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Combine cmin and cmax fields of HeapTupleHeaders into a single field, by
keeping private state in each backend that has inserted and deleted the same tuple during its current top-level transaction. This is sufficient since there is no need to be able to determine the cmin/cmax from any other transaction. This gets us back down to 23-byte headers, removing a penalty paid in 8.0 to support subtransactions. Patch by Heikki Linnakangas, with minor revisions by moi, following a design hashed out awhile back on the pghackers list.
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21 files changed

+799
-127
lines changed

21 files changed

+799
-127
lines changed

‎src/backend/access/common/heaptuple.c

Lines changed: 9 additions & 5 deletions
Original file line numberDiff line numberDiff line change
@@ -16,7 +16,7 @@
1616
*
1717
*
1818
* IDENTIFICATION
19-
* $PostgreSQL: pgsql/src/backend/access/common/heaptuple.c,v 1.114 2007/01/09 22:00:59 momjian Exp $
19+
* $PostgreSQL: pgsql/src/backend/access/common/heaptuple.c,v 1.115 2007/02/09 03:35:33 tgl Exp $
2020
*
2121
*-------------------------------------------------------------------------
2222
*/
@@ -582,14 +582,18 @@ heap_getsysattr(HeapTuple tup, int attnum, TupleDesc tupleDesc, bool *isnull)
582582
case MinTransactionIdAttributeNumber:
583583
result = TransactionIdGetDatum(HeapTupleHeaderGetXmin(tup->t_data));
584584
break;
585-
case MinCommandIdAttributeNumber:
586-
result = CommandIdGetDatum(HeapTupleHeaderGetCmin(tup->t_data));
587-
break;
588585
case MaxTransactionIdAttributeNumber:
589586
result = TransactionIdGetDatum(HeapTupleHeaderGetXmax(tup->t_data));
590587
break;
588+
case MinCommandIdAttributeNumber:
591589
case MaxCommandIdAttributeNumber:
592-
result = CommandIdGetDatum(HeapTupleHeaderGetCmax(tup->t_data));
590+
/*
591+
* cmin and cmax are now both aliases for the same field,
592+
* which can in fact also be a combo command id. XXX perhaps we
593+
* should return the "real" cmin or cmax if possible, that is
594+
* if we are inside the originating transaction?
595+
*/
596+
result = CommandIdGetDatum(HeapTupleHeaderGetRawCommandId(tup->t_data));
593597
break;
594598
case TableOidAttributeNumber:
595599
result = ObjectIdGetDatum(tup->t_tableOid);

‎src/backend/access/heap/heapam.c

Lines changed: 22 additions & 14 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/access/heap/heapam.c,v 1.227 2007/02/05 04:22:18 tgl Exp $
11+
* $PostgreSQL: pgsql/src/backend/access/heap/heapam.c,v 1.228 2007/02/09 03:35:33 tgl Exp $
1212
*
1313
*
1414
* INTERFACE ROUTINES
@@ -1407,8 +1407,7 @@ heap_insert(Relation relation, HeapTuple tup, CommandId cid,
14071407
tup->t_data->t_infomask |= HEAP_XMAX_INVALID;
14081408
HeapTupleHeaderSetXmin(tup->t_data, xid);
14091409
HeapTupleHeaderSetCmin(tup->t_data, cid);
1410-
HeapTupleHeaderSetXmax(tup->t_data, 0); /* zero out Datum fields */
1411-
HeapTupleHeaderSetCmax(tup->t_data, 0); /* for cleanliness */
1410+
HeapTupleHeaderSetXmax(tup->t_data, 0); /* for cleanliness */
14121411
tup->t_tableOid = RelationGetRelid(relation);
14131412

14141413
/*
@@ -1585,6 +1584,7 @@ heap_delete(Relation relation, ItemPointer tid,
15851584
PageHeader dp;
15861585
Buffer buffer;
15871586
bool have_tuple_lock = false;
1587+
bool iscombo;
15881588

