From d26bf23f344887aecac93e9cd22b1dae64f18c83 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Tue, 28 Oct 2008 15:51:03 +0000
Subject: [PATCH] Arrange to squeeze out the MINIMAL_TUPLE_PADDING in the tuple
representation written to temp files by tuplesort.c and tuplestore.c. This
saves 2 bytes per row for 32-bit machines, and 6 bytes per row for 64-bit
machines, which seems worth the slight additional uglification of the tuple
read/write routines.
---
src/backend/utils/sort/tuplesort.c | 28 ++++++++++++++++------------
src/backend/utils/sort/tuplestore.c | 28 +++++++++++++++++++---------
src/include/access/htup.h | 8 +++++++-
3 files changed, 42 insertions(+), 22 deletions(-)
diff --git a/src/backend/utils/sort/tuplesort.c b/src/backend/utils/sort/tuplesort.c
index 29a076e1384..02aee0f8b40 100644
--- a/src/backend/utils/sort/tuplesort.c
+++ b/src/backend/utils/sort/tuplesort.c
@@ -91,7 +91,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/utils/sort/tuplesort.c,v 1.87 2008/09/15 18:43:41 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/sort/tuplesort.c,v 1.88 2008/10/28 15:51:03 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -2632,18 +2632,20 @@ copytup_heap(Tuplesortstate *state, SortTuple *stup, void *tup)
&stup->isnull1);
}
-/*
- * Since MinimalTuple already has length in its first word, we don't need
- * to write that separately.
- */
static void
writetup_heap(Tuplesortstate *state, int tapenum, SortTuple *stup)
{
MinimalTuple tuple = (MinimalTuple) stup->tuple;
- unsigned int tuplen = tuple->t_len;
+ /* the part of the MinimalTuple we'll write: */
+ char *tupbody = (char *) tuple + MINIMAL_TUPLE_DATA_OFFSET;
+ unsigned int tupbodylen = tuple->t_len - MINIMAL_TUPLE_DATA_OFFSET;
+ /* total on-disk footprint: */
+ unsigned int tuplen = tupbodylen + sizeof(int);
LogicalTapeWrite(state->tapeset, tapenum,
- (void *) tuple, tuplen);
+ (void *) &tuplen, sizeof(tuplen));
+ LogicalTapeWrite(state->tapeset, tapenum,
+ (void *) tupbody, tupbodylen);
if (state->randomAccess) /* need trailing length word? */
LogicalTapeWrite(state->tapeset, tapenum,
(void *) &tuplen, sizeof(tuplen));
@@ -2656,16 +2658,18 @@ static void
readtup_heap(Tuplesortstate *state, SortTuple *stup,
int tapenum, unsigned int len)
{
- MinimalTuple tuple = (MinimalTuple) palloc(len);
- unsigned int tuplen;
+ unsigned int tupbodylen = len - sizeof(int);
+ unsigned int tuplen = tupbodylen + MINIMAL_TUPLE_DATA_OFFSET;
+ MinimalTuple tuple = (MinimalTuple) palloc(tuplen);
+ char *tupbody = (char *) tuple + MINIMAL_TUPLE_DATA_OFFSET;
HeapTupleData htup;
USEMEM(state, GetMemoryChunkSpace(tuple));
/* read in the tuple proper */
- tuple->t_len = len;
+ tuple->t_len = tuplen;
if (LogicalTapeRead(state->tapeset, tapenum,
- (void *) ((char *) tuple + sizeof(int)),
- len - sizeof(int)) != (size_t) (len - sizeof(int)))
+ (void *) tupbody,
+ tupbodylen) != (size_t) tupbodylen)
elog(ERROR, "unexpected end of data");
if (state->randomAccess) /* need trailing length word? */
if (LogicalTapeRead(state->tapeset, tapenum, (void *) &tuplen,
diff --git a/src/backend/utils/sort/tuplestore.c b/src/backend/utils/sort/tuplestore.c
index b5bd67c1b4e..a99386fa936 100644
--- a/src/backend/utils/sort/tuplestore.c
+++ b/src/backend/utils/sort/tuplestore.c
@@ -46,7 +46,7 @@
