heaptuple.c

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/*-------------------------------------------------------------------------
 *
 * heaptuple.c
 *    This file contains heap tuple accessor and mutator routines, as well
 *    as various tuple utilities.
 *
 * Some notes about varlenas and this code:
 *
 * Before Postgres 8.3 varlenas always had a 4-byte length header, and
 * therefore always needed 4-byte alignment (at least).  This wasted space
 * for short varlenas, for example CHAR(1) took 5 bytes and could need up to
 * 3 additional padding bytes for alignment.
 *
 * Now, a short varlena (up to 126 data bytes) is reduced to a 1-byte header
 * and we don't align it.  To hide this from datatype-specific functions that
 * don't want to deal with it, such a datum is considered "toasted" and will
 * be expanded back to the normal 4-byte-header format by pg_detoast_datum.
 * (In performance-critical code paths we can use pg_detoast_datum_packed
 * and the appropriate access macros to avoid that overhead.)  Note that this
 * conversion is performed directly in heap_form_tuple, without invoking
 * tuptoaster.c.
 *
 * This change will break any code that assumes it needn't detoast values
 * that have been put into a tuple but never sent to disk.  Hopefully there
 * are few such places.
 *
 * Varlenas still have alignment 'i' (or 'd') in pg_type/pg_attribute, since
 * that's the normal requirement for the untoasted format.  But we ignore that
 * for the 1-byte-header format.  This means that the actual start position
 * of a varlena datum may vary depending on which format it has.  To determine
 * what is stored, we have to require that alignment padding bytes be zero.
 * (Postgres actually has always zeroed them, but now it's required!)  Since
 * the first byte of a 1-byte-header varlena can never be zero, we can examine
 * the first byte after the previous datum to tell if it's a pad byte or the
 * start of a 1-byte-header varlena.
 *
 * Note that while formerly we could rely on the first varlena column of a
 * system catalog to be at the offset suggested by the C struct for the
 * catalog, this is now risky: it's only safe if the preceding field is
 * word-aligned, so that there will never be any padding.
 *
 * We don't pack varlenas whose attstorage is 'p', since the data type
 * isn't expecting to have to detoast values.  This is used in particular
 * by oidvector and int2vector, which are used in the system catalogs
 * and we'd like to still refer to them via C struct offsets.
 *
 *
 * Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/backend/access/common/heaptuple.c
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include "access/sysattr.h"
#include "access/tuptoaster.h"
#include "executor/tuptable.h"


/* Does att's datatype allow packing into the 1-byte-header varlena format? */
#define ATT_IS_PACKABLE(att) \
    ((att)->attlen == -1 && (att)->attstorage != 'p')
/* Use this if it's already known varlena */
#define VARLENA_ATT_IS_PACKABLE(att) \
    ((att)->attstorage != 'p')


/* ----------------------------------------------------------------
 *                      misc support routines
 * ----------------------------------------------------------------
 */


/*
 * heap_compute_data_size
 *      Determine size of the data area of a tuple to be constructed
 */
Size
heap_compute_data_size(TupleDesc tupleDesc,
                       Datum *values,
                       bool *isnull)
{
    Size        data_length = 0;
    int         i;
    int         numberOfAttributes = tupleDesc->natts;
    Form_pg_attribute *att = tupleDesc->attrs;

    for (i = 0; i < numberOfAttributes; i++)
    {
        Datum       val;

        if (isnull[i])
            continue;

        val = values[i];

        if (ATT_IS_PACKABLE(att[i]) &&
            VARATT_CAN_MAKE_SHORT(DatumGetPointer(val)))
        {
            /*
             * we're anticipating converting to a short varlena header, so
             * adjust length and don't count any alignment
             */
            data_length += VARATT_CONVERTED_SHORT_SIZE(DatumGetPointer(val));
        }
        else
        {
            data_length = att_align_datum(data_length, att[i]->attalign,
                                          att[i]->attlen, val);
            data_length = att_addlength_datum(data_length, att[i]->attlen,
                                              val);
        }
    }

    return data_length;
}

/*
 * heap_fill_tuple
 *      Load data portion of a tuple from values/isnull arrays
 *
 * We also fill the null bitmap (if any) and set the infomask bits
 * that reflect the tuple's data contents.
 *
 * NOTE: it is now REQUIRED that the caller have pre-zeroed the data area.
 */
void
heap_fill_tuple(TupleDesc tupleDesc,
                Datum *values, bool *isnull,
                char *data, Size data_size,
                uint16 *infomask, bits8 *bit)
{
    bits8      *bitP;
    int         bitmask;
    int         i;
    int         numberOfAttributes = tupleDesc->natts;
    Form_pg_attribute *att = tupleDesc->attrs;

#ifdef USE_ASSERT_CHECKING
    char       *start = data;
#endif

    if (bit != NULL)
    {
        bitP = &bit[-1];
        bitmask = HIGHBIT;
    }
    else
    {
        /* just to keep compiler quiet */
        bitP = NULL;
        bitmask = 0;
    }

    *infomask &= ~(HEAP_HASNULL | HEAP_HASVARWIDTH | HEAP_HASEXTERNAL);

    for (i = 0; i < numberOfAttributes; i++)
    {
        Size        data_length;

        if (bit != NULL)
        {
            if (bitmask != HIGHBIT)
                bitmask <<= 1;
            else
            {
                bitP += 1;
                *bitP = 0x0;
                bitmask = 1;
            }

            if (isnull[i])
            {
                *infomask |= HEAP_HASNULL;
                continue;
            }

            *bitP |= bitmask;
        }

        /*
         * XXX we use the att_align macros on the pointer value itself, not on
         * an offset.  This is a bit of a hack.
         */

        if (att[i]->attbyval)
        {
            /* pass-by-value */
            data = (char *) att_align_nominal(data, att[i]->attalign);
            store_att_byval(data, values[i], att[i]->attlen);
            data_length = att[i]->attlen;
        }
        else if (att[i]->attlen == -1)
        {
            /* varlena */
            Pointer     val = DatumGetPointer(values[i]);

