Last infomask bit

Hi,

We're running out of infomask bits in the tuple header. I bumped into
this as I tried to apply both the phantom command ids patch, and the HOT
patch simultaneously. They both require one infomask bit, so they
conflicted.

This has been discussed before; I think the best approach is to use the
extra bits available in t_natts field. Here's a patch that doesn't do
anything interesting in itself, but it renames the t_natts field to
t_infomask2, with 11 bits reserved for the number of attributes and the
other 5 bits available for future use. All references to the old t_natts
field are replaced with a HeapTupleHeaderGetNatts accessor macro.

I believe it would actually be even better to combine the t_natts and
t_infomask fields to a single 32-bit infomask field. I refrained from
doing that for now because it would've required shifting all the
existing infomask flags.

Naturally, there's no point applying this before we actually need more
infobits, but it's good to be prepared.

--
   Heikki Linnakangas
   EnterpriseDB   http://www.enterprisedb.com
Index: src/backend/access/common/heaptuple.c
===================================================================
RCS file: /home/hlinnaka/pgcvsrepository/pgsql/src/backend/access/common/heaptuple.c,v
retrieving revision 1.112
diff -c -r1.112 heaptuple.c
*** src/backend/access/common/heaptuple.c    23 Nov 2006 05:27:18 -0000    1.112
--- src/backend/access/common/heaptuple.c    5 Jan 2007 13:11:10 -0000
***************
*** 295,301 ****
  bool
  heap_attisnull(HeapTuple tup, int attnum)
  {
!     if (attnum > (int) tup->t_data->t_natts)
          return true;

      if (attnum > 0)
--- 295,301 ----
  bool
  heap_attisnull(HeapTuple tup, int attnum)
  {
!     if (attnum > (int) HeapTupleHeaderGetNatts(tup->t_data))
          return true;

      if (attnum > 0)
***************
*** 474,479 ****
--- 474,480 ----
      {
          int            j = 1;
          long        off;
+         int            natts = HeapTupleHeaderGetNatts(tup);

          /*
           * need to set cache for some atts
***************
*** 488,494 ****

          for (; j <= attnum ||
          /* Can we compute more?  We will probably need them */
!              (j < tup->t_natts &&
                att[j]->attcacheoff == -1 &&
                (HeapTupleNoNulls(tuple) || !att_isnull(j, bp)) &&
                (HeapTupleAllFixed(tuple) || att[j]->attlen > 0)); j++)
--- 489,495 ----

          for (; j <= attnum ||
          /* Can we compute more?  We will probably need them */
!              (j < natts &&
                att[j]->attcacheoff == -1 &&
                (HeapTupleNoNulls(tuple) || !att_isnull(j, bp)) &&
                (HeapTupleAllFixed(tuple) || att[j]->attlen > 0)); j++)
***************
*** 739,745 ****
      HeapTupleHeaderSetTypeId(td, tupleDescriptor->tdtypeid);
      HeapTupleHeaderSetTypMod(td, tupleDescriptor->tdtypmod);

!     td->t_natts = numberOfAttributes;
      td->t_hoff = hoff;

      if (tupleDescriptor->tdhasoid)        /* else leave infomask = 0 */
--- 740,746 ----
      HeapTupleHeaderSetTypeId(td, tupleDescriptor->tdtypeid);
      HeapTupleHeaderSetTypMod(td, tupleDescriptor->tdtypmod);

!     HeapTupleHeaderSetNatts(td, numberOfAttributes);
      td->t_hoff = hoff;

      if (tupleDescriptor->tdhasoid)        /* else leave infomask = 0 */
***************
*** 846,852 ****
      HeapTupleHeaderSetTypeId(td, tupleDescriptor->tdtypeid);
      HeapTupleHeaderSetTypMod(td, tupleDescriptor->tdtypmod);

!     td->t_natts = numberOfAttributes;
      td->t_hoff = hoff;

      if (tupleDescriptor->tdhasoid)        /* else leave infomask = 0 */
--- 847,853 ----
      HeapTupleHeaderSetTypeId(td, tupleDescriptor->tdtypeid);
      HeapTupleHeaderSetTypMod(td, tupleDescriptor->tdtypmod);

