Tag appropriate files for rc3

[postgresql] / src / include / access / htup.h

 /*-------------------------------------------------------------------------
 *
 * htup.h
 *        POSTGRES heap tuple definitions.
 *
 *
 * Portions Copyright (c) 1996-2005, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * $PostgreSQL: pgsql/src/include/access/htup.h,v 1.72 2004/12/31 22:03:21 pgsql Exp $
 *
 *-------------------------------------------------------------------------
 */
#ifndef HTUP_H
#define HTUP_H

#include "storage/bufpage.h"
#include "storage/relfilenode.h"
#include "access/transam.h"


/*
 * 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 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 */

/*----------
 * Heap tuple header.  To avoid wasting space, the fields should be
 * layed out in such a way to avoid structure padding.
 *
 * Datums of composite types (row types) share the same general structure
 * as on-disk tuples, so that the same routines can be used to build and
 * examine them.  However the requirements are slightly different: a Datum
 * does not need any transaction visibility information, and it does need
 * a length word and some embedded type information.  We can achieve this
 * by overlaying the xmin/cmin/xmax/cmax/xvac fields of a heap tuple
 * with the fields needed in the Datum case.  Typically, all tuples built
 * in-memory will be initialized with the Datum fields; but when a tuple is
 * about to be inserted in a table, the transaction fields will be filled,
 * overwriting the datum fields.
 *
 * The overall structure of a heap tuple looks like:
 *                      fixed fields (HeapTupleHeaderData struct)
 *                      nulls bitmap (if HEAP_HASNULL is set in t_infomask)
 *                      alignment padding (as needed to make user data MAXALIGN'd)
 *                      object ID (if HEAP_HASOID is set in t_infomask)
 *                      user data fields
 *
 * We store five "virtual" fields Xmin, Cmin, Xmax, Cmax, and Xvac in four
 * physical fields.  Xmin, Cmin and Xmax are always really stored, but
 * Cmax and Xvac share a field.  This works because we know that there are
 * only a limited number of states that a tuple can be in, and that Cmax
 * is only interesting for the lifetime of the deleting transaction.
 * This assumes that VACUUM FULL never tries to move a tuple whose Cmax
 * is still interesting (ie, delete-in-progress).
 *
 * Note that in 7.3 and 7.4 a similar idea was applied to Xmax and Cmin.
 * However, with the advent of subtransactions, a tuple may need both Xmax
 * and Cmin simultaneously, so this is no longer possible.
 *
 * Following the fixed header fields, the nulls bitmap is stored (beginning
 * at t_bits).  The bitmap is *not* stored if t_infomask shows that there
 * are no nulls in the tuple.  If an OID field is present (as indicated by
 * t_infomask), then it is stored just before the user data, which begins at
 * the offset shown by t_hoff.  Note that t_hoff must be a multiple of
 * MAXALIGN.
 *----------
 */

typedef struct HeapTupleFields
{
        TransactionId t_xmin;           /* inserting xact ID */
        CommandId       t_cmin;                 /* inserting command ID */
        TransactionId t_xmax;           /* deleting xact ID */

        union
        {
                CommandId       t_cmax;         /* deleting command ID */
                TransactionId t_xvac;   /* VACUUM FULL xact ID */
        }                       t_field4;
} HeapTupleFields;

typedef struct DatumTupleFields
{
        int32           datum_len;              /* required to be a varlena type */

        int32           datum_typmod;   /* -1, or identifier of a record type */

        Oid                     datum_typeid;   /* composite type OID, or RECORDOID */

        /*
         * Note: field ordering is chosen with thought that Oid might someday
         * widen to 64 bits.
         */
} DatumTupleFields;

typedef struct HeapTupleHeaderData
{
        union
        {
                HeapTupleFields t_heap;
                DatumTupleFields t_datum;
        }                       t_choice;

        ItemPointerData t_ctid;         /* current TID of this or newer tuple */

        int16           t_natts;                /* number of attributes */

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

        uint8           t_hoff;                 /* sizeof header incl. bitmap, padding */

        /* ^ - 27 bytes - ^ */

        bits8           t_bits[1];              /* bitmap of NULLs -- VARIABLE LENGTH */

        /* MORE DATA FOLLOWS AT END OF STRUCT */
} HeapTupleHeaderData;

typedef HeapTupleHeaderData *HeapTupleHeader;