            *infomask |= HEAP_HASVARWIDTH;
            if (VARATT_IS_EXTERNAL(val))
            {
                *infomask |= HEAP_HASEXTERNAL;
                /* no alignment, since it's short by definition */
                data_length = VARSIZE_EXTERNAL(val);
                memcpy(data, val, data_length);
            }
            else if (VARATT_IS_SHORT(val))
            {
                /* no alignment for short varlenas */
                data_length = VARSIZE_SHORT(val);
                memcpy(data, val, data_length);
            }
            else if (VARLENA_ATT_IS_PACKABLE(att[i]) &&
                     VARATT_CAN_MAKE_SHORT(val))
            {
                /* convert to short varlena -- no alignment */
                data_length = VARATT_CONVERTED_SHORT_SIZE(val);
                SET_VARSIZE_SHORT(data, data_length);
                memcpy(data + 1, VARDATA(val), data_length - 1);
            }
            else
            {
                /* full 4-byte header varlena */
                data = (char *) att_align_nominal(data,
                                                  att[i]->attalign);
                data_length = VARSIZE(val);
                memcpy(data, val, data_length);
            }
        }
        else if (att[i]->attlen == -2)
        {
            /* cstring ... never needs alignment */
            *infomask |= HEAP_HASVARWIDTH;
            Assert(att[i]->attalign == 'c');
            data_length = strlen(DatumGetCString(values[i])) + 1;
            memcpy(data, DatumGetPointer(values[i]), data_length);
        }
        else
        {
            /* fixed-length pass-by-reference */
            data = (char *) att_align_nominal(data, att[i]->attalign);
            Assert(att[i]->attlen > 0);
            data_length = att[i]->attlen;
            memcpy(data, DatumGetPointer(values[i]), data_length);
        }

        data += data_length;
    }

    Assert((data - start) == data_size);
}


/* ----------------------------------------------------------------
 *                      heap tuple interface
 * ----------------------------------------------------------------
 */

/* ----------------
 *      heap_attisnull  - returns TRUE iff tuple attribute is not present
 * ----------------
 */
bool
heap_attisnull(HeapTuple tup, int attnum)
{
    if (attnum > (int) HeapTupleHeaderGetNatts(tup->t_data))
        return true;

    if (attnum > 0)
    {
        if (HeapTupleNoNulls(tup))
            return false;
        return att_isnull(attnum - 1, tup->t_data->t_bits);
    }

    switch (attnum)
    {
        case TableOidAttributeNumber:
        case SelfItemPointerAttributeNumber:
        case ObjectIdAttributeNumber:
        case MinTransactionIdAttributeNumber:
        case MinCommandIdAttributeNumber:
        case MaxTransactionIdAttributeNumber:
        case MaxCommandIdAttributeNumber:
            /* these are never null */
            break;

        default:
            elog(ERROR, "invalid attnum: %d", attnum);
    }

    return false;
}

/* ----------------
 *      nocachegetattr
 *
 *      This only gets called from fastgetattr() macro, in cases where
 *      we can't use a cacheoffset and the value is not null.
 *
 *      This caches attribute offsets in the attribute descriptor.
 *
 *      An alternative way to speed things up would be to cache offsets
 *      with the tuple, but that seems more difficult unless you take
 *      the storage hit of actually putting those offsets into the
 *      tuple you send to disk.  Yuck.
 *
 *      This scheme will be slightly slower than that, but should
 *      perform well for queries which hit large #'s of tuples.  After
 *      you cache the offsets once, examining all the other tuples using
 *      the same attribute descriptor will go much quicker. -cim 5/4/91
 *
 *      NOTE: if you need to change this code, see also heap_deform_tuple.
 *      Also see nocache_index_getattr, which is the same code for index
 *      tuples.
 * ----------------
 */
Datum
nocachegetattr(HeapTuple tuple,
               int attnum,
               TupleDesc tupleDesc)
{
    HeapTupleHeader tup = tuple->t_data;
    Form_pg_attribute *att = tupleDesc->attrs;
    char       *tp;             /* ptr to data part of tuple */
    bits8      *bp = tup->t_bits;       /* ptr to null bitmap in tuple */
    bool        slow = false;   /* do we have to walk attrs? */
    int         off;            /* current offset within data */

    /* ----------------
     *   Three cases:
     *
     *   1: No nulls and no variable-width attributes.
     *   2: Has a null or a var-width AFTER att.
     *   3: Has nulls or var-widths BEFORE att.
     * ----------------
     */

    attnum--;

    if (!HeapTupleNoNulls(tuple))
    {
        /*
         * there's a null somewhere in the tuple
         *
         * check to see if any preceding bits are null...
         */
        int         byte = attnum >> 3;
        int         finalbit = attnum & 0x07;

        /* check for nulls "before" final bit of last byte */
        if ((~bp[byte]) & ((1 << finalbit) - 1))
            slow = true;
        else
        {
            /* check for nulls in any "earlier" bytes */
            int         i;

            for (i = 0; i < byte; i++)
            {
                if (bp[i] != 0xFF)
                {
                    slow = true;
                    break;
                }
            }
        }
    }

    tp = (char *) tup + tup->t_hoff;

    if (!slow)
    {
        /*
         * If we get here, there are no nulls up to and including the target
         * attribute.  If we have a cached offset, we can use it.
         */
        if (att[attnum]->attcacheoff >= 0)
        {
            return fetchatt(att[attnum],
                            tp + att[attnum]->attcacheoff);
        }