!     HeapTupleHeaderSetNatts(td, numberOfAttributes);
      td->t_hoff = hoff;

      if (tupleDescriptor->tdhasoid)        /* else leave infomask = 0 */
***************
*** 1035,1041 ****
      bits8       *bp = tup->t_bits;        /* ptr to null bitmap in tuple */
      bool        slow = false;    /* can we use/set attcacheoff? */

!     natts = tup->t_natts;

      /*
       * In inheritance situations, it is possible that the given tuple actually
--- 1036,1042 ----
      bits8       *bp = tup->t_bits;        /* ptr to null bitmap in tuple */
      bool        slow = false;    /* can we use/set attcacheoff? */

!     natts = HeapTupleHeaderGetNatts(tup);

      /*
       * In inheritance situations, it is possible that the given tuple actually
***************
*** 1128,1134 ****
      bits8       *bp = tup->t_bits;        /* ptr to null bitmap in tuple */
      bool        slow = false;    /* can we use/set attcacheoff? */

!     natts = tup->t_natts;

      /*
       * In inheritance situations, it is possible that the given tuple actually
--- 1129,1135 ----
      bits8       *bp = tup->t_bits;        /* ptr to null bitmap in tuple */
      bool        slow = false;    /* can we use/set attcacheoff? */

!     natts = HeapTupleHeaderGetNatts(tup);

      /*
       * In inheritance situations, it is possible that the given tuple actually
***************
*** 1335,1341 ****
       * than the tupdesc.)
       */
      tup = tuple->t_data;
!     if (attnum > tup->t_natts)
      {
          *isnull = true;
          return (Datum) 0;
--- 1336,1342 ----
       * than the tupdesc.)
       */
      tup = tuple->t_data;
!     if (attnum > HeapTupleHeaderGetNatts(tup))
      {
          *isnull = true;
          return (Datum) 0;
***************
*** 1401,1407 ****
      /*
       * load up any slots available from physical tuple
       */
!     attnum = tuple->t_data->t_natts;
      attnum = Min(attnum, tdesc_natts);

      slot_deform_tuple(slot, attnum);
--- 1402,1408 ----
      /*
       * load up any slots available from physical tuple
       */
!     attnum = HeapTupleHeaderGetNatts(tuple->t_data);
      attnum = Min(attnum, tdesc_natts);

      slot_deform_tuple(slot, attnum);
***************
*** 1448,1454 ****
      /*
       * load up any slots available from physical tuple
       */
!     attno = tuple->t_data->t_natts;
      attno = Min(attno, attnum);

      slot_deform_tuple(slot, attno);
--- 1449,1455 ----
      /*
       * load up any slots available from physical tuple
       */
!     attno = HeapTupleHeaderGetNatts(tuple->t_data);
      attno = Min(attno, attnum);

      slot_deform_tuple(slot, attno);
***************
*** 1601,1607 ****
       * And fill in the information.
       */
      tuple->t_len = len;
!     tuple->t_natts = numberOfAttributes;
      tuple->t_hoff = hoff + MINIMAL_TUPLE_OFFSET;

      if (tupleDescriptor->tdhasoid)        /* else leave infomask = 0 */
--- 1602,1608 ----
       * And fill in the information.
       */
      tuple->t_len = len;
!     HeapTupleHeaderSetNatts(tuple, numberOfAttributes);
      tuple->t_hoff = hoff + MINIMAL_TUPLE_OFFSET;

      if (tupleDescriptor->tdhasoid)        /* else leave infomask = 0 */
***************
*** 1663,1669 ****
      result->t_tableOid = InvalidOid;
      result->t_data = (HeapTupleHeader) ((char *) result + HEAPTUPLESIZE);
      memcpy((char *) result->t_data + MINIMAL_TUPLE_OFFSET, mtup, mtup->t_len);
!     memset(result->t_data, 0, offsetof(HeapTupleHeaderData, t_natts));
      return result;
  }

--- 1664,1670 ----
      result->t_tableOid = InvalidOid;
      result->t_data = (HeapTupleHeader) ((char *) result + HEAPTUPLESIZE);
      memcpy((char *) result->t_data + MINIMAL_TUPLE_OFFSET, mtup, mtup->t_len);
!     memset(result->t_data, 0, offsetof(HeapTupleHeaderData, t_infomask2));
      return result;
  }

