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+/*-------------------------------------------------------------------------
+ *
+ * gist_private.h
+ * private declarations for GiST -- declarations related to the
+ * internal implementation of GiST, not the public API
+ *
+ * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * src/include/access/gist_private.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef GIST_PRIVATE_H
+#define GIST_PRIVATE_H
+
+#include "access/amapi.h"
+#include "access/gist.h"
+#include "access/itup.h"
+#include "lib/pairingheap.h"
+#include "storage/bufmgr.h"
+#include "storage/buffile.h"
+#include "utils/hsearch.h"
+#include "access/genam.h"
+
+/*
+ * Maximum number of "halves" a page can be split into in one operation.
+ * Typically a split produces 2 halves, but can be more if keys have very
+ * different lengths, or when inserting multiple keys in one operation (as
+ * when inserting downlinks to an internal node). There is no theoretical
+ * limit on this, but in practice if you get more than a handful page halves
+ * in one split, there's something wrong with the opclass implementation.
+ * GIST_MAX_SPLIT_PAGES is an arbitrary limit on that, used to size some
+ * local arrays used during split. Note that there is also a limit on the
+ * number of buffers that can be held locked at a time, MAX_SIMUL_LWLOCKS,
+ * so if you raise this higher than that limit, you'll just get a different
+ * error.
+ */
+#define GIST_MAX_SPLIT_PAGES 75
+
+/* Buffer lock modes */
+#define GIST_SHARE BUFFER_LOCK_SHARE
+#define GIST_EXCLUSIVE BUFFER_LOCK_EXCLUSIVE
+#define GIST_UNLOCK BUFFER_LOCK_UNLOCK
+
+typedef struct
+{
+ BlockNumber prev;
+ uint32 freespace;
+ char tupledata[FLEXIBLE_ARRAY_MEMBER];
+} GISTNodeBufferPage;
+
+#define BUFFER_PAGE_DATA_OFFSET MAXALIGN(offsetof(GISTNodeBufferPage, tupledata))
+/* Returns free space in node buffer page */
+#define PAGE_FREE_SPACE(nbp) (nbp->freespace)
+/* Checks if node buffer page is empty */
+#define PAGE_IS_EMPTY(nbp) (nbp->freespace == BLCKSZ - BUFFER_PAGE_DATA_OFFSET)
+/* Checks if node buffers page don't contain sufficient space for index tuple */
+#define PAGE_NO_SPACE(nbp, itup) (PAGE_FREE_SPACE(nbp) < \
+ MAXALIGN(IndexTupleSize(itup)))
+
+/*
+ * GISTSTATE: information needed for any GiST index operation
+ *
+ * This struct retains call info for the index's opclass-specific support
+ * functions (per index column), plus the index's tuple descriptor.
+ *
+ * scanCxt holds the GISTSTATE itself as well as any data that lives for the
+ * lifetime of the index operation. We pass this to the support functions
+ * via fn_mcxt, so that they can store scan-lifespan data in it. The
+ * functions are invoked in tempCxt, which is typically short-lifespan
+ * (that is, it's reset after each tuple). However, tempCxt can be the same
+ * as scanCxt if we're not bothering with per-tuple context resets.
+ */
+typedef struct GISTSTATE
+{
+ MemoryContext scanCxt; /* context for scan-lifespan data */
+ MemoryContext tempCxt; /* short-term context for calling functions */
+
+ TupleDesc leafTupdesc; /* index's tuple descriptor */
+ TupleDesc nonLeafTupdesc; /* truncated tuple descriptor for non-leaf
+ * pages */
+ TupleDesc fetchTupdesc; /* tuple descriptor for tuples returned in an
+ * index-only scan */
+
+ FmgrInfo consistentFn[INDEX_MAX_KEYS];
+ FmgrInfo unionFn[INDEX_MAX_KEYS];
+ FmgrInfo compressFn[INDEX_MAX_KEYS];
+ FmgrInfo decompressFn[INDEX_MAX_KEYS];
+ FmgrInfo penaltyFn[INDEX_MAX_KEYS];
+ FmgrInfo picksplitFn[INDEX_MAX_KEYS];
+ FmgrInfo equalFn[INDEX_MAX_KEYS];
+ FmgrInfo distanceFn[INDEX_MAX_KEYS];
+ FmgrInfo fetchFn[INDEX_MAX_KEYS];
+
+ /* Collations to pass to the support functions */
+ Oid supportCollation[INDEX_MAX_KEYS];
+} GISTSTATE;
+
+
+/*
+ * During a GiST index search, we must maintain a queue of unvisited items,
+ * which can be either individual heap tuples or whole index pages. If it
+ * is an ordered search, the unvisited items should be visited in distance
+ * order. Unvisited items at the same distance should be visited in
+ * depth-first order, that is heap items first, then lower index pages, then
+ * upper index pages; this rule avoids doing extra work during a search that
+ * ends early due to LIMIT.