/*
 * information stored in t_infomask:
 */
#define HEAP_HASNULL                    0x0001  /* has null attribute(s) */
#define HEAP_HASVARWIDTH                0x0002  /* has variable-width 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_HASOID                             0x0010  /* has an object-id field */
/* 0x0020 and 0x0040 are unused */
#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  /* moved to another place by
                                                                                 * VACUUM FULL */
#define HEAP_MOVED_IN                   0x8000  /* moved from another place by
                                                                                 * VACUUM FULL */
#define HEAP_MOVED (HEAP_MOVED_OFF | HEAP_MOVED_IN)

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


/*
 * HeapTupleHeader accessor macros
 *
 * Note: beware of multiple evaluations of "tup" argument.      But the Set
 * macros evaluate their other argument only once.
 */

#define HeapTupleHeaderGetXmin(tup) \
( \
        (tup)->t_choice.t_heap.t_xmin \
)

#define HeapTupleHeaderSetXmin(tup, xid) \
( \
        TransactionIdStore((xid), &(tup)->t_choice.t_heap.t_xmin) \
)

#define HeapTupleHeaderGetXmax(tup) \
( \
        (tup)->t_choice.t_heap.t_xmax \
)

#define HeapTupleHeaderSetXmax(tup, xid) \
( \
        TransactionIdStore((xid), &(tup)->t_choice.t_heap.t_xmax) \
)

#define HeapTupleHeaderGetCmin(tup) \
( \
        (tup)->t_choice.t_heap.t_cmin \
)

#define HeapTupleHeaderSetCmin(tup, cid) \
( \
        (tup)->t_choice.t_heap.t_cmin = (cid) \
)

/*
 * Note: GetCmax will produce wrong answers after SetXvac has been executed
 * by a transaction other than the inserting one.  We could check
 * HEAP_XMAX_INVALID and return FirstCommandId if it's clear, but since that
 * bit will be set again if the deleting transaction aborts, there'd be no
 * real gain in safety from the extra test.  So, just rely on the caller not
 * to trust the value unless it's meaningful.
 */
#define HeapTupleHeaderGetCmax(tup) \
( \
        (tup)->t_choice.t_heap.t_field4.t_cmax \
)

#define HeapTupleHeaderSetCmax(tup, cid) \
do { \
        Assert(!((tup)->t_infomask & HEAP_MOVED)); \
        (tup)->t_choice.t_heap.t_field4.t_cmax = (cid); \
} while (0)

#define HeapTupleHeaderGetXvac(tup) \
( \
        ((tup)->t_infomask & HEAP_MOVED) ? \
                (tup)->t_choice.t_heap.t_field4.t_xvac \
        : \
                InvalidTransactionId \
)

#define HeapTupleHeaderSetXvac(tup, xid) \
do { \
        Assert((tup)->t_infomask & HEAP_MOVED); \
        TransactionIdStore((xid), &(tup)->t_choice.t_heap.t_field4.t_xvac); \
} while (0)

#define HeapTupleHeaderGetDatumLength(tup) \
( \
        (tup)->t_choice.t_datum.datum_len \
)

#define HeapTupleHeaderSetDatumLength(tup, len) \
( \
        (tup)->t_choice.t_datum.datum_len = (len) \
)

#define HeapTupleHeaderGetTypeId(tup) \
( \
        (tup)->t_choice.t_datum.datum_typeid \
)

#define HeapTupleHeaderSetTypeId(tup, typeid) \
( \
        (tup)->t_choice.t_datum.datum_typeid = (typeid) \
)

#define HeapTupleHeaderGetTypMod(tup) \
( \
        (tup)->t_choice.t_datum.datum_typmod \
)

#define HeapTupleHeaderSetTypMod(tup, typmod) \
( \
        (tup)->t_choice.t_datum.datum_typmod = (typmod) \
)

#define HeapTupleHeaderGetOid(tup) \
( \
        ((tup)->t_infomask & HEAP_HASOID) ? \
                *((Oid *) ((char *)(tup) + (tup)->t_hoff - sizeof(Oid))) \
        : \
                InvalidOid \
)

#define HeapTupleHeaderSetOid(tup, oid) \
do { \
        Assert((tup)->t_infomask & HEAP_HASOID); \
        *((Oid *) ((char *)(tup) + (tup)->t_hoff - sizeof(Oid))) = (oid); \
} while (0)


