genam.h

Go to the documentation of this file.

/*-------------------------------------------------------------------------
 *
 * genam.h
 *    POSTGRES generalized index access method definitions.
 *
 *
 * Portions Copyright (c) 1996-2013, 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/sdir.h"
#include "access/skey.h"
#include "nodes/tidbitmap.h"
#include "storage/lock.h"
#include "utils/relcache.h"
#include "utils/snapshot.h"

/*
 * 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).  It will
 * always just be an estimate during ambulkdelete.
 */
typedef struct IndexVacuumInfo
{
    Relation    index;          /* the index being vacuumed */
    bool        analyze_only;   /* ANALYZE (without any actual vacuum) */
    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_removed is the amount by which the index physically shrank,
 * if any (ie the change in its total size on disk).  pages_deleted and
 * pages_free refer to free space within the index file.  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 */
    BlockNumber pages_removed;  /* # removed during vacuum operation */
    bool        estimated_count;    /* num_index_tuples is an estimate */
    double      num_index_tuples;       /* tuples remaining */
    double      tuples_removed; /* # removed during vacuum operation */
    BlockNumber pages_deleted;  /* # unused pages in index */
    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;

/*
 * 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;


/*
 * generalized index_ interface routines (in indexam.c)
 */

/*
 * IndexScanIsValid
 *      True iff the index scan is valid.
 */
#define IndexScanIsValid(scan) PointerIsValid(scan)

extern Relation 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);

extern IndexScanDesc index_beginscan(Relation heapRelation,
                Relation indexRelation,
                Snapshot snapshot,
                int nkeys, int norderbys);
extern IndexScanDesc index_beginscan_bitmap(Relation indexRelation,
                       Snapshot snapshot,
                       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 ItemPointer index_getnext_tid(IndexScanDesc scan,
                  ScanDirection direction);
extern HeapTuple index_fetch_heap(IndexScanDesc scan);
extern HeapTuple index_getnext(IndexScanDesc scan, ScanDirection direction);
extern int64 index_getbitmap(IndexScanDesc scan, TIDBitmap *bitmap);

extern IndexBulkDeleteResult *index_bulk_delete(IndexVacuumInfo *info,
                  IndexBulkDeleteResult *stats,
                  IndexBulkDeleteCallback callback,
                  void *callback_state);
extern IndexBulkDeleteResult *index_vacuum_cleanup(IndexVacuumInfo *info,
                     IndexBulkDeleteResult *stats);
extern bool index_can_return(Relation indexRelation);
extern RegProcedure index_getprocid(Relation irel, AttrNumber attnum,
                uint16 procnum);
extern FmgrInfo *index_getprocinfo(Relation irel, AttrNumber attnum,
                  uint16 procnum);

/*
 * 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,
                           Datum *values, bool *isnull);

/*
 * 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);

#endif   /* GENAM_H */