* Portions Copyright (c) 1994, Regents of the University of California
*
* IDENTIFICATION
- * $PostgreSQL: pgsql/src/backend/utils/sort/tuplestore.c,v 1.42 2008/10/07 00:05:55 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/sort/tuplestore.c,v 1.43 2008/10/28 15:51:03 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -1173,9 +1173,17 @@ static void
writetup_heap(Tuplestorestate *state, void *tup)
{
MinimalTuple tuple = (MinimalTuple) tup;
- unsigned int tuplen = tuple->t_len;
-
- if (BufFileWrite(state->myfile, (void *) tuple, tuplen) != (size_t) tuplen)
+ /* the part of the MinimalTuple we'll write: */
+ char *tupbody = (char *) tuple + MINIMAL_TUPLE_DATA_OFFSET;
+ unsigned int tupbodylen = tuple->t_len - MINIMAL_TUPLE_DATA_OFFSET;
+ /* total on-disk footprint: */
+ unsigned int tuplen = tupbodylen + sizeof(int);
+
+ if (BufFileWrite(state->myfile, (void *) &tuplen,
+ sizeof(tuplen)) != sizeof(tuplen))
+ elog(ERROR, "write failed");
+ if (BufFileWrite(state->myfile, (void *) tupbody,
+ tupbodylen) != (size_t) tupbodylen)
elog(ERROR, "write failed");
if (state->backward) /* need trailing length word? */
if (BufFileWrite(state->myfile, (void *) &tuplen,
@@ -1189,14 +1197,16 @@ writetup_heap(Tuplestorestate *state, void *tup)
static void *
readtup_heap(Tuplestorestate *state, unsigned int len)
{
- MinimalTuple tuple = (MinimalTuple) palloc(len);
- unsigned int tuplen;
+ unsigned int tupbodylen = len - sizeof(int);
+ unsigned int tuplen = tupbodylen + MINIMAL_TUPLE_DATA_OFFSET;
+ MinimalTuple tuple = (MinimalTuple) palloc(tuplen);
+ char *tupbody = (char *) tuple + MINIMAL_TUPLE_DATA_OFFSET;
USEMEM(state, GetMemoryChunkSpace(tuple));
/* read in the tuple proper */
- tuple->t_len = len;
- if (BufFileRead(state->myfile, (void *) ((char *) tuple + sizeof(int)),
- len - sizeof(int)) != (size_t) (len - sizeof(int)))
+ tuple->t_len = tuplen;
+ if (BufFileRead(state->myfile, (void *) tupbody,
+ tupbodylen) != (size_t) tupbodylen)
elog(ERROR, "unexpected end of data");
if (state->backward) /* need trailing length word? */
if (BufFileRead(state->myfile, (void *) &tuplen,
diff --git a/src/include/access/htup.h b/src/include/access/htup.h
index 85271c26c3a..0803c1b2c77 100644
--- a/src/include/access/htup.h
+++ b/src/include/access/htup.h
@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $PostgreSQL: pgsql/src/include/access/htup.h,v 1.101 2008/08/11 11:05:11 heikki Exp $
+ * $PostgreSQL: pgsql/src/include/access/htup.h,v 1.102 2008/10/28 15:51:03 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -420,11 +420,17 @@ do { \
*
* Note that t_hoff is computed the same as in a full tuple, hence it includes
* the MINIMAL_TUPLE_OFFSET distance. t_len does not include that, however.
+ *
+ * MINIMAL_TUPLE_DATA_OFFSET is the offset to the first useful (non-pad) data
+ * other than the length word. tuplesort.c and tuplestore.c use this to avoid
+ * writing the padding to disk.
*/
#define MINIMAL_TUPLE_OFFSET \
((offsetof(HeapTupleHeaderData, t_infomask2) - sizeof(uint32)) / MAXIMUM_ALIGNOF * MAXIMUM_ALIGNOF)
#define MINIMAL_TUPLE_PADDING \
((offsetof(HeapTupleHeaderData, t_infomask2) - sizeof(uint32)) % MAXIMUM_ALIGNOF)
+#define MINIMAL_TUPLE_DATA_OFFSET \
+ offsetof(MinimalTupleData, t_infomask2)
typedef struct MinimalTupleData
{
--
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