        /*
         * Otherwise, check for non-fixed-length attrs up to and including
         * target.  If there aren't any, it's safe to cheaply initialize the
         * cached offsets for these attrs.
         */
        if (HeapTupleHasVarWidth(tuple))
        {
            int         j;

            for (j = 0; j <= attnum; j++)
            {
                if (att[j]->attlen <= 0)
                {
                    slow = true;
                    break;
                }
            }
        }
    }

    if (!slow)
    {
        int         natts = tupleDesc->natts;
        int         j = 1;

        /*
         * If we get here, we have a tuple with no nulls or var-widths up to
         * and including the target attribute, so we can use the cached offset
         * ... only we don't have it yet, or we'd not have got here.  Since
         * it's cheap to compute offsets for fixed-width columns, we take the
         * opportunity to initialize the cached offsets for *all* the leading
         * fixed-width columns, in hope of avoiding future visits to this
         * routine.
         */
        att[0]->attcacheoff = 0;

        /* we might have set some offsets in the slow path previously */
        while (j < natts && att[j]->attcacheoff > 0)
            j++;

        off = att[j - 1]->attcacheoff + att[j - 1]->attlen;

        for (; j < natts; j++)
        {
            if (att[j]->attlen <= 0)
                break;

            off = att_align_nominal(off, att[j]->attalign);

            att[j]->attcacheoff = off;

            off += att[j]->attlen;
        }

        Assert(j > attnum);

        off = att[attnum]->attcacheoff;
    }
    else
    {
        bool        usecache = true;
        int         i;

        /*
         * Now we know that we have to walk the tuple CAREFULLY.  But we still
         * might be able to cache some offsets for next time.
         *
         * Note - This loop is a little tricky.  For each non-null attribute,
         * we have to first account for alignment padding before the attr,
         * then advance over the attr based on its length.  Nulls have no
         * storage and no alignment padding either.  We can use/set
         * attcacheoff until we reach either a null or a var-width attribute.
         */
        off = 0;
        for (i = 0;; i++)       /* loop exit is at "break" */
        {
            if (HeapTupleHasNulls(tuple) && att_isnull(i, bp))
            {
                usecache = false;
                continue;       /* this cannot be the target att */
            }

            /* If we know the next offset, we can skip the rest */
            if (usecache && att[i]->attcacheoff >= 0)
                off = att[i]->attcacheoff;
            else if (att[i]->attlen == -1)
            {
                /*
                 * We can only cache the offset for a varlena attribute if the
                 * offset is already suitably aligned, so that there would be
                 * no pad bytes in any case: then the offset will be valid for
                 * either an aligned or unaligned value.
                 */
                if (usecache &&
                    off == att_align_nominal(off, att[i]->attalign))
                    att[i]->attcacheoff = off;
                else
                {
                    off = att_align_pointer(off, att[i]->attalign, -1,
                                            tp + off);
                    usecache = false;
                }
            }
            else
            {
                /* not varlena, so safe to use att_align_nominal */
                off = att_align_nominal(off, att[i]->attalign);

                if (usecache)
                    att[i]->attcacheoff = off;
            }

            if (i == attnum)
                break;

            off = att_addlength_pointer(off, att[i]->attlen, tp + off);

            if (usecache && att[i]->attlen <= 0)
                usecache = false;
        }
    }

    return fetchatt(att[attnum], tp + off);
}

/* ----------------
 *      heap_getsysattr
 *
 *      Fetch the value of a system attribute for a tuple.
 *
 * This is a support routine for the heap_getattr macro.  The macro
 * has already determined that the attnum refers to a system attribute.
 * ----------------
 */
Datum
heap_getsysattr(HeapTuple tup, int attnum, TupleDesc tupleDesc, bool *isnull)
{
    Datum       result;

    Assert(tup);

    /* Currently, no sys attribute ever reads as NULL. */
    *isnull = false;

    switch (attnum)
    {
        case SelfItemPointerAttributeNumber:
            /* pass-by-reference datatype */
            result = PointerGetDatum(&(tup->t_self));
            break;
        case ObjectIdAttributeNumber:
            result = ObjectIdGetDatum(HeapTupleGetOid(tup));
            break;
        case MinTransactionIdAttributeNumber:
            result = TransactionIdGetDatum(HeapTupleHeaderGetXmin(tup->t_data));
            break;
        case MaxTransactionIdAttributeNumber:
            result = TransactionIdGetDatum(HeapTupleHeaderGetRawXmax(tup->t_data));
            break;
        case MinCommandIdAttributeNumber:
        case MaxCommandIdAttributeNumber:

            /*
             * cmin and cmax are now both aliases for the same field, which
             * can in fact also be a combo command id.  XXX perhaps we should
             * return the "real" cmin or cmax if possible, that is if we are
             * inside the originating transaction?
             */
            result = CommandIdGetDatum(HeapTupleHeaderGetRawCommandId(tup->t_data));
            break;
        case TableOidAttributeNumber:
            result = ObjectIdGetDatum(tup->t_tableOid);
            break;
        default:
            elog(ERROR, "invalid attnum: %d", attnum);
            result = 0;         /* keep compiler quiet */
            break;
    }
    return result;
}

/* ----------------
 *      heap_copytuple
 *
 *      returns a copy of an entire tuple
 *
 * The HeapTuple struct, tuple header, and tuple data are all allocated
 * as a single palloc() block.
 * ----------------
 */
HeapTuple
heap_copytuple(HeapTuple tuple)
{
    HeapTuple   newTuple;

    if (!HeapTupleIsValid(tuple) || tuple->t_data == NULL)
        return NULL;

    newTuple = (HeapTuple) palloc(HEAPTUPLESIZE + tuple->t_len);
    newTuple->t_len = tuple->t_len;
    newTuple->t_self = tuple->t_self;
    newTuple->t_tableOid = tuple->t_tableOid;
    newTuple->t_data = (HeapTupleHeader) ((char *) newTuple + HEAPTUPLESIZE);
    memcpy((char *) newTuple->t_data, (char *) tuple->t_data, tuple->t_len);
    return newTuple;
}

