Introduce CompactAttribute array in TupleDesc, take 2

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.

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
Reviewed-by: Andres Freund, Victor Yegorov
Discussion: https://postgr.es/m/CAApHDvrBztXP3yx=NKNmo3xwFAFhEdyPnvrDg3=M0RhDs+4vYw@mail.gmail.com

Author: david-rowley

contrib/amcheck/verify_heapam.c

@@ -1571,11 +1571,11 @@ check_tuple_attribute(HeapCheckContext *ctx)
 	struct varlena *attr;
 	char	   *tp;				/* pointer to the tuple data */
 	uint16		infomask;
-	Form_pg_attribute thisatt;
+	CompactAttribute *thisatt;
 	struct varatt_external toast_pointer;
 
 	infomask = ctx->tuphdr->t_infomask;
-	thisatt = TupleDescAttr(RelationGetDescr(ctx->rel), ctx->attnum);
+	thisatt = TupleDescCompactAttr(RelationGetDescr(ctx->rel), ctx->attnum);
 
 	tp = (char *) ctx->tuphdr + ctx->tuphdr->t_hoff;
 

contrib/pageinspect/gistfuncs.c

@@ -242,8 +242,8 @@ gist_page_items(PG_FUNCTION_ARGS)
 	}
 	else
 	{
-		tupdesc = CreateTupleDescCopy(RelationGetDescr(indexRel));
-		tupdesc->natts = IndexRelationGetNumberOfKeyAttributes(indexRel);
+		tupdesc = CreateTupleDescTruncatedCopy(RelationGetDescr(indexRel),
+											   IndexRelationGetNumberOfKeyAttributes(indexRel));
 		printflags |= RULE_INDEXDEF_KEYS_ONLY;
 	}
 

contrib/pageinspect/heapfuncs.c

@@ -334,11 +334,11 @@ tuple_data_split_internal(Oid relid, char *tupdata,
 
 	for (i = 0; i < nattrs; i++)
 	{
-		Form_pg_attribute attr;
+		CompactAttribute *attr;
 		bool		is_null;
 		bytea	   *attr_data = NULL;
 
-		attr = TupleDescAttr(tupdesc, i);
+		attr = TupleDescCompactAttr(tupdesc, i);
 
 		/*
 		 * Tuple header can specify fewer attributes than tuple descriptor as

contrib/postgres_fdw/postgres_fdw.c

@@ -1818,7 +1818,7 @@ postgresPlanForeignModify(PlannerInfo *root,
 
 		for (attnum = 1; attnum <= tupdesc->natts; attnum++)
 		{
-			Form_pg_attribute attr = TupleDescAttr(tupdesc, attnum - 1);
+			CompactAttribute *attr = TupleDescCompactAttr(tupdesc, attnum - 1);
 
 			if (!attr->attisdropped)
 				targetAttrs = lappend_int(targetAttrs, attnum);
@@ -2191,7 +2191,7 @@ postgresBeginForeignInsert(ModifyTableState *mtstate,
 	/* We transmit all columns that are defined in the foreign table. */
 	for (attnum = 1; attnum <= tupdesc->natts; attnum++)
 	{
-		Form_pg_attribute attr = TupleDescAttr(tupdesc, attnum - 1);
+		CompactAttribute *attr = TupleDescCompactAttr(tupdesc, attnum - 1);
 
 		if (!attr->attisdropped)
 			targetAttrs = lappend_int(targetAttrs, attnum);
@@ -4311,7 +4311,7 @@ convert_prep_stmt_params(PgFdwModifyState *fmstate,
 			foreach(lc, fmstate->target_attrs)
 			{
 				int			attnum = lfirst_int(lc);
-				Form_pg_attribute attr = TupleDescAttr(tupdesc, attnum - 1);
+				CompactAttribute *attr = TupleDescCompactAttr(tupdesc, attnum - 1);
 				Datum		value;
 				bool		isnull;
 

src/backend/access/brin/brin_inclusion.c

@@ -146,12 +146,12 @@ brin_inclusion_add_value(PG_FUNCTION_ARGS)
 	Datum		result;
 	bool		new = false;
 	AttrNumber	attno;
-	Form_pg_attribute attr;
+	CompactAttribute *attr;
 
