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

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
@@ -479,7 +479,7 @@ 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;
 
@@ -487,7 +487,7 @@ brin_inclusion_union(PG_FUNCTION_ARGS)
 	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))
 		{

src/backend/access/common/indextuple.c

@@ -303,13 +303,13 @@ nocache_index_getattr(IndexTuple 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);
 
@@ -324,7 +324,7 @@ nocache_index_getattr(IndexTuple tup,
 
 			for (j = 0; j <= attnum; j++)
 			{
-				if (TupleDescAttr(tupleDesc, j)->attlen <= 0)
+				if (TupleDescCompactAttr(tupleDesc, j)->attlen <= 0)
 				{
 					slow = true;
 					break;
@@ -347,18 +347,18 @@ nocache_index_getattr(IndexTuple 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;
@@ -372,7 +372,7 @@ nocache_index_getattr(IndexTuple tup,
 
 		Assert(j > attnum);
 
-		off = TupleDescAttr(tupleDesc, attnum)->attcacheoff;
+		off = TupleDescCompactAttr(tupleDesc, attnum)->attcacheoff;
 	}
 	else
 	{
@@ -392,7 +392,7 @@ nocache_index_getattr(IndexTuple 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 (IndexTupleHasNulls(tup) && att_isnull(i, bp))
 			{
@@ -440,7 +440,7 @@ nocache_index_getattr(IndexTuple tup,
 		}
 	}
 
-	return fetchatt(TupleDescAttr(tupleDesc, attnum), tp + off);
+	return fetchatt(TupleDescCompactAttr(tupleDesc, attnum), tp + off);
 }
 
 /*
@@ -490,7 +490,7 @@ index_deform_tuple_internal(TupleDesc tupleDescriptor,
 
 	for (attnum = 0; attnum < natts; attnum++)
 	{
-		Form_pg_attribute thisatt = TupleDescAttr(tupleDescriptor, attnum);
+		CompactAttribute *thisatt = TupleDescCompactAttr(tupleDescriptor, attnum);
 
 		if (hasnulls && att_isnull(attnum, bp))
 		{
@@ -587,10 +587,8 @@ index_truncate_tuple(TupleDesc sourceDescriptor, IndexTuple source,
 	if (leavenatts == sourceDescriptor->natts)
 		return CopyIndexTuple(source);
 
-	/* Create temporary descriptor to scribble on */
-	truncdesc = palloc(TupleDescSize(sourceDescriptor));
-	TupleDescCopy(truncdesc, sourceDescriptor);
-	truncdesc->natts = leavenatts;
+	/* Create temporary truncated tuple descriptor */
+	truncdesc = CreateTupleDescTruncatedCopy(sourceDescriptor, leavenatts);
 
 	/* Deform, form copy of tuple with fewer attributes */
 	index_deform_tuple(source, truncdesc, values, isnull);

src/backend/access/common/tupdesc.c

@@ -56,6 +56,33 @@ ResourceOwnerForgetTupleDesc(ResourceOwner owner, TupleDesc tupdesc)
 	ResourceOwnerForget(owner, PointerGetDatum(tupdesc), &tupdesc_resowner_desc);
 }
 
+/*
+ * populate_compact_attribute
+ *		Fill in the corresponding CompactAttribute element from the
+ *		Form_pg_attribute for the given attribute number.  This must be called
+ *		whenever a change is made to a Form_pg_attribute in the TupleDesc.
+ */
+void
+populate_compact_attribute(TupleDesc tupdesc, int attnum)
+{
+	Form_pg_attribute src = TupleDescAttr(tupdesc, attnum);
+	CompactAttribute *dst = &tupdesc->compact_attrs[attnum];
+
+	memset(dst, 0, sizeof(CompactAttribute));
+
+	dst->attcacheoff = -1;
+	dst->attlen = src->attlen;
+
+	dst->attbyval = src->attbyval;
+	dst->attispackable = (src->attstorage != TYPSTORAGE_PLAIN);
+	dst->atthasmissing = src->atthasmissing;
+	dst->attisdropped = src->attisdropped;
+	dst->attgenerated = (src->attgenerated != '\0');
+	dst->attnotnull = src->attnotnull;
+
+	dst->attalign = src->attalign;
+}
+
 /*
  * CreateTemplateTupleDesc
  *		This function allocates an empty tuple descriptor structure.
@@ -74,18 +101,20 @@ CreateTemplateTupleDesc(int natts)
 	Assert(natts >= 0);
 