/*
 * BITMAPLEN(NATTS) -
 *              Computes size of null bitmap given number of data columns.
 */
#define BITMAPLEN(NATTS)        (((int)(NATTS) + 7) / 8)

/*
 * MaxTupleSize is the maximum allowed size of a tuple, including header and
 * MAXALIGN alignment padding.  Basically it's BLCKSZ minus the other stuff
 * that has to be on a disk page.  The "other stuff" includes access-method-
 * dependent "special space", which we assume will be no more than
 * MaxSpecialSpace bytes (currently, on heap pages it's actually zero).
 *
 * NOTE: we do not need to count an ItemId for the tuple because
 * sizeof(PageHeaderData) includes the first ItemId on the page.
 */
#define MaxSpecialSpace  32

#define MaxTupleSize    \
        (BLCKSZ - MAXALIGN(sizeof(PageHeaderData) + MaxSpecialSpace))

/*
 * MaxAttrSize is a somewhat arbitrary upper limit on the declared size of
 * data fields of char(n) and similar types.  It need not have anything
 * directly to do with the *actual* upper limit of varlena values, which
 * is currently 1Gb (see struct varattrib in postgres.h).  I've set it
 * at 10Mb which seems like a reasonable number --- tgl 8/6/00.
 */
#define MaxAttrSize             (10 * 1024 * 1024)


/*
 * Attribute numbers for the system-defined attributes
 */
#define SelfItemPointerAttributeNumber                  (-1)
#define ObjectIdAttributeNumber                                 (-2)
#define MinTransactionIdAttributeNumber                 (-3)
#define MinCommandIdAttributeNumber                             (-4)
#define MaxTransactionIdAttributeNumber                 (-5)
#define MaxCommandIdAttributeNumber                             (-6)
#define TableOidAttributeNumber                                 (-7)
#define FirstLowInvalidHeapAttributeNumber              (-8)


/*
 * 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:
 *
 * 1. t_len moved off on-disk tuple data - ItemIdData is used to get len;
 * 2. t_ctid above is not self tuple TID now - it may point to
 *        updated version of tuple (required by MVCC);
 * 3. someday someone let tuple to cross block boundaries -
 *        he have to add something below...
 *
 * Change for 7.0:
 *        Up to now t_data could be NULL, the memory location directly following
 *        HeapTupleData, or pointing into a buffer. Now, it could also point to
 *        a separate allocation that was done in the t_datamcxt memory context.
 */
typedef struct HeapTupleData
{
        uint32          t_len;                  /* length of *t_data */
        ItemPointerData t_self;         /* SelfItemPointer */
        Oid                     t_tableOid;             /* table the tuple came from */
        MemoryContext t_datamcxt;       /* memory context of allocation */
        HeapTupleHeader t_data;         /* -> tuple header and data */
} HeapTupleData;

typedef HeapTupleData *HeapTuple;

#define HEAPTUPLESIZE   MAXALIGN(sizeof(HeapTupleData))

/*
 * GETSTRUCT - given a HeapTuple pointer, return address of the user data
 */
#define GETSTRUCT(TUP) ((char *) ((TUP)->t_data) + (TUP)->t_data->t_hoff)

/*
 * Accessor macros to be used with HeapTuple pointers.
 */
#define HeapTupleIsValid(tuple) PointerIsValid(tuple)

#define HeapTupleHasNulls(tuple) \
                (((tuple)->t_data->t_infomask & HEAP_HASNULL) != 0)

#define HeapTupleNoNulls(tuple) \
                (!((tuple)->t_data->t_infomask & HEAP_HASNULL))

#define HeapTupleHasVarWidth(tuple) \
                (((tuple)->t_data->t_infomask & HEAP_HASVARWIDTH) != 0)

#define HeapTupleAllFixed(tuple) \
                (!((tuple)->t_data->t_infomask & HEAP_HASVARWIDTH))

#define HeapTupleHasExternal(tuple) \
                (((tuple)->t_data->t_infomask & HEAP_HASEXTERNAL) != 0)

#define HeapTupleHasCompressed(tuple) \
                (((tuple)->t_data->t_infomask & HEAP_HASCOMPRESSED) != 0)

#define HeapTupleHasExtended(tuple) \
                (((tuple)->t_data->t_infomask & HEAP_HASEXTENDED) != 0)