+ *
+ * To perform an ordered search, we use a pairing heap to manage the
+ * distance-order queue. In a non-ordered search (no order-by operators),
+ * we use it to return heap tuples before unvisited index pages, to
+ * ensure depth-first order, but all entries are otherwise considered
+ * equal.
+ */
+
+/* Individual heap tuple to be visited */
+typedef struct GISTSearchHeapItem
+{
+ ItemPointerData heapPtr;
+ bool recheck; /* T if quals must be rechecked */
+ bool recheckDistances; /* T if distances must be rechecked */
+ HeapTuple recontup; /* data reconstructed from the index, used in
+ * index-only scans */
+ OffsetNumber offnum; /* track offset in page to mark tuple as
+ * LP_DEAD */
+} GISTSearchHeapItem;
+
+/* Unvisited item, either index page or heap tuple */
+typedef struct GISTSearchItem
+{
+ pairingheap_node phNode;
+ BlockNumber blkno; /* index page number, or InvalidBlockNumber */
+ union
+ {
+ GistNSN parentlsn; /* parent page's LSN, if index page */
+ /* we must store parentlsn to detect whether a split occurred */
+ GISTSearchHeapItem heap; /* heap info, if heap tuple */
+ } data;
+
+ /* numberOfOrderBys entries */
+ IndexOrderByDistance distances[FLEXIBLE_ARRAY_MEMBER];
+} GISTSearchItem;
+
+#define GISTSearchItemIsHeap(item) ((item).blkno == InvalidBlockNumber)
+
+#define SizeOfGISTSearchItem(n_distances) \
+ (offsetof(GISTSearchItem, distances) + \
+ sizeof(IndexOrderByDistance) * (n_distances))
+
+/*
+ * GISTScanOpaqueData: private state for a scan of a GiST index
+ */
+typedef struct GISTScanOpaqueData
+{
+ GISTSTATE *giststate; /* index information, see above */
+ Oid *orderByTypes; /* datatypes of ORDER BY expressions */
+
+ pairingheap *queue; /* queue of unvisited items */
+ MemoryContext queueCxt; /* context holding the queue */
+ bool qual_ok; /* false if qual can never be satisfied */
+ bool firstCall; /* true until first gistgettuple call */
+
+ /* pre-allocated workspace arrays */
+ IndexOrderByDistance *distances; /* output area for gistindex_keytest */
+
+ /* info about killed items if any (killedItems is NULL if never used) */
+ OffsetNumber *killedItems; /* offset numbers of killed items */
+ int numKilled; /* number of currently stored items */
+ BlockNumber curBlkno; /* current number of block */
+ GistNSN curPageLSN; /* pos in the WAL stream when page was read */
+
+ /* In a non-ordered search, returnable heap items are stored here: */
+ GISTSearchHeapItem pageData[BLCKSZ / sizeof(IndexTupleData)];
+ OffsetNumber nPageData; /* number of valid items in array */
+ OffsetNumber curPageData; /* next item to return */
+ MemoryContext pageDataCxt; /* context holding the fetched tuples, for
+ * index-only scans */
+} GISTScanOpaqueData;
+
+typedef GISTScanOpaqueData *GISTScanOpaque;
+
+/* despite the name, gistxlogPage is not part of any xlog record */
+typedef struct gistxlogPage
+{
+ BlockNumber blkno;
+ int num; /* number of index tuples following */
+} gistxlogPage;
+
+/* SplitedPageLayout - gistSplit function result */
+typedef struct SplitedPageLayout
+{
+ gistxlogPage block;
+ IndexTupleData *list;
+ int lenlist;
+ IndexTuple itup; /* union key for page */
+ Page page; /* to operate */
+ Buffer buffer; /* to write after all proceed */
+
+ struct SplitedPageLayout *next;
+} SplitedPageLayout;
+
+/*
+ * GISTInsertStack used for locking buffers and transfer arguments during
+ * insertion
+ */
+typedef struct GISTInsertStack
+{
+ /* current page */
+ BlockNumber blkno;
+ Buffer buffer;
+ Page page;
+
+ /*
+ * log sequence number from page->lsn to recognize page update and compare
+ * it with page's nsn to recognize page split
+ */
+ GistNSN lsn;
+
+ /*
+ * If set, we split the page while descending the tree to find an
+ * insertion target. It means that we need to retry from the parent,
+ * because the downlink of this page might no longer cover the new key.
