heapam.h

Go to the documentation of this file.

/*-------------------------------------------------------------------------
 *
 * heapam.h
 *    POSTGRES heap access method definitions.
 *
 *
 * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/access/heapam.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef HEAPAM_H
#define HEAPAM_H
 
#include "access/relation.h"    /* for backward compatibility */
#include "access/relscan.h"
#include "access/sdir.h"
#include "access/skey.h"
#include "access/table.h"       /* for backward compatibility */
#include "access/tableam.h"
#include "nodes/lockoptions.h"
#include "nodes/primnodes.h"
#include "storage/bufpage.h"
#include "storage/dsm.h"
#include "storage/lockdefs.h"
#include "storage/read_stream.h"
#include "storage/shm_toc.h"
#include "utils/relcache.h"
#include "utils/snapshot.h"
 
 
/* "options" flag bits for heap_insert */
#define HEAP_INSERT_SKIP_FSM    TABLE_INSERT_SKIP_FSM
#define HEAP_INSERT_FROZEN      TABLE_INSERT_FROZEN
#define HEAP_INSERT_NO_LOGICAL  TABLE_INSERT_NO_LOGICAL
#define HEAP_INSERT_SPECULATIVE 0x0010
 
/* "options" flag bits for heap_page_prune_and_freeze */
#define HEAP_PAGE_PRUNE_MARK_UNUSED_NOW     (1 << 0)
#define HEAP_PAGE_PRUNE_FREEZE              (1 << 1)
 
typedef struct BulkInsertStateData *BulkInsertState;
struct TupleTableSlot;
struct VacuumCutoffs;
 
#define MaxLockTupleMode    LockTupleExclusive
 
/*
 * Descriptor for heap table scans.
 */
typedef struct HeapScanDescData
{
    TableScanDescData rs_base;  /* AM independent part of the descriptor */
 
    /* state set up at initscan time */
    BlockNumber rs_nblocks;     /* total number of blocks in rel */
    BlockNumber rs_startblock;  /* block # to start at */
    BlockNumber rs_numblocks;   /* max number of blocks to scan */
    /* rs_numblocks is usually InvalidBlockNumber, meaning "scan whole rel" */
 
    /* scan current state */
    bool        rs_inited;      /* false = scan not init'd yet */
    OffsetNumber rs_coffset;    /* current offset # in non-page-at-a-time mode */
    BlockNumber rs_cblock;      /* current block # in scan, if any */
    Buffer      rs_cbuf;        /* current buffer in scan, if any */
    /* NB: if rs_cbuf is not InvalidBuffer, we hold a pin on that buffer */
 
    BufferAccessStrategy rs_strategy;   /* access strategy for reads */
 
    HeapTupleData rs_ctup;      /* current tuple in scan, if any */
 
    /* For scans that stream reads */
    ReadStream *rs_read_stream;
 
    /*
     * For sequential scans and TID range scans to stream reads. The read
     * stream is allocated at the beginning of the scan and reset on rescan or
     * when the scan direction changes. The scan direction is saved each time
     * a new page is requested. If the scan direction changes from one page to
     * the next, the read stream releases all previously pinned buffers and
     * resets the prefetch block.
     */
    ScanDirection rs_dir;
    BlockNumber rs_prefetch_block;
 
    /*
     * For parallel scans to store page allocation data.  NULL when not
     * performing a parallel scan.
     */
    ParallelBlockTableScanWorkerData *rs_parallelworkerdata;
 
    /*
     * These fields are only used for bitmap scans for the "skip fetch"
     * optimization. Bitmap scans needing no fields from the heap may skip
     * fetching an all visible block, instead using the number of tuples per
     * block reported by the bitmap to determine how many NULL-filled tuples
     * to return.
     */
    Buffer      rs_vmbuffer;
    int         rs_empty_tuples_pending;
 