/* ----------------
 *      heap_copytuple_with_tuple
 *
 *      copy a tuple into a caller-supplied HeapTuple management struct
 *
 * Note that after calling this function, the "dest" HeapTuple will not be
 * allocated as a single palloc() block (unlike with heap_copytuple()).
 * ----------------
 */
void
heap_copytuple_with_tuple(HeapTuple src, HeapTuple dest)
{
    if (!HeapTupleIsValid(src) || src->t_data == NULL)
    {
        dest->t_data = NULL;
        return;
    }

    dest->t_len = src->t_len;
    dest->t_self = src->t_self;
    dest->t_tableOid = src->t_tableOid;
    dest->t_data = (HeapTupleHeader) palloc(src->t_len);
    memcpy((char *) dest->t_data, (char *) src->t_data, src->t_len);
}

/*
 * heap_form_tuple
 *      construct a tuple from the given values[] and isnull[] arrays,
 *      which are of the length indicated by tupleDescriptor->natts
 *
 * The result is allocated in the current memory context.
 */
HeapTuple
heap_form_tuple(TupleDesc tupleDescriptor,
                Datum *values,
                bool *isnull)
{
    HeapTuple   tuple;          /* return tuple */
    HeapTupleHeader td;         /* tuple data */
    Size        len,
                data_len;
    int         hoff;
    bool        hasnull = false;
    Form_pg_attribute *att = tupleDescriptor->attrs;
    int         numberOfAttributes = tupleDescriptor->natts;
    int         i;

    if (numberOfAttributes > MaxTupleAttributeNumber)
        ereport(ERROR,
                (errcode(ERRCODE_TOO_MANY_COLUMNS),
                 errmsg("number of columns (%d) exceeds limit (%d)",
                        numberOfAttributes, MaxTupleAttributeNumber)));

    /*
     * Check for nulls and embedded tuples; expand any toasted attributes in
     * embedded tuples.  This preserves the invariant that toasting can only
     * go one level deep.
     *
     * We can skip calling toast_flatten_tuple_attribute() if the attribute
     * couldn't possibly be of composite type.  All composite datums are
     * varlena and have alignment 'd'; furthermore they aren't arrays. Also,
     * if an attribute is already toasted, it must have been sent to disk
     * already and so cannot contain toasted attributes.
     */
    for (i = 0; i < numberOfAttributes; i++)
    {
        if (isnull[i])
            hasnull = true;
        else if (att[i]->attlen == -1 &&
                 att[i]->attalign == 'd' &&
                 att[i]->attndims == 0 &&
                 !VARATT_IS_EXTENDED(DatumGetPointer(values[i])))
        {
            values[i] = toast_flatten_tuple_attribute(values[i],
                                                      att[i]->atttypid,
                                                      att[i]->atttypmod);
        }
    }

    /*
     * Determine total space needed
     */
    len = offsetof(HeapTupleHeaderData, t_bits);

    if (hasnull)
        len += BITMAPLEN(numberOfAttributes);

    if (tupleDescriptor->tdhasoid)
        len += sizeof(Oid);

    hoff = len = MAXALIGN(len); /* align user data safely */

    data_len = heap_compute_data_size(tupleDescriptor, values, isnull);

    len += data_len;

    /*
     * Allocate and zero the space needed.  Note that the tuple body and
     * HeapTupleData management structure are allocated in one chunk.
     */
    tuple = (HeapTuple) palloc0(HEAPTUPLESIZE + len);
    tuple->t_data = td = (HeapTupleHeader) ((char *) tuple + HEAPTUPLESIZE);

    /*
     * And fill in the information.  Note we fill the Datum fields even though
     * this tuple may never become a Datum.
     */
    tuple->t_len = len;
    ItemPointerSetInvalid(&(tuple->t_self));
    tuple->t_tableOid = InvalidOid;

    HeapTupleHeaderSetDatumLength(td, len);
    HeapTupleHeaderSetTypeId(td, tupleDescriptor->tdtypeid);
    HeapTupleHeaderSetTypMod(td, tupleDescriptor->tdtypmod);

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

    if (tupleDescriptor->tdhasoid)      /* else leave infomask = 0 */
        td->t_infomask = HEAP_HASOID;

    heap_fill_tuple(tupleDescriptor,
                    values,
                    isnull,
                    (char *) td + hoff,
                    data_len,
                    &td->t_infomask,
                    (hasnull ? td->t_bits : NULL));

    return tuple;
}

/*
 *      heap_formtuple
 *
 *      construct a tuple from the given values[] and nulls[] arrays
 *
 *      Null attributes are indicated by a 'n' in the appropriate byte
 *      of nulls[]. Non-null attributes are indicated by a ' ' (space).
 *
 * OLD API with char 'n'/' ' convention for indicating nulls.
 * This is deprecated and should not be used in new code, but we keep it
 * around for use by old add-on modules.
 */
HeapTuple
heap_formtuple(TupleDesc tupleDescriptor,
               Datum *values,
               char *nulls)
{
    HeapTuple   tuple;          /* return tuple */
    int         numberOfAttributes = tupleDescriptor->natts;
    bool       *boolNulls = (bool *) palloc(numberOfAttributes * sizeof(bool));
    int         i;

    for (i = 0; i < numberOfAttributes; i++)
        boolNulls[i] = (nulls[i] == 'n');

    tuple = heap_form_tuple(tupleDescriptor, values, boolNulls);

    pfree(boolNulls);

    return tuple;
}


/*
 * heap_modify_tuple
 *      form a new tuple from an old tuple and a set of replacement values.
 *
 * The replValues, replIsnull, and doReplace arrays must be of the length
 * indicated by tupleDesc->natts.  The new tuple is constructed using the data
 * from replValues/replIsnull at columns where doReplace is true, and using
 * the data from the old tuple at columns where doReplace is false.
 *
 * The result is allocated in the current memory context.
 */
HeapTuple
heap_modify_tuple(HeapTuple tuple,
                  TupleDesc tupleDesc,
                  Datum *replValues,
                  bool *replIsnull,
                  bool *doReplace)
{
    int         numberOfAttributes = tupleDesc->natts;
    int         attoff;
    Datum      *values;
    bool       *isnull;
    HeapTuple   newTuple;

