spgist_private.h

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/*-------------------------------------------------------------------------
 *
 * spgist_private.h
 *    Private declarations for SP-GiST access method.
 *
 *
 * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/access/spgist_private.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef SPGIST_PRIVATE_H
#define SPGIST_PRIVATE_H

#include "access/itup.h"
#include "access/spgist.h"
#include "nodes/tidbitmap.h"
#include "storage/buf.h"
#include "utils/relcache.h"


/* Page numbers of fixed-location pages */
#define SPGIST_METAPAGE_BLKNO    (0)    /* metapage */
#define SPGIST_ROOT_BLKNO        (1)    /* root for normal entries */
#define SPGIST_NULL_BLKNO        (2)    /* root for null-value entries */
#define SPGIST_LAST_FIXED_BLKNO  SPGIST_NULL_BLKNO

#define SpGistBlockIsRoot(blkno) \
    ((blkno) == SPGIST_ROOT_BLKNO || (blkno) == SPGIST_NULL_BLKNO)
#define SpGistBlockIsFixed(blkno) \
    ((BlockNumber) (blkno) <= (BlockNumber) SPGIST_LAST_FIXED_BLKNO)

/*
 * Contents of page special space on SPGiST index pages
 */
typedef struct SpGistPageOpaqueData
{
    uint16      flags;          /* see bit definitions below */
    uint16      nRedirection;   /* number of redirection tuples on page */
    uint16      nPlaceholder;   /* number of placeholder tuples on page */
    /* note there's no count of either LIVE or DEAD tuples ... */
    uint16      spgist_page_id; /* for identification of SP-GiST indexes */
} SpGistPageOpaqueData;

typedef SpGistPageOpaqueData *SpGistPageOpaque;

/* Flag bits in page special space */
#define SPGIST_META         (1<<0)
#define SPGIST_DELETED      (1<<1)  /* never set, but keep for backwards
                                     * compatibility */
#define SPGIST_LEAF         (1<<2)
#define SPGIST_NULLS        (1<<3)

#define SpGistPageGetOpaque(page) ((SpGistPageOpaque) PageGetSpecialPointer(page))
#define SpGistPageIsMeta(page) (SpGistPageGetOpaque(page)->flags & SPGIST_META)
#define SpGistPageIsDeleted(page) (SpGistPageGetOpaque(page)->flags & SPGIST_DELETED)
#define SpGistPageIsLeaf(page) (SpGistPageGetOpaque(page)->flags & SPGIST_LEAF)
#define SpGistPageStoresNulls(page) (SpGistPageGetOpaque(page)->flags & SPGIST_NULLS)

/*
 * The page ID is for the convenience of pg_filedump and similar utilities,
 * which otherwise would have a hard time telling pages of different index
 * types apart.  It should be the last 2 bytes on the page.  This is more or
 * less "free" due to alignment considerations.
 *
 * See comments above GinPageOpaqueData.
 */
#define SPGIST_PAGE_ID      0xFF82

/*
 * Each backend keeps a cache of last-used page info in its index->rd_amcache
 * area.  This is initialized from, and occasionally written back to,
 * shared storage in the index metapage.
 */
typedef struct SpGistLastUsedPage
{
    BlockNumber blkno;          /* block number, or InvalidBlockNumber */
    int         freeSpace;      /* page's free space (could be obsolete!) */
} SpGistLastUsedPage;

/* Note: indexes in cachedPage[] match flag assignments for SpGistGetBuffer */
#define SPGIST_CACHED_PAGES 8

typedef struct SpGistLUPCache
{
    SpGistLastUsedPage cachedPage[SPGIST_CACHED_PAGES];
} SpGistLUPCache;

/*
 * metapage
 */
typedef struct SpGistMetaPageData
{
    uint32      magicNumber;    /* for identity cross-check */
    SpGistLUPCache lastUsedPages;   /* shared storage of last-used info */
} SpGistMetaPageData;

#define SPGIST_MAGIC_NUMBER (0xBA0BABEE)

#define SpGistPageGetMeta(p) \
    ((SpGistMetaPageData *) PageGetContents(p))

/*
 * Private state of index AM.  SpGistState is common to both insert and
 * search code; SpGistScanOpaque is for searches only.
 */

/* Per-datatype info needed in SpGistState */
typedef struct SpGistTypeDesc
{
    Oid         type;
    bool        attbyval;
    int16       attlen;
} SpGistTypeDesc;

typedef struct SpGistState
{
    spgConfigOut config;        /* filled in by opclass config method */

