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Introduce CompactAttribute array in TupleDesc
The new compact_attrs array stores a few select fields from FormData_pg_attribute in a more compact way, using only 16 bytes per column instead of the 104 bytes that FormData_pg_attribute uses. Using CompactAttribute allows performance-critical operations such as tuple deformation to be performed without looking at the FormData_pg_attribute element in TupleDesc which means fewer cacheline accesses. With this change, NAMEDATALEN could be increased with a much smaller negative impact on performance. For some workloads, tuple deformation can be the most CPU intensive part of processing the query. Some testing with 16 columns on a table where the first column is variable length showed around a 10% increase in transactions per second for an OLAP type query performing aggregation on the 16th column. However, in certain cases, the increases were much higher, up to ~25% on one AMD Zen4 machine. This also makes pg_attribute.attcacheoff redundant. A follow-on commit will remove it, thus shrinking the FormData_pg_attribute struct by 4 bytes. Author: David Rowley Discussion: https://postgr.es/m/CAApHDvrBztXP3yx=NKNmo3xwFAFhEdyPnvrDg3=M0RhDs+4vYw@mail.gmail.com Reviewed-by: Andres Freund, Victor Yegorov
1 parent e4c8865 commit d28dff3

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14 files changed

+246
-68
lines changed

14 files changed

+246
-68
lines changed

‎src/backend/access/common/heaptuple.c

Lines changed: 28 additions & 25 deletions
Original file line numberDiff line numberDiff line change
@@ -83,6 +83,10 @@
8383
#define VARLENA_ATT_IS_PACKABLE(att) \
8484
((att)->attstorage != TYPSTORAGE_PLAIN)
8585

86+
/* FormData_pg_attribute.attstorage != TYPSTORAGE_PLAIN and an attlen of -1 */
87+
#define COMPACT_ATTR_IS_PACKABLE(att) \
88+
((att)->attlen == -1 && (att)->attispackable)
89+
8690
/*
8791
* Setup for caching pass-by-ref missing attributes in a way that survives
8892
* tupleDesc destruction.
@@ -147,12 +151,12 @@ Datum
147151
getmissingattr(TupleDesc tupleDesc,
148152
int attnum, bool *isnull)
149153
{
150-
Form_pg_attribute att;
154+
CompactAttribute *att;
151155

152156
Assert(attnum <= tupleDesc->natts);
153157
Assert(attnum > 0);
154158

155-
att = TupleDescAttr(tupleDesc, attnum - 1);
159+
att = TupleDescCompactAttr(tupleDesc, attnum - 1);
156160

157161
if (att->atthasmissing)
158162
{
@@ -223,15 +227,15 @@ heap_compute_data_size(TupleDesc tupleDesc,
223227
for (i = 0; i < numberOfAttributes; i++)
224228
{
225229
Datum val;
226-
Form_pg_attribute atti;
230+
CompactAttribute *atti;
227231

228232
if (isnull[i])
229233
continue;
230234

231235
val = values[i];
232-
atti = TupleDescAttr(tupleDesc, i);
236+
atti = TupleDescCompactAttr(tupleDesc, i);
233237

234-
if (ATT_IS_PACKABLE(atti) &&
238+
if (COMPACT_ATTR_IS_PACKABLE(atti) &&
235239
VARATT_CAN_MAKE_SHORT(DatumGetPointer(val)))
236240
{
237241
/*
@@ -268,7 +272,7 @@ heap_compute_data_size(TupleDesc tupleDesc,
268272
* Fill in either a data value or a bit in the null bitmask
269273
*/
270274
static inline void
271-
fill_val(Form_pg_attribute att,
275+
fill_val(CompactAttribute *att,
272276
bits8 **bit,
273277
int *bitmask,
274278
char **dataP,
@@ -349,8 +353,7 @@ fill_val(Form_pg_attribute att,
349353
data_length = VARSIZE_SHORT(val);
350354
memcpy(data, val, data_length);
351355
}
352-
else if (VARLENA_ATT_IS_PACKABLE(att) &&
353-
VARATT_CAN_MAKE_SHORT(val))
356+
else if (att->attispackable && VARATT_CAN_MAKE_SHORT(val))
354357
{
355358
/* convert to short varlena -- no alignment */
356359
data_length = VARATT_CONVERTED_SHORT_SIZE(val);
@@ -427,7 +430,7 @@ heap_fill_tuple(TupleDesc tupleDesc,
427430

428431
for (i = 0; i < numberOfAttributes; i++)
429432
{
430-
Form_pg_attribute attr = TupleDescAttr(tupleDesc, i);
433+
CompactAttribute *attr = TupleDescCompactAttr(tupleDesc, i);
431434