 	/*
-	 * Allocate enough memory for the tuple descriptor, including the
-	 * attribute rows.
+	 * Allocate enough memory for the tuple descriptor, the CompactAttribute
+	 * array and also an array of FormData_pg_attribute.
 	 *
-	 * Note: the attribute array stride is sizeof(FormData_pg_attribute),
-	 * since we declare the array elements as FormData_pg_attribute for
-	 * notational convenience.  However, we only guarantee that the first
-	 * ATTRIBUTE_FIXED_PART_SIZE bytes of each entry are valid; most code that
-	 * copies tupdesc entries around copies just that much.  In principle that
-	 * could be less due to trailing padding, although with the current
-	 * definition of pg_attribute there probably isn't any padding.
+	 * Note: the FormData_pg_attribute array stride is
+	 * sizeof(FormData_pg_attribute), since we declare the array elements as
+	 * FormData_pg_attribute for notational convenience.  However, we only
+	 * guarantee that the first ATTRIBUTE_FIXED_PART_SIZE bytes of each entry
+	 * are valid; most code that copies tupdesc entries around copies just
+	 * that much.  In principle that could be less due to trailing padding,
+	 * although with the current definition of pg_attribute there probably
+	 * isn't any padding.
 	 */
-	desc = (TupleDesc) palloc(offsetof(struct TupleDescData, attrs) +
+	desc = (TupleDesc) palloc(offsetof(struct TupleDescData, compact_attrs) +
+							  natts * sizeof(CompactAttribute) +
 							  natts * sizeof(FormData_pg_attribute));
 
 	/*
@@ -117,8 +146,10 @@ CreateTupleDesc(int natts, Form_pg_attribute *attrs)
 	desc = CreateTemplateTupleDesc(natts);
 
 	for (i = 0; i < natts; ++i)
+	{
 		memcpy(TupleDescAttr(desc, i), attrs[i], ATTRIBUTE_FIXED_PART_SIZE);
-
+		populate_compact_attribute(desc, i);
+	}
 	return desc;
 }
 
@@ -155,6 +186,54 @@ CreateTupleDescCopy(TupleDesc tupdesc)
 		att->atthasmissing = false;
 		att->attidentity = '\0';
 		att->attgenerated = '\0';
+
+		populate_compact_attribute(desc, i);
+	}
+
+	/* We can copy the tuple type identification, too */
+	desc->tdtypeid = tupdesc->tdtypeid;
+	desc->tdtypmod = tupdesc->tdtypmod;
+
+	return desc;
+}
+
+/*
+ * CreateTupleDescTruncatedCopy
+ *		This function creates a new TupleDesc with only the first 'natts'
+ *		attributes from an existing TupleDesc
+ *
+ * !!! Constraints and defaults are not copied !!!
+ */
+TupleDesc
+CreateTupleDescTruncatedCopy(TupleDesc tupdesc, int natts)
+{
+	TupleDesc	desc;
+	int			i;
+
+	Assert(natts <= tupdesc->natts);
+
+	desc = CreateTemplateTupleDesc(natts);
+
+	/* Flat-copy the attribute array */
+	memcpy(TupleDescAttr(desc, 0),
+		   TupleDescAttr(tupdesc, 0),
+		   desc->natts * sizeof(FormData_pg_attribute));
+
+	/*
+	 * Since we're not copying constraints and defaults, clear fields
+	 * associated with them.
+	 */
+	for (i = 0; i < desc->natts; i++)
+	{
+		Form_pg_attribute att = TupleDescAttr(desc, i);
+
+		att->attnotnull = false;
+		att->atthasdef = false;
+		att->atthasmissing = false;
+		att->attidentity = '\0';
+		att->attgenerated = '\0';
+
+		populate_compact_attribute(desc, i);
 	}
 