+ */
+ bool retry_from_parent;
+
+ /* offset of the downlink in the parent page, that points to this page */
+ OffsetNumber downlinkoffnum;
+
+ /* pointer to parent */
+ struct GISTInsertStack *parent;
+} GISTInsertStack;
+
+/* Working state and results for multi-column split logic in gistsplit.c */
+typedef struct GistSplitVector
+{
+ GIST_SPLITVEC splitVector; /* passed to/from user PickSplit method */
+
+ Datum spl_lattr[INDEX_MAX_KEYS]; /* Union of subkeys in
+ * splitVector.spl_left */
+ bool spl_lisnull[INDEX_MAX_KEYS];
+
+ Datum spl_rattr[INDEX_MAX_KEYS]; /* Union of subkeys in
+ * splitVector.spl_right */
+ bool spl_risnull[INDEX_MAX_KEYS];
+
+ bool *spl_dontcare; /* flags tuples which could go to either side
+ * of the split for zero penalty */
+} GistSplitVector;
+
+typedef struct
+{
+ Relation r;
+ Relation heapRel;
+ Size freespace; /* free space to be left */
+ bool is_build;
+
+ GISTInsertStack *stack;
+} GISTInsertState;
+
+/* root page of a gist index */
+#define GIST_ROOT_BLKNO 0
+
+/*
+ * Before PostgreSQL 9.1, we used to rely on so-called "invalid tuples" on
+ * inner pages to finish crash recovery of incomplete page splits. If a crash
+ * happened in the middle of a page split, so that the downlink pointers were
+ * not yet inserted, crash recovery inserted a special downlink pointer. The
+ * semantics of an invalid tuple was that it if you encounter one in a scan,
+ * it must always be followed, because we don't know if the tuples on the
+ * child page match or not.
+ *
+ * We no longer create such invalid tuples, we now mark the left-half of such
+ * an incomplete split with the F_FOLLOW_RIGHT flag instead, and finish the
+ * split properly the next time we need to insert on that page. To retain
+ * on-disk compatibility for the sake of pg_upgrade, we still store 0xffff as
+ * the offset number of all inner tuples. If we encounter any invalid tuples
+ * with 0xfffe during insertion, we throw an error, though scans still handle
+ * them. You should only encounter invalid tuples if you pg_upgrade a pre-9.1
+ * gist index which already has invalid tuples in it because of a crash. That
+ * should be rare, and you are recommended to REINDEX anyway if you have any
+ * invalid tuples in an index, so throwing an error is as far as we go with
+ * supporting that.
+ */
+#define TUPLE_IS_VALID 0xffff
+#define TUPLE_IS_INVALID 0xfffe
+
+#define GistTupleIsInvalid(itup) ( ItemPointerGetOffsetNumber( &((itup)->t_tid) ) == TUPLE_IS_INVALID )
+#define GistTupleSetValid(itup) ItemPointerSetOffsetNumber( &((itup)->t_tid), TUPLE_IS_VALID )
+
+
+
+
+/*
+ * A buffer attached to an internal node, used when building an index in
+ * buffering mode.