    /*
     * allocate and fill values and isnull arrays from either the tuple or the
     * repl information, as appropriate.
     *
     * NOTE: it's debatable whether to use heap_deform_tuple() here or just
     * heap_getattr() only the non-replaced colums.  The latter could win if
     * there are many replaced columns and few non-replaced ones. However,
     * heap_deform_tuple costs only O(N) while the heap_getattr way would cost
     * O(N^2) if there are many non-replaced columns, so it seems better to
     * err on the side of linear cost.
     */
    values = (Datum *) palloc(numberOfAttributes * sizeof(Datum));
    isnull = (bool *) palloc(numberOfAttributes * sizeof(bool));

    heap_deform_tuple(tuple, tupleDesc, values, isnull);

    for (attoff = 0; attoff < numberOfAttributes; attoff++)
    {
        if (doReplace[attoff])
        {
            values[attoff] = replValues[attoff];
            isnull[attoff] = replIsnull[attoff];
        }
    }

    /*
     * create a new tuple from the values and isnull arrays
     */
    newTuple = heap_form_tuple(tupleDesc, values, isnull);

    pfree(values);
    pfree(isnull);

    /*
     * copy the identification info of the old tuple: t_ctid, t_self, and OID
     * (if any)
     */
    newTuple->t_data->t_ctid = tuple->t_data->t_ctid;
    newTuple->t_self = tuple->t_self;
    newTuple->t_tableOid = tuple->t_tableOid;
    if (tupleDesc->tdhasoid)
        HeapTupleSetOid(newTuple, HeapTupleGetOid(tuple));

    return newTuple;
}

/*
 *      heap_modifytuple
 *
 *      forms a new tuple from an old tuple and a set of replacement values.
 *      returns a new palloc'ed tuple.
 *
 * OLD API with char 'n'/' ' convention for indicating nulls, and
 * char 'r'/' ' convention for indicating whether to replace columns.
 * This is deprecated and should not be used in new code, but we keep it
 * around for use by old add-on modules.
 */
HeapTuple
heap_modifytuple(HeapTuple tuple,
                 TupleDesc tupleDesc,
                 Datum *replValues,
                 char *replNulls,
                 char *replActions)
{
    HeapTuple   result;
    int         numberOfAttributes = tupleDesc->natts;
    bool       *boolNulls = (bool *) palloc(numberOfAttributes * sizeof(bool));
    bool       *boolActions = (bool *) palloc(numberOfAttributes * sizeof(bool));
    int         attnum;

    for (attnum = 0; attnum < numberOfAttributes; attnum++)
    {
        boolNulls[attnum] = (replNulls[attnum] == 'n');
        boolActions[attnum] = (replActions[attnum] == 'r');
    }

    result = heap_modify_tuple(tuple, tupleDesc, replValues, boolNulls, boolActions);

    pfree(boolNulls);
    pfree(boolActions);

    return result;
}

/*
 * heap_deform_tuple
 *      Given a tuple, extract data into values/isnull arrays; this is
 *      the inverse of heap_form_tuple.
 *
 *      Storage for the values/isnull arrays is provided by the caller;
 *      it should be sized according to tupleDesc->natts not
 *      HeapTupleHeaderGetNatts(tuple->t_data).
 *
 *      Note that for pass-by-reference datatypes, the pointer placed
 *      in the Datum will point into the given tuple.
 *
 *      When all or most of a tuple's fields need to be extracted,
 *      this routine will be significantly quicker than a loop around
 *      heap_getattr; the loop will become O(N^2) as soon as any
 *      noncacheable attribute offsets are involved.
 */
void
heap_deform_tuple(HeapTuple tuple, TupleDesc tupleDesc,
                  Datum *values, bool *isnull)
{
    HeapTupleHeader tup = tuple->t_data;
    bool        hasnulls = HeapTupleHasNulls(tuple);
    Form_pg_attribute *att = tupleDesc->attrs;
    int         tdesc_natts = tupleDesc->natts;
    int         natts;          /* number of atts to extract */
    int         attnum;
    char       *tp;             /* ptr to tuple data */
    long        off;            /* offset in tuple data */
    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
     * has more fields than the caller is expecting.  Don't run off the end of
     * the caller's arrays.
     */
    natts = Min(natts, tdesc_natts);

    tp = (char *) tup + tup->t_hoff;

    off = 0;

    for (attnum = 0; attnum < natts; attnum++)
    {
        Form_pg_attribute thisatt = att[attnum];

        if (hasnulls && att_isnull(attnum, bp))
        {
            values[attnum] = (Datum) 0;
            isnull[attnum] = true;
            slow = true;        /* can't use attcacheoff anymore */
            continue;
        }

        isnull[attnum] = false;

        if (!slow && thisatt->attcacheoff >= 0)
            off = thisatt->attcacheoff;
        else if (thisatt->attlen == -1)
        {
            /*
             * We can only cache the offset for a varlena attribute if the
             * offset is already suitably aligned, so that there would be no
             * pad bytes in any case: then the offset will be valid for either
             * an aligned or unaligned value.
             */
            if (!slow &&
                off == att_align_nominal(off, thisatt->attalign))
                thisatt->attcacheoff = off;
            else
            {
                off = att_align_pointer(off, thisatt->attalign, -1,
                                        tp + off);
                slow = true;
            }
        }
        else
        {
            /* not varlena, so safe to use att_align_nominal */
            off = att_align_nominal(off, thisatt->attalign);

            if (!slow)
                thisatt->attcacheoff = off;
        }

        values[attnum] = fetchatt(thisatt, tp + off);

        off = att_addlength_pointer(off, thisatt->attlen, tp + off);

        if (thisatt->attlen <= 0)
            slow = true;        /* can't use attcacheoff anymore */
    }

