommandId cid, Snapshot crosscheck, bool wait)
{
HTSU_Result result;
TransactionId xid = GetCurrentTransactionId();
@@ -1236,11 +1290,11 @@ heap_delete(Relation relation, ItemPointer tid,
dp = (PageHeader) BufferGetPage(buffer);
lp = PageGetItemId(dp, ItemPointerGetOffsetNumber(tid));
+
tp.t_datamcxt = NULL;
- tp.t_data = (HeapTupleHeader) PageGetItem((Page) dp, lp);
+ tp.t_data = (HeapTupleHeader) PageGetItem(dp, lp);
tp.t_len = ItemIdGetLength(lp);
tp.t_self = *tid;
- tp.t_tableOid = relation->rd_id;
l1:
result = HeapTupleSatisfiesUpdate(tp.t_data, cid, buffer);
@@ -1360,7 +1414,9 @@ l1:
Assert(result == HeapTupleSelfUpdated ||
result == HeapTupleUpdated ||
result == HeapTupleBeingUpdated);
+ Assert(!(tp.t_data->t_infomask & HEAP_XMAX_INVALID));
*ctid = tp.t_data->t_ctid;
+ *update_xmax = HeapTupleHeaderGetXmax(tp.t_data);
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
ReleaseBuffer(buffer);
if (have_tuple_lock)
@@ -1457,11 +1513,12 @@ l1:
void
simple_heap_delete(Relation relation, ItemPointer tid)
{
- ItemPointerData ctid;
HTSU_Result result;
+ ItemPointerData update_ctid;
+ TransactionId update_xmax;
result = heap_delete(relation, tid,
- &ctid,
+ &update_ctid, &update_xmax,
GetCurrentCommandId(), InvalidSnapshot,
true /* wait for commit */ );
switch (result)
@@ -1491,27 +1548,33 @@ simple_heap_delete(Relation relation, ItemPointer tid)
* NB: do not call this directly unless you are prepared to deal with
* concurrent-update conditions. Use simple_heap_update instead.
*
- * relation - table to be modified
+ * relation - table to be modified (caller must hold suitable lock)
* otid - TID of old tuple to be replaced
* 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
+ * update_xmax - output parameter, used only for failure case (see below)
+ * cid - update command ID (used for visibility test, and stored into
+ * cmax/cmin if successful)
* 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
* actually means we *did* update it. Failure return codes are
* HeapTupleSelfUpdated, HeapTupleUpdated, or HeapTupleBeingUpdated
- * (the last only possible if wait == false). On a failure return,
- * *ctid is set to the ctid link of the old tuple (possibly a later
- * version of the row).
+ * (the last only possible if wait == false).
+ *
* On success, newtup->t_self is set to the TID where the new tuple
* was inserted.
+ *
+ * In the failure cases, the routine returns the tuple's t_ctid and t_xmax.
+ * If t_ctid is the same as otid, the tuple was deleted; if different, the
+ * tuple was updated, and t_ctid is the location of the replacement tuple.
+ * (t_xmax is needed to verify that the replacement tuple matches.)
*/
HTSU_Result
heap_update(Relation relation, ItemPointer otid, HeapTuple newtup,
- ItemPointer ctid, CommandId cid,
- Snapshot crosscheck, bool wait)
+ ItemPointer ctid, TransactionId *update_xmax,
+ CommandId cid, Snapshot crosscheck, bool wait)
{
HTSU_Result result;
TransactionId xid = GetCurrentTransactionId();
@@ -1664,7 +1727,9 @@ l2:
Assert(result == HeapTupleSelfUpdated ||
result == HeapTupleUpdated ||
result == HeapTupleBeingUpdated);
+ Assert(!(oldtup.t_data->t_infomask & HEAP_XMAX_INVALID));
*ctid = oldtup.t_data->t_ctid;
+ *update_xmax = HeapTupleHeaderGetXmax(oldtup.t_data);
LockBuffer(buffer, BUFFER_LOCK_UNLOCK);
ReleaseBuffer(buffer);
if (have_tuple_lock)
@@ -1878,11 +1943,12 @@ l2:
void
simple_heap_update(Relation relation, ItemPointer otid, HeapTuple tup)
{
- ItemPointerData ctid;
HTSU_Result result;
+ ItemPointerData update_ctid;
+ TransactionId update_xmax;
result = heap_update(relation, otid, tup,
- &ctid,
+ &update_ctid, &update_xmax,
GetCurrentCommandId(), InvalidSnapshot,
true /* wait for commit */ );
switch (result)
@@ -1907,7 +1973,34 @@ simple_heap_update(Relation relation, ItemPointer otid, HeapTuple tup)
}
/*
- * heap_lock_tuple - lock a tuple in shared or exclusive mode
+ * heap_lock_tuple - lock a tuple in shared or exclusive mode
+ *
+ * Note that this acquires a buffer pin, which the caller must release.
+ *
+ * Input parameters:
+ * relation: relation containing tuple (caller must hold suitable lock)
+ * tuple->t_self: TID of tuple to lock (rest of struct need not be valid)
+ * cid: current command ID (used for visibility test, and stored into
+ * tuple's cmax if lock is successful)
+ * mode: indicates if shared or exclusive tuple lock is desired
+ * nowait: if true, ereport rather than blocking if lock not available
+ *
+ * Output parameters:
+ * *tuple: all fields filled in
+ * *buffer: set to buffer holding tuple (pinned but not locked at exit)
+ * *ctid: set to tuple's t_ctid, but only in failure cases
+ * *update_xmax: set to tuple's xmax, but only in failure cases
+ *
+ * Function result may be:
+ * HeapTupleMayBeUpdated: lock was successfully acquired
+ * HeapTupleSelfUpdated: lock failed because tuple updated by self
+ * HeapTupleUpdated: lock failed because tuple updated by other xact
+ *
+ * In the failure cases, the routine returns the tuple's t_ctid and t_xmax.
+ * If t_ctid is the same as t_self, the tuple was deleted; if different, the
+ * tuple was updated, and t_ctid is the location of the replacement tuple.
+ * (t_xmax is needed to verify that the replacement tuple matches.)
