Cosmetic improvements for faster column addition.

Changed the name of few structure members for the sake of clarity and
removed spurious whitespace.

Reported-by: Amit Kapila
Author: Amit Kapila, based on suggestion by Andrew Dunstan
Reviewed-by: Alvaro Herrera
Discussion: https://postgr.es/m/CAA4eK1K2znsFpC+NQ9A4vxT4uDxADN4RmvHX0L6Y=aHVo9gB4Q@mail.gmail.com

Author: Amit Kapila

src/backend/access/common/heaptuple.c

@@ -100,10 +100,10 @@ getmissingattr(TupleDesc tupleDesc,
 
 		attrmiss = tupleDesc->constr->missing + (attnum - 1);
 
-		if (attrmiss->ammissingPresent)
+		if (attrmiss->am_present)
 		{
 			*isnull = false;
-			return attrmiss->ammissing;
+			return attrmiss->am_value;
 		}
 	}
 
@@ -142,9 +142,8 @@ slot_getmissingattrs(TupleTableSlot *slot, int startAttNum, int lastAttNum)
 			 missattnum < lastAttNum;
 			 missattnum++)
 		{
-			slot->tts_values[missattnum] = attrmiss[missattnum].ammissing;
-			slot->tts_isnull[missattnum] =
-				!attrmiss[missattnum].ammissingPresent;
+			slot->tts_values[missattnum] = attrmiss[missattnum].am_value;
+			slot->tts_isnull[missattnum] = !attrmiss[missattnum].am_present;
 		}
 	}
 }
@@ -822,7 +821,7 @@ expand_tuple(HeapTuple *targetHeapTuple,
 			 firstmissingnum < natts;
 			 firstmissingnum++)
 		{
-			if (attrmiss[firstmissingnum].ammissingPresent)
+			if (attrmiss[firstmissingnum].am_present)
 				break;
 		}
 
@@ -844,18 +843,18 @@ expand_tuple(HeapTuple *targetHeapTuple,
 				 attnum < natts;
 				 attnum++)
 			{
-				if (attrmiss[attnum].ammissingPresent)
+				if (attrmiss[attnum].am_present)
 				{
 					Form_pg_attribute att = TupleDescAttr(tupleDesc, attnum);
 
 					targetDataLen = att_align_datum(targetDataLen,
 													att->attalign,
 													att->attlen,
-													attrmiss[attnum].ammissing);
+													attrmiss[attnum].am_value);
 
 					targetDataLen = att_addlength_pointer(targetDataLen,
 														  att->attlen,
-														  attrmiss[attnum].ammissing);
+														  attrmiss[attnum].am_value);
 				}
 				else
 				{
@@ -981,14 +980,14 @@ expand_tuple(HeapTuple *targetHeapTuple,
 
 		Form_pg_attribute attr = TupleDescAttr(tupleDesc, attnum);
 
-		if (attrmiss && attrmiss[attnum].ammissingPresent)
+		if (attrmiss && attrmiss[attnum].am_present)
 		{
 			fill_val(attr,
 					 nullBits ? &nullBits : NULL,
 					 &bitMask,
 					 &targetData,
 					 infoMask,
-					 attrmiss[attnum].ammissing,
+					 attrmiss[attnum].am_value,
 					 false);
 		}
 		else

src/backend/access/common/tupdesc.c

@@ -185,13 +185,13 @@ CreateTupleDescCopyConstr(TupleDesc tupdesc)
 			memcpy(cpy->missing, constr->missing, tupdesc->natts * sizeof(AttrMissing));
 			for (i = tupdesc->natts - 1; i >= 0; i--)
 			{
-				if (constr->missing[i].ammissingPresent)
+				if (constr->missing[i].am_present)
 				{
 					Form_pg_attribute attr = TupleDescAttr(tupdesc, i);
 
-					cpy->missing[i].ammissing = datumCopy(constr->missing[i].ammissing,
-														  attr->attbyval,
-														  attr->attlen);
+					cpy->missing[i].am_value = datumCopy(constr->missing[i].am_value,
+														 attr->attbyval,
+														 attr->attlen);
 				}
 			}
 		}
@@ -337,9 +337,9 @@ FreeTupleDesc(TupleDesc tupdesc)
 
 			for (i = tupdesc->natts - 1; i >= 0; i--)
 			{
-				if (attrmiss[i].ammissingPresent
+				if (attrmiss[i].am_present
 					&& !TupleDescAttr(tupdesc, i)->attbyval)
-					pfree(DatumGetPointer(attrmiss[i].ammissing));
+					pfree(DatumGetPointer(attrmiss[i].am_value));
 			}
 			pfree(attrmiss);
 		}
@@ -512,13 +512,13 @@ equalTupleDescs(TupleDesc tupdesc1, TupleDesc tupdesc2)
 				AttrMissing *missval1 = constr1->missing + i;
 				AttrMissing *missval2 = constr2->missing + i;
 
-				if (missval1->ammissingPresent != missval2->ammissingPresent)
+				if (missval1->am_present != missval2->am_present)
 					return false;
-				if (missval1->ammissingPresent)
+				if (missval1->am_present)
 				{
 					Form_pg_attribute missatt1 = TupleDescAttr(tupdesc1, i);
 
-					if (!datumIsEqual(missval1->ammissing, missval2->ammissing,
+					if (!datumIsEqual(missval1->am_value, missval2->am_value,
 									  missatt1->attbyval, missatt1->attlen))
 						return false;
 				}

src/backend/utils/cache/relcache.c

@@ -614,18 +614,18 @@ RelationBuildTupleDesc(Relation relation)
 				if (attp->attbyval)
 				{
 					/* for copy by val just copy the datum direct */
-					attrmiss[attnum - 1].ammissing = missval;
+					attrmiss[attnum - 1].am_value = missval;
 				}
 				else
 				{
 					/* otherwise copy in the correct context */
 					oldcxt = MemoryContextSwitchTo(CacheMemoryContext);
-					attrmiss[attnum - 1].ammissing = datumCopy(missval,
-															   attp->attbyval,
-															   attp->attlen);
+					attrmiss[attnum - 1].am_value = datumCopy(missval,
+															  attp->attbyval,
+															  attp->attlen);
 					MemoryContextSwitchTo(oldcxt);
 				}
-				attrmiss[attnum - 1].ammissingPresent = true;
+				attrmiss[attnum - 1].am_present = true;
 			}
 		}
 		need--;

src/include/access/tupdesc_details.h

@@ -19,11 +19,10 @@
  * Structure used to represent value to be used when the attribute is not
  * present at all in a tuple, i.e. when the column was created after the tuple
  */
-
 typedef struct attrMissing
 {
-	bool		ammissingPresent;	/* true if non-NULL missing value exists */
-	Datum		ammissing;		/* value when attribute is missing */
+	bool		am_present;		/* true if non-NULL missing value exists */
+	Datum		am_value;		/* value when attribute is missing */
 } AttrMissing;
 
 #endif							/* TUPDESC_DETAILS_H */