    /*
     * If tuple doesn't have all the atts indicated by tupleDesc, read the
     * rest as null
     */
    for (; attnum < tdesc_natts; attnum++)
    {
        values[attnum] = (Datum) 0;
        isnull[attnum] = true;
    }
}

/*
 *      heap_deformtuple
 *
 *      Given a tuple, extract data into values/nulls arrays; this is
 *      the inverse of heap_formtuple.
 *
 *      Storage for the values/nulls arrays is provided by the caller;
 *      it should be sized according to tupleDesc->natts not
 *      HeapTupleHeaderGetNatts(tuple->t_data).
 *
 *      Note that for pass-by-reference datatypes, the pointer placed
 *      in the Datum will point into the given tuple.
 *
 *      When all or most of a tuple's fields need to be extracted,
 *      this routine will be significantly quicker than a loop around
 *      heap_getattr; the loop will become O(N^2) as soon as any
 *      noncacheable attribute offsets are involved.
 *
 * OLD API with char 'n'/' ' convention for indicating nulls.
 * This is deprecated and should not be used in new code, but we keep it
 * around for use by old add-on modules.
 */
void
heap_deformtuple(HeapTuple tuple,
                 TupleDesc tupleDesc,
                 Datum *values,
                 char *nulls)
{
    int         natts = tupleDesc->natts;
    bool       *boolNulls = (bool *) palloc(natts * sizeof(bool));
    int         attnum;

    heap_deform_tuple(tuple, tupleDesc, values, boolNulls);

    for (attnum = 0; attnum < natts; attnum++)
        nulls[attnum] = (boolNulls[attnum] ? 'n' : ' ');

    pfree(boolNulls);
}

/*
 * slot_deform_tuple
 *      Given a TupleTableSlot, extract data from the slot's physical tuple
 *      into its Datum/isnull arrays.  Data is extracted up through the
 *      natts'th column (caller must ensure this is a legal column number).
 *
 *      This is essentially an incremental version of heap_deform_tuple:
 *      on each call we extract attributes up to the one needed, without
 *      re-computing information about previously extracted attributes.
 *      slot->tts_nvalid is the number of attributes already extracted.
 */
static void
slot_deform_tuple(TupleTableSlot *slot, int natts)
{
    HeapTuple   tuple = slot->tts_tuple;
    TupleDesc   tupleDesc = slot->tts_tupleDescriptor;
    Datum      *values = slot->tts_values;
    bool       *isnull = slot->tts_isnull;
    HeapTupleHeader tup = tuple->t_data;
    bool        hasnulls = HeapTupleHasNulls(tuple);
    Form_pg_attribute *att = tupleDesc->attrs;
    int         attnum;
    char       *tp;             /* ptr to tuple data */
    long        off;            /* offset in tuple data */
    bits8      *bp = tup->t_bits;       /* ptr to null bitmap in tuple */
    bool        slow;           /* can we use/set attcacheoff? */

    /*
     * Check whether the first call for this tuple, and initialize or restore
     * loop state.
     */
    attnum = slot->tts_nvalid;
    if (attnum == 0)
    {
        /* Start from the first attribute */
        off = 0;
        slow = false;
    }
    else
    {
        /* Restore state from previous execution */
        off = slot->tts_off;
        slow = slot->tts_slow;
    }

    tp = (char *) tup + tup->t_hoff;

    for (; attnum < natts; attnum++)
    {
        Form_pg_attribute thisatt = att[attnum];

        if (hasnulls && att_isnull(attnum, bp))
        {
            values[attnum] = (Datum) 0;
            isnull[attnum] = true;
            slow = true;        /* can't use attcacheoff anymore */
            continue;
        }

        isnull[attnum] = false;

        if (!slow && thisatt->attcacheoff >= 0)
            off = thisatt->attcacheoff;
        else if (thisatt->attlen == -1)
        {
            /*
             * We can only cache the offset for a varlena attribute if the
             * offset is already suitably aligned, so that there would be no
             * pad bytes in any case: then the offset will be valid for either
             * an aligned or unaligned value.
             */
            if (!slow &&
                off == att_align_nominal(off, thisatt->attalign))
                thisatt->attcacheoff = off;
            else
            {
                off = att_align_pointer(off, thisatt->attalign, -1,
                                        tp + off);
                slow = true;
            }
        }
        else
        {
            /* not varlena, so safe to use att_align_nominal */
            off = att_align_nominal(off, thisatt->attalign);

            if (!slow)
                thisatt->attcacheoff = off;
        }

        values[attnum] = fetchatt(thisatt, tp + off);

        off = att_addlength_pointer(off, thisatt->attlen, tp + off);

        if (thisatt->attlen <= 0)
            slow = true;        /* can't use attcacheoff anymore */
    }

    /*
     * Save state for next execution
     */
    slot->tts_nvalid = attnum;
    slot->tts_off = off;
    slot->tts_slow = slow;
}