+ *
*
* NOTES: because the shared-memory lock table is of finite size, but users
* could reasonably want to lock large numbers of tuples, we do not rely on
@@ -1943,7 +2036,8 @@ simple_heap_update(Relation relation, ItemPointer otid, HeapTuple tup)
*/
HTSU_Result
heap_lock_tuple(Relation relation, HeapTuple tuple, Buffer *buffer,
- CommandId cid, LockTupleMode mode, bool nowait)
+ ItemPointer ctid, TransactionId *update_xmax,
+ CommandId cid, LockTupleMode mode, bool nowait)
{
HTSU_Result result;
ItemPointer tid = &(tuple->t_self);
@@ -1961,9 +2055,12 @@ heap_lock_tuple(Relation relation, HeapTuple tuple, Buffer *buffer,
dp = (PageHeader) BufferGetPage(*buffer);
lp = PageGetItemId(dp, ItemPointerGetOffsetNumber(tid));
+ Assert(ItemIdIsUsed(lp));
+
tuple->t_datamcxt = NULL;
tuple->t_data = (HeapTupleHeader) PageGetItem((Page) dp, lp);
tuple->t_len = ItemIdGetLength(lp);
+ tuple->t_tableOid = RelationGetRelid(relation);
l3:
result = HeapTupleSatisfiesUpdate(tuple->t_data, cid, *buffer);
@@ -2112,14 +2209,13 @@ l3:
if (result != HeapTupleMayBeUpdated)
{
- ItemPointerData newctid = tuple->t_data->t_ctid;
-
Assert(result == HeapTupleSelfUpdated || result == HeapTupleUpdated);
+ Assert(!(tuple->t_data->t_infomask & HEAP_XMAX_INVALID));
+ *ctid = tuple->t_data->t_ctid;
+ *update_xmax = HeapTupleHeaderGetXmax(tuple->t_data);
LockBuffer(*buffer, BUFFER_LOCK_UNLOCK);
if (have_tuple_lock)
UnlockTuple(relation, tid, tuple_lock_type);
- /* can't overwrite t_self (== *tid) until after above Unlock */
- tuple->t_self = newctid;
return result;
}
diff --git a/src/backend/commands/async.c b/src/backend/commands/async.c
index 142b02dfaf88d7cf9eabe16e022c59379ab0b5f5..e2c6203891d48fcb9951bc9142a286affa1fe2a7 100644
--- 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 1.123 2005/06/17 22:32:43 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/commands/async.c,v 1.124 2005/08/20 00:39:53 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -550,8 +550,9 @@ AtCommit_Notify(void)
}
else if (listener->notification == 0)
{
- ItemPointerData ctid;
HTSU_Result result;
+ ItemPointerData update_ctid;
+ TransactionId update_xmax;
rTuple = heap_modifytuple(lTuple, tdesc,
value, nulls, repl);
@@ -573,7 +574,7 @@ AtCommit_Notify(void)
* heap_update calls.
*/
result = heap_update(lRel, &lTuple->t_self, rTuple,
- &ctid,
+ &update_ctid, &update_xmax,
GetCurrentCommandId(), InvalidSnapshot,
false /* no wait for commit */ );
switch (result)
@@ -585,7 +586,6 @@ AtCommit_Notify(void)
case HeapTupleMayBeUpdated:
/* done successfully */
-
#ifdef NOT_USED /* currently there are no indexes */
CatalogUpdateIndexes(lRel, rTuple);
#endif
diff --git a/src/backend/commands/trigger.c b/src/backend/commands/trigger.c
index 4ea973ae7fa4422e7dbb1eb55757b3ab6ce39717..562f676f4b8b4f91919f794681544cf5a0a68bd1 100644
--- a/src/backend/commands/trigger.c
+++ b/src/backend/commands/trigger.c
@@ -7,7 +7,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/commands/trigger.c,v 1.191 2005/08/12 01:35:57 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/commands/trigger.c,v 1.192 2005/08/20 00:39:54 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -1592,14 +1592,18 @@ GetTupleForTrigger(EState *estate, ResultRelInfo *relinfo,
if (newSlot != NULL)
{
HTSU_Result test;
+ ItemPointerData update_ctid;
+ TransactionId update_xmax;
+
+ *newSlot = NULL;
/*
* lock tuple for update
*/
- *newSlot = NULL;
- tuple.t_self = *tid;
ltrmark:;
- test = heap_lock_tuple(relation, &tuple, &buffer, cid,
+ tuple.t_self = *tid;
+ test = heap_lock_tuple(relation, &tuple, &buffer,
+ &update_ctid, &update_xmax, cid,
LockTupleExclusive, false);
switch (test)
{
@@ -1617,15 +1621,18 @@ ltrmark:;
ereport(ERROR,
(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
errmsg("could not serialize access due to concurrent update")));
- else if (!(ItemPointerEquals(&(tuple.t_self), tid)))
+ else if (!ItemPointerEquals(&update_ctid, &tuple.t_self))
{
- TupleTableSlot *epqslot = EvalPlanQual(estate,
- relinfo->ri_RangeTableIndex,
- &(tuple.t_self));
-
- if (!(TupIsNull(epqslot)))
+ /* it was updated, so look at the updated version */
+ TupleTableSlot *epqslot;
+
+ epqslot = EvalPlanQual(estate,
+ relinfo->ri_RangeTableIndex,
+ &update_ctid,
+ update_xmax);
+ if (!TupIsNull(epqslot))
{
- *tid = tuple.t_self;
+ *tid = update_ctid;
*newSlot = epqslot;
goto ltrmark;
}
@@ -1639,7 +1646,7 @@ ltrmark:;
default:
ReleaseBuffer(buffer);
- elog(ERROR, "invalid heap_lock_tuple status: %d", test);
+ elog(ERROR, "unrecognized heap_lock_tuple status: %u", test);
return NULL; /* keep compiler quiet */
}
}
@@ -1659,6 +1666,7 @@ ltrmark:;
tuple.t_data = (HeapTupleHeader) PageGetItem((Page) dp, lp);
tuple.t_len = ItemIdGetLength(lp);
tuple.t_self = *tid;
+ tuple.t_tableOid = RelationGetRelid(relation);
}
result = heap_copytuple(&tuple);
diff --git a/src/backend/commands/vacuum.c b/src/backend/commands/vacuum.c
index 9db91209448624a17730b2e79f3be5d25ac0ac0c..ef199c5f0734c56b3376d147b6315e008321c638 100644
--- a/src/backend/commands/vacuum.c
+++ b/src/backend/commands/vacuum.c
@@ -13,7 +13,7 @@
*
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.312 2005/07/29 19:30:03 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/commands/vacuum.c,v 1.313 2005/08/20 00:39:54 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -51,6 +51,10 @@
#include "pgstat.h"
+/*
+ * VacPage structures keep track of each page on which we find useful
+ * amounts of free space.
