ginblock.h

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/*--------------------------------------------------------------------------
 * ginblock.h
 *    details of structures stored in GIN index blocks
 *
 *  Copyright (c) 2006-2025, PostgreSQL Global Development Group
 *
 *  src/include/access/ginblock.h
 *--------------------------------------------------------------------------
 */
#ifndef GINBLOCK_H
#define GINBLOCK_H
 
#include "access/transam.h"
#include "storage/block.h"
#include "storage/bufpage.h"
#include "storage/itemptr.h"
#include "storage/off.h"
 
/*
 * Page opaque data in an inverted index page.
 *
 * Note: GIN does not include a page ID word as do the other index types.
 * This is OK because the opaque data is only 8 bytes and so can be reliably
 * distinguished by size.  Revisit this if the size ever increases.
 * Further note: as of 9.2, SP-GiST also uses 8-byte special space, as does
 * BRIN as of 9.5.  This is still OK, as long as GIN isn't using all of the
 * high-order bits in its flags word, because that way the flags word cannot
 * match the page IDs used by SP-GiST and BRIN.
 */
typedef struct GinPageOpaqueData
{
    BlockNumber rightlink;      /* next page if any */
    OffsetNumber maxoff;        /* number of PostingItems on GIN_DATA &
                                 * ~GIN_LEAF page. On GIN_LIST page, number of
                                 * heap tuples. */
    uint16      flags;          /* see bit definitions below */
} GinPageOpaqueData;
 
typedef GinPageOpaqueData *GinPageOpaque;
 
#define GIN_DATA          (1 << 0)
#define GIN_LEAF          (1 << 1)
#define GIN_DELETED       (1 << 2)
#define GIN_META          (1 << 3)
#define GIN_LIST          (1 << 4)
#define GIN_LIST_FULLROW  (1 << 5)  /* makes sense only on GIN_LIST page */
#define GIN_INCOMPLETE_SPLIT (1 << 6)   /* page was split, but parent not
                                         * updated */
#define GIN_COMPRESSED    (1 << 7)
 
/* Page numbers of fixed-location pages */
#define GIN_METAPAGE_BLKNO  (0)
#define GIN_ROOT_BLKNO      (1)
 
typedef struct GinMetaPageData
{
    /*
     * Pointers to head and tail of pending list, which consists of GIN_LIST
     * pages.  These store fast-inserted entries that haven't yet been moved
     * into the regular GIN structure.
     */
    BlockNumber head;
    BlockNumber tail;
 
    /*
     * Free space in bytes in the pending list's tail page.
     */
    uint32      tailFreeSize;
 
    /*
     * We store both number of pages and number of heap tuples that are in the
     * pending list.
     */
    BlockNumber nPendingPages;
    int64       nPendingHeapTuples;
 
    /*
     * Statistics for planner use (accurate as of last VACUUM)
     */
    BlockNumber nTotalPages;
    BlockNumber nEntryPages;
    BlockNumber nDataPages;
    int64       nEntries;
 
    /*
     * GIN version number (ideally this should have been at the front, but too
     * late now.  Don't move it!)
     *
     * Currently 2 (for indexes initialized in 9.4 or later)
     *
     * Version 1 (indexes initialized in version 9.1, 9.2 or 9.3), is
     * compatible, but may contain uncompressed posting tree (leaf) pages and
     * posting lists. They will be converted to compressed format when
     * modified.
     *
     * Version 0 (indexes initialized in 9.0 or before) is compatible but may
     * be missing null entries, including both null keys and placeholders.
     * Reject full-index-scan attempts on such indexes.
     */
    int32       ginVersion;
} GinMetaPageData;
 
#define GIN_CURRENT_VERSION     2
 
#define GinPageGetMeta(p) \
    ((GinMetaPageData *) PageGetContents(p))
 
/*
 * Macros for accessing a GIN index page's opaque data
 */
#define GinPageGetOpaque(page) ( (GinPageOpaque) PageGetSpecialPointer(page) )
 