    SpGistTypeDesc attType;     /* type of input data and leaf values */
    SpGistTypeDesc attPrefixType;   /* type of inner-tuple prefix values */
    SpGistTypeDesc attLabelType;    /* type of node label values */

    char       *deadTupleStorage;   /* workspace for spgFormDeadTuple */

    TransactionId myXid;        /* XID to use when creating a redirect tuple */
    bool        isBuild;        /* true if doing index build */
} SpGistState;

/*
 * Private state of an index scan
 */
typedef struct SpGistScanOpaqueData
{
    SpGistState state;          /* see above */
    MemoryContext tempCxt;      /* short-lived memory context */

    /* Control flags showing whether to search nulls and/or non-nulls */
    bool        searchNulls;    /* scan matches (all) null entries */
    bool        searchNonNulls; /* scan matches (some) non-null entries */

    /* Index quals to be passed to opclass (null-related quals removed) */
    int         numberOfKeys;   /* number of index qualifier conditions */
    ScanKey     keyData;        /* array of index qualifier descriptors */

    /* Stack of yet-to-be-visited pages */
    List       *scanStack;      /* List of ScanStackEntrys */

    /* These fields are only used in amgetbitmap scans: */
    TIDBitmap  *tbm;            /* bitmap being filled */
    int64       ntids;          /* number of TIDs passed to bitmap */

    /* These fields are only used in amgettuple scans: */
    bool        want_itup;      /* are we reconstructing tuples? */
    TupleDesc   indexTupDesc;   /* if so, tuple descriptor for them */
    int         nPtrs;          /* number of TIDs found on current page */
    int         iPtr;           /* index for scanning through same */
    ItemPointerData heapPtrs[MaxIndexTuplesPerPage];    /* TIDs from cur page */
    bool        recheck[MaxIndexTuplesPerPage]; /* their recheck flags */
    HeapTuple   reconTups[MaxIndexTuplesPerPage];   /* reconstructed tuples */

    /*
     * Note: using MaxIndexTuplesPerPage above is a bit hokey since
     * SpGistLeafTuples aren't exactly IndexTuples; however, they are larger,
     * so this is safe.
     */
} SpGistScanOpaqueData;

typedef SpGistScanOpaqueData *SpGistScanOpaque;

/*
 * This struct is what we actually keep in index->rd_amcache.  It includes
 * static configuration information as well as the lastUsedPages cache.
 */
typedef struct SpGistCache
{
    spgConfigOut config;        /* filled in by opclass config method */

    SpGistTypeDesc attType;     /* type of input data and leaf values */
    SpGistTypeDesc attPrefixType;   /* type of inner-tuple prefix values */
    SpGistTypeDesc attLabelType;    /* type of node label values */

    SpGistLUPCache lastUsedPages;   /* local storage of last-used info */
} SpGistCache;


/*
 * SPGiST tuple types.  Note: inner, leaf, and dead tuple structs
 * must have the same tupstate field in the same position!  Real inner and
 * leaf tuples always have tupstate = LIVE; if the state is something else,
 * use the SpGistDeadTuple struct to inspect the tuple.
 */

/* values of tupstate (see README for more info) */
#define SPGIST_LIVE         0   /* normal live tuple (either inner or leaf) */
#define SPGIST_REDIRECT     1   /* temporary redirection placeholder */
#define SPGIST_DEAD         2   /* dead, cannot be removed because of links */
#define SPGIST_PLACEHOLDER  3   /* placeholder, used to preserve offsets */

/*
 * SPGiST inner tuple: list of "nodes" that subdivide a set of tuples
 *
 * Inner tuple layout:
 * header/optional prefix/array of nodes, which are SpGistNodeTuples
 *
 * size and prefixSize must be multiples of MAXALIGN
 */
typedef struct SpGistInnerTupleData
{
    unsigned int tupstate:2,    /* LIVE/REDIRECT/DEAD/PLACEHOLDER */
                allTheSame:1,   /* all nodes in tuple are equivalent */
                nNodes:13,      /* number of nodes within inner tuple */
                prefixSize:16;  /* size of prefix, or 0 if none */
    uint16      size;           /* total size of inner tuple */
    /* On most machines there will be a couple of wasted bytes here */
    /* prefix datum follows, then nodes */
} SpGistInnerTupleData;

typedef SpGistInnerTupleData *SpGistInnerTuple;

/* these must match largest values that fit in bit fields declared above */
#define SGITMAXNNODES       0x1FFF
#define SGITMAXPREFIXSIZE   0xFFFF
#define SGITMAXSIZE         0xFFFF

