heapam_xlog.h

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/*-------------------------------------------------------------------------
 *
 * heapam_xlog.h
 *    POSTGRES heap access XLOG definitions.
 *
 *
 * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 * src/include/access/heapam_xlog.h
 *
 *-------------------------------------------------------------------------
 */
#ifndef HEAPAM_XLOG_H
#define HEAPAM_XLOG_H
 
#include "access/htup.h"
#include "access/xlogreader.h"
#include "lib/stringinfo.h"
#include "storage/buf.h"
#include "storage/bufpage.h"
#include "storage/relfilelocator.h"
#include "utils/relcache.h"
 
 
/*
 * WAL record definitions for heapam.c's WAL operations
 *
 * XLOG allows to store some information in high 4 bits of log
 * record xl_info field.  We use 3 for opcode and one for init bit.
 */
#define XLOG_HEAP_INSERT        0x00
#define XLOG_HEAP_DELETE        0x10
#define XLOG_HEAP_UPDATE        0x20
#define XLOG_HEAP_TRUNCATE      0x30
#define XLOG_HEAP_HOT_UPDATE    0x40
#define XLOG_HEAP_CONFIRM       0x50
#define XLOG_HEAP_LOCK          0x60
#define XLOG_HEAP_INPLACE       0x70
 
#define XLOG_HEAP_OPMASK        0x70
/*
 * When we insert 1st item on new page in INSERT, UPDATE, HOT_UPDATE,
 * or MULTI_INSERT, we can (and we do) restore entire page in redo
 */
#define XLOG_HEAP_INIT_PAGE     0x80
/*
 * We ran out of opcodes, so heapam.c now has a second RmgrId.  These opcodes
 * are associated with RM_HEAP2_ID, but are not logically different from
 * the ones above associated with RM_HEAP_ID.  XLOG_HEAP_OPMASK applies to
 * these, too.
 *
 * There's no difference between XLOG_HEAP2_PRUNE_ON_ACCESS,
 * XLOG_HEAP2_PRUNE_VACUUM_SCAN and XLOG_HEAP2_PRUNE_VACUUM_CLEANUP records.
 * They have separate opcodes just for debugging and analysis purposes, to
 * indicate why the WAL record was emitted.
 */
#define XLOG_HEAP2_REWRITE      0x00
#define XLOG_HEAP2_PRUNE_ON_ACCESS      0x10
#define XLOG_HEAP2_PRUNE_VACUUM_SCAN    0x20
#define XLOG_HEAP2_PRUNE_VACUUM_CLEANUP 0x30
#define XLOG_HEAP2_VISIBLE      0x40
#define XLOG_HEAP2_MULTI_INSERT 0x50
#define XLOG_HEAP2_LOCK_UPDATED 0x60
#define XLOG_HEAP2_NEW_CID      0x70
 
/*
 * xl_heap_insert/xl_heap_multi_insert flag values, 8 bits are available.
 */
/* PD_ALL_VISIBLE was cleared */
#define XLH_INSERT_ALL_VISIBLE_CLEARED          (1<<0)
#define XLH_INSERT_LAST_IN_MULTI                (1<<1)
#define XLH_INSERT_IS_SPECULATIVE               (1<<2)
#define XLH_INSERT_CONTAINS_NEW_TUPLE           (1<<3)
#define XLH_INSERT_ON_TOAST_RELATION            (1<<4)
 
/* all_frozen_set always implies all_visible_set */
#define XLH_INSERT_ALL_FROZEN_SET               (1<<5)
 
/*
 * xl_heap_update flag values, 8 bits are available.
 */
/* PD_ALL_VISIBLE was cleared */
#define XLH_UPDATE_OLD_ALL_VISIBLE_CLEARED      (1<<0)
/* PD_ALL_VISIBLE was cleared in the 2nd page */
#define XLH_UPDATE_NEW_ALL_VISIBLE_CLEARED      (1<<1)
#define XLH_UPDATE_CONTAINS_OLD_TUPLE           (1<<2)
#define XLH_UPDATE_CONTAINS_OLD_KEY             (1<<3)
#define XLH_UPDATE_CONTAINS_NEW_TUPLE           (1<<4)
#define XLH_UPDATE_PREFIX_FROM_OLD              (1<<5)
#define XLH_UPDATE_SUFFIX_FROM_OLD              (1<<6)
 