#define HeapTupleGetOid(tuple) \
                HeapTupleHeaderGetOid((tuple)->t_data)

#define HeapTupleSetOid(tuple, oid) \
                HeapTupleHeaderSetOid((tuple)->t_data, (oid))


/*
 * WAL record definitions for heapam.c's WAL operations
 *
 * XLOG allows to store some information in high 4 bits of log
 * record xl_info field.  We use 3 for opcode and one for init bit.
 */
#define XLOG_HEAP_INSERT        0x00
#define XLOG_HEAP_DELETE        0x10
#define XLOG_HEAP_UPDATE        0x20
#define XLOG_HEAP_MOVE          0x30
#define XLOG_HEAP_CLEAN         0x40
#define XLOG_HEAP_NEWPAGE       0x50
/* opcodes 0x60, 0x70 still free */
#define XLOG_HEAP_OPMASK        0x70
/*
 * When we insert 1st item on new page in INSERT/UPDATE
 * we can (and we do) restore entire page in redo
 */
#define XLOG_HEAP_INIT_PAGE 0x80

/*
 * All what we need to find changed tuple
 *
 * NB: on most machines, sizeof(xl_heaptid) will include some trailing pad
 * bytes for alignment.  We don't want to store the pad space in the XLOG,
 * so use SizeOfHeapTid for space calculations.  Similar comments apply for
 * the other xl_FOO structs.
 */
typedef struct xl_heaptid
{
        RelFileNode node;
        ItemPointerData tid;            /* changed tuple id */
} xl_heaptid;

#define SizeOfHeapTid           (offsetof(xl_heaptid, tid) + SizeOfIptrData)

/* This is what we need to know about delete */
typedef struct xl_heap_delete
{
        xl_heaptid      target;                 /* deleted tuple id */
} xl_heap_delete;

#define SizeOfHeapDelete        (offsetof(xl_heap_delete, target) + SizeOfHeapTid)

/*
 * We don't store the whole fixed part (HeapTupleHeaderData) of an inserted
 * or updated tuple in WAL; we can save a few bytes by reconstructing the
 * fields that are available elsewhere in the WAL record, or perhaps just
 * plain needn't be reconstructed.  These are the fields we must store.
 * NOTE: t_hoff could be recomputed, but we may as well store it because
 * it will come for free due to alignment considerations.
 */
typedef struct xl_heap_header
{
        int16           t_natts;
        uint16          t_infomask;
        uint8           t_hoff;
} xl_heap_header;

#define SizeOfHeapHeader        (offsetof(xl_heap_header, t_hoff) + sizeof(uint8))

/* This is what we need to know about insert */
typedef struct xl_heap_insert
{
        xl_heaptid      target;                 /* inserted tuple id */
        /* xl_heap_header & TUPLE DATA FOLLOWS AT END OF STRUCT */
} xl_heap_insert;

#define SizeOfHeapInsert        (offsetof(xl_heap_insert, target) + SizeOfHeapTid)

/* This is what we need to know about update|move */
typedef struct xl_heap_update
{
        xl_heaptid      target;                 /* deleted tuple id */
        ItemPointerData newtid;         /* new inserted tuple id */
        /* NEW TUPLE xl_heap_header (PLUS xmax & xmin IF MOVE OP) */
        /* and TUPLE DATA FOLLOWS AT END OF STRUCT */
} xl_heap_update;

#define SizeOfHeapUpdate        (offsetof(xl_heap_update, newtid) + SizeOfIptrData)

/* This is what we need to know about vacuum page cleanup */
typedef struct xl_heap_clean
{
        RelFileNode node;
        BlockNumber block;
        /* UNUSED OFFSET NUMBERS FOLLOW AT THE END */
} xl_heap_clean;

#define SizeOfHeapClean (offsetof(xl_heap_clean, block) + sizeof(BlockNumber))

/* This is for replacing a page's contents in toto */
/* NB: this is used for indexes as well as heaps */
typedef struct xl_heap_newpage
{
        RelFileNode node;
        BlockNumber blkno;                      /* location of new page */
        /* entire page contents follow at end of record */
} xl_heap_newpage;

#define SizeOfHeapNewpage       (offsetof(xl_heap_newpage, blkno) + sizeof(BlockNumber))

#endif   /* HTUP_H */