+ */
+typedef struct
+{
+ BlockNumber nodeBlocknum; /* index block # this buffer is for */
+ int32 blocksCount; /* current # of blocks occupied by buffer */
+
+ BlockNumber pageBlocknum; /* temporary file block # */
+ GISTNodeBufferPage *pageBuffer; /* in-memory buffer page */
+
+ /* is this buffer queued for emptying? */
+ bool queuedForEmptying;
+
+ /* is this a temporary copy, not in the hash table? */
+ bool isTemp;
+
+ int level; /* 0 == leaf */
+} GISTNodeBuffer;
+
+/*
+ * Does specified level have buffers? (Beware of multiple evaluation of
+ * arguments.)
+ */
+#define LEVEL_HAS_BUFFERS(nlevel, gfbb) \
+ ((nlevel) != 0 && (nlevel) % (gfbb)->levelStep == 0 && \
+ (nlevel) != (gfbb)->rootlevel)
+
+/* Is specified buffer at least half-filled (should be queued for emptying)? */
+#define BUFFER_HALF_FILLED(nodeBuffer, gfbb) \
+ ((nodeBuffer)->blocksCount > (gfbb)->pagesPerBuffer / 2)
+
+/*
+ * Is specified buffer full? Our buffers can actually grow indefinitely,
+ * beyond the "maximum" size, so this just means whether the buffer has grown
+ * beyond the nominal maximum size.
+ */
+#define BUFFER_OVERFLOWED(nodeBuffer, gfbb) \
+ ((nodeBuffer)->blocksCount > (gfbb)->pagesPerBuffer)
+
+/*
+ * Data structure with general information about build buffers.
+ */
+typedef struct GISTBuildBuffers
+{
+ /* Persistent memory context for the buffers and metadata. */
+ MemoryContext context;
+
+ BufFile *pfile; /* Temporary file to store buffers in */
+ long nFileBlocks; /* Current size of the temporary file */
+
+ /*
+ * resizable array of free blocks.
+ */
+ long *freeBlocks;
+ int nFreeBlocks; /* # of currently free blocks in the array */
+ int freeBlocksLen; /* current allocated length of the array */
+
+ /* Hash for buffers by block number */
+ HTAB *nodeBuffersTab;
+
+ /* List of buffers scheduled for emptying */
+ List *bufferEmptyingQueue;
+
+ /*
+ * Parameters to the buffering build algorithm. levelStep determines which
+ * levels in the tree have buffers, and pagesPerBuffer determines how
+ * large each buffer is.
+ */
+ int levelStep;
+ int pagesPerBuffer;
+
+ /* Array of lists of buffers on each level, for final emptying */
+ List **buffersOnLevels;
+ int buffersOnLevelsLen;
+
+ /*
+ * Dynamically-sized array of buffers that currently have their last page
+ * loaded in main memory.
+ */
+ GISTNodeBuffer **loadedBuffers;
+ int loadedBuffersCount; /* # of entries in loadedBuffers */
+ int loadedBuffersLen; /* allocated size of loadedBuffers */
+
+ /* Level of the current root node (= height of the index tree - 1) */
+ int rootlevel;
+} GISTBuildBuffers;
+
+/* GiSTOptions->buffering_mode values */
+typedef enum GistOptBufferingMode
+{
+ GIST_OPTION_BUFFERING_AUTO,
+ GIST_OPTION_BUFFERING_ON,
+ GIST_OPTION_BUFFERING_OFF
+} GistOptBufferingMode;
+
+/*
+ * Storage type for GiST's reloptions
+ */
+typedef struct GiSTOptions
+{
+ int32 vl_len_; /* varlena header (do not touch directly!) */
+ int fillfactor; /* page fill factor in percent (0..100) */
+ GistOptBufferingMode buffering_mode; /* buffering build mode */
+} GiSTOptions;
+
+/* gist.c */
+extern void gistbuildempty(Relation index);