+ */
typedef struct VacPageData
{
BlockNumber blkno; /* BlockNumber of this Page */
@@ -73,30 +77,54 @@ typedef struct VacPageListData
typedef VacPageListData *VacPageList;
+/*
+ * The "vtlinks" array keeps information about each recently-updated tuple
+ * ("recent" meaning its XMAX is too new to let us recycle the tuple).
+ * We store the tuple's own TID as well as its t_ctid (its link to the next
+ * newer tuple version). Searching in this array allows us to follow update
+ * chains backwards from newer to older tuples. When we move a member of an
+ * update chain, we must move *all* the live members of the chain, so that we
+ * can maintain their t_ctid link relationships (we must not just overwrite
+ * t_ctid in an existing tuple).
+ *
+ * Note: because t_ctid links can be stale (this would only occur if a prior
+ * VACUUM crashed partway through), it is possible that new_tid points to an
+ * empty slot or unrelated tuple. We have to check the linkage as we follow
+ * it, just as is done in EvalPlanQual.
+ */
typedef struct VTupleLinkData
{
- ItemPointerData new_tid;
- ItemPointerData this_tid;
+ ItemPointerData new_tid; /* t_ctid of an updated tuple */
+ ItemPointerData this_tid; /* t_self of the tuple */
} VTupleLinkData;
typedef VTupleLinkData *VTupleLink;
+/*
+ * We use an array of VTupleMoveData to plan a chain tuple move fully
+ * before we do it.
+ */
typedef struct VTupleMoveData
{
ItemPointerData tid; /* tuple ID */
- VacPage vacpage; /* where to move */
- bool cleanVpd; /* clean vacpage before using */
+ VacPage vacpage; /* where to move it to */
+ bool cleanVpd; /* clean vacpage before using? */
} VTupleMoveData;
typedef VTupleMoveData *VTupleMove;
+/*
+ * VRelStats contains the data acquired by scan_heap for use later
+ */
typedef struct VRelStats
{
+ /* miscellaneous statistics */
BlockNumber rel_pages;
double rel_tuples;
Size min_tlen;
Size max_tlen;
bool hasindex;
+ /* vtlinks array for tuple chain following - sorted by new_tid */
int num_vtlinks;
VTupleLink vtlinks;
} VRelStats;
@@ -117,6 +145,7 @@ typedef struct ExecContextData
EState *estate;
TupleTableSlot *slot;
} ExecContextData;
+
typedef ExecContextData *ExecContext;
static void
@@ -1802,18 +1831,25 @@ repair_frag(VRelStats *vacrelstats, Relation onerel,
}
/*
- * If this tuple is in the chain of tuples created in updates
- * by "recent" transactions then we have to move all chain of
- * tuples to another places.
+ * If this tuple is in a chain of tuples created in updates
+ * by "recent" transactions then we have to move the whole chain
+ * of tuples to other places, so that we can write new t_ctid
+ * links that preserve the chain relationship.
+ *
+ * This test is complicated. Read it as "if tuple is a recently
+ * created updated version, OR if it is an obsoleted version".
+ * (In the second half of the test, we needn't make any check
+ * on XMAX --- it must be recently obsoleted, else scan_heap
+ * would have deemed it removable.)
*
* NOTE: this test is not 100% accurate: it is possible for a
* tuple to be an updated one with recent xmin, and yet not
- * have a corresponding tuple in the vtlinks list. Presumably
+ * match any new_tid entry in the vtlinks list. Presumably
* there was once a parent tuple with xmax matching the xmin,
* but it's possible that that tuple has been removed --- for
- * example, if it had xmin = xmax then
- * HeapTupleSatisfiesVacuum would deem it removable as soon as
- * the xmin xact completes.
+ * example, if it had xmin = xmax and wasn't itself an updated
+ * version, then HeapTupleSatisfiesVacuum would deem it removable
+ * as soon as the xmin xact completes.
*
* To be on the safe side, we abandon the repair_frag process if
* we cannot find the parent tuple in vtlinks. This may be
@@ -1854,72 +1890,85 @@ repair_frag(VRelStats *vacrelstats, Relation onerel,
break; /* out of walk-along-page loop */
}
- vtmove = (VTupleMove) palloc(100 * sizeof(VTupleMoveData));
- num_vtmove = 0;
- free_vtmove = 100;
-
/*
* If this tuple is in the begin/middle of the chain then
- * we have to move to the end of chain.
+ * we have to move to the end of chain. As with any
+ * t_ctid chase, we have to verify that each new tuple
+ * is really the descendant of the tuple we came from.
*/
while (!(tp.t_data->t_infomask & (HEAP_XMAX_INVALID |
HEAP_IS_LOCKED)) &&
!(ItemPointerEquals(&(tp.t_self),
&(tp.t_data->t_ctid))))
{
- Page Cpage;
- ItemId Citemid;
- ItemPointerData Ctid;
-
- Ctid = tp.t_data->t_ctid;
- if (freeCbuf)
- ReleaseBuffer(Cbuf);
- freeCbuf = true;
- Cbuf = ReadBuffer(onerel,
- ItemPointerGetBlockNumber(&Ctid));
- Cpage = BufferGetPage(Cbuf);
- Citemid = PageGetItemId(Cpage,
- ItemPointerGetOffsetNumber(&Ctid));
- if (!ItemIdIsUsed(Citemid))
+ ItemPointerData nextTid;
+ TransactionId priorXmax;
+ Buffer nextBuf;
+ Page nextPage;
+ OffsetNumber nextOffnum;
+ ItemId nextItemid;
+ HeapTupleHeader nextTdata;
+
+ nextTid = tp.t_data->t_ctid;
+ priorXmax = HeapTupleHeaderGetXmax(tp.t_data);
+ /* assume block# is OK (see heap_fetch comments) */
+ nextBuf = ReadBuffer(onerel,
+ ItemPointerGetBlockNumber(&nextTid));
+ nextPage = BufferGetPage(nextBuf);
+ /* If bogus or unused slot, assume tp is end of chain */
+ nextOffnum = ItemPointerGetOffsetNumber(&nextTid);
+ if (nextOffnum < FirstOffsetNumber ||
+ nextOffnum > PageGetMaxOffsetNumber(nextPage))
{
- /*
- * This means that in the middle of chain there
- * was tuple updated by older (than OldestXmin)
- * xaction and this tuple is already deleted by
- * me. Actually, upper part of chain should be
- * removed and seems that this should be handled
- * in scan_heap(), but it's not implemented at the
- * moment and so we just stop shrinking here.
