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Fix misstatements added by Bruce.

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This commit is contained in:
Tom Lane 2002-01-16 23:51:56 +00:00
parent d781138235
commit b7bf03c9ed
1 changed files with 27 additions and 31 deletions
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58
src/backend/utils/time/tqual.c
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@ -16,7 +16,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
* $Header: /cvsroot/pgsql/src/backend/utils/time/tqual.c,v 1.48 2002/01/16 23:09:09 momjian Exp $
* $Header: /cvsroot/pgsql/src/backend/utils/time/tqual.c,v 1.49 2002/01/16 23:51:56 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -38,10 +38,10 @@ bool ReferentialIntegritySnapshotOverride = false;
/*
* HeapTupleSatisfiesItself
* True iff heap tuple is valid "for itself".
*
* Visible tuples are those of:
*
* transactions committed before our _command_ started (READ COMMITTED)
* Here, we consider the effects of:
* all committed transactions (as of the current instant)
* previous commands of this transaction
* changes made by the current command
*
@ -156,13 +156,15 @@ HeapTupleSatisfiesItself(HeapTupleHeader tuple)
/*
* HeapTupleSatisfiesNow
* True iff heap tuple is valid "now".
*
* Visible tuples are those of:
*
* transactions committed before our _command_ started (READ COMMITTED)
* Here, we consider the effects of:
* all committed transactions (as of the current instant)
* previous commands of this transaction
*
* Does _not_ include changes made by the current command
* Note we do _not_ include changes made by the current command. This
* solves the "Halloween problem" wherein an UPDATE might try to re-update
* its own output tuples.
*
* Note:
* Assumes heap tuple is valid.
@ -302,8 +304,7 @@ HeapTupleSatisfiesNow(HeapTupleHeader tuple)
/*
* HeapTupleSatisfiesToast
*
* Valid if the heap tuple is valid for TOAST usage.
* True iff heap tuple is valid as a TOAST row.
*
* This is a simplified version that only checks for VACUUM moving conditions.
* It's appropriate for TOAST usage because TOAST really doesn't want to do
@ -361,12 +362,8 @@ HeapTupleSatisfiesToast(HeapTupleHeader tuple)
/*
* HeapTupleSatisfiesUpdate
*
* Same as HeapTupleSatisfiesNow, but returns more information needed
* by UPDATE.
*
* This applies the same checks as HeapTupleSatisfiesNow,
* but returns a more detailed result code, since UPDATE needs to know
* more than "is it visible?".
* Same logic as HeapTupleSatisfiesNow, but returns a more detailed result
* code, since UPDATE needs to know more than "is it visible?".
*/
int
HeapTupleSatisfiesUpdate(HeapTuple htuple)
@ -484,13 +481,14 @@ HeapTupleSatisfiesUpdate(HeapTuple htuple)
return HeapTupleUpdated; /* updated by other */
}
/* HeapTupleSatisfiesDirty
/*
* HeapTupleSatisfiesDirty
* True iff heap tuple is valid including effects of open transactions.
*
* Visible tuples are those of:
*
* _any_ in-progress transaction
* Here, we consider the effects of:
* all committed and in-progress transactions (as of the current instant)
* previous commands of this transaction
* changes by the current command
* changes made by the current command
*
* This is essentially like HeapTupleSatisfiesItself as far as effects of
* the current transaction and committed/aborted xacts are concerned.
@ -614,15 +612,15 @@ HeapTupleSatisfiesDirty(HeapTupleHeader tuple)
/*
* HeapTupleSatisfiesSnapshot
* True iff heap tuple is valid for the given snapshot.
*
* Visible tuples are those of:
*
* transactions committed before our transaction started (SERIALIZABLE)
* Here, we consider the effects of:
* all transactions committed as of the time of the given snapshot
* previous commands of this transaction
*
* Does _not_ include:
* transactions in-progress when our transaction started
* transactions committed after our transaction started
* transactions shown as in-progress by the snapshot
* transactions started after the snapshot was taken
* changes made by the current command
*
* This is the same as HeapTupleSatisfiesNow, except that transactions that
@ -770,11 +768,9 @@ HeapTupleSatisfiesSnapshot(HeapTupleHeader tuple, Snapshot snapshot)
/*
* HeapTupleSatisfiesVacuum
*
* Visible tuples are those of:
*
* tuples visible by any running transaction
*
* Used by VACUUM and related operations.
* Determine the status of tuples for VACUUM purposes. Here, what
* we mainly want to know is if a tuple is potentially visible to *any*
* running transaction. If so, it can't be removed yet by VACUUM.
*
* OldestXmin is a cutoff XID (obtained from GetOldestXmin()). Tuples
* deleted by XIDs >= OldestXmin are deemed "recently dead"; they might