    /* these fields only used in page-at-a-time mode and for bitmap scans */
    int         rs_cindex;      /* current tuple's index in vistuples */
    int         rs_ntuples;     /* number of visible tuples on page */
    OffsetNumber rs_vistuples[MaxHeapTuplesPerPage];    /* their offsets */
}           HeapScanDescData;
typedef struct HeapScanDescData *HeapScanDesc;
 
/*
 * Descriptor for fetches from heap via an index.
 */
typedef struct IndexFetchHeapData
{
    IndexFetchTableData xs_base;    /* AM independent part of the descriptor */
 
    Buffer      xs_cbuf;        /* current heap buffer in scan, if any */
    /* NB: if xs_cbuf is not InvalidBuffer, we hold a pin on that buffer */
} IndexFetchHeapData;
 
/* Result codes for HeapTupleSatisfiesVacuum */
typedef enum
{
    HEAPTUPLE_DEAD,             /* tuple is dead and deletable */
    HEAPTUPLE_LIVE,             /* tuple is live (committed, no deleter) */
    HEAPTUPLE_RECENTLY_DEAD,    /* tuple is dead, but not deletable yet */
    HEAPTUPLE_INSERT_IN_PROGRESS,   /* inserting xact is still in progress */
    HEAPTUPLE_DELETE_IN_PROGRESS,   /* deleting xact is still in progress */
} HTSV_Result;
 
/*
 * heap_prepare_freeze_tuple may request that heap_freeze_execute_prepared
 * check any tuple's to-be-frozen xmin and/or xmax status using pg_xact
 */
#define     HEAP_FREEZE_CHECK_XMIN_COMMITTED    0x01
#define     HEAP_FREEZE_CHECK_XMAX_ABORTED      0x02
 
/* heap_prepare_freeze_tuple state describing how to freeze a tuple */
typedef struct HeapTupleFreeze
{
    /* Fields describing how to process tuple */
    TransactionId xmax;
    uint16      t_infomask2;
    uint16      t_infomask;
    uint8       frzflags;
 
    /* xmin/xmax check flags */
    uint8       checkflags;
    /* Page offset number for tuple */
    OffsetNumber offset;
} HeapTupleFreeze;
 
/*
 * State used by VACUUM to track the details of freezing all eligible tuples
 * on a given heap page.
 *
 * VACUUM prepares freeze plans for each page via heap_prepare_freeze_tuple
 * calls (every tuple with storage gets its own call).  This page-level freeze
 * state is updated across each call, which ultimately determines whether or
 * not freezing the page is required.
 *
 * Aside from the basic question of whether or not freezing will go ahead, the
 * state also tracks the oldest extant XID/MXID in the table as a whole, for
 * the purposes of advancing relfrozenxid/relminmxid values in pg_class later
 * on.  Each heap_prepare_freeze_tuple call pushes NewRelfrozenXid and/or
 * NewRelminMxid back as required to avoid unsafe final pg_class values.  Any
 * and all unfrozen XIDs or MXIDs that remain after VACUUM finishes _must_
 * have values >= the final relfrozenxid/relminmxid values in pg_class.  This
 * includes XIDs that remain as MultiXact members from any tuple's xmax.
 *
 * When 'freeze_required' flag isn't set after all tuples are examined, the
 * final choice on freezing is made by vacuumlazy.c.  It can decide to trigger
 * freezing based on whatever criteria it deems appropriate.  However, it is
 * recommended that vacuumlazy.c avoid early freezing when freezing does not
 * enable setting the target page all-frozen in the visibility map afterwards.
 */
typedef struct HeapPageFreeze
{
    /* Is heap_prepare_freeze_tuple caller required to freeze page? */
    bool        freeze_required;
 