/*
 * slot_getattr
 *      This function fetches an attribute of the slot's current tuple.
 *      It is functionally equivalent to heap_getattr, but fetches of
 *      multiple attributes of the same tuple will be optimized better,
 *      because we avoid O(N^2) behavior from multiple calls of
 *      nocachegetattr(), even when attcacheoff isn't usable.
 *
 *      A difference from raw heap_getattr is that attnums beyond the
 *      slot's tupdesc's last attribute will be considered NULL even
 *      when the physical tuple is longer than the tupdesc.
 */
Datum
slot_getattr(TupleTableSlot *slot, int attnum, bool *isnull)
{
    HeapTuple   tuple = slot->tts_tuple;
    TupleDesc   tupleDesc = slot->tts_tupleDescriptor;
    HeapTupleHeader tup;

    /*
     * system attributes are handled by heap_getsysattr
     */
    if (attnum <= 0)
    {
        if (tuple == NULL)      /* internal error */
            elog(ERROR, "cannot extract system attribute from virtual tuple");
        if (tuple == &(slot->tts_minhdr))       /* internal error */
            elog(ERROR, "cannot extract system attribute from minimal tuple");
        return heap_getsysattr(tuple, attnum, tupleDesc, isnull);
    }

    /*
     * fast path if desired attribute already cached
     */
    if (attnum <= slot->tts_nvalid)
    {
        *isnull = slot->tts_isnull[attnum - 1];
        return slot->tts_values[attnum - 1];
    }

    /*
     * return NULL if attnum is out of range according to the tupdesc
     */
    if (attnum > tupleDesc->natts)
    {
        *isnull = true;
        return (Datum) 0;
    }

    /*
     * otherwise we had better have a physical tuple (tts_nvalid should equal
     * natts in all virtual-tuple cases)
     */
    if (tuple == NULL)          /* internal error */
        elog(ERROR, "cannot extract attribute from empty tuple slot");

    /*
     * return NULL if attnum is out of range according to the tuple
     *
     * (We have to check this separately because of various inheritance and
     * table-alteration scenarios: the tuple could be either longer or shorter
     * than the tupdesc.)
     */
    tup = tuple->t_data;
    if (attnum > HeapTupleHeaderGetNatts(tup))
    {
        *isnull = true;
        return (Datum) 0;
    }

    /*
     * check if target attribute is null: no point in groveling through tuple
     */
    if (HeapTupleHasNulls(tuple) && att_isnull(attnum - 1, tup->t_bits))
    {
        *isnull = true;
        return (Datum) 0;
    }

    /*
     * If the attribute's column has been dropped, we force a NULL result.
     * This case should not happen in normal use, but it could happen if we
     * are executing a plan cached before the column was dropped.
     */
    if (tupleDesc->attrs[attnum - 1]->attisdropped)
    {
        *isnull = true;
        return (Datum) 0;
    }

    /*
     * Extract the attribute, along with any preceding attributes.
     */
    slot_deform_tuple(slot, attnum);

    /*
     * The result is acquired from tts_values array.
     */
    *isnull = slot->tts_isnull[attnum - 1];
    return slot->tts_values[attnum - 1];
}

/*
 * slot_getallattrs
 *      This function forces all the entries of the slot's Datum/isnull
 *      arrays to be valid.  The caller may then extract data directly
 *      from those arrays instead of using slot_getattr.
 */
void
slot_getallattrs(TupleTableSlot *slot)
{
    int         tdesc_natts = slot->tts_tupleDescriptor->natts;
    int         attnum;
    HeapTuple   tuple;

    /* Quick out if we have 'em all already */
    if (slot->tts_nvalid == tdesc_natts)
        return;

    /*
     * otherwise we had better have a physical tuple (tts_nvalid should equal
     * natts in all virtual-tuple cases)
     */
    tuple = slot->tts_tuple;
    if (tuple == NULL)          /* internal error */
        elog(ERROR, "cannot extract attribute from empty tuple slot");

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

    slot_deform_tuple(slot, attnum);

    /*
     * If tuple doesn't have all the atts indicated by tupleDesc, read the
     * rest as null
     */
    for (; attnum < tdesc_natts; attnum++)
    {
        slot->tts_values[attnum] = (Datum) 0;
        slot->tts_isnull[attnum] = true;
    }
    slot->tts_nvalid = tdesc_natts;
}

/*
 * slot_getsomeattrs
 *      This function forces the entries of the slot's Datum/isnull
 *      arrays to be valid at least up through the attnum'th entry.
 */
void
slot_getsomeattrs(TupleTableSlot *slot, int attnum)
{
    HeapTuple   tuple;
    int         attno;

    /* Quick out if we have 'em all already */
    if (slot->tts_nvalid >= attnum)
        return;

    /* Check for caller error */
    if (attnum <= 0 || attnum > slot->tts_tupleDescriptor->natts)
        elog(ERROR, "invalid attribute number %d", attnum);

    /*
     * otherwise we had better have a physical tuple (tts_nvalid should equal
     * natts in all virtual-tuple cases)
     */
    tuple = slot->tts_tuple;
    if (tuple == NULL)          /* internal error */
        elog(ERROR, "cannot extract attribute from empty tuple slot");

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

    slot_deform_tuple(slot, attno);

    /*
     * If tuple doesn't have all the atts indicated by tupleDesc, read the
     * rest as null
     */
    for (; attno < attnum; attno++)
    {
        slot->tts_values[attno] = (Datum) 0;
        slot->tts_isnull[attno] = true;
    }
    slot->tts_nvalid = attnum;
}

/*
 * slot_attisnull
 *      Detect whether an attribute of the slot is null, without
 *      actually fetching it.
 */
bool
slot_attisnull(TupleTableSlot *slot, int attnum)
{
    HeapTuple   tuple = slot->tts_tuple;
    TupleDesc   tupleDesc = slot->tts_tupleDescriptor;

