From 3212cf94176ff439095104693f45108f3c6d3a6d Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Mon, 27 May 2002 19:53:33 +0000
Subject: [PATCH] Distinguish between MaxHeapAttributeNumber and
MaxTupleAttributeNumber, where the latter is made slightly larger to allow
for in-memory tuples containing resjunk attributes. Responds to today's
complaint that one cannot UPDATE a table containing the allegedly-legal
maximum number of columns.
Also, apply Manfred Koizar's recent patch to avoid extra alignment padding
when there is a null bitmap. This saves bytes in some cases while not
creating any backward-compatibility problem AFAICS.
---
src/backend/access/common/heaptuple.c | 22 ++++-----
src/backend/access/heap/tuptoaster.c | 32 +++++-------
src/include/access/htup.h | 70 ++++++++++++++++-----------
3 files changed, 63 insertions(+), 61 deletions(-)
diff --git a/src/backend/access/common/heaptuple.c b/src/backend/access/common/heaptuple.c
index 5b005b3163c..daad2bd5370 100644
--- a/src/backend/access/common/heaptuple.c
+++ b/src/backend/access/common/heaptuple.c
@@ -9,7 +9,7 @@
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/access/common/heaptuple.c,v 1.74 2001/10/25 05:49:20 momjian Exp $
+ * $Header: /cvsroot/pgsql/src/backend/access/common/heaptuple.c,v 1.75 2002/05/27 19:53:33 tgl Exp $
*
* NOTES
* The old interface functions have been converted to macros
@@ -571,18 +571,15 @@ heap_formtuple(TupleDesc tupleDescriptor,
{
HeapTuple tuple; /* return tuple */
HeapTupleHeader td; /* tuple data */
- int bitmaplen;
unsigned long len;
int hoff;
bool hasnull = false;
int i;
int numberOfAttributes = tupleDescriptor->natts;
- if (numberOfAttributes > MaxHeapAttributeNumber)
- elog(ERROR, "heap_formtuple: numberOfAttributes of %d > %d",
- numberOfAttributes, MaxHeapAttributeNumber);
-
- len = offsetof(HeapTupleHeaderData, t_bits);
+ if (numberOfAttributes > MaxTupleAttributeNumber)
+ elog(ERROR, "heap_formtuple: numberOfAttributes %d exceeds limit %d",
+ numberOfAttributes, MaxTupleAttributeNumber);
for (i = 0; i < numberOfAttributes; i++)
{
@@ -593,13 +590,12 @@ heap_formtuple(TupleDesc tupleDescriptor,
}
}
+ len = offsetof(HeapTupleHeaderData, t_bits);
+
if (hasnull)
- {
- bitmaplen = BITMAPLEN(numberOfAttributes);
- len += bitmaplen;
- }
+ len += BITMAPLEN(numberOfAttributes);
- hoff = len = MAXALIGN(len); /* be conservative here */
+ hoff = len = MAXALIGN(len); /* align user data safely */
len += ComputeDataSize(tupleDescriptor, value, nulls);
@@ -615,7 +611,7 @@ heap_formtuple(TupleDesc tupleDescriptor,
td->t_natts = numberOfAttributes;
td->t_hoff = hoff;
- DataFill((char *) td + td->t_hoff,
+ DataFill((char *) td + hoff,
tupleDescriptor,
value,
nulls,
diff --git a/src/backend/access/heap/tuptoaster.c b/src/backend/access/heap/tuptoaster.c
index ab5e96f8cc9..3c66aed1db1 100644
--- a/src/backend/access/heap/tuptoaster.c
+++ b/src/backend/access/heap/tuptoaster.c
@@ -8,7 +8,7 @@
*
*
* IDENTIFICATION
- * $Header: /cvsroot/pgsql/src/backend/access/heap/tuptoaster.c,v 1.31 2002/05/24 18:57:55 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/access/heap/tuptoaster.c,v 1.32 2002/05/27 19:53:33 tgl Exp $
*
*
* INTERFACE ROUTINES
@@ -715,39 +715,34 @@ toast_insert_or_update(Relation rel, HeapTuple newtup, HeapTuple oldtup)
*/
if (need_change)
{
+ HeapTupleHeader olddata = newtup->t_data;
char *new_data;
int32 new_len;
- MemoryContext oldcxt;
- HeapTupleHeader olddata;
/*
- * Calculate the new size of the tuple
+ * Calculate the new size of the tuple. Header size should not
+ * change, but data size might.
