genam.h

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/*-------------------------------------------------------------------------
 *
 * genam.h
 *    POSTGRES generalized index access method definitions.
 *
 *
 * Portions Copyright (c) 1996-2026, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/access/genam.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef GENAM_H
#define GENAM_H
 
#include "access/htup.h"
#include "access/sdir.h"
#include "access/skey.h"
#include "executor/instrument_node.h"
#include "storage/buf.h"
#include "storage/lockdefs.h"
#include "utils/snapshot.h"
 
 
/*
 * forward references in this file
 */
typedef struct IndexInfo IndexInfo;
typedef struct RelationData *Relation;
typedef struct TIDBitmap TIDBitmap;
typedef struct TupleTableSlot TupleTableSlot;
 
 
/*
 * Struct for statistics returned by ambuild
 */
typedef struct IndexBuildResult
{
    double      heap_tuples;    /* # of tuples seen in parent table */
    double      index_tuples;   /* # of tuples inserted into index */
} IndexBuildResult;
 
/*
 * Struct for input arguments passed to ambulkdelete and amvacuumcleanup
 *
 * num_heap_tuples is accurate only when estimated_count is false;
 * otherwise it's just an estimate (currently, the estimate is the
 * prior value of the relation's pg_class.reltuples field, so it could
 * even be -1).  It will always just be an estimate during ambulkdelete.
 */
typedef struct IndexVacuumInfo
{
    Relation    index;          /* the index being vacuumed */
    Relation    heaprel;        /* the heap relation the index belongs to */
    bool        analyze_only;   /* ANALYZE (without any actual vacuum) */
    bool        report_progress;    /* emit progress.h status reports */
    bool        estimated_count;    /* num_heap_tuples is an estimate */
    int         message_level;  /* ereport level for progress messages */
    double      num_heap_tuples;    /* tuples remaining in heap */
    BufferAccessStrategy strategy;  /* access strategy for reads */
} IndexVacuumInfo;
 
/*
 * Struct for statistics returned by ambulkdelete and amvacuumcleanup
 *
 * This struct is normally allocated by the first ambulkdelete call and then
 * passed along through subsequent ones until amvacuumcleanup; however,
 * amvacuumcleanup must be prepared to allocate it in the case where no
 * ambulkdelete calls were made (because no tuples needed deletion).
 * Note that an index AM could choose to return a larger struct
 * of which this is just the first field; this provides a way for ambulkdelete
 * to communicate additional private data to amvacuumcleanup.
 *
 * Note: pages_newly_deleted is the number of pages in the index that were
 * deleted by the current vacuum operation.  pages_deleted and pages_free
 * refer to free space within the index file.
 *
 * Note: Some index AMs may compute num_index_tuples by reference to
 * num_heap_tuples, in which case they should copy the estimated_count field
 * from IndexVacuumInfo.
 */
typedef struct IndexBulkDeleteResult
{
    BlockNumber num_pages;      /* pages remaining in index */
    bool        estimated_count;    /* num_index_tuples is an estimate */
    double      num_index_tuples;   /* tuples remaining */
    double      tuples_removed; /* # removed during vacuum operation */
    BlockNumber pages_newly_deleted;    /* # pages marked deleted by us  */
    BlockNumber pages_deleted;  /* # pages marked deleted (could be by us) */
    BlockNumber pages_free;     /* # pages available for reuse */
} IndexBulkDeleteResult;
 
/* Typedef for callback function to determine if a tuple is bulk-deletable */
typedef bool (*IndexBulkDeleteCallback) (ItemPointer itemptr, void *state);
 
/* struct definitions appear in relscan.h */
typedef struct IndexScanDescData *IndexScanDesc;
typedef struct SysScanDescData *SysScanDesc;
 
typedef struct ParallelIndexScanDescData *ParallelIndexScanDesc;
 
/*
 * Enumeration specifying the type of uniqueness check to perform in
 * index_insert().
 *
 * UNIQUE_CHECK_YES is the traditional Postgres immediate check, possibly
 * blocking to see if a conflicting transaction commits.
 *
 * For deferrable unique constraints, UNIQUE_CHECK_PARTIAL is specified at
 * insertion time.  The index AM should test if the tuple is unique, but
 * should not throw error, block, or prevent the insertion if the tuple
 * appears not to be unique.  We'll recheck later when it is time for the
 * constraint to be enforced.  The AM must return true if the tuple is
 * known unique, false if it is possibly non-unique.  In the "true" case
 * it is safe to omit the later recheck.
 *
 * When it is time to recheck the deferred constraint, a pseudo-insertion
 * call is made with UNIQUE_CHECK_EXISTING.  The tuple is already in the
 * index in this case, so it should not be inserted again.  Rather, just
 * check for conflicting live tuples (possibly blocking).
 */
typedef enum IndexUniqueCheck
{
    UNIQUE_CHECK_NO,            /* Don't do any uniqueness checking */
    UNIQUE_CHECK_YES,           /* Enforce uniqueness at insertion time */
    UNIQUE_CHECK_PARTIAL,       /* Test uniqueness, but no error */
    UNIQUE_CHECK_EXISTING,      /* Check if existing tuple is unique */
} IndexUniqueCheck;
 
 
/* Nullable "ORDER BY col op const" distance */
typedef struct IndexOrderByDistance
{
    double      value;
    bool        isnull;
} IndexOrderByDistance;
 
