Movatterモバイル変換

[0]ホーム
URL:

Skip to content

Navigation Menu

Sign in
Appearance settings

Search code, repositories, users, issues, pull requests...

Provide feedback

We read every piece of feedback, and take your input very seriously.

Saved searches

Use saved searches to filter your results more quickly

 Sign up
Appearance settings

Commit7f52e0c

Browse files
committed
Tweak writetup_heap/readtup_heap to avoid storing the tuple identity
and transaction visibility fields of tuples being sorted. These arealways uninteresting in a tuple being sorted (if the fields were actuallyselected, they'd have been pulled out into user columns beforehand).This saves about 24 bytes per row being sorted, which is a useful savingsfor any but the widest of sort rows. Per recent discussion.
1 parent672f0be commit7f52e0c

File tree

2 files changed

+91
-20
lines changed

2 files changed

+91
-20
lines changed

‎src/backend/utils/sort/tuplesort.c

Lines changed: 85 additions & 18 deletions
Original file line numberDiff line numberDiff line change
@@ -91,7 +91,7 @@
9191
* Portions Copyright (c) 1994, Regents of the University of California
9292
*
9393
* IDENTIFICATION
94-
* $PostgreSQL: pgsql/src/backend/utils/sort/tuplesort.c,v 1.65 2006/03/10 23:19:00 tgl Exp $
94+
* $PostgreSQL: pgsql/src/backend/utils/sort/tuplesort.c,v 1.66 2006/05/23 21:37:59 tgl Exp $
9595
*
9696
*-------------------------------------------------------------------------
9797
*/
@@ -2329,23 +2329,53 @@ copytup_heap(Tuplesortstate *state, SortTuple *stup, void *tup)
23292329
}
23302330

23312331
/*
2332-
* We don't bother to write the HeapTupleData part of the tuple.
2332+
* When writing HeapTuples to tape, we strip off all tuple identity and
2333+
* transaction visibility information, because those fields aren't really
2334+
* interesting for in-memory tuples (they may or may not be valid in the
2335+
* incoming tuples, depending on the plan that's feeding the sort). We
2336+
* only need to store t_natts, t_infomask, the nulls bitmap if any, and
2337+
* the user data.
2338+
*
2339+
* You might think that we could omit storing t_natts, but you'd be wrong:
2340+
* the incoming tuple might be a physical disk tuple with fewer columns
2341+
* than the table's current logical tupdesc.
23332342
*/
2343+
typedefstructTapeTupleHeader
2344+
{
2345+
unsignedinttuplen;/* required header of a tape item */
2346+
int16natts;/* number of attributes */
2347+
uint16infomask;/* various flag bits */
2348+
/* nulls bitmap follows if HEAP_HASNULL, then actual tuple data */
2349+
}TapeTupleHeader;
23342350

23352351
staticvoid
23362352
writetup_heap(Tuplesortstate*state,inttapenum,SortTuple*stup)
23372353
{
23382354
HeapTupletuple= (HeapTuple)stup->tuple;
2339-
unsignedinttuplen;
2340-
2341-
tuplen=tuple->t_len+sizeof(tuplen);
2355+
HeapTupleHeadert_data=tuple->t_data;
2356+
TapeTupleHeadertapehdr;
2357+
unsignedintdatalen;
2358+
unsignedintnullslen;
2359+
2360+
Assert(tuple->t_len >=t_data->t_hoff);
2361+
datalen=tuple->t_len-t_data->t_hoff;
2362+
if (HeapTupleHasNulls(tuple))
2363+
nullslen=BITMAPLEN(t_data->t_natts);
2364+
else
2365+
nullslen=0;
2366+
tapehdr.tuplen=sizeof(TapeTupleHeader)+nullslen+datalen;
2367+
tapehdr.natts=t_data->t_natts;
2368+
tapehdr.infomask=t_data->t_infomask;
23422369
LogicalTapeWrite(state->tapeset,tapenum,
2343-
(void*)&tuplen,sizeof(tuplen));
2370+
(void*)&tapehdr,sizeof(tapehdr));
2371+
if (nullslen)
2372+
LogicalTapeWrite(state->tapeset,tapenum,
2373+
(void*)t_data->t_bits,nullslen);
23442374
LogicalTapeWrite(state->tapeset,tapenum,
2345-
(void*)tuple->t_data,tuple->t_len);
2375+
(char*)t_data+t_data->t_hoff,datalen);
23462376
if (state->randomAccess)/* need trailing length word? */
23472377
LogicalTapeWrite(state->tapeset,tapenum,
2348-
(void*)&tuplen,sizeof(tuplen));
2378+
(void*)&tapehdr.tuplen,sizeof(tapehdr.tuplen));
23492379

23502380
FREEMEM(state,GetMemoryChunkSpace(tuple));
23512381
heap_freetuple(tuple);
@@ -2355,22 +2385,59 @@ static void
23552385
readtup_heap(Tuplesortstate*state,SortTuple*stup,
23562386
inttapenum,unsignedintlen)
23572387
{
2358-
unsignedinttuplen=len-sizeof(unsignedint)+HEAPTUPLESIZE;
2359-
HeapTupletuple= (HeapTuple)palloc(tuplen);
2388+
TapeTupleHeadertapehdr;
2389+
unsignedintdatalen;
2390+
unsignedintnullslen;
2391+
unsignedinthoff;
2392+
HeapTupletuple;
2393+
HeapTupleHeadert_data;
23602394