 	Assert(!isnull);
 
 	attno = column->bv_attno;
-	attr = TupleDescAttr(bdesc->bd_tupdesc, attno - 1);
+	attr = TupleDescCompactAttr(bdesc->bd_tupdesc, attno - 1);
 
 	/*
 	 * If the recorded value is null, copy the new value (which we know to be
@@ -479,15 +479,15 @@ brin_inclusion_union(PG_FUNCTION_ARGS)
 	BrinValues *col_b = (BrinValues *) PG_GETARG_POINTER(2);
 	Oid			colloid = PG_GET_COLLATION();
 	AttrNumber	attno;
-	Form_pg_attribute attr;
+	CompactAttribute *attr;
 	FmgrInfo   *finfo;
 	Datum		result;
 
 	Assert(col_a->bv_attno == col_b->bv_attno);
 	Assert(!col_a->bv_allnulls && !col_b->bv_allnulls);
 
 	attno = col_a->bv_attno;
-	attr = TupleDescAttr(bdesc->bd_tupdesc, attno - 1);
+	attr = TupleDescCompactAttr(bdesc->bd_tupdesc, attno - 1);
 
 	/* If B includes empty elements, mark A similarly, if needed. */
 	if (!DatumGetBool(col_a->bv_values[INCLUSION_CONTAINS_EMPTY]) &&

src/backend/access/brin/brin_tuple.c

@@ -699,7 +699,7 @@ brin_deconstruct_tuple(BrinDesc *brdesc,
 			 datumno < brdesc->bd_info[attnum]->oi_nstored;
 			 datumno++)
 		{
-			Form_pg_attribute thisatt = TupleDescAttr(diskdsc, stored);
+			CompactAttribute *thisatt = TupleDescCompactAttr(diskdsc, stored);
 
 			if (thisatt->attlen == -1)
 			{

src/backend/access/common/attmap.c

@@ -135,7 +135,7 @@ build_attrmap_by_position(TupleDesc indesc,
 	/* Check for unused input columns */
 	for (; j < indesc->natts; j++)
 	{
-		if (TupleDescAttr(indesc, j)->attisdropped)
+		if (TupleDescCompactAttr(indesc, j)->attisdropped)
 			continue;
 		nincols++;
 		same = false;			/* we'll complain below */
@@ -299,8 +299,8 @@ check_attrmap_match(TupleDesc indesc,
 
 	for (i = 0; i < attrMap->maplen; i++)
 	{
-		Form_pg_attribute inatt = TupleDescAttr(indesc, i);
-		Form_pg_attribute outatt = TupleDescAttr(outdesc, i);
+		CompactAttribute *inatt = TupleDescCompactAttr(indesc, i);
+		CompactAttribute *outatt;
 
 		/*
 		 * If the input column has a missing attribute, we need a conversion.
@@ -311,6 +311,8 @@ check_attrmap_match(TupleDesc indesc,
 		if (attrMap->attnums[i] == (i + 1))
 			continue;
 
+		outatt = TupleDescCompactAttr(outdesc, i);
+
 		/*
 		 * If it's a dropped column and the corresponding input column is also
 		 * dropped, we don't need a conversion.  However, attlen and attalign

src/backend/access/common/heaptuple.c

@@ -83,6 +83,10 @@
 #define VARLENA_ATT_IS_PACKABLE(att) \
 	((att)->attstorage != TYPSTORAGE_PLAIN)
 
