do not align pass-by-value type in additional info. It saves ~30% size of index

feodor · feodor · commit 2c94e218c056 · 2016-05-17T22:59:54.000+03:00
diff --git a/rum.h b/rum.h
@@ -851,9 +851,47 @@ rumDataPageLeafRead(Pointer ptr, OffsetNumber attnum, ItemPointer iptr,
 	if (!isNull)
 	{
 		attr = rumstate->addAttrs[attnum - 1];
-		ptr = (Pointer) att_align_pointer(ptr, attr->attalign, attr->attlen, ptr);
-		if (addInfo)
-			*addInfo = fetch_att(ptr,  attr->attbyval,  attr->attlen);
+
+		if (attr->attbyval)
+		{
+			/* do not use aligment for pass-by-value types */
+			if (addInfo)
+			{
+				union {
+					int16	i16;
+					int32	i32;
+				} u;
+
+				switch(attr->attlen)
+				{
+					case sizeof(char):
+						*addInfo = Int8GetDatum(*ptr);
+						break;
+					case sizeof(int16):
+						memcpy(&u.i16, ptr, sizeof(int16));
+						*addInfo = Int16GetDatum(u.i16);
+						break;
+					case sizeof(int32):
+						memcpy(&u.i32, ptr, sizeof(int32));
+						*addInfo = Int32GetDatum(u.i32);
+						break;
+#if SIZEOF_DATUM == 8
+					case sizeof(Datum):
+						memcpy(addInfo, ptr, sizeof(Datum));
+						break;
+#endif
+					default:
+						elog(ERROR, "unsupported byval length: %d", (int) (attr->attlen));
+				}
+			}
+		}
+		else
+		{
+			ptr = (Pointer) att_align_pointer(ptr, attr->attalign, attr->attlen, ptr);
+			if (addInfo)
+				*addInfo = fetch_att(ptr,  attr->attbyval,  attr->attlen);
+		}
+
 		ptr = (Pointer) att_addlength_pointer(ptr, attr->attlen, ptr);
 	}
 	return ptr;
diff --git a/rumdatapage.c b/rumdatapage.c
@@ -36,6 +36,12 @@ rumComputeDatumSize(Size data_length, Datum val, bool typbyval, char typalign,
 		 */
 		data_length += VARATT_CONVERTED_SHORT_SIZE(DatumGetPointer(val));
 	}
+	else if (typbyval)
+	{
+		/* do not align type pass-by-value because anyway we
+		 * will copy Datum */
+		data_length = att_addlength_datum(data_length, typlen, val);
+	}
 	else
 	{
 		data_length = att_align_datum(data_length, typalign, typlen, val);
@@ -60,8 +66,34 @@ rumDatumWrite(Pointer ptr, Datum datum, bool typbyval, char typalign,
 	if (typbyval)
 	{
 		/* pass-by-value */
-		ptr = (char *) att_align_nominal(ptr, typalign);
-		store_att_byval(ptr, datum, typlen);
+		union {
+			int16	i16;
+			int32	i32;
+		} u;
+
+		/* align-safe version of store_att_byval(ptr, datum, typlen); */
+		switch(typlen)
+		{
+			case sizeof(char):
+				*ptr = DatumGetChar(datum);
+				break;
+			case sizeof(int16):
+				u.i16 = DatumGetInt16(datum);
+				memcpy(ptr, &u.i16, sizeof(int16));
+				break;
+			case sizeof(int32):
+				u.i32 = DatumGetInt32(datum);
+				memcpy(ptr, &u.i32, sizeof(int32));
+				break;
+#if SIZEOF_DATUM == 8
+			case sizeof(Datum):
+				memcpy(ptr, &datum, sizeof(Datum));
+				break;
+#endif
+			default:
+				elog(ERROR, "unsupported byval length: %d", (int) (typlen));
+		}
+
 		data_length = typlen;
 	}
 	else if (typlen == -1)