*/
new_len = offsetof(HeapTupleHeaderData, t_bits);
if (has_nulls)
new_len += BITMAPLEN(numAttrs);
new_len = MAXALIGN(new_len);
+ Assert(new_len == olddata->t_hoff);
new_len += ComputeDataSize(tupleDesc, toast_values, toast_nulls);
/*
- * Remember the old memory location of the tuple (for below),
- * switch to the memory context of the HeapTuple structure and
- * allocate the new tuple.
+ * Allocate new tuple in same context as old one.
*/
- olddata = newtup->t_data;
- oldcxt = MemoryContextSwitchTo(newtup->t_datamcxt);
- new_data = palloc(new_len);
+ new_data = (char *) MemoryContextAlloc(newtup->t_datamcxt, new_len);
+ newtup->t_data = (HeapTupleHeader) new_data;
+ newtup->t_len = new_len;
/*
* Put the tuple header and the changed values into place
*/
- memcpy(new_data, newtup->t_data, newtup->t_data->t_hoff);
- newtup->t_data = (HeapTupleHeader) new_data;
- newtup->t_len = new_len;
+ memcpy(new_data, olddata, olddata->t_hoff);
- DataFill((char *) (MAXALIGN((long) new_data +
- offsetof(HeapTupleHeaderData, t_bits) +
- ((has_nulls) ? BITMAPLEN(numAttrs) : 0))),
+ DataFill((char *) new_data + olddata->t_hoff,
tupleDesc,
toast_values,
toast_nulls,
@@ -760,11 +755,6 @@ toast_insert_or_update(Relation rel, HeapTuple newtup, HeapTuple oldtup)
*/
if ((char *) olddata != ((char *) newtup + HEAPTUPLESIZE))
pfree(olddata);
-
- /*
- * Switch back to the old memory context
- */
- MemoryContextSwitchTo(oldcxt);
}
/*
diff --git a/src/include/access/htup.h b/src/include/access/htup.h
index 08506bbf8fe..4860c4ec577 100644
--- a/src/include/access/htup.h
+++ b/src/include/access/htup.h
@@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
- * $Id: htup.h,v 1.51 2001/11/05 17:46:31 momjian Exp $
+ * $Id: htup.h,v 1.52 2002/05/27 19:53:33 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@@ -17,25 +17,44 @@
#include "storage/bufpage.h"
#include "storage/relfilenode.h"
-#define MinHeapTupleBitmapSize 32 /* 8 * 4 */
/*
- * MaxHeapAttributeNumber limits the number of (user) columns in a table.
+ * MaxTupleAttributeNumber limits the number of (user) columns in a tuple.
* The key limit on this value is that the size of the fixed overhead for
* a tuple, plus the size of the null-values bitmap (at 1 bit per column),
* plus MAXALIGN alignment, must fit into t_hoff which is uint8. On most
- * machines the absolute upper limit without making t_hoff wider would be
- * about 1700. Note, however, that depending on column data types you will
- * likely also be running into the disk-block-based limit on overall tuple
- * size if you have more than a thousand or so columns. TOAST won't help.
+ * machines the upper limit without making t_hoff wider would be a little
+ * over 1700. We use round numbers here and for MaxHeapAttributeNumber
+ * so that alterations in HeapTupleHeaderData layout won't change the
+ * supported max number of columns.
+ */
+#define MaxTupleAttributeNumber 1664 /* 8 * 208 */
+
+/*----------
+ * MaxHeapAttributeNumber limits the number of (user) columns in a table.
+ * This should be somewhat less than MaxTupleAttributeNumber. It must be
+ * at least one less, else we will fail to do UPDATEs on a maximal-width
+ * table (because UPDATE has to form working tuples that include CTID).
+ * In practice we want some additional daylight so that we can gracefully
+ * support operations that add hidden "resjunk" columns, for example
+ * SELECT * FROM wide_table ORDER BY foo, bar, baz.
+ * In any case, depending on column data types you will likely be running
+ * into the disk-block-based limit on overall tuple size if you have more
+ * than a thousand or so columns. TOAST won't help.
+ *----------
*/
#define MaxHeapAttributeNumber 1600 /* 8 * 200 */
/*
- * This is the on-disk copy of the tuple.