 	/* We can copy the tuple type identification, too */
@@ -183,6 +262,9 @@ CreateTupleDescCopyConstr(TupleDesc tupdesc)
 		   TupleDescAttr(tupdesc, 0),
 		   desc->natts * sizeof(FormData_pg_attribute));
 
+	for (i = 0; i < desc->natts; i++)
+		populate_compact_attribute(desc, i);
+
 	/* Copy the TupleConstr data structure, if any */
 	if (constr)
 	{
@@ -207,7 +289,7 @@ CreateTupleDescCopyConstr(TupleDesc tupdesc)
 			{
 				if (constr->missing[i].am_present)
 				{
-					Form_pg_attribute attr = TupleDescAttr(tupdesc, i);
+					CompactAttribute *attr = TupleDescCompactAttr(tupdesc, i);
 
 					cpy->missing[i].am_value = datumCopy(constr->missing[i].am_value,
 														 attr->attbyval,
@@ -252,7 +334,7 @@ TupleDescCopy(TupleDesc dst, TupleDesc src)
 {
 	int			i;
 
-	/* Flat-copy the header and attribute array */
+	/* Flat-copy the header and attribute arrays */
 	memcpy(dst, src, TupleDescSize(src));
 
 	/*
@@ -268,6 +350,8 @@ TupleDescCopy(TupleDesc dst, TupleDesc src)
 		att->atthasmissing = false;
 		att->attidentity = '\0';
 		att->attgenerated = '\0';
+
+		populate_compact_attribute(dst, i);
 	}
 	dst->constr = NULL;
 
@@ -322,6 +406,8 @@ TupleDescCopyEntry(TupleDesc dst, AttrNumber dstAttno,
 	dstAtt->atthasmissing = false;
 	dstAtt->attidentity = '\0';
 	dstAtt->attgenerated = '\0';
+
+	populate_compact_attribute(dst, dstAttno - 1);
 }
 
 /*
@@ -521,7 +607,7 @@ equalTupleDescs(TupleDesc tupdesc1, TupleDesc tupdesc2)
 					return false;
 				if (missval1->am_present)
 				{
-					Form_pg_attribute missatt1 = TupleDescAttr(tupdesc1, i);
+					CompactAttribute *missatt1 = TupleDescCompactAttr(tupdesc1, i);
 
 					if (!datumIsEqual(missval1->am_value, missval2->am_value,
 									  missatt1->attbyval, missatt1->attlen))
@@ -714,6 +800,8 @@ TupleDescInitEntry(TupleDesc desc,
 	att->attcompression = InvalidCompressionMethod;
 	att->attcollation = typeForm->typcollation;
 
+	populate_compact_attribute(desc, attributeNumber - 1);
+
 	ReleaseSysCache(tuple);
 }
 
@@ -821,6 +909,8 @@ TupleDescInitBuiltinEntry(TupleDesc desc,
 		default:
 			elog(ERROR, "unsupported type %u", oidtypeid);
 	}
+
+	populate_compact_attribute(desc, attributeNumber - 1);
 }
 
 /*

src/backend/access/gin/ginbulk.c

@@ -127,10 +127,10 @@ ginInitBA(BuildAccumulator *accum)
 static Datum
 getDatumCopy(BuildAccumulator *accum, OffsetNumber attnum, Datum value)
 {
-	Form_pg_attribute att;
+	CompactAttribute *att;
 	Datum		res;
 