- */
- elog(DEBUG2, "child itemid in update-chain marked as unused --- can't continue repair_frag");
- chain_move_failed = true;
- break; /* out of loop to move to chain end */
+ ReleaseBuffer(nextBuf);
+ break;
+ }
+ nextItemid = PageGetItemId(nextPage, nextOffnum);
+ if (!ItemIdIsUsed(nextItemid))
+ {
+ ReleaseBuffer(nextBuf);
+ break;
}
+ /* if not matching XMIN, assume tp is end of chain */
+ nextTdata = (HeapTupleHeader) PageGetItem(nextPage,
+ nextItemid);
+ if (!TransactionIdEquals(HeapTupleHeaderGetXmin(nextTdata),
+ priorXmax))
+ {
+ ReleaseBuffer(nextBuf);
+ break;
+ }
+ /* OK, switch our attention to the next tuple in chain */
tp.t_datamcxt = NULL;
- tp.t_data = (HeapTupleHeader) PageGetItem(Cpage, Citemid);
- tp.t_self = Ctid;
- tlen = tp.t_len = ItemIdGetLength(Citemid);
- }
- if (chain_move_failed)
- {
+ tp.t_data = nextTdata;
+ tp.t_self = nextTid;
+ tlen = tp.t_len = ItemIdGetLength(nextItemid);
if (freeCbuf)
ReleaseBuffer(Cbuf);
- pfree(vtmove);
- break; /* out of walk-along-page loop */
+ Cbuf = nextBuf;
+ freeCbuf = true;
}
+ /* Set up workspace for planning the chain move */
+ vtmove = (VTupleMove) palloc(100 * sizeof(VTupleMoveData));
+ num_vtmove = 0;
+ free_vtmove = 100;
+
/*
- * Check if all items in chain can be moved
+ * Now, walk backwards up the chain (towards older tuples)
+ * and check if all items in chain can be moved. We record
+ * all the moves that need to be made in the vtmove array.
*/
for (;;)
{
Buffer Pbuf;
Page Ppage;
ItemId Pitemid;
- HeapTupleData Ptp;
+ HeapTupleHeader PTdata;
VTupleLinkData vtld,
*vtlp;
+ /* Identify a target page to move this tuple to */
if (to_vacpage == NULL ||
!enough_space(to_vacpage, tlen))
{
@@ -1942,6 +1991,8 @@ repair_frag(VRelStats *vacrelstats, Relation onerel,
if (to_vacpage->offsets_used >= to_vacpage->offsets_free)
to_vacpage->free -= sizeof(ItemIdData);
(to_vacpage->offsets_used)++;
+
+ /* Add an entry to vtmove list */
if (free_vtmove == 0)
{
free_vtmove = 1000;
@@ -1959,13 +2010,13 @@ repair_frag(VRelStats *vacrelstats, Relation onerel,
free_vtmove--;
num_vtmove++;
- /* At beginning of chain? */
+ /* Done if at beginning of chain */
if (!(tp.t_data->t_infomask & HEAP_UPDATED) ||
TransactionIdPrecedes(HeapTupleHeaderGetXmin(tp.t_data),
OldestXmin))
- break;
+ break; /* out of check-all-items loop */
- /* No, move to tuple with prior row version */
+ /* Move to tuple with prior row version */
vtld.new_tid = tp.t_self;
vtlp = (VTupleLink)
vac_bsearch((void *) &vtld,
@@ -1989,18 +2040,17 @@ repair_frag(VRelStats *vacrelstats, Relation onerel,
/* this can't happen since we saw tuple earlier: */
if (!ItemIdIsUsed(Pitemid))
elog(ERROR, "parent itemid marked as unused");
- Ptp.t_datamcxt = NULL;
- Ptp.t_data = (HeapTupleHeader) PageGetItem(Ppage, Pitemid);
+ PTdata = (HeapTupleHeader) PageGetItem(Ppage, Pitemid);
/* ctid should not have changed since we saved it */
Assert(ItemPointerEquals(&(vtld.new_tid),
- &(Ptp.t_data->t_ctid)));
+ &(PTdata->t_ctid)));
/*
- * Read above about cases when !ItemIdIsUsed(Citemid)
+ * Read above about cases when !ItemIdIsUsed(nextItemid)
* (child item is removed)... Due to the fact that at
* the moment we don't remove unuseful part of
- * update-chain, it's possible to get too old parent
+ * update-chain, it's possible to get non-matching parent
* row here. Like as in the case which caused this
* problem, we stop shrinking here. I could try to
* find real parent row but want not to do it because
@@ -2008,8 +2058,8 @@ repair_frag(VRelStats *vacrelstats, Relation onerel,
* and we are too close to 6.5 release. - vadim
* 06/11/99
*/
- if (Ptp.t_data->t_infomask & HEAP_XMAX_IS_MULTI ||
- !(TransactionIdEquals(HeapTupleHeaderGetXmax(Ptp.t_data),
+ if ((PTdata->t_infomask & HEAP_XMAX_IS_MULTI) ||
+ !(TransactionIdEquals(HeapTupleHeaderGetXmax(PTdata),
HeapTupleHeaderGetXmin(tp.t_data))))
{
ReleaseBuffer(Pbuf);
@@ -2017,8 +2067,8 @@ repair_frag(VRelStats *vacrelstats, Relation onerel,
chain_move_failed = true;
break; /* out of check-all-items loop */
}
- tp.t_datamcxt = Ptp.t_datamcxt;
- tp.t_data = Ptp.t_data;
+ tp.t_datamcxt = NULL;
+ tp.t_data = PTdata;
tlen = tp.t_len = ItemIdGetLength(Pitemid);
if (freeCbuf)
ReleaseBuffer(Cbuf);
@@ -2047,7 +2097,9 @@ repair_frag(VRelStats *vacrelstats, Relation onerel,
}
/*
- * Okay, move the whole tuple chain
+ * Okay, move the whole tuple chain in reverse order.
+ *
+ * Ctid tracks the new location of the previously-moved tuple.
