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Clean up the representation of special snapshots by including a "method

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pointer" in every Snapshot struct.  This allows removal of the case-by-case
tests in HeapTupleSatisfiesVisibility, which should make it a bit faster
(I didn't try any performance tests though).  More importantly, we are no
longer violating portable C practices by assuming that small integers are
distinct from all pointer values, and HeapTupleSatisfiesDirty no longer
has a non-reentrant API involving side-effects on a global variable.

There were a couple of places calling HeapTupleSatisfiesXXX routines
directly rather than through the HeapTupleSatisfiesVisibility macro.
Since these places had to be changed anyway, I chose to make them go
through the macro for uniformity.

Along the way I renamed HeapTupleSatisfiesSnapshot to HeapTupleSatisfiesMVCC
to emphasize that it's only used with MVCC-type snapshots.  I was sorely
tempted to rename HeapTupleSatisfiesVisibility to HeapTupleSatisfiesSnapshot,
but forebore for the moment to avoid confusion and reduce the likelihood that
this patch breaks some of the pending patches.  Might want to reconsider
doing that later.
This commit is contained in:
Tom Lane
2007-03-25 19:45:14 +00:00
parent 75c6519ff6
commit e85a01df67
10 changed files with 148 additions and 121 deletions
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4
src/backend/storage/ipc/procarray.c
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@ -23,7 +23,7 @@
*
*
* IDENTIFICATION
* $PostgreSQL: pgsql/src/backend/storage/ipc/procarray.c,v 1.22 2007/03/23 03:16:39 momjian Exp $
* $PostgreSQL: pgsql/src/backend/storage/ipc/procarray.c,v 1.23 2007/03/25 19:45:14 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -484,7 +484,7 @@ GetOldestXmin(bool allDbs, bool ignoreVacuum)
* limited cache area for subxact XIDs, full information may not be
* available. If we find any overflowed subxid arrays, we have to mark
* the snapshot's subxid data as overflowed, and extra work will need to
* be done to determine what's running (see XidInSnapshot() in tqual.c).
* be done to determine what's running (see XidInMVCCSnapshot() in tqual.c).
*
* We also update the following backend-global variables:
* TransactionXmin: the oldest xmin of any snapshot in use in the