amapi.h

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/*-------------------------------------------------------------------------
 *
 * amapi.h
 *    API for Postgres index access methods.
 *
 * Copyright (c) 2015-2021, PostgreSQL Global Development Group
 *
 * src/include/access/amapi.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef AMAPI_H
#define AMAPI_H

#include "access/genam.h"

/*
 * We don't wish to include planner header files here, since most of an index
 * AM's implementation isn't concerned with those data structures.  To allow
 * declaring amcostestimate_function here, use forward struct references.
 */
struct PlannerInfo;
struct IndexPath;

/* Likewise, this file shouldn't depend on execnodes.h. */
struct IndexInfo;


/*
 * Properties for amproperty API.  This list covers properties known to the
 * core code, but an index AM can define its own properties, by matching the
 * string property name.
 */
typedef enum IndexAMProperty
{
    AMPROP_UNKNOWN = 0,         /* anything not known to core code */
    AMPROP_ASC,                 /* column properties */
    AMPROP_DESC,
    AMPROP_NULLS_FIRST,
    AMPROP_NULLS_LAST,
    AMPROP_ORDERABLE,
    AMPROP_DISTANCE_ORDERABLE,
    AMPROP_RETURNABLE,
    AMPROP_SEARCH_ARRAY,
    AMPROP_SEARCH_NULLS,
    AMPROP_CLUSTERABLE,         /* index properties */
    AMPROP_INDEX_SCAN,
    AMPROP_BITMAP_SCAN,
    AMPROP_BACKWARD_SCAN,
    AMPROP_CAN_ORDER,           /* AM properties */
    AMPROP_CAN_UNIQUE,
    AMPROP_CAN_MULTI_COL,
    AMPROP_CAN_EXCLUDE,
    AMPROP_CAN_INCLUDE
} IndexAMProperty;

/*
 * We use lists of this struct type to keep track of both operators and
 * support functions while building or adding to an opclass or opfamily.
 * amadjustmembers functions receive lists of these structs, and are allowed
 * to alter their "ref" fields.
 *
 * The "ref" fields define how the pg_amop or pg_amproc entry should depend
 * on the associated objects (that is, which dependency type to use, and
 * which opclass or opfamily it should depend on).
 *
 * If ref_is_hard is true, the entry will have a NORMAL dependency on the
 * operator or support func, and an INTERNAL dependency on the opclass or
 * opfamily.  This forces the opclass or opfamily to be dropped if the
 * operator or support func is dropped, and requires the CASCADE option
 * to do so.  Nor will ALTER OPERATOR FAMILY DROP be allowed.  This is
 * the right behavior for objects that are essential to an opclass.
 *
 * If ref_is_hard is false, the entry will have an AUTO dependency on the
 * operator or support func, and also an AUTO dependency on the opclass or
 * opfamily.  This allows ALTER OPERATOR FAMILY DROP, and causes that to
 * happen automatically if the operator or support func is dropped.  This
 * is the right behavior for inessential ("loose") objects.
 */
typedef struct OpFamilyMember
{
    bool        is_func;        /* is this an operator, or support func? */
    Oid         object;         /* operator or support func's OID */
    int         number;         /* strategy or support func number */
    Oid         lefttype;       /* lefttype */
    Oid         righttype;      /* righttype */
    Oid         sortfamily;     /* ordering operator's sort opfamily, or 0 */
    bool        ref_is_hard;    /* hard or soft dependency? */
    bool        ref_is_family;  /* is dependency on opclass or opfamily? */
    Oid         refobjid;       /* OID of opclass or opfamily */
} OpFamilyMember;


/*
 * Callback function signatures --- see indexam.sgml for more info.
 */

/* build new index */
typedef IndexBuildResult *(*ambuild_function) (Relation heapRelation,
                                               Relation indexRelation,
                                               struct IndexInfo *indexInfo);

/* build empty index */
typedef void (*ambuildempty_function) (Relation indexRelation);

/* insert this tuple */
typedef bool (*aminsert_function) (Relation indexRelation,
                                   Datum *values,
                                   bool *isnull,
                                   ItemPointer heap_tid,
                                   Relation heapRelation,
                                   IndexUniqueCheck checkUnique,
                                   bool indexUnchanged,
                                   struct IndexInfo *indexInfo);

/* bulk delete */
typedef IndexBulkDeleteResult *(*ambulkdelete_function) (IndexVacuumInfo *info,
                                                         IndexBulkDeleteResult *stats,
                                                         IndexBulkDeleteCallback callback,
                                                         void *callback_state);

/* post-VACUUM cleanup */
typedef IndexBulkDeleteResult *(*amvacuumcleanup_function) (IndexVacuumInfo *info,
                                                            IndexBulkDeleteResult *stats);

/* can indexscan return IndexTuples? */
typedef bool (*amcanreturn_function) (Relation indexRelation, int attno);

/* estimate cost of an indexscan */
typedef void (*amcostestimate_function) (struct PlannerInfo *root,
                                         struct IndexPath *path,
                                         double loop_count,
                                         Cost *indexStartupCost,
                                         Cost *indexTotalCost,
                                         Selectivity *indexSelectivity,
                                         double *indexCorrelation,
                                         double *indexPages);

/* parse index reloptions */
typedef bytea *(*amoptions_function) (Datum reloptions,
                                      bool validate);