*/
ItemPointerSetInvalid(&Ctid);
for (ti = 0; ti < num_vtmove; ti++)
@@ -2077,10 +2129,6 @@ repair_frag(VRelStats *vacrelstats, Relation onerel,
tuple.t_data = (HeapTupleHeader) PageGetItem(Cpage, Citemid);
tuple_len = tuple.t_len = ItemIdGetLength(Citemid);
- /*
- * make a copy of the source tuple, and then mark the
- * source tuple MOVED_OFF.
- */
move_chain_tuple(onerel, Cbuf, Cpage, &tuple,
dst_buffer, dst_page, destvacpage,
&ec, &Ctid, vtmove[ti].cleanVpd);
@@ -2143,7 +2191,6 @@ repair_frag(VRelStats *vacrelstats, Relation onerel,
move_plain_tuple(onerel, buf, page, &tuple,
dst_buffer, dst_page, dst_vacpage, &ec);
-
num_moved++;
if (dst_vacpage->blkno > last_move_dest_block)
last_move_dest_block = dst_vacpage->blkno;
@@ -2474,6 +2521,9 @@ move_chain_tuple(Relation rel,
ItemId newitemid;
Size tuple_len = old_tup->t_len;
+ /*
+ * make a modifiable copy of the source tuple.
+ */
heap_copytuple_with_tuple(old_tup, &newtup);
/*
@@ -2484,6 +2534,9 @@ move_chain_tuple(Relation rel,
/* NO EREPORT(ERROR) TILL CHANGES ARE LOGGED */
START_CRIT_SECTION();
+ /*
+ * mark the source tuple MOVED_OFF.
+ */
old_tup->t_data->t_infomask &= ~(HEAP_XMIN_COMMITTED |
HEAP_XMIN_INVALID |
HEAP_MOVED_IN);
@@ -2529,16 +2582,27 @@ move_chain_tuple(Relation rel,
newoff = PageAddItem(dst_page, (Item) newtup.t_data, tuple_len,
InvalidOffsetNumber, LP_USED);
if (newoff == InvalidOffsetNumber)
- {
elog(PANIC, "failed to add item with len = %lu to page %u while moving tuple chain",
(unsigned long) tuple_len, dst_vacpage->blkno);
- }
newitemid = PageGetItemId(dst_page, newoff);
+ /* drop temporary copy, and point to the version on the dest page */
pfree(newtup.t_data);
newtup.t_datamcxt = NULL;
newtup.t_data = (HeapTupleHeader) PageGetItem(dst_page, newitemid);
+
ItemPointerSet(&(newtup.t_self), dst_vacpage->blkno, newoff);
+ /*
+ * Set new tuple's t_ctid pointing to itself if last tuple in chain,
+ * and to next tuple in chain otherwise. (Since we move the chain
+ * in reverse order, this is actually the previously processed tuple.)
+ */
+ if (!ItemPointerIsValid(ctid))
+ newtup.t_data->t_ctid = newtup.t_self;
+ else
+ newtup.t_data->t_ctid = *ctid;
+ *ctid = newtup.t_self;
+
/* XLOG stuff */
if (!rel->rd_istemp)
{
@@ -2563,17 +2627,6 @@ move_chain_tuple(Relation rel,
END_CRIT_SECTION();
- /*
- * Set new tuple's t_ctid pointing to itself for last tuple in chain,
- * and to next tuple in chain otherwise.
- */
- /* Is this ok after log_heap_move() and END_CRIT_SECTION()? */
- if (!ItemPointerIsValid(ctid))
- newtup.t_data->t_ctid = newtup.t_self;
- else
- newtup.t_data->t_ctid = *ctid;
- *ctid = newtup.t_self;
-
LockBuffer(dst_buf, BUFFER_LOCK_UNLOCK);
if (dst_buf != old_buf)
LockBuffer(old_buf, BUFFER_LOCK_UNLOCK);
@@ -2638,12 +2691,10 @@ move_plain_tuple(Relation rel,
newoff = PageAddItem(dst_page, (Item) newtup.t_data, tuple_len,
InvalidOffsetNumber, LP_USED);
if (newoff == InvalidOffsetNumber)
- {
elog(PANIC, "failed to add item with len = %lu to page %u (free space %lu, nusd %u, noff %u)",
(unsigned long) tuple_len,
dst_vacpage->blkno, (unsigned long) dst_vacpage->free,
dst_vacpage->offsets_used, dst_vacpage->offsets_free);
- }
newitemid = PageGetItemId(dst_page, newoff);
pfree(newtup.t_data);
newtup.t_datamcxt = NULL;
diff --git a/src/backend/executor/execMain.c b/src/backend/executor/execMain.c
index eb485ad5476a7ba35579bfbaf033ef52b75b7cec..9f5c008fa9f72e3d92fee9750e9b4c437dee736e 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 1.253 2005/08/18 21:34:20 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/executor/execMain.c,v 1.254 2005/08/20 00:39:55 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -1165,8 +1165,10 @@ lnext: ;
foreach(l, estate->es_rowMarks)
{
execRowMark *erm = lfirst(l);
- Buffer buffer;
HeapTupleData tuple;
+ Buffer buffer;
+ ItemPointerData update_ctid;
+ TransactionId update_xmax;
TupleTableSlot *newSlot;
LockTupleMode lockmode;
HTSU_Result test;
@@ -1183,15 +1185,17 @@ lnext: ;
if (isNull)
elog(ERROR, "\"%s\" is NULL", erm->resname);
+ tuple.t_self = *((ItemPointer) DatumGetPointer(datum));
+
if (estate->es_forUpdate)
lockmode = LockTupleExclusive;
else
lockmode = LockTupleShared;
- tuple.t_self = *((ItemPointer) DatumGetPointer(datum));
test = heap_lock_tuple(erm->relation, &tuple, &buffer,
- estate->es_snapshot->curcid,
- lockmode, estate->es_rowNoWait);
+ &update_ctid, &update_xmax,
+ estate->es_snapshot->curcid,
+ lockmode, estate->es_rowNoWait);
ReleaseBuffer(buffer);
switch (test)
{
@@ -1207,11 +1211,15 @@ lnext: ;
ereport(ERROR,
(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
errmsg("could not serialize access due to concurrent update")));
- if (!(ItemPointerEquals(&(tuple.t_self),
- (ItemPointer) DatumGetPointer(datum))))
+ if (!ItemPointerEquals(&update_ctid,
+ &tuple.t_self))
{
- newSlot = EvalPlanQual(estate, erm->rti, &(tuple.t_self));
- if (!(TupIsNull(newSlot)))