***************
*** 1729,1735 ****

      /* we don't bother to fill the Datum fields */

!     td->t_natts = natts;
      td->t_hoff = hoff;

      if (withoid)                /* else leave infomask = 0 */
--- 1730,1736 ----

      /* we don't bother to fill the Datum fields */

!     HeapTupleHeaderSetNatts(td, natts);
      td->t_hoff = hoff;

      if (withoid)                /* else leave infomask = 0 */
Index: src/backend/access/heap/heapam.c
===================================================================
RCS file: /home/hlinnaka/pgcvsrepository/pgsql/src/backend/access/heap/heapam.c,v
retrieving revision 1.222
diff -c -r1.222 heapam.c
*** src/backend/access/heap/heapam.c    17 Nov 2006 18:00:14 -0000    1.222
--- src/backend/access/heap/heapam.c    5 Jan 2007 13:13:30 -0000
***************
*** 1455,1461 ****
          rdata[0].buffer = InvalidBuffer;
          rdata[0].next = &(rdata[1]);

!         xlhdr.t_natts = heaptup->t_data->t_natts;
          xlhdr.t_infomask = heaptup->t_data->t_infomask;
          xlhdr.t_hoff = heaptup->t_data->t_hoff;

--- 1455,1461 ----
          rdata[0].buffer = InvalidBuffer;
          rdata[0].next = &(rdata[1]);

!         xlhdr.t_infomask2 = heaptup->t_data->t_infomask2;
          xlhdr.t_infomask = heaptup->t_data->t_infomask;
          xlhdr.t_hoff = heaptup->t_data->t_hoff;

***************
*** 3204,3210 ****
      rdata[1].buffer_std = true;
      rdata[1].next = &(rdata[2]);

!     xlhdr.hdr.t_natts = newtup->t_data->t_natts;
      xlhdr.hdr.t_infomask = newtup->t_data->t_infomask;
      xlhdr.hdr.t_hoff = newtup->t_data->t_hoff;
      if (move)                    /* remember xmax & xmin */
--- 3204,3210 ----
      rdata[1].buffer_std = true;
      rdata[1].next = &(rdata[2]);

!     xlhdr.hdr.t_infomask2 = newtup->t_data->t_infomask2;
      xlhdr.hdr.t_infomask = newtup->t_data->t_infomask;
      xlhdr.hdr.t_hoff = newtup->t_data->t_hoff;
      if (move)                    /* remember xmax & xmin */
***************
*** 3503,3509 ****
             (char *) xlrec + SizeOfHeapInsert + SizeOfHeapHeader,
             newlen);
      newlen += offsetof(HeapTupleHeaderData, t_bits);
!     htup->t_natts = xlhdr.t_natts;
      htup->t_infomask = xlhdr.t_infomask;
      htup->t_hoff = xlhdr.t_hoff;
      HeapTupleHeaderSetXmin(htup, record->xl_xid);
--- 3503,3509 ----
             (char *) xlrec + SizeOfHeapInsert + SizeOfHeapHeader,
             newlen);
      newlen += offsetof(HeapTupleHeaderData, t_bits);
!     htup->t_infomask2 = xlhdr.t_infomask2;
      htup->t_infomask = xlhdr.t_infomask;
      htup->t_hoff = xlhdr.t_hoff;
      HeapTupleHeaderSetXmin(htup, record->xl_xid);
***************
*** 3666,3672 ****
             (char *) xlrec + hsize,
             newlen);
      newlen += offsetof(HeapTupleHeaderData, t_bits);
!     htup->t_natts = xlhdr.t_natts;
      htup->t_infomask = xlhdr.t_infomask;
      htup->t_hoff = xlhdr.t_hoff;

--- 3666,3672 ----
             (char *) xlrec + hsize,
             newlen);
      newlen += offsetof(HeapTupleHeaderData, t_bits);
!     htup->t_infomask2 = xlhdr.t_infomask2;
      htup->t_infomask = xlhdr.t_infomask;
      htup->t_hoff = xlhdr.t_hoff;