    /*
     * "Freeze" NewRelfrozenXid/NewRelminMxid trackers.
     *
     * Trackers used when heap_freeze_execute_prepared freezes, or when there
     * are zero freeze plans for a page.  It is always valid for vacuumlazy.c
     * to freeze any page, by definition.  This even includes pages that have
     * no tuples with storage to consider in the first place.  That way the
     * 'totally_frozen' results from heap_prepare_freeze_tuple can always be
     * used in the same way, even when no freeze plans need to be executed to
     * "freeze the page".  Only the "freeze" path needs to consider the need
     * to set pages all-frozen in the visibility map under this scheme.
     *
     * When we freeze a page, we generally freeze all XIDs < OldestXmin, only
     * leaving behind XIDs that are ineligible for freezing, if any.  And so
     * you might wonder why these trackers are necessary at all; why should
     * _any_ page that VACUUM freezes _ever_ be left with XIDs/MXIDs that
     * ratchet back the top-level NewRelfrozenXid/NewRelminMxid trackers?
     *
     * It is useful to use a definition of "freeze the page" that does not
     * overspecify how MultiXacts are affected.  heap_prepare_freeze_tuple
     * generally prefers to remove Multis eagerly, but lazy processing is used
     * in cases where laziness allows VACUUM to avoid allocating a new Multi.
     * The "freeze the page" trackers enable this flexibility.
     */
    TransactionId FreezePageRelfrozenXid;
    MultiXactId FreezePageRelminMxid;
 
    /*
     * "No freeze" NewRelfrozenXid/NewRelminMxid trackers.
     *
     * These trackers are maintained in the same way as the trackers used when
     * VACUUM scans a page that isn't cleanup locked.  Both code paths are
     * based on the same general idea (do less work for this page during the
     * ongoing VACUUM, at the cost of having to accept older final values).
     */
    TransactionId NoFreezePageRelfrozenXid;
    MultiXactId NoFreezePageRelminMxid;
 
} HeapPageFreeze;
 
/*
 * Per-page state returned by heap_page_prune_and_freeze()
 */
typedef struct PruneFreezeResult
{
    int         ndeleted;       /* Number of tuples deleted from the page */
    int         nnewlpdead;     /* Number of newly LP_DEAD items */
    int         nfrozen;        /* Number of tuples we froze */
 
    /* Number of live and recently dead tuples on the page, after pruning */
    int         live_tuples;
    int         recently_dead_tuples;
 
    /*
     * all_visible and all_frozen indicate if the all-visible and all-frozen
     * bits in the visibility map can be set for this page, after pruning.
     *
     * vm_conflict_horizon is the newest xmin of live tuples on the page.  The
     * caller can use it as the conflict horizon when setting the VM bits.  It
     * is only valid if we froze some tuples (nfrozen > 0), and all_frozen is
     * true.
     *
     * These are only set if the HEAP_PRUNE_FREEZE option is set.
     */
    bool        all_visible;
    bool        all_frozen;
    TransactionId vm_conflict_horizon;
 
    /*
     * Whether or not the page makes rel truncation unsafe.  This is set to
     * 'true', even if the page contains LP_DEAD items.  VACUUM will remove
     * them before attempting to truncate.
     */
    bool        hastup;
 
    /*
     * LP_DEAD items on the page after pruning.  Includes existing LP_DEAD
     * items.
     */
    int         lpdead_items;
    OffsetNumber deadoffsets[MaxHeapTuplesPerPage];
} PruneFreezeResult;
 
/* 'reason' codes for heap_page_prune_and_freeze() */
typedef enum
{
    PRUNE_ON_ACCESS,            /* on-access pruning */
    PRUNE_VACUUM_SCAN,          /* VACUUM 1st heap pass */
    PRUNE_VACUUM_CLEANUP,       /* VACUUM 2nd heap pass */
} PruneReason;
 
/* ----------------
 *      function prototypes for heap access method
 *
 * heap_create, heap_create_with_catalog, and heap_drop_with_catalog
 * are declared in catalog/heap.h
 * ----------------
 */
 