+ /* updated, so look at updated version */
+ newSlot = EvalPlanQual(estate,
+ erm->rti,
+ &update_ctid,
+ update_xmax);
+ if (!TupIsNull(newSlot))
{
slot = newSlot;
estate->es_useEvalPlan = true;
@@ -1454,8 +1462,9 @@ ExecDelete(TupleTableSlot *slot,
{
ResultRelInfo *resultRelInfo;
Relation resultRelationDesc;
- ItemPointerData ctid;
HTSU_Result result;
+ ItemPointerData update_ctid;
+ TransactionId update_xmax;
/*
* get information on the (current) result relation
@@ -1486,7 +1495,7 @@ ExecDelete(TupleTableSlot *slot,
*/
ldelete:;
result = heap_delete(resultRelationDesc, tupleid,
- &ctid,
+ &update_ctid, &update_xmax,
estate->es_snapshot->curcid,
estate->es_crosscheck_snapshot,
true /* wait for commit */ );
@@ -1504,14 +1513,17 @@ ldelete:;
ereport(ERROR,
(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
errmsg("could not serialize access due to concurrent update")));
- else if (!(ItemPointerEquals(tupleid, &ctid)))
+ else if (!ItemPointerEquals(tupleid, &update_ctid))
{
- TupleTableSlot *epqslot = EvalPlanQual(estate,
- resultRelInfo->ri_RangeTableIndex, &ctid);
+ TupleTableSlot *epqslot;
+ epqslot = EvalPlanQual(estate,
+ resultRelInfo->ri_RangeTableIndex,
+ &update_ctid,
+ update_xmax);
if (!TupIsNull(epqslot))
{
- *tupleid = ctid;
+ *tupleid = update_ctid;
goto ldelete;
}
}
@@ -1558,8 +1570,9 @@ ExecUpdate(TupleTableSlot *slot,
HeapTuple tuple;
ResultRelInfo *resultRelInfo;
Relation resultRelationDesc;
- ItemPointerData ctid;
HTSU_Result result;
+ ItemPointerData update_ctid;
+ TransactionId update_xmax;
/*
* abort the operation if not running transactions
@@ -1627,7 +1640,7 @@ lreplace:;
* referential integrity updates in serializable transactions.
*/
result = heap_update(resultRelationDesc, tupleid, tuple,
- &ctid,
+ &update_ctid, &update_xmax,
estate->es_snapshot->curcid,
estate->es_crosscheck_snapshot,
true /* wait for commit */ );
@@ -1645,14 +1658,17 @@ lreplace:;
ereport(ERROR,
(errcode(ERRCODE_T_R_SERIALIZATION_FAILURE),
errmsg("could not serialize access due to concurrent update")));
- else if (!(ItemPointerEquals(tupleid, &ctid)))
+ else if (!ItemPointerEquals(tupleid, &update_ctid))
{
- TupleTableSlot *epqslot = EvalPlanQual(estate,
- resultRelInfo->ri_RangeTableIndex, &ctid);
+ TupleTableSlot *epqslot;
+ epqslot = EvalPlanQual(estate,
+ resultRelInfo->ri_RangeTableIndex,
+ &update_ctid,
+ update_xmax);
if (!TupIsNull(epqslot))
{
- *tupleid = ctid;
+ *tupleid = update_ctid;
slot = ExecFilterJunk(estate->es_junkFilter, epqslot);
tuple = ExecMaterializeSlot(slot);
goto lreplace;
@@ -1791,9 +1807,21 @@ ExecConstraints(ResultRelInfo *resultRelInfo,
* under READ COMMITTED rules.
*
* See backend/executor/README for some info about how this works.
+ *
+ * estate - executor state data
+ * rti - rangetable index of table containing tuple
+ * *tid - t_ctid from the outdated tuple (ie, next updated version)
+ * priorXmax - t_xmax from the outdated tuple
+ *
+ * *tid is also an output parameter: it's modified to hold the TID of the
+ * latest version of the tuple (note this may be changed even on failure)
+ *
+ * Returns a slot containing the new candidate update/delete tuple, or
+ * NULL if we determine we shouldn't process the row.
*/
TupleTableSlot *
-EvalPlanQual(EState *estate, Index rti, ItemPointer tid)
+EvalPlanQual(EState *estate, Index rti,
+ ItemPointer tid, TransactionId priorXmax)
{
evalPlanQual *epq;
EState *epqstate;
@@ -1837,11 +1865,24 @@ EvalPlanQual(EState *estate, Index rti, ItemPointer tid)
{
Buffer buffer;
- if (heap_fetch(relation, SnapshotDirty, &tuple, &buffer, false, NULL))
+ if (heap_fetch(relation, SnapshotDirty, &tuple, &buffer, true, NULL))
{
- TransactionId xwait = SnapshotDirty->xmax;
+ /*
+ * If xmin isn't what we're expecting, the slot must have been
+ * recycled and reused for an unrelated tuple. This implies
+ * that the latest version of the row was deleted, so we need
+ * do nothing. (Should be safe to examine xmin without getting
+ * buffer's content lock, since xmin never changes in an existing
+ * tuple.)
+ */
+ if (!TransactionIdEquals(HeapTupleHeaderGetXmin(tuple.t_data),
+ priorXmax))
+ {
+ ReleaseBuffer(buffer);
+ return NULL;
+ }
- /* xmin should not be dirty... */
+ /* otherwise xmin should not be dirty... */
if (TransactionIdIsValid(SnapshotDirty->xmin))
elog(ERROR, "t_xmin is uncommitted in tuple to be updated");
@@ -1849,11 +1890,11 @@ EvalPlanQual(EState *estate, Index rti, ItemPointer tid)
* If tuple is being updated by other transaction then we have
* to wait for its commit/abort.
*/
- if (TransactionIdIsValid(xwait))
+ if (TransactionIdIsValid(SnapshotDirty->xmax))
{
ReleaseBuffer(buffer);
- XactLockTableWait(xwait);
- continue;
+ XactLockTableWait(SnapshotDirty->xmax);
+ continue; /* loop back to repeat heap_fetch */
}
/*
@@ -1865,22 +1906,50 @@ EvalPlanQual(EState *estate, Index rti, ItemPointer tid)
}
/*
- * Oops! Invalid tuple. Have to check is it updated or deleted.