15891589
Assert(ItemPointerIsValid(tid));
15901590

@@ -1724,6 +1724,9 @@ heap_delete(Relation relation, ItemPointer tid,
17241724
return result;
17251725
}
17261726

1727+
/* replace cid with a combo cid if necessary */
1728+
HeapTupleHeaderAdjustCmax(tp.t_data, &cid, &iscombo);
1729+
17271730
START_CRIT_SECTION();
17281731

17291732
/* store transaction information of xact deleting the tuple */
@@ -1733,7 +1736,7 @@ heap_delete(Relation relation, ItemPointer tid,
17331736
HEAP_IS_LOCKED |
17341737
HEAP_MOVED);
17351738
HeapTupleHeaderSetXmax(tp.t_data, xid);
1736-
HeapTupleHeaderSetCmax(tp.t_data, cid);
1739+
HeapTupleHeaderSetCmax(tp.t_data, cid, iscombo);
17371740
/* Make sure there is no forward chain link in t_ctid */
17381741
tp.t_data->t_ctid = tp.t_self;
17391742

@@ -1893,6 +1896,7 @@ heap_update(Relation relation, ItemPointer otid, HeapTuple newtup,
18931896
Size newtupsize,
18941897
pagefree;
18951898
bool have_tuple_lock = false;
1899+
bool iscombo;
18961900

18971901
Assert(ItemPointerIsValid(otid));
18981902

@@ -2058,8 +2062,13 @@ heap_update(Relation relation, ItemPointer otid, HeapTuple newtup,
20582062
newtup->t_data->t_infomask |= (HEAP_XMAX_INVALID | HEAP_UPDATED);
20592063
HeapTupleHeaderSetXmin(newtup->t_data, xid);
20602064
HeapTupleHeaderSetCmin(newtup->t_data, cid);
2061-
HeapTupleHeaderSetXmax(newtup->t_data, 0); /* zero out Datum fields */
2062-
HeapTupleHeaderSetCmax(newtup->t_data, 0); /* for cleanliness */
2065+
HeapTupleHeaderSetXmax(newtup->t_data, 0); /* for cleanliness */
2066+
2067+
/*
2068+
* Replace cid with a combo cid if necessary. Note that we already put
2069+
* the plain cid into the new tuple.
2070+
*/
2071+
HeapTupleHeaderAdjustCmax(oldtup.t_data, &cid, &iscombo);
20632072

20642073
/*
20652074
* If the toaster needs to be activated, OR if the new tuple will not fit
@@ -2088,7 +2097,7 @@ heap_update(Relation relation, ItemPointer otid, HeapTuple newtup,
20882097
HEAP_IS_LOCKED |
20892098
HEAP_MOVED);
20902099
HeapTupleHeaderSetXmax(oldtup.t_data, xid);
2091-
HeapTupleHeaderSetCmax(oldtup.t_data, cid);
2100+
HeapTupleHeaderSetCmax(oldtup.t_data, cid, iscombo);
20922101
/* temporarily make it look not-updated */
20932102
oldtup.t_data->t_ctid = oldtup.t_self;
20942103
already_marked = true;
@@ -2183,7 +2192,7 @@ heap_update(Relation relation, ItemPointer otid, HeapTuple newtup,
21832192
HEAP_IS_LOCKED |
21842193
HEAP_MOVED);
21852194
HeapTupleHeaderSetXmax(oldtup.t_data, xid);
2186-
HeapTupleHeaderSetCmax(oldtup.t_data, cid);
2195+
HeapTupleHeaderSetCmax(oldtup.t_data, cid, iscombo);
21872196
}
21882197