/* convenience macro for checking whether any form of old tuple was logged */
#define XLH_UPDATE_CONTAINS_OLD                     \
    (XLH_UPDATE_CONTAINS_OLD_TUPLE | XLH_UPDATE_CONTAINS_OLD_KEY)
 
/*
 * xl_heap_delete flag values, 8 bits are available.
 */
/* PD_ALL_VISIBLE was cleared */
#define XLH_DELETE_ALL_VISIBLE_CLEARED          (1<<0)
#define XLH_DELETE_CONTAINS_OLD_TUPLE           (1<<1)
#define XLH_DELETE_CONTAINS_OLD_KEY             (1<<2)
#define XLH_DELETE_IS_SUPER                     (1<<3)
#define XLH_DELETE_IS_PARTITION_MOVE            (1<<4)
 
/* convenience macro for checking whether any form of old tuple was logged */
#define XLH_DELETE_CONTAINS_OLD                     \
    (XLH_DELETE_CONTAINS_OLD_TUPLE | XLH_DELETE_CONTAINS_OLD_KEY)
 
/* This is what we need to know about delete */
typedef struct xl_heap_delete
{
    TransactionId xmax;         /* xmax of the deleted tuple */
    OffsetNumber offnum;        /* deleted tuple's offset */
    uint8       infobits_set;   /* infomask bits */
    uint8       flags;
} xl_heap_delete;
 
#define SizeOfHeapDelete    (offsetof(xl_heap_delete, flags) + sizeof(uint8))
 
/*
 * xl_heap_truncate flag values, 8 bits are available.
 */
#define XLH_TRUNCATE_CASCADE                    (1<<0)
#define XLH_TRUNCATE_RESTART_SEQS               (1<<1)
 
/*
 * For truncate we list all truncated relids in an array, followed by all
 * sequence relids that need to be restarted, if any.
 * All rels are always within the same database, so we just list dbid once.
 */
typedef struct xl_heap_truncate
{
    Oid         dbId;
    uint32      nrelids;
    uint8       flags;
    Oid         relids[FLEXIBLE_ARRAY_MEMBER];
} xl_heap_truncate;
 
#define SizeOfHeapTruncate  (offsetof(xl_heap_truncate, relids))
 
/*
 * We don't store the whole fixed part (HeapTupleHeaderData) of an inserted
 * or updated tuple in WAL; we can save a few bytes by reconstructing the
 * fields that are available elsewhere in the WAL record, or perhaps just
 * plain needn't be reconstructed.  These are the fields we must store.
 */
typedef struct xl_heap_header
{
    uint16      t_infomask2;
    uint16      t_infomask;
    uint8       t_hoff;
} xl_heap_header;
 
#define SizeOfHeapHeader    (offsetof(xl_heap_header, t_hoff) + sizeof(uint8))
 
/* This is what we need to know about insert */
typedef struct xl_heap_insert
{
    OffsetNumber offnum;        /* inserted tuple's offset */
    uint8       flags;
 
    /* xl_heap_header & TUPLE DATA in backup block 0 */
} xl_heap_insert;
 
#define SizeOfHeapInsert    (offsetof(xl_heap_insert, flags) + sizeof(uint8))
 
/*
 * This is what we need to know about a multi-insert.
 *
 * The main data of the record consists of this xl_heap_multi_insert header.
 * 'offsets' array is omitted if the whole page is reinitialized
 * (XLOG_HEAP_INIT_PAGE).
 *
 * In block 0's data portion, there is an xl_multi_insert_tuple struct,
 * followed by the tuple data for each tuple. There is padding to align
 * each xl_multi_insert_tuple struct.
 */
typedef struct xl_heap_multi_insert
{
    uint8       flags;
    uint16      ntuples;
    OffsetNumber offsets[FLEXIBLE_ARRAY_MEMBER];
} xl_heap_multi_insert;
 
#define SizeOfHeapMultiInsert   offsetof(xl_heap_multi_insert, offsets)
 
typedef struct xl_multi_insert_tuple
{
    uint16      datalen;        /* size of tuple data that follows */
    uint16      t_infomask2;
    uint16      t_infomask;
    uint8       t_hoff;
    /* TUPLE DATA FOLLOWS AT END OF STRUCT */
} xl_multi_insert_tuple;
 