432435
fill_val(attr,
433436
bitP ? &bitP : NULL,
@@ -461,7 +464,8 @@ heap_attisnull(HeapTuple tup, int attnum, TupleDesc tupleDesc)
461464
Assert(!tupleDesc || attnum <= tupleDesc->natts);
462465
if (attnum > (int) HeapTupleHeaderGetNatts(tup->t_data))
463466
{
464-
if (tupleDesc && TupleDescAttr(tupleDesc, attnum - 1)->atthasmissing)
467+
if (tupleDesc &&
468+
TupleDescCompactAttr(tupleDesc, attnum - 1)->atthasmissing)
465469
return false;
466470
else
467471
return true;
@@ -570,13 +574,13 @@ nocachegetattr(HeapTuple tup,
570574

571575
if (!slow)
572576
{
573-
Form_pg_attribute att;
577+
CompactAttribute *att;
574578

575579
/*
576580
* If we get here, there are no nulls up to and including the target
577581
* attribute. If we have a cached offset, we can use it.
578582
*/
579-
att = TupleDescAttr(tupleDesc, attnum);
583+
att = TupleDescCompactAttr(tupleDesc, attnum);
580584
if (att->attcacheoff >= 0)
581585
return fetchatt(att, tp + att->attcacheoff);
582586

@@ -591,7 +595,7 @@ nocachegetattr(HeapTuple tup,
591595

592596
for (j = 0; j <= attnum; j++)
593597
{
594-
if (TupleDescAttr(tupleDesc, j)->attlen <= 0)
598+
if (TupleDescCompactAttr(tupleDesc, j)->attlen <= 0)
595599
{
596600
slow = true;
597601
break;
@@ -614,18 +618,18 @@ nocachegetattr(HeapTuple tup,
614618
* fixed-width columns, in hope of avoiding future visits to this
615619
* routine.
616620
*/
617-
TupleDescAttr(tupleDesc, 0)->attcacheoff = 0;
621+
TupleDescCompactAttr(tupleDesc, 0)->attcacheoff = 0;
618622

619623
/* we might have set some offsets in the slow path previously */
620-
while (j < natts && TupleDescAttr(tupleDesc, j)->attcacheoff > 0)
624+
while (j < natts && TupleDescCompactAttr(tupleDesc, j)->attcacheoff > 0)
621625
j++;
622626

623-
off = TupleDescAttr(tupleDesc, j - 1)->attcacheoff +
624-
TupleDescAttr(tupleDesc, j - 1)->attlen;
627+
off = TupleDescCompactAttr(tupleDesc, j - 1)->attcacheoff +
628+
TupleDescCompactAttr(tupleDesc, j - 1)->attlen;
625629

626630
for (; j < natts; j++)
627631
{
628-
Form_pg_attribute att = TupleDescAttr(tupleDesc, j);
632+
CompactAttribute *att = TupleDescCompactAttr(tupleDesc, j);
629633

630634
if (att->attlen <= 0)
631635
break;
@@ -639,7 +643,7 @@ nocachegetattr(HeapTuple tup,
639643

640644
Assert(j > attnum);
641645

642-
off = TupleDescAttr(tupleDesc, attnum)->attcacheoff;
646+
off = TupleDescCompactAttr(tupleDesc, attnum)->attcacheoff;
643647
}
644648
else
645649
{
@@ -659,7 +663,7 @@ nocachegetattr(HeapTuple tup,
659663
off = 0;
660664
for (i = 0;; i++) /* loop exit is at "break" */
661665
{
662-
Form_pg_attribute att = TupleDescAttr(tupleDesc, i);
666+
CompactAttribute *att = TupleDescCompactAttr(tupleDesc, i);
663667

664668
if (HeapTupleHasNulls(tup) && att_isnull(i, bp))
665669
{
@@ -707,7 +711,7 @@ nocachegetattr(HeapTuple tup,
707711
}
708712
}
709713

710-
return fetchatt(TupleDescAttr(tupleDesc, attnum), tp + off);
714+
return fetchatt(TupleDescCompactAttr(tupleDesc, attnum), tp + off);
711715
}
712716

713717
/* ----------------
@@ -892,7 +896,7 @@ expand_tuple(HeapTuple *targetHeapTuple,
892896
{
893897
if (attrmiss[attnum].am_present)
894898
{
895-
Form_pg_attribute att = TupleDescAttr(tupleDesc, attnum);
899+
CompactAttribute *att = TupleDescCompactAttr(tupleDesc, attnum);
896900

897901
targetDataLen = att_align_datum(targetDataLen,
898902
att->attalign,
@@ -1020,8 +1024,7 @@ expand_tuple(HeapTuple *targetHeapTuple,
10201024
/* Now fill in the missing values */
10211025
for (attnum = sourceNatts; attnum < natts; attnum++)
10221026
{
1023-
1024-
Form_pg_attribute attr = TupleDescAttr(tupleDesc, attnum);
1027+
CompactAttribute *attr = TupleDescCompactAttr(tupleDesc, attnum);
10251028

10261029
if (attrmiss && attrmiss[attnum].am_present)
10271030
{
@@ -1370,7 +1373,7 @@ heap_deform_tuple(HeapTuple tuple, TupleDesc tupleDesc,
13701373