#define GinPageIsLeaf(page)    ( (GinPageGetOpaque(page)->flags & GIN_LEAF) != 0 )
#define GinPageSetLeaf(page)   ( GinPageGetOpaque(page)->flags |= GIN_LEAF )
#define GinPageSetNonLeaf(page)    ( GinPageGetOpaque(page)->flags &= ~GIN_LEAF )
#define GinPageIsData(page)    ( (GinPageGetOpaque(page)->flags & GIN_DATA) != 0 )
#define GinPageSetData(page)   ( GinPageGetOpaque(page)->flags |= GIN_DATA )
#define GinPageIsList(page)    ( (GinPageGetOpaque(page)->flags & GIN_LIST) != 0 )
#define GinPageSetList(page)   ( GinPageGetOpaque(page)->flags |= GIN_LIST )
#define GinPageHasFullRow(page)    ( (GinPageGetOpaque(page)->flags & GIN_LIST_FULLROW) != 0 )
#define GinPageSetFullRow(page)   ( GinPageGetOpaque(page)->flags |= GIN_LIST_FULLROW )
#define GinPageIsCompressed(page)    ( (GinPageGetOpaque(page)->flags & GIN_COMPRESSED) != 0 )
#define GinPageSetCompressed(page)   ( GinPageGetOpaque(page)->flags |= GIN_COMPRESSED )
 
#define GinPageIsDeleted(page) ( (GinPageGetOpaque(page)->flags & GIN_DELETED) != 0 )
#define GinPageSetDeleted(page)    ( GinPageGetOpaque(page)->flags |= GIN_DELETED)
#define GinPageSetNonDeleted(page) ( GinPageGetOpaque(page)->flags &= ~GIN_DELETED)
#define GinPageIsIncompleteSplit(page) ( (GinPageGetOpaque(page)->flags & GIN_INCOMPLETE_SPLIT) != 0 )
 
#define GinPageRightMost(page) ( GinPageGetOpaque(page)->rightlink == InvalidBlockNumber)
 
/*
 * We should reclaim deleted page only once every transaction started before
 * its deletion is over.
 */
#define GinPageGetDeleteXid(page) ( ((PageHeader) (page))->pd_prune_xid )
#define GinPageSetDeleteXid(page, xid) ( ((PageHeader) (page))->pd_prune_xid = xid)
extern bool GinPageIsRecyclable(Page page);
 
/*
 * We use our own ItemPointerGet(BlockNumber|OffsetNumber)
 * to avoid Asserts, since sometimes the ip_posid isn't "valid"
 */
#define GinItemPointerGetBlockNumber(pointer) \
    (ItemPointerGetBlockNumberNoCheck(pointer))
 
#define GinItemPointerGetOffsetNumber(pointer) \
    (ItemPointerGetOffsetNumberNoCheck(pointer))
 
#define GinItemPointerSetBlockNumber(pointer, blkno) \
    (ItemPointerSetBlockNumber((pointer), (blkno)))
 
#define GinItemPointerSetOffsetNumber(pointer, offnum) \
    (ItemPointerSetOffsetNumber((pointer), (offnum)))
 
 
/*
 * Special-case item pointer values needed by the GIN search logic.
 *  MIN: sorts less than any valid item pointer
 *  MAX: sorts greater than any valid item pointer
 *  LOSSY PAGE: indicates a whole heap page, sorts after normal item
 *              pointers for that page
 * Note that these are all distinguishable from an "invalid" item pointer
 * (which is InvalidBlockNumber/0) as well as from all normal item
 * pointers (which have item numbers in the range 1..MaxHeapTuplesPerPage).
 */
#define ItemPointerSetMin(p)  \
    ItemPointerSet((p), (BlockNumber)0, (OffsetNumber)0)
#define ItemPointerIsMin(p)  \
    (GinItemPointerGetOffsetNumber(p) == (OffsetNumber)0 && \
     GinItemPointerGetBlockNumber(p) == (BlockNumber)0)
#define ItemPointerSetMax(p)  \
    ItemPointerSet((p), InvalidBlockNumber, (OffsetNumber)0xffff)
#define ItemPointerSetLossyPage(p, b)  \
    ItemPointerSet((p), (b), (OffsetNumber)0xffff)
#define ItemPointerIsLossyPage(p)  \
    (GinItemPointerGetOffsetNumber(p) == (OffsetNumber)0xffff && \
     GinItemPointerGetBlockNumber(p) != InvalidBlockNumber)
 
/*
 * Posting item in a non-leaf posting-tree page
 */
typedef struct
{
    /* We use BlockIdData not BlockNumber to avoid padding space wastage */
    BlockIdData child_blkno;
    ItemPointerData key;
} PostingItem;
 