#define SGITHDRSZ           MAXALIGN(sizeof(SpGistInnerTupleData))
#define _SGITDATA(x)        (((char *) (x)) + SGITHDRSZ)
#define SGITDATAPTR(x)      ((x)->prefixSize ? _SGITDATA(x) : NULL)
#define SGITDATUM(x, s)     ((x)->prefixSize ? \
                             ((s)->attPrefixType.attbyval ? \
                              *(Datum *) _SGITDATA(x) : \
                              PointerGetDatum(_SGITDATA(x))) \
                             : (Datum) 0)
#define SGITNODEPTR(x)      ((SpGistNodeTuple) (_SGITDATA(x) + (x)->prefixSize))

/* Macro for iterating through the nodes of an inner tuple */
#define SGITITERATE(x, i, nt)   \
    for ((i) = 0, (nt) = SGITNODEPTR(x); \
         (i) < (x)->nNodes; \
         (i)++, (nt) = (SpGistNodeTuple) (((char *) (nt)) + IndexTupleSize(nt)))

/*
 * SPGiST node tuple: one node within an inner tuple
 *
 * Node tuples use the same header as ordinary Postgres IndexTuples, but
 * we do not use a null bitmap, because we know there is only one column
 * so the INDEX_NULL_MASK bit suffices.  Also, pass-by-value datums are
 * stored as a full Datum, the same convention as for inner tuple prefixes
 * and leaf tuple datums.
 */

typedef IndexTupleData SpGistNodeTupleData;

typedef SpGistNodeTupleData *SpGistNodeTuple;

#define SGNTHDRSZ           MAXALIGN(sizeof(SpGistNodeTupleData))
#define SGNTDATAPTR(x)      (((char *) (x)) + SGNTHDRSZ)
#define SGNTDATUM(x, s)     ((s)->attLabelType.attbyval ? \
                             *(Datum *) SGNTDATAPTR(x) : \
                             PointerGetDatum(SGNTDATAPTR(x)))

/*
 * SPGiST leaf tuple: carries a datum and a heap tuple TID
 *
 * In the simplest case, the datum is the same as the indexed value; but
 * it could also be a suffix or some other sort of delta that permits
 * reconstruction given knowledge of the prefix path traversed to get here.
 *
 * The size field is wider than could possibly be needed for an on-disk leaf
 * tuple, but this allows us to form leaf tuples even when the datum is too
 * wide to be stored immediately, and it costs nothing because of alignment
 * considerations.
 *
 * Normally, nextOffset links to the next tuple belonging to the same parent
 * node (which must be on the same page).  But when the root page is a leaf
 * page, we don't chain its tuples, so nextOffset is always 0 on the root.
 *
 * size must be a multiple of MAXALIGN; also, it must be at least SGDTSIZE
 * so that the tuple can be converted to REDIRECT status later.  (This
 * restriction only adds bytes for the null-datum case, otherwise alignment
 * restrictions force it anyway.)
 *
 * In a leaf tuple for a NULL indexed value, there's no useful datum value;
 * however, the SGDTSIZE limit ensures that's there's a Datum word there
 * anyway, so SGLTDATUM can be applied safely as long as you don't do
 * anything with the result.
 */
typedef struct SpGistLeafTupleData
{
    unsigned int tupstate:2,    /* LIVE/REDIRECT/DEAD/PLACEHOLDER */
                size:30;        /* large enough for any palloc'able value */
    OffsetNumber nextOffset;    /* next tuple in chain, or InvalidOffset */
    ItemPointerData heapPtr;    /* TID of represented heap tuple */
    /* leaf datum follows */
} SpGistLeafTupleData;

typedef SpGistLeafTupleData *SpGistLeafTuple;

#define SGLTHDRSZ           MAXALIGN(sizeof(SpGistLeafTupleData))
#define SGLTDATAPTR(x)      (((char *) (x)) + SGLTHDRSZ)
#define SGLTDATUM(x, s)     ((s)->attType.attbyval ? \
                             *(Datum *) SGLTDATAPTR(x) : \
                             PointerGetDatum(SGLTDATAPTR(x)))

/*
 * SPGiST dead tuple: declaration for examining non-live tuples
 *
 * The tupstate field of this struct must match those of regular inner and
 * leaf tuples, and its size field must match a leaf tuple's.
 * Also, the pointer field must be in the same place as a leaf tuple's heapPtr
 * field, to satisfy some Asserts that we make when replacing a leaf tuple
 * with a dead tuple.
 * We don't use nextOffset, but it's needed to align the pointer field.
 * pointer and xid are only valid when tupstate = REDIRECT.
 */
typedef struct SpGistDeadTupleData
{
    unsigned int tupstate:2,    /* LIVE/REDIRECT/DEAD/PLACEHOLDER */
                size:30;
    OffsetNumber nextOffset;    /* not used in dead tuples */
    ItemPointerData pointer;    /* redirection inside index */
    TransactionId xid;          /* ID of xact that inserted this tuple */
} SpGistDeadTupleData;

typedef SpGistDeadTupleData *SpGistDeadTuple;

