pg_backup_directory.c

Go to the documentation of this file.

/*-------------------------------------------------------------------------
 *
 * pg_backup_directory.c
 *
 *  A directory format dump is a directory, which contains a "toc.dat" file
 *  for the TOC, and a separate file for each data entry, named "<oid>.dat".
 *  Large objects are stored in separate files named "blob_<oid>.dat",
 *  and there's a plain-text TOC file for each BLOBS TOC entry named
 *  "blobs_<dumpID>.toc" (or just "blobs.toc" in archive versions before 16).
 *
 *  If compression is used, each data file is individually compressed and the
 *  ".gz" suffix is added to the filenames. The TOC files are never
 *  compressed by pg_dump, however they are accepted with the .gz suffix too,
 *  in case the user has manually compressed them with 'gzip'.
 *
 *  NOTE: This format is identical to the files written in the tar file in
 *  the 'tar' format, except that we don't write the restore.sql file (TODO),
 *  and the tar format doesn't support compression. Please keep the formats in
 *  sync.
 *
 *
 *  Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
 *  Portions Copyright (c) 1994, Regents of the University of California
 *  Portions Copyright (c) 2000, Philip Warner
 *
 *  Rights are granted to use this software in any way so long
 *  as this notice is not removed.
 *
 *  The author is not responsible for loss or damages that may
 *  result from its use.
 *
 * IDENTIFICATION
 *      src/bin/pg_dump/pg_backup_directory.c
 *
 *-------------------------------------------------------------------------
 */
#include "postgres_fe.h"
 
#include <dirent.h>
#include <sys/stat.h>
 
#include "common/file_utils.h"
#include "compress_io.h"
#include "parallel.h"
#include "pg_backup_utils.h"
 
typedef struct
{
    /*
     * Our archive location. This is basically what the user specified as his
     * backup file but of course here it is a directory.
     */
    char       *directory;
 
    CompressFileHandle *dataFH; /* currently open data file */
    CompressFileHandle *LOsTocFH;   /* file handle for blobs_NNN.toc */
    ParallelState *pstate;      /* for parallel backup / restore */
} lclContext;
 
typedef struct
{
    char       *filename;       /* filename excluding the directory (basename) */
} lclTocEntry;
 
/* prototypes for private functions */
static void _ArchiveEntry(ArchiveHandle *AH, TocEntry *te);
static void _StartData(ArchiveHandle *AH, TocEntry *te);
static void _EndData(ArchiveHandle *AH, TocEntry *te);
static void _WriteData(ArchiveHandle *AH, const void *data, size_t dLen);
static int  _WriteByte(ArchiveHandle *AH, const int i);
static int  _ReadByte(ArchiveHandle *AH);
static void _WriteBuf(ArchiveHandle *AH, const void *buf, size_t len);
static void _ReadBuf(ArchiveHandle *AH, void *buf, size_t len);
static void _CloseArchive(ArchiveHandle *AH);
static void _ReopenArchive(ArchiveHandle *AH);
static void _PrintTocData(ArchiveHandle *AH, TocEntry *te);
 
static void _WriteExtraToc(ArchiveHandle *AH, TocEntry *te);
static void _ReadExtraToc(ArchiveHandle *AH, TocEntry *te);
static void _PrintExtraToc(ArchiveHandle *AH, TocEntry *te);
 
static void _StartLOs(ArchiveHandle *AH, TocEntry *te);
static void _StartLO(ArchiveHandle *AH, TocEntry *te, Oid oid);
static void _EndLO(ArchiveHandle *AH, TocEntry *te, Oid oid);
static void _EndLOs(ArchiveHandle *AH, TocEntry *te);
static void _LoadLOs(ArchiveHandle *AH, TocEntry *te);
 
static void _PrepParallelRestore(ArchiveHandle *AH);
static void _Clone(ArchiveHandle *AH);
static void _DeClone(ArchiveHandle *AH);
 
static int  _WorkerJobRestoreDirectory(ArchiveHandle *AH, TocEntry *te);
static int  _WorkerJobDumpDirectory(ArchiveHandle *AH, TocEntry *te);
 
static void setFilePath(ArchiveHandle *AH, char *buf,
                        const char *relativeFilename);
 
/*
 *  Init routine required by ALL formats. This is a global routine
 *  and should be declared in pg_backup_archiver.h
 *
 *  Its task is to create any extra archive context (using AH->formatData),
 *  and to initialize the supported function pointers.
 *
 *  It should also prepare whatever its input source is for reading/writing,
 *  and in the case of a read mode connection, it should load the Header & TOC.
 */
void
InitArchiveFmt_Directory(ArchiveHandle *AH)
{
    lclContext *ctx;
 