#define PostingItemGetBlockNumber(pointer) \
    BlockIdGetBlockNumber(&(pointer)->child_blkno)
 
#define PostingItemSetBlockNumber(pointer, blockNumber) \
    BlockIdSet(&((pointer)->child_blkno), (blockNumber))
 
/*
 * Category codes to distinguish placeholder nulls from ordinary NULL keys.
 *
 * The first two code values were chosen to be compatible with the usual usage
 * of bool isNull flags.  However, casting between bool and GinNullCategory is
 * risky because of the possibility of different bit patterns and type sizes,
 * so it is no longer done.
 *
 * GIN_CAT_EMPTY_QUERY is never stored in the index; and notice that it is
 * chosen to sort before not after regular key values.
 */
typedef signed char GinNullCategory;
 
#define GIN_CAT_NORM_KEY        0   /* normal, non-null key value */
#define GIN_CAT_NULL_KEY        1   /* null key value */
#define GIN_CAT_EMPTY_ITEM      2   /* placeholder for zero-key item */
#define GIN_CAT_NULL_ITEM       3   /* placeholder for null item */
#define GIN_CAT_EMPTY_QUERY     (-1)    /* placeholder for full-scan query */
 
/*
 * Access macros for null category byte in entry tuples
 */
#define GinCategoryOffset(itup,ginstate) \
    (IndexInfoFindDataOffset((itup)->t_info) + \
     ((ginstate)->oneCol ? 0 : sizeof(int16)))
#define GinGetNullCategory(itup,ginstate) \
    (*((GinNullCategory *) ((char*)(itup) + GinCategoryOffset(itup,ginstate))))
#define GinSetNullCategory(itup,ginstate,c) \
    (*((GinNullCategory *) ((char*)(itup) + GinCategoryOffset(itup,ginstate))) = (c))
 
/*
 * Access macros for leaf-page entry tuples (see discussion in README)
 */
#define GinGetNPosting(itup)    GinItemPointerGetOffsetNumber(&(itup)->t_tid)
#define GinSetNPosting(itup,n)  ItemPointerSetOffsetNumber(&(itup)->t_tid,n)
#define GIN_TREE_POSTING        ((OffsetNumber)0xffff)
#define GinIsPostingTree(itup)  (GinGetNPosting(itup) == GIN_TREE_POSTING)
#define GinSetPostingTree(itup, blkno)  ( GinSetNPosting((itup),GIN_TREE_POSTING), ItemPointerSetBlockNumber(&(itup)->t_tid, blkno) )
#define GinGetPostingTree(itup) GinItemPointerGetBlockNumber(&(itup)->t_tid)
 
#define GIN_ITUP_COMPRESSED     (1U << 31)
#define GinGetPostingOffset(itup)   (GinItemPointerGetBlockNumber(&(itup)->t_tid) & (~GIN_ITUP_COMPRESSED))
#define GinSetPostingOffset(itup,n) ItemPointerSetBlockNumber(&(itup)->t_tid,(n)|GIN_ITUP_COMPRESSED)
#define GinGetPosting(itup)         ((Pointer) ((char*)(itup) + GinGetPostingOffset(itup)))
#define GinItupIsCompressed(itup)   ((GinItemPointerGetBlockNumber(&(itup)->t_tid) & GIN_ITUP_COMPRESSED) != 0)
 
/*
 * Maximum size of an item on entry tree page. Make sure that we fit at least
 * three items on each page. (On regular B-tree indexes, we must fit at least
 * three items: two data items and the "high key". In GIN entry tree, we don't
 * currently store the high key explicitly, we just use the rightmost item on
 * the page, so it would actually be enough to fit two items.)
 */
#define GinMaxItemSize \
    Min(INDEX_SIZE_MASK, \
        MAXALIGN_DOWN(((BLCKSZ - \
                        MAXALIGN(SizeOfPageHeaderData + 3 * sizeof(ItemIdData)) - \
                        MAXALIGN(sizeof(GinPageOpaqueData))) / 3)))
 
/*
 * Access macros for non-leaf entry tuples
 */
#define GinGetDownlink(itup)    GinItemPointerGetBlockNumber(&(itup)->t_tid)
#define GinSetDownlink(itup,blkno)  ItemPointerSet(&(itup)->t_tid, blkno, InvalidOffsetNumber)
 