-	att = TupleDescAttr(accum->ginstate->origTupdesc, attnum - 1);
+	att = TupleDescCompactAttr(accum->ginstate->origTupdesc, attnum - 1);
 	if (att->attbyval)
 		res = value;
 	else

src/backend/access/gin/ginget.c

@@ -122,7 +122,7 @@ collectMatchBitmap(GinBtreeData *btree, GinBtreeStack *stack,
 				   GinScanEntry scanEntry, Snapshot snapshot)
 {
 	OffsetNumber attnum;
-	Form_pg_attribute attr;
+	CompactAttribute *attr;
 
 	/* Initialize empty bitmap result */
 	scanEntry->matchBitmap = tbm_create(work_mem * 1024L, NULL);
@@ -134,7 +134,7 @@ collectMatchBitmap(GinBtreeData *btree, GinBtreeStack *stack,
 
 	/* Locate tupdesc entry for key column (for attbyval/attlen data) */
 	attnum = scanEntry->attnum;
-	attr = TupleDescAttr(btree->ginstate->origTupdesc, attnum - 1);
+	attr = TupleDescCompactAttr(btree->ginstate->origTupdesc, attnum - 1);
 
 	/*
 	 * Predicate lock entry leaf page, following pages will be locked by

src/backend/access/gist/gist.c

@@ -1557,9 +1557,8 @@ initGISTstate(Relation index)
 	 * tuples during page split.  Also, B-tree is not adjusting tuples on
 	 * internal pages the way GiST does.
 	 */
-	giststate->nonLeafTupdesc = CreateTupleDescCopyConstr(index->rd_att);
-	giststate->nonLeafTupdesc->natts =
-		IndexRelationGetNumberOfKeyAttributes(index);
+	giststate->nonLeafTupdesc = CreateTupleDescTruncatedCopy(index->rd_att,
+															 IndexRelationGetNumberOfKeyAttributes(index));
 
 	for (i = 0; i < IndexRelationGetNumberOfKeyAttributes(index); i++)
 	{

src/backend/access/gist/gistbuild.c

@@ -657,10 +657,12 @@ gistInitBuffering(GISTBuildState *buildstate)
 	itupMinSize = (Size) MAXALIGN(sizeof(IndexTupleData));
 	for (i = 0; i < index->rd_att->natts; i++)
 	{
-		if (TupleDescAttr(index->rd_att, i)->attlen < 0)
+		CompactAttribute *attr = TupleDescCompactAttr(index->rd_att, i);
+
+		if (attr->attlen < 0)
 			itupMinSize += VARHDRSZ;
 		else
-			itupMinSize += TupleDescAttr(index->rd_att, i)->attlen;
+			itupMinSize += attr->attlen;
 	}
 
 	/* Calculate average and maximal number of index tuples which fit to page */

src/backend/access/heap/heapam.c

@@ -4200,8 +4200,6 @@ static bool
 heap_attr_equals(TupleDesc tupdesc, int attrnum, Datum value1, Datum value2,
 				 bool isnull1, bool isnull2)
 {
-	Form_pg_attribute att;
-
 	/*
 	 * If one value is NULL and other is not, then they are certainly not
 	 * equal
@@ -4231,8 +4229,10 @@ heap_attr_equals(TupleDesc tupdesc, int attrnum, Datum value1, Datum value2,
 	}
 	else
 	{
+		CompactAttribute *att;
+
 		Assert(attrnum <= tupdesc->natts);
-		att = TupleDescAttr(tupdesc, attrnum - 1);
+		att = TupleDescCompactAttr(tupdesc, attrnum - 1);
 		return datumIsEqual(value1, value2, att->attbyval, att->attlen);
 	}
 }
@@ -4314,7 +4314,7 @@ HeapDetermineColumnsInfo(Relation relation,
 		 * that system attributes can't be stored externally.
 		 */
 		if (attrnum < 0 || isnull1 ||
-			TupleDescAttr(tupdesc, attrnum - 1)->attlen != -1)
+			TupleDescCompactAttr(tupdesc, attrnum - 1)->attlen != -1)
 			continue;
 