    /* Assuming static functions, this can be copied for each format. */
    AH->ArchiveEntryPtr = _ArchiveEntry;
    AH->StartDataPtr = _StartData;
    AH->WriteDataPtr = _WriteData;
    AH->EndDataPtr = _EndData;
    AH->WriteBytePtr = _WriteByte;
    AH->ReadBytePtr = _ReadByte;
    AH->WriteBufPtr = _WriteBuf;
    AH->ReadBufPtr = _ReadBuf;
    AH->ClosePtr = _CloseArchive;
    AH->ReopenPtr = _ReopenArchive;
    AH->PrintTocDataPtr = _PrintTocData;
    AH->ReadExtraTocPtr = _ReadExtraToc;
    AH->WriteExtraTocPtr = _WriteExtraToc;
    AH->PrintExtraTocPtr = _PrintExtraToc;
 
    AH->StartLOsPtr = _StartLOs;
    AH->StartLOPtr = _StartLO;
    AH->EndLOPtr = _EndLO;
    AH->EndLOsPtr = _EndLOs;
 
    AH->PrepParallelRestorePtr = _PrepParallelRestore;
    AH->ClonePtr = _Clone;
    AH->DeClonePtr = _DeClone;
 
    AH->WorkerJobRestorePtr = _WorkerJobRestoreDirectory;
    AH->WorkerJobDumpPtr = _WorkerJobDumpDirectory;
 
    /* Set up our private context */
    ctx = (lclContext *) pg_malloc0(sizeof(lclContext));
    AH->formatData = (void *) ctx;
 
    ctx->dataFH = NULL;
    ctx->LOsTocFH = NULL;
 
    /*
     * Now open the TOC file
     */
 
    if (!AH->fSpec || strcmp(AH->fSpec, "") == 0)
        pg_fatal("no output directory specified");
 
    ctx->directory = AH->fSpec;
 
    if (AH->mode == archModeWrite)
    {
        struct stat st;
        bool        is_empty = false;
 
        /* we accept an empty existing directory */
        if (stat(ctx->directory, &st) == 0 && S_ISDIR(st.st_mode))
        {
            DIR        *dir = opendir(ctx->directory);
 
            if (dir)
            {
                struct dirent *d;
 
                is_empty = true;
                while (errno = 0, (d = readdir(dir)))
                {
                    if (strcmp(d->d_name, ".") != 0 && strcmp(d->d_name, "..") != 0)
                    {
                        is_empty = false;
                        break;
                    }
                }
 
                if (errno)
                    pg_fatal("could not read directory \"%s\": %m",
                             ctx->directory);
 
                if (closedir(dir))
                    pg_fatal("could not close directory \"%s\": %m",
                             ctx->directory);
            }
        }
 
        if (!is_empty && mkdir(ctx->directory, 0700) < 0)
            pg_fatal("could not create directory \"%s\": %m",
                     ctx->directory);
    }
    else
    {                           /* Read Mode */
        char        fname[MAXPGPATH];
        CompressFileHandle *tocFH;
 
        setFilePath(AH, fname, "toc.dat");
 
        tocFH = InitDiscoverCompressFileHandle(fname, PG_BINARY_R);
        if (tocFH == NULL)
            pg_fatal("could not open input file \"%s\": %m", fname);
 
        ctx->dataFH = tocFH;
 
        /*
         * The TOC of a directory format dump shares the format code of the
         * tar format.
         */
        AH->format = archTar;
        ReadHead(AH);
        AH->format = archDirectory;
        ReadToc(AH);
 
        /* Nothing else in the file, so close it again... */
        if (!EndCompressFileHandle(tocFH))
            pg_fatal("could not close TOC file: %m");
        ctx->dataFH = NULL;
    }
}
 