 
/*
 * HeapScanIsValid
 *      True iff the heap scan is valid.
 */
#define HeapScanIsValid(scan) PointerIsValid(scan)
 
extern TableScanDesc heap_beginscan(Relation relation, Snapshot snapshot,
                                    int nkeys, ScanKey key,
                                    ParallelTableScanDesc parallel_scan,
                                    uint32 flags);
extern void heap_setscanlimits(TableScanDesc sscan, BlockNumber startBlk,
                               BlockNumber numBlks);
extern void heap_prepare_pagescan(TableScanDesc sscan);
extern void heap_rescan(TableScanDesc sscan, ScanKey key, bool set_params,
                        bool allow_strat, bool allow_sync, bool allow_pagemode);
extern void heap_endscan(TableScanDesc sscan);
extern HeapTuple heap_getnext(TableScanDesc sscan, ScanDirection direction);
extern bool heap_getnextslot(TableScanDesc sscan,
                             ScanDirection direction, struct TupleTableSlot *slot);
extern void heap_set_tidrange(TableScanDesc sscan, ItemPointer mintid,
                              ItemPointer maxtid);
extern bool heap_getnextslot_tidrange(TableScanDesc sscan,
                                      ScanDirection direction,
                                      TupleTableSlot *slot);
extern bool heap_fetch(Relation relation, Snapshot snapshot,
                       HeapTuple tuple, Buffer *userbuf, bool keep_buf);
extern bool heap_hot_search_buffer(ItemPointer tid, Relation relation,
                                   Buffer buffer, Snapshot snapshot, HeapTuple heapTuple,
                                   bool *all_dead, bool first_call);
 
extern void heap_get_latest_tid(TableScanDesc sscan, ItemPointer tid);
 
extern BulkInsertState GetBulkInsertState(void);
extern void FreeBulkInsertState(BulkInsertState);
extern void ReleaseBulkInsertStatePin(BulkInsertState bistate);
 
extern void heap_insert(Relation relation, HeapTuple tup, CommandId cid,
                        int options, BulkInsertState bistate);
extern void heap_multi_insert(Relation relation, struct TupleTableSlot **slots,
                              int ntuples, CommandId cid, int options,
                              BulkInsertState bistate);
extern TM_Result heap_delete(Relation relation, ItemPointer tid,
                             CommandId cid, Snapshot crosscheck, bool wait,
                             struct TM_FailureData *tmfd, bool changingPart);
extern void heap_finish_speculative(Relation relation, ItemPointer tid);
extern void heap_abort_speculative(Relation relation, ItemPointer tid);
extern TM_Result heap_update(Relation relation, ItemPointer otid,
                             HeapTuple newtup,
                             CommandId cid, Snapshot crosscheck, bool wait,
                             struct TM_FailureData *tmfd, LockTupleMode *lockmode,
                             TU_UpdateIndexes *update_indexes);
extern TM_Result heap_lock_tuple(Relation relation, HeapTuple tuple,
                                 CommandId cid, LockTupleMode mode, LockWaitPolicy wait_policy,
                                 bool follow_updates,
                                 Buffer *buffer, struct TM_FailureData *tmfd);
 
extern void heap_inplace_update(Relation relation, HeapTuple tuple);
extern bool heap_prepare_freeze_tuple(HeapTupleHeader tuple,
                                      const struct VacuumCutoffs *cutoffs,
                                      HeapPageFreeze *pagefrz,
                                      HeapTupleFreeze *frz, bool *totally_frozen);
 
extern void heap_pre_freeze_checks(Buffer buffer,
                                   HeapTupleFreeze *tuples, int ntuples);
extern void heap_freeze_prepared_tuples(Buffer buffer,
                                        HeapTupleFreeze *tuples, int ntuples);
extern bool heap_freeze_tuple(HeapTupleHeader tuple,
                              TransactionId relfrozenxid, TransactionId relminmxid,
                              TransactionId FreezeLimit, TransactionId MultiXactCutoff);
extern bool heap_tuple_should_freeze(HeapTupleHeader tuple,
                                     const struct VacuumCutoffs *cutoffs,
                                     TransactionId *NoFreezePageRelfrozenXid,
                                     MultiXactId *NoFreezePageRelminMxid);
extern bool heap_tuple_needs_eventual_freeze(HeapTupleHeader tuple);
 