 		/*

src/backend/access/heap/heapam_handler.c

@@ -2550,7 +2550,7 @@ reform_and_rewrite_tuple(HeapTuple tuple,
 	/* Be sure to null out any dropped columns */
 	for (i = 0; i < newTupDesc->natts; i++)
 	{
-		if (TupleDescAttr(newTupDesc, i)->attisdropped)
+		if (TupleDescCompactAttr(newTupDesc, i)->attisdropped)
 			isnull[i] = true;
 	}
 

src/backend/access/heap/heaptoast.c

@@ -369,7 +369,7 @@ toast_flatten_tuple(HeapTuple tup, TupleDesc tupleDesc)
 		/*
 		 * Look at non-null varlena attributes
 		 */
-		if (!toast_isnull[i] && TupleDescAttr(tupleDesc, i)->attlen == -1)
+		if (!toast_isnull[i] && TupleDescCompactAttr(tupleDesc, i)->attlen == -1)
 		{
 			struct varlena *new_value;
 
@@ -483,7 +483,7 @@ toast_flatten_tuple_to_datum(HeapTupleHeader tup,
 		 */
 		if (toast_isnull[i])
 			has_nulls = true;
-		else if (TupleDescAttr(tupleDesc, i)->attlen == -1)
+		else if (TupleDescCompactAttr(tupleDesc, i)->attlen == -1)
 		{
 			struct varlena *new_value;
 
@@ -584,7 +584,7 @@ toast_build_flattened_tuple(TupleDesc tupleDesc,
 		/*
 		 * Look at non-null varlena attributes
 		 */
-		if (!isnull[i] && TupleDescAttr(tupleDesc, i)->attlen == -1)
+		if (!isnull[i] && TupleDescCompactAttr(tupleDesc, i)->attlen == -1)
 		{
 			struct varlena *new_value;
 

src/backend/access/nbtree/nbtutils.c

@@ -4890,11 +4890,11 @@ _bt_keep_natts_fast(Relation rel, IndexTuple lastleft, IndexTuple firstright)
 					datum2;
 		bool		isNull1,
 					isNull2;
-		Form_pg_attribute att;
+		CompactAttribute *att;
 
 		datum1 = index_getattr(lastleft, attnum, itupdesc, &isNull1);
 		datum2 = index_getattr(firstright, attnum, itupdesc, &isNull2);
-		att = TupleDescAttr(itupdesc, attnum - 1);
+		att = TupleDescCompactAttr(itupdesc, attnum - 1);
 
 		if (isNull1 != isNull2)
 			break;

src/backend/access/spgist/spgdoinsert.c

@@ -1974,7 +1974,7 @@ spgdoinsert(Relation index, SpGistState *state,
 	{
 		if (!isnulls[i])
 		{
-			if (TupleDescAttr(leafDescriptor, i)->attlen == -1)
+			if (TupleDescCompactAttr(leafDescriptor, i)->attlen == -1)
 				leafDatums[i] = PointerGetDatum(PG_DETOAST_DATUM(datums[i]));
 			else
 				leafDatums[i] = datums[i];

src/backend/access/spgist/spgutils.c

@@ -331,7 +331,9 @@ getSpGistTupleDesc(Relation index, SpGistTypeDesc *keyType)
 		att->attcollation = InvalidOid;
 		/* In case we changed typlen, we'd better reset following offsets */
 		for (int i = spgFirstIncludeColumn; i < outTupDesc->natts; i++)
-			TupleDescAttr(outTupDesc, i)->attcacheoff = -1;
+			TupleDescCompactAttr(outTupDesc, i)->attcacheoff = -1;
+
+		populate_compact_attribute(outTupDesc, spgKeyColumn);
 	}
 	return outTupDesc;
 }

src/backend/access/table/toast_helper.c

@@ -324,7 +324,7 @@ toast_delete_external(Relation rel, const Datum *values, const bool *isnull,
 
 	for (i = 0; i < numAttrs; i++)
 	{
-		if (TupleDescAttr(tupleDesc, i)->attlen == -1)
+		if (TupleDescCompactAttr(tupleDesc, i)->attlen == -1)
 		{
 			Datum		value = values[i];