/*
 * Called by the Archiver when the dumper creates a new TOC entry.
 *
 * We determine the filename for this entry.
*/
static void
_ArchiveEntry(ArchiveHandle *AH, TocEntry *te)
{
    lclTocEntry *tctx;
    char        fn[MAXPGPATH];
 
    tctx = (lclTocEntry *) pg_malloc0(sizeof(lclTocEntry));
    if (strcmp(te->desc, "BLOBS") == 0)
    {
        snprintf(fn, MAXPGPATH, "blobs_%d.toc", te->dumpId);
        tctx->filename = pg_strdup(fn);
    }
    else if (te->dataDumper)
    {
        snprintf(fn, MAXPGPATH, "%d.dat", te->dumpId);
        tctx->filename = pg_strdup(fn);
    }
    else
        tctx->filename = NULL;
 
    te->formatData = (void *) tctx;
}
 
/*
 * Called by the Archiver to save any extra format-related TOC entry
 * data.
 *
 * Use the Archiver routines to write data - they are non-endian, and
 * maintain other important file information.
 */
static void
_WriteExtraToc(ArchiveHandle *AH, TocEntry *te)
{
    lclTocEntry *tctx = (lclTocEntry *) te->formatData;
 
    /*
     * A dumpable object has set tctx->filename, any other object has not.
     * (see _ArchiveEntry).
     */
    if (tctx->filename)
        WriteStr(AH, tctx->filename);
    else
        WriteStr(AH, "");
}
 
/*
 * Called by the Archiver to read any extra format-related TOC data.
 *
 * Needs to match the order defined in _WriteExtraToc, and should also
 * use the Archiver input routines.
 */
static void
_ReadExtraToc(ArchiveHandle *AH, TocEntry *te)
{
    lclTocEntry *tctx = (lclTocEntry *) te->formatData;
 
    if (tctx == NULL)
    {
        tctx = (lclTocEntry *) pg_malloc0(sizeof(lclTocEntry));
        te->formatData = (void *) tctx;
    }
 
    tctx->filename = ReadStr(AH);
    if (strlen(tctx->filename) == 0)
    {
        free(tctx->filename);
        tctx->filename = NULL;
    }
}
 
/*
 * Called by the Archiver when restoring an archive to output a comment
 * that includes useful information about the TOC entry.
 */
static void
_PrintExtraToc(ArchiveHandle *AH, TocEntry *te)
{
    lclTocEntry *tctx = (lclTocEntry *) te->formatData;
 
    if (AH->public.verbose && tctx->filename)
        ahprintf(AH, "-- File: %s\n", tctx->filename);
}
 
/*
 * Called by the archiver when saving TABLE DATA (not schema). This routine
 * should save whatever format-specific information is needed to read
 * the archive back.
 *
 * It is called just prior to the dumper's 'DataDumper' routine being called.
 *
 * We create the data file for writing.
 */
static void
_StartData(ArchiveHandle *AH, TocEntry *te)
{
    lclTocEntry *tctx = (lclTocEntry *) te->formatData;
    lclContext *ctx = (lclContext *) AH->formatData;
    char        fname[MAXPGPATH];
 
    setFilePath(AH, fname, tctx->filename);
 
    ctx->dataFH = InitCompressFileHandle(AH->compression_spec);
 
    if (!ctx->dataFH->open_write_func(fname, PG_BINARY_W, ctx->dataFH))
        pg_fatal("could not open output file \"%s\": %m", fname);
}
 
/*
 * Called by archiver when dumper calls WriteData. This routine is
 * called for both LO and table data; it is the responsibility of
 * the format to manage each kind of data using StartLO/StartData.
 *
 * It should only be called from within a DataDumper routine.
 *
 * We write the data to the open data file.
 */
static void
_WriteData(ArchiveHandle *AH, const void *data, size_t dLen)
{
    lclContext *ctx = (lclContext *) AH->formatData;
    CompressFileHandle *CFH = ctx->dataFH;
 
    errno = 0;
    if (dLen > 0 && !CFH->write_func(data, dLen, CFH))
    {
        /* if write didn't set errno, assume problem is no disk space */
        if (errno == 0)
            errno = ENOSPC;
        pg_fatal("could not write to output file: %s",
                 CFH->get_error_func(CFH));
    }
}
 
/*
 * Called by the archiver when a dumper's 'DataDumper' routine has
 * finished.
 *
 * We close the data file.
 */
static void
_EndData(ArchiveHandle *AH, TocEntry *te)
{
    lclContext *ctx = (lclContext *) AH->formatData;
 
    /* Close the file */
    if (!EndCompressFileHandle(ctx->dataFH))
        pg_fatal("could not close data file: %m");
 
    ctx->dataFH = NULL;
}
 
/*
 * Print data for a given file (can be a LO as well)
 */
static void
_PrintFileData(ArchiveHandle *AH, char *filename)
{
    size_t      cnt = 0;
    char       *buf;
    size_t      buflen;
    CompressFileHandle *CFH;
 
    if (!filename)
        return;
 