Index: src/backend/executor/spi.c
===================================================================
RCS file: /home/hlinnaka/pgcvsrepository/pgsql/src/backend/executor/spi.c,v
retrieving revision 1.165.2.2
diff -c -r1.165.2.2 spi.c
*** src/backend/executor/spi.c    26 Dec 2006 16:56:22 -0000    1.165.2.2
--- src/backend/executor/spi.c    5 Jan 2007 13:16:42 -0000
***************
*** 651,657 ****

      SPI_result = 0;

!     if (fnumber > tuple->t_data->t_natts || fnumber == 0 ||
          fnumber <= FirstLowInvalidHeapAttributeNumber)
      {
          SPI_result = SPI_ERROR_NOATTRIBUTE;
--- 651,657 ----

      SPI_result = 0;

!     if (fnumber > HeapTupleHeaderGetNatts(tuple->t_data) || fnumber == 0 ||
          fnumber <= FirstLowInvalidHeapAttributeNumber)
      {
          SPI_result = SPI_ERROR_NOATTRIBUTE;
***************
*** 692,698 ****
  {
      SPI_result = 0;

!     if (fnumber > tuple->t_data->t_natts || fnumber == 0 ||
          fnumber <= FirstLowInvalidHeapAttributeNumber)
      {
          SPI_result = SPI_ERROR_NOATTRIBUTE;
--- 692,698 ----
  {
      SPI_result = 0;

!     if (fnumber > HeapTupleHeaderGetNatts(tuple->t_data) || fnumber == 0 ||
          fnumber <= FirstLowInvalidHeapAttributeNumber)
      {
          SPI_result = SPI_ERROR_NOATTRIBUTE;
Index: src/include/access/heapam.h
===================================================================
RCS file: /home/hlinnaka/pgcvsrepository/pgsql/src/include/access/heapam.h,v
retrieving revision 1.117
diff -c -r1.117 heapam.h
*** src/include/access/heapam.h    5 Nov 2006 22:42:10 -0000    1.117
--- src/include/access/heapam.h    5 Jan 2007 13:15:10 -0000
***************
*** 98,104 ****
      ( \
          ((attnum) > 0) ? \
          ( \
!             ((attnum) > (int) (tup)->t_data->t_natts) ? \
              ( \
                  (((isnull) != NULL) ? (*(isnull) = true) : (dummyret)NULL), \
                  (Datum)NULL \
--- 98,104 ----
      ( \
          ((attnum) > 0) ? \
          ( \
!             ((attnum) > (int) HeapTupleHeaderGetNatts((tup)->t_data)) ? \
              ( \
                  (((isnull) != NULL) ? (*(isnull) = true) : (dummyret)NULL), \
                  (Datum)NULL \
Index: src/include/access/htup.h
===================================================================
RCS file: /home/hlinnaka/pgcvsrepository/pgsql/src/include/access/htup.h,v
retrieving revision 1.87
diff -c -r1.87 htup.h
*** src/include/access/htup.h    5 Nov 2006 22:42:10 -0000    1.87
--- src/include/access/htup.h    5 Jan 2007 13:08:41 -0000
***************
*** 139,145 ****

      /* Fields below here must match MinimalTupleData! */

!     int16        t_natts;        /* number of attributes */

      uint16        t_infomask;        /* various flag bits, see below */

--- 139,145 ----

      /* Fields below here must match MinimalTupleData! */

!     uint16        t_infomask2;    /* number of attributes + various flags */

      uint16        t_infomask;        /* various flag bits, see below */

***************
*** 182,187 ****
--- 182,195 ----

  #define HEAP_XACT_MASK            0xFFC0    /* visibility-related bits */

+ /* information stored in t_infomask2, and accessor macros */
+ #define HEAP_NATTS_MASK            0X7FF    /* 11 bits for number of attributes */
+
+ #define HeapTupleHeaderGetNatts(tup) ((tup)->t_infomask2 & HEAP_NATTS_MASK)
+ #define HeapTupleHeaderSetNatts(tup, natts) \
+ ( \
+     (tup)->t_infomask2 = ((tup)->t_infomask2 & ~HEAP_NATTS_MASK) | (natts) \
+ )