13711374
for (attnum = 0; attnum < natts; attnum++)
13721375
{
1373-
Form_pg_attribute thisatt = TupleDescAttr(tupleDesc, attnum);
1376+
CompactAttribute *thisatt = TupleDescCompactAttr(tupleDesc, attnum);
13741377

13751378
if (hasnulls && att_isnull(attnum, bp))
13761379
{

‎src/backend/access/common/indextuple.c

Lines changed: 13 additions & 13 deletions
Original file line numberDiff line numberDiff line change
@@ -303,13 +303,13 @@ nocache_index_getattr(IndexTuple tup,
303303

304304
if (!slow)
305305
{
306-
Form_pg_attribute att;
306+
CompactAttribute *att;
307307

308308
/*
309309
* If we get here, there are no nulls up to and including the target
310310
* attribute. If we have a cached offset, we can use it.
311311
*/
312-
att = TupleDescAttr(tupleDesc, attnum);
312+
att = TupleDescCompactAttr(tupleDesc, attnum);
313313
if (att->attcacheoff >= 0)
314314
return fetchatt(att, tp + att->attcacheoff);
315315

@@ -324,7 +324,7 @@ nocache_index_getattr(IndexTuple tup,
324324

325325
for (j = 0; j <= attnum; j++)
326326
{
327-
if (TupleDescAttr(tupleDesc, j)->attlen <= 0)
327+
if (TupleDescCompactAttr(tupleDesc, j)->attlen <= 0)
328328
{
329329
slow = true;
330330
break;
@@ -347,18 +347,18 @@ nocache_index_getattr(IndexTuple tup,
347347
* fixed-width columns, in hope of avoiding future visits to this
348348
* routine.
349349
*/
350-
TupleDescAttr(tupleDesc, 0)->attcacheoff = 0;
350+
TupleDescCompactAttr(tupleDesc, 0)->attcacheoff = 0;
351351

352352
/* we might have set some offsets in the slow path previously */
353-
while (j < natts && TupleDescAttr(tupleDesc, j)->attcacheoff > 0)
353+
while (j < natts && TupleDescCompactAttr(tupleDesc, j)->attcacheoff > 0)
354354
j++;
355355

356-
off = TupleDescAttr(tupleDesc, j - 1)->attcacheoff +
357-
TupleDescAttr(tupleDesc, j - 1)->attlen;
356+
off = TupleDescCompactAttr(tupleDesc, j - 1)->attcacheoff +
357+
TupleDescCompactAttr(tupleDesc, j - 1)->attlen;
358358

359359
for (; j < natts; j++)
360360
{
361-
Form_pg_attribute att = TupleDescAttr(tupleDesc, j);
361+
CompactAttribute *att = TupleDescCompactAttr(tupleDesc, j);
362362

363363
if (att->attlen <= 0)
364364
break;
@@ -372,7 +372,7 @@ nocache_index_getattr(IndexTuple tup,
372372

373373
Assert(j > attnum);
374374

375-
off = TupleDescAttr(tupleDesc, attnum)->attcacheoff;
375+
off = TupleDescCompactAttr(tupleDesc, attnum)->attcacheoff;
376376
}
377377
else
378378
{
@@ -392,7 +392,7 @@ nocache_index_getattr(IndexTuple tup,
392392
off = 0;
393393
for (i = 0;; i++) /* loop exit is at "break" */
394394
{
395-
Form_pg_attribute att = TupleDescAttr(tupleDesc, i);
395+
CompactAttribute *att = TupleDescCompactAttr(tupleDesc, i);
396396

397397
if (IndexTupleHasNulls(tup) && att_isnull(i, bp))
398398
{
@@ -440,7 +440,7 @@ nocache_index_getattr(IndexTuple tup,
440440
}
441441
}
442442

443-
return fetchatt(TupleDescAttr(tupleDesc, attnum), tp + off);
443+
return fetchatt(TupleDescCompactAttr(tupleDesc, attnum), tp + off);
444444
}
445445

446446
/*
@@ -490,7 +490,7 @@ index_deform_tuple_internal(TupleDesc tupleDescriptor,
490490

491491
for (attnum = 0; attnum < natts; attnum++)
492492
{
493-
Form_pg_attribute thisatt = TupleDescAttr(tupleDescriptor, attnum);
493+
CompactAttribute *thisatt = TupleDescCompactAttr(tupleDescriptor, attnum);
494494

495495
if (hasnulls && att_isnull(attnum, bp))
496496
{
@@ -588,7 +588,7 @@ index_truncate_tuple(TupleDesc sourceDescriptor, IndexTuple source,
588588
return CopyIndexTuple(source);
589589

590590
/* Create temporary descriptor to scribble on */
591-
truncdesc = palloc(TupleDescSize(sourceDescriptor));
591+
truncdesc = CreateTemplateTupleDesc(sourceDescriptor->natts);
592592
TupleDescCopy(truncdesc, sourceDescriptor);
593593
truncdesc->natts = leavenatts;
594594

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