extern void simple_heap_insert(Relation relation, HeapTuple tup);
extern void simple_heap_delete(Relation relation, ItemPointer tid);
extern void simple_heap_update(Relation relation, ItemPointer otid,
                               HeapTuple tup, TU_UpdateIndexes *update_indexes);
 
extern TransactionId heap_index_delete_tuples(Relation rel,
                                              TM_IndexDeleteOp *delstate);
 
/* in heap/pruneheap.c */
struct GlobalVisState;
extern void heap_page_prune_opt(Relation relation, Buffer buffer);
extern void heap_page_prune_and_freeze(Relation relation, Buffer buffer,
                                       struct GlobalVisState *vistest,
                                       int options,
                                       struct VacuumCutoffs *cutoffs,
                                       PruneFreezeResult *presult,
                                       PruneReason reason,
                                       OffsetNumber *off_loc,
                                       TransactionId *new_relfrozen_xid,
                                       MultiXactId *new_relmin_mxid);
extern void heap_page_prune_execute(Buffer buffer, bool lp_truncate_only,
                                    OffsetNumber *redirected, int nredirected,
                                    OffsetNumber *nowdead, int ndead,
                                    OffsetNumber *nowunused, int nunused);
extern void heap_get_root_tuples(Page page, OffsetNumber *root_offsets);
extern void log_heap_prune_and_freeze(Relation relation, Buffer buffer,
                                      TransactionId conflict_xid,
                                      bool lp_truncate_only,
                                      PruneReason reason,
                                      HeapTupleFreeze *frozen, int nfrozen,
                                      OffsetNumber *redirected, int nredirected,
                                      OffsetNumber *dead, int ndead,
                                      OffsetNumber *unused, int nunused);
 
/* in heap/vacuumlazy.c */
struct VacuumParams;
extern void heap_vacuum_rel(Relation rel,
                            struct VacuumParams *params, BufferAccessStrategy bstrategy);
 
/* in heap/heapam_visibility.c */
extern bool HeapTupleSatisfiesVisibility(HeapTuple htup, Snapshot snapshot,
                                         Buffer buffer);
extern TM_Result HeapTupleSatisfiesUpdate(HeapTuple htup, CommandId curcid,
                                          Buffer buffer);
extern HTSV_Result HeapTupleSatisfiesVacuum(HeapTuple htup, TransactionId OldestXmin,
                                            Buffer buffer);
extern HTSV_Result HeapTupleSatisfiesVacuumHorizon(HeapTuple htup, Buffer buffer,
                                                   TransactionId *dead_after);
extern void HeapTupleSetHintBits(HeapTupleHeader tuple, Buffer buffer,
                                 uint16 infomask, TransactionId xid);
extern bool HeapTupleHeaderIsOnlyLocked(HeapTupleHeader tuple);
extern bool HeapTupleIsSurelyDead(HeapTuple htup,
                                  struct GlobalVisState *vistest);
 
/*
 * To avoid leaking too much knowledge about reorderbuffer implementation
 * details this is implemented in reorderbuffer.c not heapam_visibility.c
 */
struct HTAB;
extern bool ResolveCminCmaxDuringDecoding(struct HTAB *tuplecid_data,
                                          Snapshot snapshot,
                                          HeapTuple htup,
                                          Buffer buffer,
                                          CommandId *cmin, CommandId *cmax);
extern void HeapCheckForSerializableConflictOut(bool visible, Relation relation, HeapTuple tuple,
                                                Buffer buffer, Snapshot snapshot);
 
#endif                          /* HEAPAM_H */