    /*
     * system attributes are handled by heap_attisnull
     */
    if (attnum <= 0)
    {
        if (tuple == NULL)      /* internal error */
            elog(ERROR, "cannot extract system attribute from virtual tuple");
        if (tuple == &(slot->tts_minhdr))       /* internal error */
            elog(ERROR, "cannot extract system attribute from minimal tuple");
        return heap_attisnull(tuple, attnum);
    }

    /*
     * fast path if desired attribute already cached
     */
    if (attnum <= slot->tts_nvalid)
        return slot->tts_isnull[attnum - 1];

    /*
     * return NULL if attnum is out of range according to the tupdesc
     */
    if (attnum > tupleDesc->natts)
        return true;

    /*
     * otherwise we had better have a physical tuple (tts_nvalid should equal
     * natts in all virtual-tuple cases)
     */
    if (tuple == NULL)          /* internal error */
        elog(ERROR, "cannot extract attribute from empty tuple slot");

    /* and let the tuple tell it */
    return heap_attisnull(tuple, attnum);
}

/*
 * heap_freetuple
 */
void
heap_freetuple(HeapTuple htup)
{
    pfree(htup);
}


/*
 * heap_form_minimal_tuple
 *      construct a MinimalTuple from the given values[] and isnull[] arrays,
 *      which are of the length indicated by tupleDescriptor->natts
 *
 * This is exactly like heap_form_tuple() except that the result is a
 * "minimal" tuple lacking a HeapTupleData header as well as room for system
 * columns.
 *
 * The result is allocated in the current memory context.
 */
MinimalTuple
heap_form_minimal_tuple(TupleDesc tupleDescriptor,
                        Datum *values,
                        bool *isnull)
{
    MinimalTuple tuple;         /* return tuple */
    Size        len,
                data_len;
    int         hoff;
    bool        hasnull = false;
    Form_pg_attribute *att = tupleDescriptor->attrs;
    int         numberOfAttributes = tupleDescriptor->natts;
    int         i;

    if (numberOfAttributes > MaxTupleAttributeNumber)
        ereport(ERROR,
                (errcode(ERRCODE_TOO_MANY_COLUMNS),
                 errmsg("number of columns (%d) exceeds limit (%d)",
                        numberOfAttributes, MaxTupleAttributeNumber)));

    /*
     * Check for nulls and embedded tuples; expand any toasted attributes in
     * embedded tuples.  This preserves the invariant that toasting can only
     * go one level deep.
     *
     * We can skip calling toast_flatten_tuple_attribute() if the attribute
     * couldn't possibly be of composite type.  All composite datums are
     * varlena and have alignment 'd'; furthermore they aren't arrays. Also,
     * if an attribute is already toasted, it must have been sent to disk
     * already and so cannot contain toasted attributes.
     */
    for (i = 0; i < numberOfAttributes; i++)
    {
        if (isnull[i])
            hasnull = true;
        else if (att[i]->attlen == -1 &&
                 att[i]->attalign == 'd' &&
                 att[i]->attndims == 0 &&
                 !VARATT_IS_EXTENDED(values[i]))
        {
            values[i] = toast_flatten_tuple_attribute(values[i],
                                                      att[i]->atttypid,
                                                      att[i]->atttypmod);
        }
    }

    /*
     * Determine total space needed
     */
    len = offsetof(MinimalTupleData, t_bits);

    if (hasnull)
        len += BITMAPLEN(numberOfAttributes);

    if (tupleDescriptor->tdhasoid)
        len += sizeof(Oid);

    hoff = len = MAXALIGN(len); /* align user data safely */

    data_len = heap_compute_data_size(tupleDescriptor, values, isnull);

    len += data_len;

    /*
     * Allocate and zero the space needed.
     */
    tuple = (MinimalTuple) palloc0(len);

    /*
     * 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 */
        tuple->t_infomask = HEAP_HASOID;

    heap_fill_tuple(tupleDescriptor,
                    values,
                    isnull,
                    (char *) tuple + hoff,
                    data_len,
                    &tuple->t_infomask,
                    (hasnull ? tuple->t_bits : NULL));

    return tuple;
}

/*
 * heap_free_minimal_tuple
 */
void
heap_free_minimal_tuple(MinimalTuple mtup)
{
    pfree(mtup);
}

/*
 * heap_copy_minimal_tuple
 *      copy a MinimalTuple
 *
 * The result is allocated in the current memory context.
 */
MinimalTuple
heap_copy_minimal_tuple(MinimalTuple mtup)
{
    MinimalTuple result;

    result = (MinimalTuple) palloc(mtup->t_len);
    memcpy(result, mtup, mtup->t_len);
    return result;
}

/*
 * heap_tuple_from_minimal_tuple
 *      create a HeapTuple by copying from a MinimalTuple;
 *      system columns are filled with zeroes
 *
 * The result is allocated in the current memory context.
 * The HeapTuple struct, tuple header, and tuple data are all allocated
 * as a single palloc() block.
 */
HeapTuple
heap_tuple_from_minimal_tuple(MinimalTuple mtup)
{
    HeapTuple   result;
    uint32      len = mtup->t_len + MINIMAL_TUPLE_OFFSET;

    result = (HeapTuple) palloc(HEAPTUPLESIZE + len);
    result->t_len = len;
    ItemPointerSetInvalid(&(result->t_self));
    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;
}

/*
 * minimal_tuple_from_heap_tuple
 *      create a MinimalTuple by copying from a HeapTuple
 *
 * The result is allocated in the current memory context.
 */
MinimalTuple
minimal_tuple_from_heap_tuple(HeapTuple htup)
{
    MinimalTuple result;
    uint32      len;

    Assert(htup->t_len > MINIMAL_TUPLE_OFFSET);
    len = htup->t_len - MINIMAL_TUPLE_OFFSET;
    result = (MinimalTuple) palloc(len);
    memcpy(result, (char *) htup->t_data + MINIMAL_TUPLE_OFFSET, len);
    result->t_len = len;
    return result;
}