pg_waldump.h

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/*-------------------------------------------------------------------------
 *
 * pg_waldump.h - decode and display WAL
 *
 * Copyright (c) 2026, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *        src/bin/pg_waldump/pg_waldump.h
 *-------------------------------------------------------------------------
 */
#ifndef PG_WALDUMP_H
#define PG_WALDUMP_H
 
#include "access/xlogdefs.h"
#include "fe_utils/astreamer.h"
 
/* Forward declaration */
struct ArchivedWALFile;
struct ArchivedWAL_hash;
 
/* Temporary directory for spilling out-of-order WAL segments from archives */
extern char *TmpWalSegDir;
 
/* Contains the necessary information to drive WAL decoding */
typedef struct XLogDumpPrivate
{
    TimeLineID  timeline;
    int         segsize;
    XLogRecPtr  startptr;
    XLogRecPtr  endptr;
    bool        endptr_reached;
    bool        decoding_started;
 
    /* Fields required to read WAL from archive */
    char       *archive_dir;
    char       *archive_name;   /* Tar archive filename */
    int         archive_fd;     /* File descriptor for the open tar file */
    bool        archive_fd_eof; /* Have we reached EOF on archive_fd? */
 
    astreamer  *archive_streamer;
    char       *archive_read_buf;   /* Reusable read buffer for archive I/O */
    size_t      archive_read_buf_size;
 
    /*
     * The buffer for the WAL file the archive streamer is currently reading,
     * or NULL if none.  It is quite risky to examine this anywhere except in
     * astreamer_waldump_content(), since it can change multiple times during
     * a single read_archive_file() call.  However, it is safe to assume that
     * if cur_file is different from a particular ArchivedWALFile of interest,
     * then the archive streamer has finished reading that file.
     */
    struct ArchivedWALFile *cur_file;
 
    /*
     * Hash table of WAL segments currently buffered from the archive,
     * including any segment currently being streamed.  Entries are removed
     * once consumed, so this does not accumulate all segments ever read.
     */
    struct ArchivedWAL_hash *archive_wal_htab;
 
    /*
     * Pre-computed segment numbers derived from startptr and endptr. Caching
     * them avoids repeated XLByteToSeg() calls when filtering each archive
     * member against the requested WAL range.  end_segno is initialized to
     * UINT64_MAX when no end limit is requested.
     */
    XLogSegNo   start_segno;
    XLogSegNo   end_segno;
} XLogDumpPrivate;
 
extern int  open_file_in_directory(const char *directory, const char *fname);
 
extern void init_archive_reader(XLogDumpPrivate *privateInfo,
                                pg_compress_algorithm compression);
extern void free_archive_reader(XLogDumpPrivate *privateInfo);
extern int  read_archive_wal_page(XLogDumpPrivate *privateInfo,
                                  XLogRecPtr targetPagePtr,
                                  size_t count, char *readBuff);
extern void free_archive_wal_entry(const char *fname,
                                   XLogDumpPrivate *privateInfo);
 
#endif                          /* PG_WALDUMP_H */