  /*
   * HeapTupleHeader accessor macros
***************
*** 367,374 ****
   * and thereby prevent accidental use of the nonexistent fields.
   *
   * MinimalTupleData contains a length word, some padding, and fields matching
!  * HeapTupleHeaderData beginning with t_natts.    The padding is chosen so that
!  * offsetof(t_natts) is the same modulo MAXIMUM_ALIGNOF in both structs.
   * This makes data alignment rules equivalent in both cases.
   *
   * When a minimal tuple is accessed via a HeapTupleData pointer, t_data is
--- 375,382 ----
   * and thereby prevent accidental use of the nonexistent fields.
   *
   * MinimalTupleData contains a length word, some padding, and fields matching
!  * HeapTupleHeaderData beginning with t_infomask2. The padding is chosen so that
!  * offsetof(t_infomask2) is the same modulo MAXIMUM_ALIGNOF in both structs.
   * This makes data alignment rules equivalent in both cases.
   *
   * When a minimal tuple is accessed via a HeapTupleData pointer, t_data is
***************
*** 380,388 ****
   * the MINIMAL_TUPLE_OFFSET distance.  t_len does not include that, however.
   */
  #define MINIMAL_TUPLE_OFFSET \
!     ((offsetof(HeapTupleHeaderData, t_natts) - sizeof(uint32)) / MAXIMUM_ALIGNOF * MAXIMUM_ALIGNOF)
  #define MINIMAL_TUPLE_PADDING \
!     ((offsetof(HeapTupleHeaderData, t_natts) - sizeof(uint32)) % MAXIMUM_ALIGNOF)

  typedef struct MinimalTupleData
  {
--- 388,396 ----
   * the MINIMAL_TUPLE_OFFSET distance.  t_len does not include that, however.
   */
  #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)

  typedef struct MinimalTupleData
  {
***************
*** 392,398 ****

      /* Fields below here must match HeapTupleHeaderData! */

!     int16        t_natts;        /* number of attributes */

      uint16        t_infomask;        /* various flag bits, see below */

--- 400,406 ----

      /* Fields below here must match HeapTupleHeaderData! */

!     uint16        t_infomask2;    /* number of attributes + various flags */

      uint16        t_infomask;        /* various flag bits, see below */

***************
*** 552,558 ****
   */
  typedef struct xl_heap_header
  {
!     int16        t_natts;
      uint16        t_infomask;
      uint8        t_hoff;
  } xl_heap_header;
--- 560,566 ----
   */
  typedef struct xl_heap_header
  {
!     uint16        t_infomask2;
      uint16        t_infomask;
      uint8        t_hoff;
  } xl_heap_header;
Index: src/pl/plpgsql/src/pl_exec.c
===================================================================
RCS file: /home/hlinnaka/pgcvsrepository/pgsql/src/pl/plpgsql/src/pl_exec.c,v
retrieving revision 1.180
diff -c -r1.180 pl_exec.c
*** src/pl/plpgsql/src/pl_exec.c    4 Oct 2006 00:30:13 -0000    1.180
--- src/pl/plpgsql/src/pl_exec.c    5 Jan 2007 13:19:14 -0000
***************
*** 4092,4098 ****
       * Row is a bit more complicated in that we assign the individual
       * attributes of the tuple to the variables the row points to.
       *
!      * NOTE: this code used to demand row->nfields == tup->t_data->t_natts,
       * but that's wrong.  The tuple might have more fields than we expected if
       * it's from an inheritance-child table of the current table, or it might
       * have fewer if the table has had columns added by ALTER TABLE. Ignore
--- 4092,4098 ----
       * Row is a bit more complicated in that we assign the individual
       * attributes of the tuple to the variables the row points to.
       *
!      * NOTE: this code used to demand row->nfields == HeapTupleHeaderGetNatts(tup->t_data,
       * but that's wrong.  The tuple might have more fields than we expected if
       * it's from an inheritance-child table of the current table, or it might
       * have fewer if the table has had columns added by ALTER TABLE. Ignore
***************
*** 4110,4116 ****
          int            anum;

          if (HeapTupleIsValid(tup))
!             t_natts = tup->t_data->t_natts;
          else
              t_natts = 0;

--- 4110,4116 ----
          int            anum;

          if (HeapTupleIsValid(tup))
!             t_natts = HeapTupleHeaderGetNatts(tup->t_data);
          else
              t_natts = 0;