+/* FormData_pg_attribute.attstorage != TYPSTORAGE_PLAIN and an attlen of -1 */
+#define COMPACT_ATTR_IS_PACKABLE(att) \
+	((att)->attlen == -1 && (att)->attispackable)
+
 /*
  * Setup for caching pass-by-ref missing attributes in a way that survives
  * tupleDesc destruction.
@@ -147,12 +151,12 @@ Datum
 getmissingattr(TupleDesc tupleDesc,
 			   int attnum, bool *isnull)
 {
-	Form_pg_attribute att;
+	CompactAttribute *att;
 
 	Assert(attnum <= tupleDesc->natts);
 	Assert(attnum > 0);
 
-	att = TupleDescAttr(tupleDesc, attnum - 1);
+	att = TupleDescCompactAttr(tupleDesc, attnum - 1);
 
 	if (att->atthasmissing)
 	{
@@ -223,15 +227,15 @@ heap_compute_data_size(TupleDesc tupleDesc,
 	for (i = 0; i < numberOfAttributes; i++)
 	{
 		Datum		val;
-		Form_pg_attribute atti;
+		CompactAttribute *atti;
 
 		if (isnull[i])
 			continue;
 
 		val = values[i];
-		atti = TupleDescAttr(tupleDesc, i);
+		atti = TupleDescCompactAttr(tupleDesc, i);
 
-		if (ATT_IS_PACKABLE(atti) &&
+		if (COMPACT_ATTR_IS_PACKABLE(atti) &&
 			VARATT_CAN_MAKE_SHORT(DatumGetPointer(val)))
 		{
 			/*
@@ -268,7 +272,7 @@ heap_compute_data_size(TupleDesc tupleDesc,
  * Fill in either a data value or a bit in the null bitmask
  */
 static inline void
-fill_val(Form_pg_attribute att,
+fill_val(CompactAttribute *att,
 		 bits8 **bit,
 		 int *bitmask,
 		 char **dataP,
@@ -349,8 +353,7 @@ fill_val(Form_pg_attribute att,
 			data_length = VARSIZE_SHORT(val);
 			memcpy(data, val, data_length);
 		}
-		else if (VARLENA_ATT_IS_PACKABLE(att) &&
-				 VARATT_CAN_MAKE_SHORT(val))
+		else if (att->attispackable && VARATT_CAN_MAKE_SHORT(val))
 		{
 			/* convert to short varlena -- no alignment */
 			data_length = VARATT_CONVERTED_SHORT_SIZE(val);
@@ -427,7 +430,7 @@ heap_fill_tuple(TupleDesc tupleDesc,
 
 	for (i = 0; i < numberOfAttributes; i++)
 	{
-		Form_pg_attribute attr = TupleDescAttr(tupleDesc, i);
+		CompactAttribute *attr = TupleDescCompactAttr(tupleDesc, i);
 
 		fill_val(attr,
 				 bitP ? &bitP : NULL,
@@ -461,7 +464,8 @@ heap_attisnull(HeapTuple tup, int attnum, TupleDesc tupleDesc)
 	Assert(!tupleDesc || attnum <= tupleDesc->natts);
 	if (attnum > (int) HeapTupleHeaderGetNatts(tup->t_data))
 	{
-		if (tupleDesc && TupleDescAttr(tupleDesc, attnum - 1)->atthasmissing)
+		if (tupleDesc &&
+			TupleDescCompactAttr(tupleDesc, attnum - 1)->atthasmissing)
 			return false;
 		else
 			return true;
@@ -570,13 +574,13 @@ nocachegetattr(HeapTuple tup,
 
 	if (!slow)
 	{
-		Form_pg_attribute att;
+		CompactAttribute *att;
 
 		/*
 		 * If we get here, there are no nulls up to and including the target
 		 * attribute.  If we have a cached offset, we can use it.
 		 */
-		att = TupleDescAttr(tupleDesc, attnum);
+		att = TupleDescCompactAttr(tupleDesc, attnum);
 		if (att->attcacheoff >= 0)
 			return fetchatt(att, tp + att->attcacheoff);
 