    CFH = InitDiscoverCompressFileHandle(filename, PG_BINARY_R);
    if (!CFH)
        pg_fatal("could not open input file \"%s\": %m", filename);
 
    buflen = DEFAULT_IO_BUFFER_SIZE;
    buf = pg_malloc(buflen);
 
    while (CFH->read_func(buf, buflen, &cnt, CFH) && cnt > 0)
    {
        ahwrite(buf, 1, cnt, AH);
    }
 
    free(buf);
    if (!EndCompressFileHandle(CFH))
        pg_fatal("could not close data file \"%s\": %m", filename);
}
 
/*
 * Print data for a given TOC entry
*/
static void
_PrintTocData(ArchiveHandle *AH, TocEntry *te)
{
    lclTocEntry *tctx = (lclTocEntry *) te->formatData;
 
    if (!tctx->filename)
        return;
 
    if (strcmp(te->desc, "BLOBS") == 0)
        _LoadLOs(AH, te);
    else
    {
        char        fname[MAXPGPATH];
 
        setFilePath(AH, fname, tctx->filename);
        _PrintFileData(AH, fname);
    }
}
 
static void
_LoadLOs(ArchiveHandle *AH, TocEntry *te)
{
    Oid         oid;
    lclContext *ctx = (lclContext *) AH->formatData;
    lclTocEntry *tctx = (lclTocEntry *) te->formatData;
    CompressFileHandle *CFH;
    char        tocfname[MAXPGPATH];
    char        line[MAXPGPATH];
 
    StartRestoreLOs(AH);
 
    /*
     * Note: before archive v16, there was always only one BLOBS TOC entry,
     * now there can be multiple.  We don't need to worry what version we are
     * reading though, because tctx->filename should be correct either way.
     */
    setFilePath(AH, tocfname, tctx->filename);
 
    CFH = ctx->LOsTocFH = InitDiscoverCompressFileHandle(tocfname, PG_BINARY_R);
 
    if (ctx->LOsTocFH == NULL)
        pg_fatal("could not open large object TOC file \"%s\" for input: %m",
                 tocfname);
 
    /* Read the LOs TOC file line-by-line, and process each LO */
    while ((CFH->gets_func(line, MAXPGPATH, CFH)) != NULL)
    {
        char        lofname[MAXPGPATH + 1];
        char        path[MAXPGPATH];
 
        /* Can't overflow because line and lofname are the same length */
        if (sscanf(line, "%u %" CppAsString2(MAXPGPATH) "s\n", &oid, lofname) != 2)
            pg_fatal("invalid line in large object TOC file \"%s\": \"%s\"",
                     tocfname, line);
 
        StartRestoreLO(AH, oid, AH->public.ropt->dropSchema);
        snprintf(path, MAXPGPATH, "%s/%s", ctx->directory, lofname);
        _PrintFileData(AH, path);
        EndRestoreLO(AH, oid);
    }
    if (!CFH->eof_func(CFH))
        pg_fatal("error reading large object TOC file \"%s\"",
                 tocfname);
 
    if (!EndCompressFileHandle(ctx->LOsTocFH))
        pg_fatal("could not close large object TOC file \"%s\": %m",
                 tocfname);
 
    ctx->LOsTocFH = NULL;
 
    EndRestoreLOs(AH);
}
 
 
/*
 * Write a byte of data to the archive.
 * Called by the archiver to do integer & byte output to the archive.
 * These routines are only used to read & write the headers & TOC.
 */
static int
_WriteByte(ArchiveHandle *AH, const int i)
{
    unsigned char c = (unsigned char) i;
    lclContext *ctx = (lclContext *) AH->formatData;
    CompressFileHandle *CFH = ctx->dataFH;
 
    errno = 0;
    if (!CFH->write_func(&c, 1, CFH))
    {
        /* if write didn't set errno, assume problem is no disk space */
        if (errno == 0)
            errno = ENOSPC;
        pg_fatal("could not write to output file: %s",
                 CFH->get_error_func(CFH));
    }
 
    return 1;
}
 
/*
 * Read a byte of data from the archive.
 * Called by the archiver to read bytes & integers from the archive.
 * These routines are only used to read & write headers & TOC.
 * EOF should be treated as a fatal error.
 */
static int
_ReadByte(ArchiveHandle *AH)
{
    lclContext *ctx = (lclContext *) AH->formatData;
    CompressFileHandle *CFH = ctx->dataFH;
 
    return CFH->getc_func(CFH);
}
 
/*
 * Write a buffer of data to the archive.
 * Called by the archiver to write a block of bytes to the TOC or a data file.
 */
static void
_WriteBuf(ArchiveHandle *AH, const void *buf, size_t len)
{
    lclContext *ctx = (lclContext *) AH->formatData;
    CompressFileHandle *CFH = ctx->dataFH;
 
    errno = 0;
    if (!CFH->write_func(buf, len, CFH))
    {
        /* if write didn't set errno, assume problem is no disk space */
        if (errno == 0)
            errno = ENOSPC;
        pg_fatal("could not write to output file: %s",
                 CFH->get_error_func(CFH));
    }
}
 