#define SGDTSIZE        MAXALIGN(sizeof(SpGistDeadTupleData))

/*
 * Macros for doing free-space calculations.  Note that when adding up the
 * space needed for tuples, we always consider each tuple to need the tuple's
 * size plus sizeof(ItemIdData) (for the line pointer).  This works correctly
 * so long as tuple sizes are always maxaligned.
 */

/* Page capacity after allowing for fixed header and special space */
#define SPGIST_PAGE_CAPACITY  \
    MAXALIGN_DOWN(BLCKSZ - \
                  SizeOfPageHeaderData - \
                  MAXALIGN(sizeof(SpGistPageOpaqueData)))

/*
 * Compute free space on page, assuming that up to n placeholders can be
 * recycled if present (n should be the number of tuples to be inserted)
 */
#define SpGistPageGetFreeSpace(p, n) \
    (PageGetExactFreeSpace(p) + \
     Min(SpGistPageGetOpaque(p)->nPlaceholder, n) * \
     (SGDTSIZE + sizeof(ItemIdData)))

/*
 * XLOG stuff
 */

#define STORE_STATE(s, d)  \
    do { \
        (d).myXid = (s)->myXid; \
        (d).isBuild = (s)->isBuild; \
    } while(0)

/*
 * The "flags" argument for SpGistGetBuffer should be either GBUF_LEAF to
 * get a leaf page, or GBUF_INNER_PARITY(blockNumber) to get an inner
 * page in the same triple-parity group as the specified block number.
 * (Typically, this should be GBUF_INNER_PARITY(parentBlockNumber + 1)
 * to follow the rule described in spgist/README.)
 * In addition, GBUF_NULLS can be OR'd in to get a page for storage of
 * null-valued tuples.
 *
 * Note: these flag values are used as indexes into lastUsedPages.
 */
#define GBUF_LEAF               0x03
#define GBUF_INNER_PARITY(x)    ((x) % 3)
#define GBUF_NULLS              0x04

#define GBUF_PARITY_MASK        0x03
#define GBUF_REQ_LEAF(flags)    (((flags) & GBUF_PARITY_MASK) == GBUF_LEAF)
#define GBUF_REQ_NULLS(flags)   ((flags) & GBUF_NULLS)

/* spgutils.c */
extern SpGistCache *spgGetCache(Relation index);
extern void initSpGistState(SpGistState *state, Relation index);
extern Buffer SpGistNewBuffer(Relation index);
extern void SpGistUpdateMetaPage(Relation index);
extern Buffer SpGistGetBuffer(Relation index, int flags,
                int needSpace, bool *isNew);
extern void SpGistSetLastUsedPage(Relation index, Buffer buffer);
extern void SpGistInitPage(Page page, uint16 f);
extern void SpGistInitBuffer(Buffer b, uint16 f);
extern void SpGistInitMetapage(Page page);
extern unsigned int SpGistGetTypeSize(SpGistTypeDesc *att, Datum datum);
extern SpGistLeafTuple spgFormLeafTuple(SpGistState *state,
                 ItemPointer heapPtr,
                 Datum datum, bool isnull);
extern SpGistNodeTuple spgFormNodeTuple(SpGistState *state,
                 Datum label, bool isnull);
extern SpGistInnerTuple spgFormInnerTuple(SpGistState *state,
                  bool hasPrefix, Datum prefix,
                  int nNodes, SpGistNodeTuple *nodes);
extern SpGistDeadTuple spgFormDeadTuple(SpGistState *state, int tupstate,
                 BlockNumber blkno, OffsetNumber offnum);
extern Datum *spgExtractNodeLabels(SpGistState *state,
                     SpGistInnerTuple innerTuple);
extern OffsetNumber SpGistPageAddNewItem(SpGistState *state, Page page,
                     Item item, Size size,
                     OffsetNumber *startOffset,
                     bool errorOK);

/* spgdoinsert.c */
extern void spgUpdateNodeLink(SpGistInnerTuple tup, int nodeN,
                  BlockNumber blkno, OffsetNumber offset);
extern void spgPageIndexMultiDelete(SpGistState *state, Page page,
                        OffsetNumber *itemnos, int nitems,
                        int firststate, int reststate,
                        BlockNumber blkno, OffsetNumber offnum);
extern bool spgdoinsert(Relation index, SpGistState *state,
            ItemPointer heapPtr, Datum datum, bool isnull);

#endif                          /* SPGIST_PRIVATE_H */