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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 * Portions Copyright (c) 1994, Regents of the University of California
* *
* IDENTIFICATION * 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 * HeapTupleSatisfiesItself
* True iff heap tuple is valid "for itself".
* *
* Visible tuples are those of: * Here, we consider the effects of:
* * all committed transactions (as of the current instant)
* transactions committed before our _command_ started (READ COMMITTED)
* previous commands of this transaction * previous commands of this transaction
* changes made by the current command * changes made by the current command
* *
@ -156,13 +156,15 @@ HeapTupleSatisfiesItself(HeapTupleHeader tuple)
/* /*
* HeapTupleSatisfiesNow * HeapTupleSatisfiesNow
* True iff heap tuple is valid "now".
* *
* Visible tuples are those of: * Here, we consider the effects of:
* * all committed transactions (as of the current instant)
* transactions committed before our _command_ started (READ COMMITTED)
* previous commands of this transaction * 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: * Note:
* Assumes heap tuple is valid. * Assumes heap tuple is valid.
@ -302,8 +304,7 @@ HeapTupleSatisfiesNow(HeapTupleHeader tuple)
/* /*
* HeapTupleSatisfiesToast * HeapTupleSatisfiesToast
* * True iff heap tuple is valid as a TOAST row.
* Valid if the heap tuple is valid for TOAST usage.
* *
* This is a simplified version that only checks for VACUUM moving conditions. * 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 * It's appropriate for TOAST usage because TOAST really doesn't want to do
@ -361,12 +362,8 @@ HeapTupleSatisfiesToast(HeapTupleHeader tuple)
/* /*
* HeapTupleSatisfiesUpdate * HeapTupleSatisfiesUpdate
* *
* Same as HeapTupleSatisfiesNow, but returns more information needed * Same logic as HeapTupleSatisfiesNow, but returns a more detailed result
* by UPDATE. * code, since UPDATE needs to know more than "is it visible?".
*
* This applies the same checks as HeapTupleSatisfiesNow,
* but returns a more detailed result code, since UPDATE needs to know
* more than "is it visible?".
*/ */
int int
HeapTupleSatisfiesUpdate(HeapTuple htuple) HeapTupleSatisfiesUpdate(HeapTuple htuple)
@ -484,13 +481,14 @@ HeapTupleSatisfiesUpdate(HeapTuple htuple)
return HeapTupleUpdated; /* updated by other */ return HeapTupleUpdated; /* updated by other */
} }
/* HeapTupleSatisfiesDirty /*
* HeapTupleSatisfiesDirty
* True iff heap tuple is valid including effects of open transactions.
* *
* Visible tuples are those of: * Here, we consider the effects of:
* * all committed and in-progress transactions (as of the current instant)
* _any_ in-progress transaction
* previous commands of this transaction * 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 * This is essentially like HeapTupleSatisfiesItself as far as effects of
* the current transaction and committed/aborted xacts are concerned. * the current transaction and committed/aborted xacts are concerned.
@ -614,15 +612,15 @@ HeapTupleSatisfiesDirty(HeapTupleHeader tuple)
/* /*
* HeapTupleSatisfiesSnapshot * HeapTupleSatisfiesSnapshot
* True iff heap tuple is valid for the given snapshot.
* *
* Visible tuples are those of: * Here, we consider the effects of:
* * all transactions committed as of the time of the given snapshot
* transactions committed before our transaction started (SERIALIZABLE)
* previous commands of this transaction * previous commands of this transaction
* *
* Does _not_ include: * Does _not_ include:
* transactions in-progress when our transaction started * transactions shown as in-progress by the snapshot
* transactions committed after our transaction started * transactions started after the snapshot was taken
* changes made by the current command * changes made by the current command
* *
* This is the same as HeapTupleSatisfiesNow, except that transactions that * This is the same as HeapTupleSatisfiesNow, except that transactions that
@ -770,11 +768,9 @@ HeapTupleSatisfiesSnapshot(HeapTupleHeader tuple, Snapshot snapshot)
/* /*
* HeapTupleSatisfiesVacuum * HeapTupleSatisfiesVacuum
* *
* Visible tuples are those of: * Determine the status of tuples for VACUUM purposes. Here, what
* * we mainly want to know is if a tuple is potentially visible to *any*
* tuples visible by any running transaction * running transaction. If so, it can't be removed yet by VACUUM.
*
* Used by VACUUM and related operations.
* *
* OldestXmin is a cutoff XID (obtained from GetOldestXmin()). Tuples * OldestXmin is a cutoff XID (obtained from GetOldestXmin()). Tuples
* deleted by XIDs >= OldestXmin are deemed "recently dead"; they might * deleted by XIDs >= OldestXmin are deemed "recently dead"; they might