 
/*
 * Data (posting tree) pages
 *
 * Posting tree pages don't store regular tuples. Non-leaf pages contain
 * PostingItems, which are pairs of ItemPointers and child block numbers.
 * Leaf pages contain GinPostingLists and an uncompressed array of item
 * pointers.
 *
 * In a leaf page, the compressed posting lists are stored after the regular
 * page header, one after each other. Although we don't store regular tuples,
 * pd_lower is used to indicate the end of the posting lists. After that, free
 * space follows.  This layout is compatible with the "standard" heap and
 * index page layout described in bufpage.h, so that we can e.g set buffer_std
 * when writing WAL records.
 *
 * In the special space is the GinPageOpaque struct.
 */
#define GinDataLeafPageGetPostingList(page) \
    (GinPostingList *) ((PageGetContents(page) + MAXALIGN(sizeof(ItemPointerData))))
#define GinDataLeafPageGetPostingListSize(page) \
    (((PageHeader) page)->pd_lower - MAXALIGN(SizeOfPageHeaderData) - MAXALIGN(sizeof(ItemPointerData)))
 
#define GinDataLeafPageIsEmpty(page) \
    (GinPageIsCompressed(page) ? (GinDataLeafPageGetPostingListSize(page) == 0) : (GinPageGetOpaque(page)->maxoff < FirstOffsetNumber))
 
#define GinDataLeafPageGetFreeSpace(page) PageGetExactFreeSpace(page)
 
#define GinDataPageGetRightBound(page)  ((ItemPointer) PageGetContents(page))
/*
 * Pointer to the data portion of a posting tree page. For internal pages,
 * that's the beginning of the array of PostingItems. For compressed leaf
 * pages, the first compressed posting list. For uncompressed (pre-9.4) leaf
 * pages, it's the beginning of the ItemPointer array.
 */
#define GinDataPageGetData(page)    \
    (PageGetContents(page) + MAXALIGN(sizeof(ItemPointerData)))
/* non-leaf pages contain PostingItems */
#define GinDataPageGetPostingItem(page, i)  \
    ((PostingItem *) (GinDataPageGetData(page) + ((i)-1) * sizeof(PostingItem)))
 
/*
 * Note: there is no GinDataPageGetDataSize macro, because before version
 * 9.4, we didn't set pd_lower on data pages. There can be pages in the index
 * that were binary-upgraded from earlier versions and still have an invalid
 * pd_lower, so we cannot trust it in general. Compressed posting tree leaf
 * pages are new in 9.4, however, so we can trust them; see
 * GinDataLeafPageGetPostingListSize.
 */
#define GinDataPageSetDataSize(page, size) \
    { \
        Assert(size <= GinDataPageMaxDataSize); \
        ((PageHeader) page)->pd_lower = (size) + MAXALIGN(SizeOfPageHeaderData) + MAXALIGN(sizeof(ItemPointerData)); \
    }
 
#define GinNonLeafDataPageGetFreeSpace(page)    \
    (GinDataPageMaxDataSize - \
     GinPageGetOpaque(page)->maxoff * sizeof(PostingItem))
 
#define GinDataPageMaxDataSize  \
    (BLCKSZ - MAXALIGN(SizeOfPageHeaderData) \
     - MAXALIGN(sizeof(ItemPointerData)) \
     - MAXALIGN(sizeof(GinPageOpaqueData)))
 
/*
 * List pages
 */
#define GinListPageSize  \
    ( BLCKSZ - SizeOfPageHeaderData - MAXALIGN(sizeof(GinPageOpaqueData)) )
 
/*
 * A compressed posting list.
 *
 * Note: This requires 2-byte alignment.
 */
typedef struct
{
    ItemPointerData first;      /* first item in this posting list (unpacked) */
    uint16      nbytes;         /* number of bytes that follow */
    unsigned char bytes[FLEXIBLE_ARRAY_MEMBER]; /* varbyte encoded items */
} GinPostingList;
 
#define SizeOfGinPostingList(plist) (offsetof(GinPostingList, bytes) + SHORTALIGN((plist)->nbytes) )
#define GinNextPostingListSegment(cur) ((GinPostingList *) (((char *) (cur)) + SizeOfGinPostingList((cur))))
 
#endif                          /* GINBLOCK_H */