+extern bool gistinsert(Relation r, Datum *values, bool *isnull,
+ ItemPointer ht_ctid, Relation heapRel,
+ IndexUniqueCheck checkUnique,
+ bool indexUnchanged,
+ struct IndexInfo *indexInfo);
+extern MemoryContext createTempGistContext(void);
+extern GISTSTATE *initGISTstate(Relation index);
+extern void freeGISTstate(GISTSTATE *giststate);
+extern void gistdoinsert(Relation r,
+ IndexTuple itup,
+ Size freespace,
+ GISTSTATE *giststate,
+ Relation heapRel,
+ bool is_build);
+
+/* A List of these is returned from gistplacetopage() in *splitinfo */
+typedef struct
+{
+ Buffer buf; /* the split page "half" */
+ IndexTuple downlink; /* downlink for this half. */
+} GISTPageSplitInfo;
+
+extern bool gistplacetopage(Relation rel, Size freespace, GISTSTATE *giststate,
+ Buffer buffer,
+ IndexTuple *itup, int ntup,
+ OffsetNumber oldoffnum, BlockNumber *newblkno,
+ Buffer leftchildbuf,
+ List **splitinfo,
+ bool markfollowright,
+ Relation heapRel,
+ bool is_build);
+
+extern SplitedPageLayout *gistSplit(Relation r, Page page, IndexTuple *itup,
+ int len, GISTSTATE *giststate);
+
+/* gistxlog.c */
+extern XLogRecPtr gistXLogPageDelete(Buffer buffer,
+ FullTransactionId xid, Buffer parentBuffer,
+ OffsetNumber downlinkOffset);
+
+extern void gistXLogPageReuse(Relation rel, Relation heaprel, BlockNumber blkno,
+ FullTransactionId deleteXid);
+
+extern XLogRecPtr gistXLogUpdate(Buffer buffer,
+ OffsetNumber *todelete, int ntodelete,
+ IndexTuple *itup, int ituplen,
+ Buffer leftchildbuf);
+
+extern XLogRecPtr gistXLogDelete(Buffer buffer, OffsetNumber *todelete,
+ int ntodelete, TransactionId snapshotConflictHorizon,
+ Relation heaprel);
+
+extern XLogRecPtr gistXLogSplit(bool page_is_leaf,
+ SplitedPageLayout *dist,
+ BlockNumber origrlink, GistNSN orignsn,
+ Buffer leftchildbuf, bool markfollowright);
+
+extern XLogRecPtr gistXLogAssignLSN(void);
+
+/* gistget.c */
+extern bool gistgettuple(IndexScanDesc scan, ScanDirection dir);
+extern int64 gistgetbitmap(IndexScanDesc scan, TIDBitmap *tbm);
+extern bool gistcanreturn(Relation index, int attno);
+
+/* gistvalidate.c */
+extern bool gistvalidate(Oid opclassoid);
+extern void gistadjustmembers(Oid opfamilyoid,
+ Oid opclassoid,
+ List *operators,
+ List *functions);
+
+/* gistutil.c */
+
+#define GiSTPageSize \
+ ( BLCKSZ - SizeOfPageHeaderData - MAXALIGN(sizeof(GISTPageOpaqueData)) )
+
+#define GIST_MIN_FILLFACTOR 10
+#define GIST_DEFAULT_FILLFACTOR 90
+
+extern bytea *gistoptions(Datum reloptions, bool validate);
+extern bool gistproperty(Oid index_oid, int attno,
+ IndexAMProperty prop, const char *propname,
+ bool *res, bool *isnull);
+extern bool gistfitpage(IndexTuple *itvec, int len);
+extern bool gistnospace(Page page, IndexTuple *itvec, int len, OffsetNumber todelete, Size freespace);
+extern void gistcheckpage(Relation rel, Buffer buf);
+extern Buffer gistNewBuffer(Relation r, Relation heaprel);
+extern bool gistPageRecyclable(Page page);
+extern void gistfillbuffer(Page page, IndexTuple *itup, int len,
+ OffsetNumber off);
+extern IndexTuple *gistextractpage(Page page, int *len /* out */ );