#define SizeOfMultiInsertTuple  (offsetof(xl_multi_insert_tuple, t_hoff) + sizeof(uint8))
 
/*
 * This is what we need to know about update|hot_update
 *
 * Backup blk 0: new page
 *
 * If XLH_UPDATE_PREFIX_FROM_OLD or XLH_UPDATE_SUFFIX_FROM_OLD flags are set,
 * the prefix and/or suffix come first, as one or two uint16s.
 *
 * After that, xl_heap_header and new tuple data follow.  The new tuple
 * data doesn't include the prefix and suffix, which are copied from the
 * old tuple on replay.
 *
 * If XLH_UPDATE_CONTAINS_NEW_TUPLE flag is given, the tuple data is
 * included even if a full-page image was taken.
 *
 * Backup blk 1: old page, if different. (no data, just a reference to the blk)
 */
typedef struct xl_heap_update
{
    TransactionId old_xmax;     /* xmax of the old tuple */
    OffsetNumber old_offnum;    /* old tuple's offset */
    uint8       old_infobits_set;   /* infomask bits to set on old tuple */
    uint8       flags;
    TransactionId new_xmax;     /* xmax of the new tuple */
    OffsetNumber new_offnum;    /* new tuple's offset */
 
    /*
     * If XLH_UPDATE_CONTAINS_OLD_TUPLE or XLH_UPDATE_CONTAINS_OLD_KEY flags
     * are set, xl_heap_header and tuple data for the old tuple follow.
     */
} xl_heap_update;
 
#define SizeOfHeapUpdate    (offsetof(xl_heap_update, new_offnum) + sizeof(OffsetNumber))
 
/*
 * These structures and flags encode VACUUM pruning and freezing and on-access
 * pruning page modifications.
 *
 * xl_heap_prune is the main record.  The XLHP_HAS_* flags indicate which
 * "sub-records" are included and the other XLHP_* flags provide additional
 * information about the conditions for replay.
 *
 * The data for block reference 0 contains "sub-records" depending on which of
 * the XLHP_HAS_* flags are set.  See xlhp_* struct definitions below.  The
 * sub-records appear in the same order as the XLHP_* flags.  An example
 * record with every sub-record included:
 *
 *-----------------------------------------------------------------------------
 * Main data section:
 *
 *  xl_heap_prune
 *      uint8               flags
 *  TransactionId           snapshot_conflict_horizon
 *
 * Block 0 data section:
 *
 *  xlhp_freeze_plans
 *      uint16              nplans
 *      [2 bytes of padding]
 *      xlhp_freeze_plan    plans[nplans]
 *
 *  xlhp_prune_items
 *      uint16              nredirected
 *      OffsetNumber        redirected[2 * nredirected]
 *
 *  xlhp_prune_items
 *      uint16              ndead
 *      OffsetNumber        nowdead[ndead]
 *
 *  xlhp_prune_items
 *      uint16              nunused
 *      OffsetNumber        nowunused[nunused]
 *
 *  OffsetNumber            frz_offsets[sum([plan.ntuples for plan in plans])]
 *-----------------------------------------------------------------------------
 *
 * NOTE: because the record data is assembled from many optional parts, we
 * have to pay close attention to alignment.  In the main data section,
 * 'snapshot_conflict_horizon' is stored unaligned after 'flags', to save
 * space.  In the block 0 data section, the freeze plans appear first, because
 * they contain TransactionId fields that require 4-byte alignment.  All the
 * other fields require only 2-byte alignment.  This is also the reason that
 * 'frz_offsets' is stored separately from the xlhp_freeze_plan structs.
 */
typedef struct xl_heap_prune
{
    uint8       reason;
    uint8       flags;
 
    /*
     * If XLHP_HAS_CONFLICT_HORIZON is set, the conflict horizon XID follows,
     * unaligned
     */
} xl_heap_prune;
 
#define SizeOfHeapPrune (offsetof(xl_heap_prune, flags) + sizeof(uint8))
 
/* to handle recovery conflict during logical decoding on standby */
#define     XLHP_IS_CATALOG_REL         (1 << 1)
 