/*
 * generalized index_ interface routines (in indexam.c)
 */
 
extern Relation index_open(Oid relationId, LOCKMODE lockmode);
extern Relation try_index_open(Oid relationId, LOCKMODE lockmode);
extern void index_close(Relation relation, LOCKMODE lockmode);
 
extern bool index_insert(Relation indexRelation,
                         Datum *values, bool *isnull,
                         ItemPointer heap_t_ctid,
                         Relation heapRelation,
                         IndexUniqueCheck checkUnique,
                         bool indexUnchanged,
                         IndexInfo *indexInfo);
extern void index_insert_cleanup(Relation indexRelation,
                                 IndexInfo *indexInfo);
 
extern IndexScanDesc index_beginscan(Relation heapRelation,
                                     Relation indexRelation,
                                     Snapshot snapshot,
                                     IndexScanInstrumentation *instrument,
                                     int nkeys, int norderbys);
extern IndexScanDesc index_beginscan_bitmap(Relation indexRelation,
                                            Snapshot snapshot,
                                            IndexScanInstrumentation *instrument,
                                            int nkeys);
extern void index_rescan(IndexScanDesc scan,
                         ScanKey keys, int nkeys,
                         ScanKey orderbys, int norderbys);
extern void index_endscan(IndexScanDesc scan);
extern void index_markpos(IndexScanDesc scan);
extern void index_restrpos(IndexScanDesc scan);
extern Size index_parallelscan_estimate(Relation indexRelation,
                                        int nkeys, int norderbys, Snapshot snapshot,
                                        bool instrument, bool parallel_aware,
                                        int nworkers);
extern void index_parallelscan_initialize(Relation heapRelation,
                                          Relation indexRelation, Snapshot snapshot,
                                          bool instrument, bool parallel_aware,
                                          int nworkers,
                                          SharedIndexScanInstrumentation **sharedinfo,
                                          ParallelIndexScanDesc target);
extern void index_parallelrescan(IndexScanDesc scan);
extern IndexScanDesc index_beginscan_parallel(Relation heaprel,
                                              Relation indexrel,
                                              IndexScanInstrumentation *instrument,
                                              int nkeys, int norderbys,
                                              ParallelIndexScanDesc pscan);
extern ItemPointer index_getnext_tid(IndexScanDesc scan,
                                     ScanDirection direction);
extern bool index_fetch_heap(IndexScanDesc scan, TupleTableSlot *slot);
extern bool index_getnext_slot(IndexScanDesc scan, ScanDirection direction,
                               TupleTableSlot *slot);
extern int64 index_getbitmap(IndexScanDesc scan, TIDBitmap *bitmap);
 
extern IndexBulkDeleteResult *index_bulk_delete(IndexVacuumInfo *info,
                                                IndexBulkDeleteResult *istat,
                                                IndexBulkDeleteCallback callback,
                                                void *callback_state);
extern IndexBulkDeleteResult *index_vacuum_cleanup(IndexVacuumInfo *info,
                                                   IndexBulkDeleteResult *istat);
extern bool index_can_return(Relation indexRelation, int attno);
extern RegProcedure index_getprocid(Relation irel, AttrNumber attnum,
                                    uint16 procnum);
extern FmgrInfo *index_getprocinfo(Relation irel, AttrNumber attnum,
                                   uint16 procnum);
extern void index_store_float8_orderby_distances(IndexScanDesc scan,
                                                 Oid *orderByTypes,
                                                 IndexOrderByDistance *distances,
                                                 bool recheckOrderBy);
extern bytea *index_opclass_options(Relation indrel, AttrNumber attnum,
                                    Datum attoptions, bool validate);
 
 
/*
 * index access method support routines (in genam.c)
 */
extern IndexScanDesc RelationGetIndexScan(Relation indexRelation,
                                          int nkeys, int norderbys);
extern void IndexScanEnd(IndexScanDesc scan);
extern char *BuildIndexValueDescription(Relation indexRelation,
                                        const Datum *values, const bool *isnull);
extern TransactionId index_compute_xid_horizon_for_tuples(Relation irel,
                                                          Relation hrel,
                                                          Buffer ibuf,
                                                          OffsetNumber *itemnos,
                                                          int nitems);
 
/*
 * heap-or-index access to system catalogs (in genam.c)
 */
extern SysScanDesc systable_beginscan(Relation heapRelation,
                                      Oid indexId,
                                      bool indexOK,
                                      Snapshot snapshot,
                                      int nkeys, ScanKey key);
extern HeapTuple systable_getnext(SysScanDesc sysscan);
extern bool systable_recheck_tuple(SysScanDesc sysscan, HeapTuple tup);
extern void systable_endscan(SysScanDesc sysscan);
extern SysScanDesc systable_beginscan_ordered(Relation heapRelation,
                                              Relation indexRelation,
                                              Snapshot snapshot,
                                              int nkeys, ScanKey key);
extern HeapTuple systable_getnext_ordered(SysScanDesc sysscan,
                                          ScanDirection direction);
extern void systable_endscan_ordered(SysScanDesc sysscan);
extern void systable_inplace_update_begin(Relation relation,
                                          Oid indexId,
                                          bool indexOK,
                                          Snapshot snapshot,
                                          int nkeys, const ScanKeyData *key,
                                          HeapTuple *oldtupcopy,
                                          void **state);
extern void systable_inplace_update_finish(void *state, HeapTuple tuple);
extern void systable_inplace_update_cancel(void *state);
 
#endif                          /* GENAM_H */