@@ -591,7 +595,7 @@ nocachegetattr(HeapTuple tup,
 
 			for (j = 0; j <= attnum; j++)
 			{
-				if (TupleDescAttr(tupleDesc, j)->attlen <= 0)
+				if (TupleDescCompactAttr(tupleDesc, j)->attlen <= 0)
 				{
 					slow = true;
 					break;
@@ -614,18 +618,18 @@ nocachegetattr(HeapTuple tup,
 		 * fixed-width columns, in hope of avoiding future visits to this
 		 * routine.
 		 */
-		TupleDescAttr(tupleDesc, 0)->attcacheoff = 0;
+		TupleDescCompactAttr(tupleDesc, 0)->attcacheoff = 0;
 
 		/* we might have set some offsets in the slow path previously */
-		while (j < natts && TupleDescAttr(tupleDesc, j)->attcacheoff > 0)
+		while (j < natts && TupleDescCompactAttr(tupleDesc, j)->attcacheoff > 0)
 			j++;
 
-		off = TupleDescAttr(tupleDesc, j - 1)->attcacheoff +
-			TupleDescAttr(tupleDesc, j - 1)->attlen;
+		off = TupleDescCompactAttr(tupleDesc, j - 1)->attcacheoff +
+			TupleDescCompactAttr(tupleDesc, j - 1)->attlen;
 
 		for (; j < natts; j++)
 		{
-			Form_pg_attribute att = TupleDescAttr(tupleDesc, j);
+			CompactAttribute *att = TupleDescCompactAttr(tupleDesc, j);
 
 			if (att->attlen <= 0)
 				break;
@@ -639,7 +643,7 @@ nocachegetattr(HeapTuple tup,
 
 		Assert(j > attnum);
 
-		off = TupleDescAttr(tupleDesc, attnum)->attcacheoff;
+		off = TupleDescCompactAttr(tupleDesc, attnum)->attcacheoff;
 	}
 	else
 	{
@@ -659,7 +663,7 @@ nocachegetattr(HeapTuple tup,
 		off = 0;
 		for (i = 0;; i++)		/* loop exit is at "break" */
 		{
-			Form_pg_attribute att = TupleDescAttr(tupleDesc, i);
+			CompactAttribute *att = TupleDescCompactAttr(tupleDesc, i);
 
 			if (HeapTupleHasNulls(tup) && att_isnull(i, bp))
 			{
@@ -707,7 +711,7 @@ nocachegetattr(HeapTuple tup,
 		}
 	}
 
-	return fetchatt(TupleDescAttr(tupleDesc, attnum), tp + off);
+	return fetchatt(TupleDescCompactAttr(tupleDesc, attnum), tp + off);
 }
 
 /* ----------------
@@ -892,7 +896,7 @@ expand_tuple(HeapTuple *targetHeapTuple,
 		{
 			if (attrmiss[attnum].am_present)
 			{
-				Form_pg_attribute att = TupleDescAttr(tupleDesc, attnum);
+				CompactAttribute *att = TupleDescCompactAttr(tupleDesc, attnum);
 
 				targetDataLen = att_align_datum(targetDataLen,
 												att->attalign,
@@ -1020,8 +1024,7 @@ expand_tuple(HeapTuple *targetHeapTuple,
 	/* Now fill in the missing values */
 	for (attnum = sourceNatts; attnum < natts; attnum++)
 	{
-
-		Form_pg_attribute attr = TupleDescAttr(tupleDesc, attnum);
+		CompactAttribute *attr = TupleDescCompactAttr(tupleDesc, attnum);
 
 		if (attrmiss && attrmiss[attnum].am_present)
 		{
@@ -1370,7 +1373,7 @@ heap_deform_tuple(HeapTuple tuple, TupleDesc tupleDesc,
 
 	for (attnum = 0; attnum < natts; attnum++)
 	{
-		Form_pg_attribute thisatt = TupleDescAttr(tupleDesc, attnum);
+		CompactAttribute *thisatt = TupleDescCompactAttr(tupleDesc, attnum);
 
 		if (hasnulls && att_isnull(attnum, bp))
 		{