/*
 * Does replaying the record require a cleanup-lock?
 *
 * Pruning, in VACUUM's first pass or when otherwise accessing a page,
 * requires a cleanup lock.  For freezing, and VACUUM's second pass which
 * marks LP_DEAD line pointers as unused without moving any tuple data, an
 * ordinary exclusive lock is sufficient.
 */
#define     XLHP_CLEANUP_LOCK          (1 << 2)
 
/*
 * If we remove or freeze any entries that contain xids, we need to include a
 * snapshot conflict horizon.  It's used in Hot Standby mode to ensure that
 * there are no queries running for which the removed tuples are still
 * visible, or which still consider the frozen XIDs as running.
 */
#define     XLHP_HAS_CONFLICT_HORIZON   (1 << 3)
 
/*
 * Indicates that an xlhp_freeze_plans sub-record and one or more
 * xlhp_freeze_plan sub-records are present.
 */
#define     XLHP_HAS_FREEZE_PLANS       (1 << 4)
 
/*
 * XLHP_HAS_REDIRECTIONS, XLHP_HAS_DEAD_ITEMS, and XLHP_HAS_NOW_UNUSED_ITEMS
 * indicate that xlhp_prune_items sub-records with redirected, dead, and
 * unused item offsets are present.
 */
#define     XLHP_HAS_REDIRECTIONS       (1 << 5)
#define     XLHP_HAS_DEAD_ITEMS         (1 << 6)
#define     XLHP_HAS_NOW_UNUSED_ITEMS   (1 << 7)
 
/*
 * xlhp_freeze_plan describes how to freeze a group of one or more heap tuples
 * (appears in xl_heap_prune's xlhp_freeze_plans sub-record)
 */
/* 0x01 was XLH_FREEZE_XMIN */
#define     XLH_FREEZE_XVAC     0x02
#define     XLH_INVALID_XVAC    0x04
 
typedef struct xlhp_freeze_plan
{
    TransactionId xmax;
    uint16      t_infomask2;
    uint16      t_infomask;
    uint8       frzflags;
 
    /* Length of individual page offset numbers array for this plan */
    uint16      ntuples;
} xlhp_freeze_plan;
 
/*
 * This is what we need to know about a block being frozen during vacuum
 *
 * The backup block's data contains an array of xlhp_freeze_plan structs (with
 * nplans elements).  The individual item offsets are located in an array at
 * the end of the entire record with nplans * (each plan's ntuples) members
 * Those offsets are in the same order as the plans.  The REDO routine uses
 * the offsets to freeze the corresponding heap tuples.
 *
 * (As of PostgreSQL 17, XLOG_HEAP2_PRUNE_VACUUM_SCAN records replace the
 * separate XLOG_HEAP2_FREEZE_PAGE records.)
 */
typedef struct xlhp_freeze_plans
{
    uint16      nplans;
    xlhp_freeze_plan plans[FLEXIBLE_ARRAY_MEMBER];
} xlhp_freeze_plans;
 
/*
 * Generic sub-record type contained in block reference 0 of an xl_heap_prune
 * record and used for redirect, dead, and unused items if any of
 * XLHP_HAS_REDIRECTIONS/XLHP_HAS_DEAD_ITEMS/XLHP_HAS_NOW_UNUSED_ITEMS are
 * set.  Note that in the XLHP_HAS_REDIRECTIONS variant, there are actually 2
 * * length number of OffsetNumbers in the data.
 */
typedef struct xlhp_prune_items
{
    uint16      ntargets;
    OffsetNumber data[FLEXIBLE_ARRAY_MEMBER];
} xlhp_prune_items;
 
 
/* flags for infobits_set */
#define XLHL_XMAX_IS_MULTI      0x01
#define XLHL_XMAX_LOCK_ONLY     0x02
#define XLHL_XMAX_EXCL_LOCK     0x04
#define XLHL_XMAX_KEYSHR_LOCK   0x08
#define XLHL_KEYS_UPDATED       0x10
 
/* flag bits for xl_heap_lock / xl_heap_lock_updated's flag field */
#define XLH_LOCK_ALL_FROZEN_CLEARED     0x01
 
/* This is what we need to know about lock */
typedef struct xl_heap_lock
{
    TransactionId xmax;         /* might be a MultiXactId */
    OffsetNumber offnum;        /* locked tuple's offset on page */
    uint8       infobits_set;   /* infomask and infomask2 bits to set */
    uint8       flags;          /* XLH_LOCK_* flag bits */
} xl_heap_lock;
 