- * Note that it's possible to get invalid SnapshotDirty->tid if
- * tuple updated by this transaction. Have we to check this ?
+ * If the referenced slot was actually empty, the latest version
+ * of the row must have been deleted, so we need do nothing.
*/
- if (ItemPointerIsValid(&(SnapshotDirty->tid)) &&
- !(ItemPointerEquals(&(tuple.t_self), &(SnapshotDirty->tid))))
+ if (tuple.t_data == NULL)
{
- /* updated, so look at the updated copy */
- tuple.t_self = SnapshotDirty->tid;
- continue;
+ ReleaseBuffer(buffer);
+ return NULL;
}
/*
- * Deleted or updated by this transaction; forget it.
+ * As above, if xmin isn't what we're expecting, do nothing.
*/
- return NULL;
+ if (!TransactionIdEquals(HeapTupleHeaderGetXmin(tuple.t_data),
+ priorXmax))
+ {
+ ReleaseBuffer(buffer);
+ return NULL;
+ }
+
+ /*
+ * If we get here, the tuple was found but failed SnapshotDirty.
+ * Assuming the xmin is either a committed xact or our own xact
+ * (as it certainly should be if we're trying to modify the tuple),
+ * this must mean that the row was updated or deleted by either
+ * a committed xact or our own xact. If it was deleted, we can
+ * ignore it; if it was updated then chain up to the next version
+ * and repeat the whole test.
+ *
+ * As above, it should be safe to examine xmax and t_ctid without
+ * the buffer content lock, because they can't be changing.
+ */
+ if (ItemPointerEquals(&tuple.t_self, &tuple.t_data->t_ctid))
+ {
+ /* deleted, so forget about it */
+ ReleaseBuffer(buffer);
+ return NULL;
+ }
+
+ /* updated, so look at the updated row */
+ tuple.t_self = tuple.t_data->t_ctid;
+ /* updated row should have xmin matching this xmax */
+ priorXmax = HeapTupleHeaderGetXmax(tuple.t_data);
+ ReleaseBuffer(buffer);
+ /* loop back to fetch next in chain */
}
/*
diff --git a/src/backend/utils/time/tqual.c b/src/backend/utils/time/tqual.c
index 94633249641298025fb43fa5f14388e0d099bbab..f8dcf43b64d7ff28b6077919fb4b10533d9b826a 100644
--- a/src/backend/utils/time/tqual.c
+++ b/src/backend/utils/time/tqual.c
@@ -32,7 +32,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/utils/time/tqual.c,v 1.89 2005/05/19 21:35:47 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/time/tqual.c,v 1.90 2005/08/20 00:39:57 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -677,14 +677,15 @@ HeapTupleSatisfiesUpdate(HeapTupleHeader tuple, CommandId curcid,
* 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. Also, the tuple's
- * t_ctid (forward link) is returned if it's being updated.
+ * 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.
*/
bool
HeapTupleSatisfiesDirty(HeapTupleHeader tuple, Buffer buffer)
{
SnapshotDirty->xmin = SnapshotDirty->xmax = InvalidTransactionId;
- ItemPointerSetInvalid(&(SnapshotDirty->tid));
if (!(tuple->t_infomask & HEAP_XMIN_COMMITTED))
{
@@ -781,7 +782,6 @@ HeapTupleSatisfiesDirty(HeapTupleHeader tuple, Buffer buffer)
{
if (tuple->t_infomask & HEAP_IS_LOCKED)
return true;
- SnapshotDirty->tid = tuple->t_ctid;
return false; /* updated by other */
}
@@ -824,7 +824,6 @@ HeapTupleSatisfiesDirty(HeapTupleHeader tuple, Buffer buffer)
tuple->t_infomask |= HEAP_XMAX_COMMITTED;
SetBufferCommitInfoNeedsSave(buffer);
- SnapshotDirty->tid = tuple->t_ctid;
return false; /* updated by other */
}
@@ -1224,10 +1223,13 @@ HeapTupleSatisfiesVacuum(HeapTupleHeader tuple, TransactionId OldestXmin,
HeapTupleHeaderGetXmax(tuple)))
{
/*
- * inserter also deleted it, so it was never visible to anyone
- * else
+ * Inserter also deleted it, so it was never visible to anyone
+ * else. However, we can only remove it early if it's not an
+ * updated tuple; else its parent tuple is linking to it via t_ctid,
+ * and this tuple mustn't go away before the parent does.
*/
- return HEAPTUPLE_DEAD;
+ if (!(tuple->t_infomask & HEAP_UPDATED))
+ return HEAPTUPLE_DEAD;
}
if (!TransactionIdPrecedes(HeapTupleHeaderGetXmax(tuple), OldestXmin))
diff --git a/src/include/access/heapam.h b/src/include/access/heapam.h
index 9c040b0dfd4f11db6cabf3a974cce30dfd548261..3221734a6f6f08c3a21b0894aa6e592c2c1a0689 100644
--- a/src/include/access/heapam.h
+++ b/src/include/access/heapam.h
@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/access/heapam.h,v 1.103 2005/08/01 20:31:13 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/access/heapam.h,v 1.104 2005/08/20 00:39:59 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -152,19 +152,23 @@ extern bool heap_release_fetch(Relation relation, Snapshot snapshot,
HeapTuple tuple, Buffer *userbuf, bool keep_buf,
PgStat_Info *pgstat_info);
-extern ItemPointer heap_get_latest_tid(Relation relation, Snapshot snapshot,
+extern void heap_get_latest_tid(Relation relation, Snapshot snapshot,
ItemPointer tid);
extern void setLastTid(const ItemPointer tid);
extern Oid heap_insert(Relation relation, HeapTuple tup, CommandId cid,
bool use_wal, bool use_fsm);
-extern HTSU_Result heap_delete(Relation relation, ItemPointer tid, ItemPointer ctid,
- CommandId cid, Snapshot crosscheck, bool wait);
-extern HTSU_Result heap_update(Relation relation, ItemPointer otid, HeapTuple tup,
- ItemPointer ctid, CommandId cid, Snapshot crosscheck, bool wait);
-extern HTSU_Result heap_lock_tuple(Relation relation, HeapTuple tup,
- Buffer *userbuf, CommandId cid,
- LockTupleMode mode, bool nowait);
+extern HTSU_Result heap_delete(Relation relation, ItemPointer tid,
+ ItemPointer ctid, TransactionId *update_xmax,
+ CommandId cid, Snapshot crosscheck, bool wait);
+extern HTSU_Result heap_update(Relation relation, ItemPointer otid,
+ HeapTuple newtup,
+ ItemPointer ctid, TransactionId *update_xmax,
+ CommandId cid, Snapshot crosscheck, bool wait);
+extern HTSU_Result heap_lock_tuple(Relation relation, HeapTuple tuple,
+ Buffer *buffer, ItemPointer ctid,
+ TransactionId *update_xmax, CommandId cid,
+ LockTupleMode mode, bool nowait);
extern Oid simple_heap_insert(Relation relation, HeapTuple tup);
extern void simple_heap_delete(Relation relation, ItemPointer tid);
diff --git a/src/include/access/htup.h b/src/include/access/htup.h
index e394afd31392a1e96fab99e8f333545b57e0cf1e..abc4dce9b95dfa8756284c0a4d8cd25846d3c0f6 100644
--- a/src/include/access/htup.h
+++ b/src/include/access/htup.h
@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/access/htup.h,v 1.75 2005/06/08 15:50:27 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/access/htup.h,v 1.76 2005/08/20 00:39:59 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -80,6 +80,21 @@
* However, with the advent of subtransactions, a tuple may need both Xmax
* and Cmin simultaneously, so this is no longer possible.