2395+
/* read in the rest of the header */
2396+
if (LogicalTapeRead(state->tapeset,tapenum,
2397+
(char*)&tapehdr+sizeof(unsignedint),
2398+
sizeof(tapehdr)-sizeof(unsignedint))!=
2399+
sizeof(tapehdr)-sizeof(unsignedint))
2400+
elog(ERROR,"unexpected end of data");
2401+
/* reconstruct lengths of null bitmap and data part */
2402+
if (tapehdr.infomask&HEAP_HASNULL)
2403+
nullslen=BITMAPLEN(tapehdr.natts);
2404+
else
2405+
nullslen=0;
2406+
datalen=len-sizeof(TapeTupleHeader)-nullslen;
2407+
/* determine overhead size of tuple (should match heap_form_tuple) */
2408+
hoff= offsetof(HeapTupleHeaderData,t_bits)+nullslen;
2409+
if (tapehdr.infomask&HEAP_HASOID)
2410+
hoff+=sizeof(Oid);
2411+
hoff=MAXALIGN(hoff);
2412+
/* Allocate the space in one chunk, like heap_form_tuple */
2413+
tuple= (HeapTuple)palloc(HEAPTUPLESIZE+hoff+datalen);
23612414
USEMEM(state,GetMemoryChunkSpace(tuple));
2362-
/* reconstruct the HeapTupleData portion */
2363-
tuple->t_len=len-sizeof(unsignedint);
2415+
t_data= (HeapTupleHeader) ((char*)tuple+HEAPTUPLESIZE);
2416+
/* make sure unused header fields are zeroed */
2417+
MemSetAligned(t_data,0,hoff);
2418+
/* reconstruct the HeapTupleData fields */
2419+
tuple->t_len=hoff+datalen;
23642420
ItemPointerSetInvalid(&(tuple->t_self));
23652421
tuple->t_tableOid=InvalidOid;
2366-
tuple->t_data= (HeapTupleHeader) (((char*)tuple)+HEAPTUPLESIZE);
2367-
/* read in the tuple proper */
2368-
if (LogicalTapeRead(state->tapeset,tapenum, (void*)tuple->t_data,
2369-
tuple->t_len)!=tuple->t_len)
2422+
tuple->t_data=t_data;
2423+
/* reconstruct the HeapTupleHeaderData fields */
2424+
ItemPointerSetInvalid(&(t_data->t_ctid));
2425+
t_data->t_natts=tapehdr.natts;
2426+
t_data->t_infomask= (tapehdr.infomask& ~HEAP_XACT_MASK)
2427+
| (HEAP_XMIN_INVALID |HEAP_XMAX_INVALID);
2428+
t_data->t_hoff=hoff;
2429+
/* read in the null bitmap if any */
2430+
if (nullslen)
2431+
if (LogicalTapeRead(state->tapeset,tapenum,
2432+
(void*)t_data->t_bits,nullslen)!=nullslen)
2433+
elog(ERROR,"unexpected end of data");
2434+
/* and the data proper */
2435+
if (LogicalTapeRead(state->tapeset,tapenum,
2436+
(char*)t_data+hoff,datalen)!=datalen)
23702437
elog(ERROR,"unexpected end of data");
23712438
if (state->randomAccess)/* need trailing length word? */
2372-
if (LogicalTapeRead(state->tapeset,tapenum, (void*)&tuplen,
2373-
sizeof(tuplen))!=sizeof(tuplen))
2439+
if (LogicalTapeRead(state->tapeset,tapenum, (void*)&tapehdr.tuplen,
2440+
sizeof(tapehdr.tuplen))!=sizeof(tapehdr.tuplen))
23742441
elog(ERROR,"unexpected end of data");
23752442
stup->tuple= (void*)tuple;
23762443
/* set up first-column key value */

‎src/include/utils/tuplesort.h

Lines changed: 6 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -13,7 +13,7 @@
1313
* Portions Copyright (c) 1996-2006, PostgreSQL Global Development Group
1414
* Portions Copyright (c) 1994, Regents of the University of California
1515
*
16-
* $PostgreSQL: pgsql/src/include/utils/tuplesort.h,v 1.19 2006/03/05 15:59:08 momjian Exp $
16+
* $PostgreSQL: pgsql/src/include/utils/tuplesort.h,v 1.20 2006/05/23 21:37:59 tgl Exp $
1717
*
1818
*-------------------------------------------------------------------------
1919
*/
@@ -32,7 +32,11 @@ typedef struct Tuplesortstate Tuplesortstate;
3232
* We provide two different interfaces to what is essentially the same
3333
* code: one for sorting HeapTuples and one for sorting IndexTuples.
3434
* They differ primarily in the way that the sort key information is
35-
* supplied.
35+
* supplied. Also, tuplesort.c guarantees to preserve all the header
36+
* fields of an IndexTuple, but when sorting HeapTuples only the user data
37+
* is guaranteed preserved, not the "system columns" (tuple identity and
38+
* transaction visibility info).
39+
*
3640
* Yet a third slightly different interface supports sorting bare Datums.
3741
*/
3842

0 commit comments

Comments
 (0)
[8]ページ先頭
©2009-2025 Movatter.jp