#define SizeOfHeapLock  (offsetof(xl_heap_lock, flags) + sizeof(uint8))
 
/* This is what we need to know about locking an updated version of a row */
typedef struct xl_heap_lock_updated
{
    TransactionId xmax;
    OffsetNumber offnum;
    uint8       infobits_set;
    uint8       flags;
} xl_heap_lock_updated;
 
#define SizeOfHeapLockUpdated   (offsetof(xl_heap_lock_updated, flags) + sizeof(uint8))
 
/* This is what we need to know about confirmation of speculative insertion */
typedef struct xl_heap_confirm
{
    OffsetNumber offnum;        /* confirmed tuple's offset on page */
} xl_heap_confirm;
 
#define SizeOfHeapConfirm   (offsetof(xl_heap_confirm, offnum) + sizeof(OffsetNumber))
 
/* This is what we need to know about in-place update */
typedef struct xl_heap_inplace
{
    OffsetNumber offnum;        /* updated tuple's offset on page */
    /* TUPLE DATA FOLLOWS AT END OF STRUCT */
} xl_heap_inplace;
 
#define SizeOfHeapInplace   (offsetof(xl_heap_inplace, offnum) + sizeof(OffsetNumber))
 
/*
 * This is what we need to know about setting a visibility map bit
 *
 * Backup blk 0: visibility map buffer
 * Backup blk 1: heap buffer
 */
typedef struct xl_heap_visible
{
    TransactionId snapshotConflictHorizon;
    uint8       flags;
} xl_heap_visible;
 
#define SizeOfHeapVisible (offsetof(xl_heap_visible, flags) + sizeof(uint8))
 
typedef struct xl_heap_new_cid
{
    /*
     * store toplevel xid so we don't have to merge cids from different
     * transactions
     */
    TransactionId top_xid;
    CommandId   cmin;
    CommandId   cmax;
    CommandId   combocid;       /* just for debugging */
 
    /*
     * Store the relfilelocator/ctid pair to facilitate lookups.
     */
    RelFileLocator target_locator;
    ItemPointerData target_tid;
} xl_heap_new_cid;
 
#define SizeOfHeapNewCid (offsetof(xl_heap_new_cid, target_tid) + sizeof(ItemPointerData))
 
/* logical rewrite xlog record header */
typedef struct xl_heap_rewrite_mapping
{
    TransactionId mapped_xid;   /* xid that might need to see the row */
    Oid         mapped_db;      /* DbOid or InvalidOid for shared rels */
    Oid         mapped_rel;     /* Oid of the mapped relation */
    off_t       offset;         /* How far have we written so far */
    uint32      num_mappings;   /* Number of in-memory mappings */
    XLogRecPtr  start_lsn;      /* Insert LSN at begin of rewrite */
} xl_heap_rewrite_mapping;
 
extern void HeapTupleHeaderAdvanceConflictHorizon(HeapTupleHeader tuple,
                                                  TransactionId *snapshotConflictHorizon);
 
extern void heap_redo(XLogReaderState *record);
extern void heap_desc(StringInfo buf, XLogReaderState *record);
extern const char *heap_identify(uint8 info);
extern void heap_mask(char *pagedata, BlockNumber blkno);
extern void heap2_redo(XLogReaderState *record);
extern void heap2_desc(StringInfo buf, XLogReaderState *record);
extern const char *heap2_identify(uint8 info);
extern void heap_xlog_logical_rewrite(XLogReaderState *r);
 
extern XLogRecPtr log_heap_visible(Relation rel, Buffer heap_buffer,
                                   Buffer vm_buffer,
                                   TransactionId snapshotConflictHorizon,
                                   uint8 vmflags);
 
/* in heapdesc.c, so it can be shared between frontend/backend code */
extern void heap_xlog_deserialize_prune_and_freeze(char *cursor, uint8 flags,
                                                   int *nplans, xlhp_freeze_plan **plans,
                                                   OffsetNumber **frz_offsets,
                                                   int *nredirected, OffsetNumber **redirected,
                                                   int *ndead, OffsetNumber **nowdead,
                                                   int *nunused, OffsetNumber **nowunused);
 
#endif                          /* HEAPAM_XLOG_H */