*
+ * A word about t_ctid: whenever a new tuple is stored on disk, its t_ctid
+ * is initialized with its own TID (location). If the tuple is ever updated,
+ * its t_ctid is changed to point to the replacement version of the tuple.
+ * Thus, a tuple is the latest version of its row iff XMAX is invalid or
+ * t_ctid points to itself (in which case, if XMAX is valid, the tuple is
+ * either locked or deleted). One can follow the chain of t_ctid links
+ * to find the newest version of the row. Beware however that VACUUM might
+ * erase the pointed-to (newer) tuple before erasing the pointing (older)
+ * tuple. Hence, when following a t_ctid link, it is necessary to check
+ * to see if the referenced slot is empty or contains an unrelated tuple.
+ * Check that the referenced tuple has XMIN equal to the referencing tuple's
+ * XMAX to verify that it is actually the descendant version and not an
+ * unrelated tuple stored into a slot recently freed by VACUUM. If either
+ * check fails, one may assume that there is no live descendant version.
+ *
* Following the fixed header fields, the nulls bitmap is stored (beginning
* at t_bits). The bitmap is *not* stored if t_infomask shows that there
* are no nulls in the tuple. If an OID field is present (as indicated by
@@ -334,18 +349,29 @@ do { \
/*
* HeapTupleData is an in-memory data structure that points to a tuple.
*
- * This new HeapTuple for version >= 6.5 and this is why it was changed:
+ * There are several ways in which this data structure is used:
+ *
+ * * Pointer to a tuple in a disk buffer: t_data points directly into the
+ * buffer (which the code had better be holding a pin on, but this is not
+ * reflected in HeapTupleData itself). t_datamcxt must be NULL.
+ *
+ * * Pointer to nothing: t_data and t_datamcxt are NULL. This is used as
+ * a failure indication in some functions.
+ *
+ * * Part of a palloc'd tuple: the HeapTupleData itself and the tuple
+ * form a single palloc'd chunk. t_data points to the memory location
+ * immediately following the HeapTupleData struct (at offset HEAPTUPLESIZE),
+ * and t_datamcxt is the containing context. This is used as the output
+ * format of heap_form_tuple and related routines.
*
- * 1. t_len moved off on-disk tuple data - ItemIdData is used to get len;
- * 2. t_ctid above is not self tuple TID now - it may point to
- * updated version of tuple (required by MVCC);
- * 3. someday someone let tuple to cross block boundaries -
- * he have to add something below...
+ * * Separately allocated tuple: t_data points to a palloc'd chunk that
+ * is not adjacent to the HeapTupleData, and t_datamcxt is the context
+ * containing that chunk.
*
- * Change for 7.0:
- * Up to now t_data could be NULL, the memory location directly following
- * HeapTupleData, or pointing into a buffer. Now, it could also point to
- * a separate allocation that was done in the t_datamcxt memory context.
+ * t_len should always be valid, except in the pointer-to-nothing case.
+ * t_self and t_tableOid should be valid if the HeapTupleData points to
+ * a disk buffer, or if it represents a copy of a tuple on disk. They
+ * should be explicitly set invalid in manufactured tuples.
*/
typedef struct HeapTupleData
{
diff --git a/src/include/executor/executor.h b/src/include/executor/executor.h
index 2e42894788eebdeb2f6bb05311d0659cf9904229..6064ff2f4f23eb7e3b686569418146253114c462 100644
--- a/src/include/executor/executor.h
+++ b/src/include/executor/executor.h
@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/executor/executor.h,v 1.118 2005/04/16 20:07:35 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/executor/executor.h,v 1.119 2005/08/20 00:40:13 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -98,7 +98,7 @@ extern bool ExecContextForcesOids(PlanState *planstate, bool *hasoids);
extern void ExecConstraints(ResultRelInfo *resultRelInfo,
TupleTableSlot *slot, EState *estate);
extern TupleTableSlot *EvalPlanQual(EState *estate, Index rti,
- ItemPointer tid);
+ ItemPointer tid, TransactionId priorXmax);
/*
* prototypes from functions in execProcnode.c
diff --git a/src/include/utils/tqual.h b/src/include/utils/tqual.h
index f12ae2233fd29c8b93ad9086270919b25a73fbfd..fa530ed977cc1843485f8af5b3ceaaaa796bbc7d 100644
--- a/src/include/utils/tqual.h
+++ b/src/include/utils/tqual.h
@@ -8,7 +8,7 @@
* Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/utils/tqual.h,v 1.57 2005/05/19 21:35:48 tgl Exp $
+ * $PostgreSQL: pgsql/src/include/utils/tqual.h,v 1.58 2005/08/20 00:40:32 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -42,7 +42,6 @@ typedef struct SnapshotData
TransactionId *xip; /* array of xact IDs in progress */
/* note: all ids in xip[] satisfy xmin <= xip[i] < xmax */
CommandId curcid; /* in my xact, CID < curcid are visible */
- ItemPointerData tid; /* required for Dirty snapshot -:( */
} SnapshotData;
typedef SnapshotData *Snapshot;