21892198
/* record address of new tuple in t_ctid of old one */
@@ -2687,12 +2696,11 @@ heap_lock_tuple(Relation relation, HeapTuple tuple, Buffer *buffer,
26872696
/*
26882697
* Store transaction information of xact locking the tuple.
26892698
*
2690-
* Note: our CID is meaningless if storing a MultiXactId, but no harm in
2691-
* storing it anyway.
2699+
* Note: Cmax is meaningless in this context, so don't set it; this
2700+
* avoids possibly generating a useless combo CID.
26922701
*/
26932702
tuple->t_data->t_infomask = new_infomask;
26942703
HeapTupleHeaderSetXmax(tuple->t_data, xid);
2695-
HeapTupleHeaderSetCmax(tuple->t_data, cid);
26962704
/* Make sure there is no forward chain link in t_ctid */
26972705
tuple->t_data->t_ctid = *tid;
26982706

@@ -3443,7 +3451,7 @@ heap_xlog_delete(XLogRecPtr lsn, XLogRecord *record)
34433451
HEAP_IS_LOCKED |
34443452
HEAP_MOVED);
34453453
HeapTupleHeaderSetXmax(htup, record->xl_xid);
3446-
HeapTupleHeaderSetCmax(htup, FirstCommandId);
3454+
HeapTupleHeaderSetCmax(htup, FirstCommandId, false);
34473455
/* Make sure there is no forward chain link in t_ctid */
34483456
htup->t_ctid = xlrec->target.tid;
34493457
PageSetLSN(page, lsn);
@@ -3608,7 +3616,7 @@ heap_xlog_update(XLogRecPtr lsn, XLogRecord *record, bool move)
36083616
HEAP_IS_LOCKED |
36093617
HEAP_MOVED);
36103618
HeapTupleHeaderSetXmax(htup, record->xl_xid);
3611-
HeapTupleHeaderSetCmax(htup, FirstCommandId);
3619+
HeapTupleHeaderSetCmax(htup, FirstCommandId, false);
36123620
/* Set forward chain link in t_ctid */
36133621
htup->t_ctid = xlrec->newtid;
36143622
}
@@ -3761,7 +3769,7 @@ heap_xlog_lock(XLogRecPtr lsn, XLogRecord *record)
37613769
else
37623770
htup->t_infomask |= HEAP_XMAX_EXCL_LOCK;
37633771
HeapTupleHeaderSetXmax(htup, xlrec->locking_xid);
3764-
HeapTupleHeaderSetCmax(htup, FirstCommandId);
3772+
HeapTupleHeaderSetCmax(htup, FirstCommandId, false);
37653773
/* Make sure there is no forward chain link in t_ctid */
37663774
htup->t_ctid = xlrec->target.tid;
37673775
PageSetLSN(page, lsn);

‎src/backend/access/transam/xact.c

Lines changed: 6 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -10,7 +10,7 @@
1010
*
1111
*
1212
* IDENTIFICATION
13-
* $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.233 2007/02/07 23:11:29 tgl Exp $
13+
* $PostgreSQL: pgsql/src/backend/access/transam/xact.c,v 1.234 2007/02/09 03:35:33 tgl Exp $
1414
*
1515
*-------------------------------------------------------------------------
1616
*/
@@ -38,11 +38,12 @@
3838
#include "storage/lmgr.h"
3939
#include "storage/procarray.h"
4040
#include "storage/smgr.h"
41+
#include "utils/combocid.h"
4142
#include "utils/flatfiles.h"
43+
#include "utils/guc.h"
4244
#include "utils/inval.h"
4345
#include "utils/memutils.h"
4446
#include "utils/relcache.h"
45-
#include "utils/guc.h"
4647

4748

4849
/*
@@ -1628,6 +1629,7 @@ CommitTransaction(void)
16281629
AtEOXact_Namespace(true);
16291630
/* smgrcommit already done */
16301631
AtEOXact_Files();
1632+
AtEOXact_ComboCid();
16311633
pgstat_clear_snapshot();
16321634
pgstat_count_xact_commit();
16331635
pgstat_report_txn_timestamp(0);
@@ -1845,6 +1847,7 @@ PrepareTransaction(void)
18451847
AtEOXact_Namespace(true);
18461848
/* smgrcommit already done */
18471849
AtEOXact_Files();
1850+
AtEOXact_ComboCid();
18481851
pgstat_clear_snapshot();
18491852