/*
 * Read a block of bytes from the archive.
 *
 * Called by the archiver to read a block of bytes from the archive
 */
static void
_ReadBuf(ArchiveHandle *AH, void *buf, size_t len)
{
    lclContext *ctx = (lclContext *) AH->formatData;
    CompressFileHandle *CFH = ctx->dataFH;
 
    /*
     * If there was an I/O error, we already exited in readF(), so here we
     * exit on short reads.
     */
    if (!CFH->read_func(buf, len, NULL, CFH))
        pg_fatal("could not read from input file: end of file");
}
 
/*
 * Close the archive.
 *
 * When writing the archive, this is the routine that actually starts
 * the process of saving it to files. No data should be written prior
 * to this point, since the user could sort the TOC after creating it.
 *
 * If an archive is to be written, this routine must call:
 *      WriteHead           to save the archive header
 *      WriteToc            to save the TOC entries
 *      WriteDataChunks     to save all data & LOs.
 */
static void
_CloseArchive(ArchiveHandle *AH)
{
    lclContext *ctx = (lclContext *) AH->formatData;
 
    if (AH->mode == archModeWrite)
    {
        CompressFileHandle *tocFH;
        pg_compress_specification compression_spec = {0};
        char        fname[MAXPGPATH];
 
        setFilePath(AH, fname, "toc.dat");
 
        /* this will actually fork the processes for a parallel backup */
        ctx->pstate = ParallelBackupStart(AH);
 
        /* The TOC is always created uncompressed */
        compression_spec.algorithm = PG_COMPRESSION_NONE;
        tocFH = InitCompressFileHandle(compression_spec);
        if (!tocFH->open_write_func(fname, PG_BINARY_W, tocFH))
            pg_fatal("could not open output file \"%s\": %m", fname);
        ctx->dataFH = tocFH;
 
        /*
         * Write 'tar' in the format field of the toc.dat file. The directory
         * is compatible with 'tar', so there's no point having a different
         * format code for it.
         */
        AH->format = archTar;
        WriteHead(AH);
        AH->format = archDirectory;
        WriteToc(AH);
        if (!EndCompressFileHandle(tocFH))
            pg_fatal("could not close TOC file: %m");
        WriteDataChunks(AH, ctx->pstate);
 
        ParallelBackupEnd(AH, ctx->pstate);
 
        /*
         * In directory mode, there is no need to sync all the entries
         * individually. Just recurse once through all the files generated.
         */
        if (AH->dosync)
            sync_dir_recurse(ctx->directory, AH->sync_method);
    }
    AH->FH = NULL;
}
 
/*
 * Reopen the archive's file handle.
 */
static void
_ReopenArchive(ArchiveHandle *AH)
{
    /*
     * Our TOC is in memory, our data files are opened by each child anyway as
     * they are separate. We support reopening the archive by just doing
     * nothing.
     */
}
 
/*
 * LO support
 */
 
/*
 * Called by the archiver when starting to save BLOB DATA (not schema).
 * It is called just prior to the dumper's DataDumper routine.
 *
 * We open the large object TOC file here, so that we can append a line to
 * it for each LO.
 */
static void
_StartLOs(ArchiveHandle *AH, TocEntry *te)
{
    lclContext *ctx = (lclContext *) AH->formatData;
    lclTocEntry *tctx = (lclTocEntry *) te->formatData;
    pg_compress_specification compression_spec = {0};
    char        fname[MAXPGPATH];
 
    setFilePath(AH, fname, tctx->filename);
 
    /* The LO TOC file is never compressed */
    compression_spec.algorithm = PG_COMPRESSION_NONE;
    ctx->LOsTocFH = InitCompressFileHandle(compression_spec);
    if (!ctx->LOsTocFH->open_write_func(fname, "ab", ctx->LOsTocFH))
        pg_fatal("could not open output file \"%s\": %m", fname);
}
 