/* report AM, index, or index column property */
typedef bool (*amproperty_function) (Oid index_oid, int attno,
                                     IndexAMProperty prop, const char *propname,
                                     bool *res, bool *isnull);

/* name of phase as used in progress reporting */
typedef char *(*ambuildphasename_function) (int64 phasenum);

/* validate definition of an opclass for this AM */
typedef bool (*amvalidate_function) (Oid opclassoid);

/* validate operators and support functions to be added to an opclass/family */
typedef void (*amadjustmembers_function) (Oid opfamilyoid,
                                          Oid opclassoid,
                                          List *operators,
                                          List *functions);

/* prepare for index scan */
typedef IndexScanDesc (*ambeginscan_function) (Relation indexRelation,
                                               int nkeys,
                                               int norderbys);

/* (re)start index scan */
typedef void (*amrescan_function) (IndexScanDesc scan,
                                   ScanKey keys,
                                   int nkeys,
                                   ScanKey orderbys,
                                   int norderbys);

/* next valid tuple */
typedef bool (*amgettuple_function) (IndexScanDesc scan,
                                     ScanDirection direction);

/* fetch all valid tuples */
typedef int64 (*amgetbitmap_function) (IndexScanDesc scan,
                                       TIDBitmap *tbm);

/* end index scan */
typedef void (*amendscan_function) (IndexScanDesc scan);

/* mark current scan position */
typedef void (*ammarkpos_function) (IndexScanDesc scan);

/* restore marked scan position */
typedef void (*amrestrpos_function) (IndexScanDesc scan);

/*
 * Callback function signatures - for parallel index scans.
 */

/* estimate size of parallel scan descriptor */
typedef Size (*amestimateparallelscan_function) (void);

/* prepare for parallel index scan */
typedef void (*aminitparallelscan_function) (void *target);

/* (re)start parallel index scan */
typedef void (*amparallelrescan_function) (IndexScanDesc scan);

/*
 * API struct for an index AM.  Note this must be stored in a single palloc'd
 * chunk of memory.
 */
typedef struct IndexAmRoutine
{
    NodeTag     type;

    /*
     * Total number of strategies (operators) by which we can traverse/search
     * this AM.  Zero if AM does not have a fixed set of strategy assignments.
     */
    uint16      amstrategies;
    /* total number of support functions that this AM uses */
    uint16      amsupport;
    /* opclass options support function number or 0 */
    uint16      amoptsprocnum;
    /* does AM support ORDER BY indexed column's value? */
    bool        amcanorder;
    /* does AM support ORDER BY result of an operator on indexed column? */
    bool        amcanorderbyop;
    /* does AM support backward scanning? */
    bool        amcanbackward;
    /* does AM support UNIQUE indexes? */
    bool        amcanunique;
    /* does AM support multi-column indexes? */
    bool        amcanmulticol;
    /* does AM require scans to have a constraint on the first index column? */
    bool        amoptionalkey;
    /* does AM handle ScalarArrayOpExpr quals? */
    bool        amsearcharray;
    /* does AM handle IS NULL/IS NOT NULL quals? */
    bool        amsearchnulls;
    /* can index storage data type differ from column data type? */
    bool        amstorage;
    /* can an index of this type be clustered on? */
    bool        amclusterable;
    /* does AM handle predicate locks? */
    bool        ampredlocks;
    /* does AM support parallel scan? */
    bool        amcanparallel;
    /* does AM support columns included with clause INCLUDE? */
    bool        amcaninclude;
    /* does AM use maintenance_work_mem? */
    bool        amusemaintenanceworkmem;
    /* OR of parallel vacuum flags.  See vacuum.h for flags. */
    uint8       amparallelvacuumoptions;
    /* type of data stored in index, or InvalidOid if variable */
    Oid         amkeytype;

    /*
     * If you add new properties to either the above or the below lists, then
     * they should also (usually) be exposed via the property API (see
     * IndexAMProperty at the top of the file, and utils/adt/amutils.c).
     */

    /* interface functions */
    ambuild_function ambuild;
    ambuildempty_function ambuildempty;
    aminsert_function aminsert;
    ambulkdelete_function ambulkdelete;
    amvacuumcleanup_function amvacuumcleanup;
    amcanreturn_function amcanreturn;   /* can be NULL */
    amcostestimate_function amcostestimate;
    amoptions_function amoptions;
    amproperty_function amproperty; /* can be NULL */
    ambuildphasename_function ambuildphasename; /* can be NULL */
    amvalidate_function amvalidate;
    amadjustmembers_function amadjustmembers;   /* can be NULL */
    ambeginscan_function ambeginscan;
    amrescan_function amrescan;
    amgettuple_function amgettuple; /* can be NULL */
    amgetbitmap_function amgetbitmap;   /* can be NULL */
    amendscan_function amendscan;
    ammarkpos_function ammarkpos;   /* can be NULL */
    amrestrpos_function amrestrpos; /* can be NULL */

    /* interface functions to support parallel index scans */
    amestimateparallelscan_function amestimateparallelscan; /* can be NULL */
    aminitparallelscan_function aminitparallelscan; /* can be NULL */
    amparallelrescan_function amparallelrescan; /* can be NULL */
} IndexAmRoutine;


/* Functions in access/index/amapi.c */
extern IndexAmRoutine *GetIndexAmRoutine(Oid amhandler);
extern IndexAmRoutine *GetIndexAmRoutineByAmId(Oid amoid, bool noerror);

#endif                          /* AMAPI_H */