18501853
CurrentResourceOwner = NULL;
@@ -1997,6 +2000,7 @@ AbortTransaction(void)
19972000
AtEOXact_Namespace(false);
19982001
smgrabort();
19992002
AtEOXact_Files();
2003+
AtEOXact_ComboCid();
20002004
pgstat_clear_snapshot();
20012005
pgstat_count_xact_rollback();
20022006
pgstat_report_txn_timestamp(0);

‎src/backend/utils/fmgr/fmgr.c

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -8,7 +8,7 @@
88
*
99
*
1010
* IDENTIFICATION
11-
* $PostgreSQL: pgsql/src/backend/utils/fmgr/fmgr.c,v 1.103 2007/01/05 22:19:43 momjian Exp $
11+
* $PostgreSQL: pgsql/src/backend/utils/fmgr/fmgr.c,v 1.104 2007/02/09 03:35:34 tgl Exp $
1212
*
1313
*-------------------------------------------------------------------------
1414
*/
@@ -64,7 +64,7 @@ typedef struct
6464
/* fn_oid is the hash key and so must be first! */
6565
Oid fn_oid; /* OID of an external C function */
6666
TransactionId fn_xmin; /* for checking up-to-dateness */
67-
CommandId fn_cmin;
67+
ItemPointerData fn_tid;
6868
PGFunction user_fn; /* the function's address */
6969
const Pg_finfo_record *inforec; /* address of its info record */
7070
} CFuncHashTabEntry;
@@ -483,7 +483,7 @@ lookup_C_func(HeapTuple procedureTuple)
483483
if (entry == NULL)
484484
return NULL; /* no such entry */
485485
if (entry->fn_xmin == HeapTupleHeaderGetXmin(procedureTuple->t_data) &&
486-
entry->fn_cmin == HeapTupleHeaderGetCmin(procedureTuple->t_data))
486+
ItemPointerEquals(&entry->fn_tid, &procedureTuple->t_self))
487487
return entry; /* OK */
488488
return NULL; /* entry is out of date */
489489
}
@@ -521,7 +521,7 @@ record_C_func(HeapTuple procedureTuple,
521521
&found);
522522
/* OID is already filled in */
523523
entry->fn_xmin = HeapTupleHeaderGetXmin(procedureTuple->t_data);
524-
entry->fn_cmin = HeapTupleHeaderGetCmin(procedureTuple->t_data);
524+
entry->fn_tid = procedureTuple->t_self;
525525
entry->user_fn = user_fn;
526526
entry->inforec = inforec;
527527
}

‎src/backend/utils/time/Makefile

Lines changed: 3 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -4,20 +4,20 @@
44
# Makefile for utils/time
55
#
66
# IDENTIFICATION
7-
# $PostgreSQL: pgsql/src/backend/utils/time/Makefile,v 1.11 2007/01/20 17:16:15 petere Exp $
7+
# $PostgreSQL: pgsql/src/backend/utils/time/Makefile,v 1.12 2007/02/09 03:35:34 tgl Exp $
88
#
99
#-------------------------------------------------------------------------
1010

1111
subdir = src/backend/utils/time
1212
top_builddir = ../../../..
1313
include $(top_builddir)/src/Makefile.global
1414

15-
OBJS = tqual.o
15+
OBJS = combocid.o tqual.o
1616

1717
all: SUBSYS.o
1818

1919
SUBSYS.o: $(OBJS)
2020
$(LD) $(LDREL) $(LDOUT) SUBSYS.o $(OBJS)
2121

22-
clean:
22+
clean:
2323
rm -f SUBSYS.o $(OBJS)

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