+ * On-disk heap tuple header. Currently this is also used as the header
+ * format for tuples formed in memory, although in principle they could
+ * be different.
*
* To avoid wasting space, the attributes should be layed out in such a
- * way to reduce structure padding.
+ * way to reduce structure padding. Note that t_hoff is the offset to
+ * the start of the user data, and so must be a multiple of MAXALIGN.
+ * Also note that we omit the nulls bitmap if t_infomask shows that there
+ * are no nulls in the tuple.
*/
typedef struct HeapTupleHeaderData
{
@@ -51,14 +70,13 @@ typedef struct HeapTupleHeaderData
int16 t_natts; /* number of attributes */
- uint16 t_infomask; /* various infos */
+ uint16 t_infomask; /* various flag bits, see below */
- uint8 t_hoff; /* sizeof() tuple header */
+ uint8 t_hoff; /* sizeof header incl. bitmap, padding */
/* ^ - 31 bytes - ^ */
- bits8 t_bits[MinHeapTupleBitmapSize / 8];
- /* bit map of NULLs */
+ bits8 t_bits[1]; /* bitmap of NULLs -- VARIABLE LENGTH */
/* MORE DATA FOLLOWS AT END OF STRUCT */
} HeapTupleHeaderData;
@@ -183,7 +201,7 @@ typedef struct xl_heap_clean
#define FirstLowInvalidHeapAttributeNumber (-8)
/*
- * This is the in-memory copy of the tuple.
+ * HeapTupleData is an in-memory data structure that points to a tuple.
*
* This new HeapTuple for version >= 6.5 and this is why it was changed:
*
@@ -222,11 +240,9 @@ typedef HeapTupleData *HeapTuple;
/*
* BITMAPLEN(NATTS) -
- * Computes minimum size of bitmap given number of domains.
+ * Computes size of null bitmap given number of data columns.
*/
-#define BITMAPLEN(NATTS) \
- ((((((int)(NATTS) - 1) >> 3) + 4 - (MinHeapTupleBitmapSize >> 3)) \
- & ~03) + (MinHeapTupleBitmapSize >> 3))
+#define BITMAPLEN(NATTS) (((int)(NATTS) + 7) / 8)
/*
* HeapTupleIsValid
@@ -240,26 +256,26 @@ typedef HeapTupleData *HeapTuple;
#define HEAP_HASNULL 0x0001 /* has null attribute(s) */
#define HEAP_HASVARLENA 0x0002 /* has variable length
* attribute(s) */
-#define HEAP_HASEXTERNAL 0x0004 /* has external stored */
- /* attribute(s) */
-#define HEAP_HASCOMPRESSED 0x0008 /* has compressed stored */
- /* attribute(s) */
+#define HEAP_HASEXTERNAL 0x0004 /* has external stored
+ * attribute(s) */
+#define HEAP_HASCOMPRESSED 0x0008 /* has compressed stored
+ * attribute(s) */
#define HEAP_HASEXTENDED 0x000C /* the two above combined */
-#define HEAP_XMAX_UNLOGGED 0x0080 /* to lock tuple for update */
- /* without logging */
+#define HEAP_XMAX_UNLOGGED 0x0080 /* to lock tuple for update
+ * without logging */
#define HEAP_XMIN_COMMITTED 0x0100 /* t_xmin committed */
#define HEAP_XMIN_INVALID 0x0200 /* t_xmin invalid/aborted */
#define HEAP_XMAX_COMMITTED 0x0400 /* t_xmax committed */
#define HEAP_XMAX_INVALID 0x0800 /* t_xmax invalid/aborted */
#define HEAP_MARKED_FOR_UPDATE 0x1000 /* marked for UPDATE */
#define HEAP_UPDATED 0x2000 /* this is UPDATEd version of row */
-#define HEAP_MOVED_OFF 0x4000 /* removed or moved to another
- * place by vacuum */
+#define HEAP_MOVED_OFF 0x4000 /* moved to another place by
+ * vacuum */
#define HEAP_MOVED_IN 0x8000 /* moved from another place by
* vacuum */
-#define HEAP_XACT_MASK 0xFFF0 /* */
+#define HEAP_XACT_MASK 0xFFF0 /* visibility-related bits */
#define HeapTupleNoNulls(tuple) \
(!(((HeapTuple) (tuple))->t_data->t_infomask & HEAP_HASNULL))
--
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