+extern IndexTuple *gistjoinvector(IndexTuple *itvec, int *len,
+ IndexTuple *additvec, int addlen);
+extern IndexTupleData *gistfillitupvec(IndexTuple *vec, int veclen, int *memlen);
+
+extern IndexTuple gistunion(Relation r, IndexTuple *itvec,
+ int len, GISTSTATE *giststate);
+extern IndexTuple gistgetadjusted(Relation r,
+ IndexTuple oldtup,
+ IndexTuple addtup,
+ GISTSTATE *giststate);
+extern IndexTuple gistFormTuple(GISTSTATE *giststate,
+ Relation r, Datum *attdata, bool *isnull, bool isleaf);
+extern void gistCompressValues(GISTSTATE *giststate, Relation r,
+ Datum *attdata, bool *isnull, bool isleaf, Datum *compatt);
+
+extern OffsetNumber gistchoose(Relation r, Page p,
+ IndexTuple it,
+ GISTSTATE *giststate);
+
+extern void GISTInitBuffer(Buffer b, uint32 f);
+extern void gistinitpage(Page page, uint32 f);
+extern void gistdentryinit(GISTSTATE *giststate, int nkey, GISTENTRY *e,
+ Datum k, Relation r, Page pg, OffsetNumber o,
+ bool l, bool isNull);
+
+extern float gistpenalty(GISTSTATE *giststate, int attno,
+ GISTENTRY *orig, bool isNullOrig,
+ GISTENTRY *add, bool isNullAdd);
+extern void gistMakeUnionItVec(GISTSTATE *giststate, IndexTuple *itvec, int len,
+ Datum *attr, bool *isnull);
+extern bool gistKeyIsEQ(GISTSTATE *giststate, int attno, Datum a, Datum b);
+extern void gistDeCompressAtt(GISTSTATE *giststate, Relation r, IndexTuple tuple, Page p,
+ OffsetNumber o, GISTENTRY *attdata, bool *isnull);
+extern HeapTuple gistFetchTuple(GISTSTATE *giststate, Relation r,
+ IndexTuple tuple);
+extern void gistMakeUnionKey(GISTSTATE *giststate, int attno,
+ GISTENTRY *entry1, bool isnull1,
+ GISTENTRY *entry2, bool isnull2,
+ Datum *dst, bool *dstisnull);
+
+extern XLogRecPtr gistGetFakeLSN(Relation rel);
+
+/* gistvacuum.c */
+extern IndexBulkDeleteResult *gistbulkdelete(IndexVacuumInfo *info,
+ IndexBulkDeleteResult *stats,
+ IndexBulkDeleteCallback callback,
+ void *callback_state);
+extern IndexBulkDeleteResult *gistvacuumcleanup(IndexVacuumInfo *info,
+ IndexBulkDeleteResult *stats);
+
+/* gistsplit.c */
+extern void gistSplitByKey(Relation r, Page page, IndexTuple *itup,
+ int len, GISTSTATE *giststate,
+ GistSplitVector *v,
+ int attno);
+
+/* gistbuild.c */
+extern IndexBuildResult *gistbuild(Relation heap, Relation index,
+ struct IndexInfo *indexInfo);
+
+/* gistbuildbuffers.c */
+extern GISTBuildBuffers *gistInitBuildBuffers(int pagesPerBuffer, int levelStep,
+ int maxLevel);
+extern GISTNodeBuffer *gistGetNodeBuffer(GISTBuildBuffers *gfbb,
+ GISTSTATE *giststate,
+ BlockNumber nodeBlocknum, int level);
+extern void gistPushItupToNodeBuffer(GISTBuildBuffers *gfbb,
+ GISTNodeBuffer *nodeBuffer, IndexTuple itup);
+extern bool gistPopItupFromNodeBuffer(GISTBuildBuffers *gfbb,
+ GISTNodeBuffer *nodeBuffer, IndexTuple *itup);
+extern void gistFreeBuildBuffers(GISTBuildBuffers *gfbb);
+extern void gistRelocateBuildBuffersOnSplit(GISTBuildBuffers *gfbb,
+ GISTSTATE *giststate, Relation r,
+ int level, Buffer buffer,
+ List *splitinfo);
+extern void gistUnloadNodeBuffers(GISTBuildBuffers *gfbb);
+
+#endif /* GIST_PRIVATE_H */
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