/*
 * Called by the archiver when we're about to start dumping a LO.
 *
 * We create a file to write the LO to.
 */
static void
_StartLO(ArchiveHandle *AH, TocEntry *te, Oid oid)
{
    lclContext *ctx = (lclContext *) AH->formatData;
    char        fname[MAXPGPATH];
 
    snprintf(fname, MAXPGPATH, "%s/blob_%u.dat", ctx->directory, oid);
 
    ctx->dataFH = InitCompressFileHandle(AH->compression_spec);
    if (!ctx->dataFH->open_write_func(fname, PG_BINARY_W, ctx->dataFH))
        pg_fatal("could not open output file \"%s\": %m", fname);
}
 
/*
 * Called by the archiver when the dumper is finished writing a LO.
 *
 * We close the LO file and write an entry to the LO TOC file for it.
 */
static void
_EndLO(ArchiveHandle *AH, TocEntry *te, Oid oid)
{
    lclContext *ctx = (lclContext *) AH->formatData;
    CompressFileHandle *CFH = ctx->LOsTocFH;
    char        buf[50];
    int         len;
 
    /* Close the BLOB data file itself */
    if (!EndCompressFileHandle(ctx->dataFH))
        pg_fatal("could not close LO data file: %m");
    ctx->dataFH = NULL;
 
    /* register the LO in blobs_NNN.toc */
    len = snprintf(buf, sizeof(buf), "%u blob_%u.dat\n", oid, oid);
    if (!CFH->write_func(buf, len, CFH))
    {
        /* if write didn't set errno, assume problem is no disk space */
        if (errno == 0)
            errno = ENOSPC;
        pg_fatal("could not write to LOs TOC file: %s",
                 CFH->get_error_func(CFH));
    }
}
 
/*
 * Called by the archiver when finishing saving BLOB DATA.
 *
 * We close the LOs TOC file.
 */
static void
_EndLOs(ArchiveHandle *AH, TocEntry *te)
{
    lclContext *ctx = (lclContext *) AH->formatData;
 
    if (!EndCompressFileHandle(ctx->LOsTocFH))
        pg_fatal("could not close LOs TOC file: %m");
    ctx->LOsTocFH = NULL;
}
 
/*
 * Gets a relative file name and prepends the output directory, writing the
 * result to buf. The caller needs to make sure that buf is MAXPGPATH bytes
 * big. Can't use a static char[MAXPGPATH] inside the function because we run
 * multithreaded on Windows.
 */
static void
setFilePath(ArchiveHandle *AH, char *buf, const char *relativeFilename)
{
    lclContext *ctx = (lclContext *) AH->formatData;
    char       *dname;
 
    dname = ctx->directory;
 
    if (strlen(dname) + 1 + strlen(relativeFilename) + 1 > MAXPGPATH)
        pg_fatal("file name too long: \"%s\"", dname);
 
    strcpy(buf, dname);
    strcat(buf, "/");
    strcat(buf, relativeFilename);
}
 
/*
 * Prepare for parallel restore.
 *
 * The main thing that needs to happen here is to fill in TABLE DATA and BLOBS
 * TOC entries' dataLength fields with appropriate values to guide the
 * ordering of restore jobs.  The source of said data is format-dependent,
 * as is the exact meaning of the values.
 *
 * A format module might also choose to do other setup here.
 */
static void
_PrepParallelRestore(ArchiveHandle *AH)
{
    TocEntry   *te;
 
    for (te = AH->toc->next; te != AH->toc; te = te->next)
    {
        lclTocEntry *tctx = (lclTocEntry *) te->formatData;
        char        fname[MAXPGPATH];
        struct stat st;
 
        /*
         * A dumpable object has set tctx->filename, any other object has not.
         * (see _ArchiveEntry).
         */
        if (tctx->filename == NULL)
            continue;
 
        /* We may ignore items not due to be restored */
        if ((te->reqs & REQ_DATA) == 0)
            continue;
 
        /*
         * Stat the file and, if successful, put its size in dataLength.  When
         * using compression, the physical file size might not be a very good
         * guide to the amount of work involved in restoring the file, but we
         * only need an approximate indicator of that.
         */
        setFilePath(AH, fname, tctx->filename);
 
        if (stat(fname, &st) == 0)
            te->dataLength = st.st_size;
        else if (AH->compression_spec.algorithm != PG_COMPRESSION_NONE)
        {
            if (AH->compression_spec.algorithm == PG_COMPRESSION_GZIP)
                strlcat(fname, ".gz", sizeof(fname));
            else if (AH->compression_spec.algorithm == PG_COMPRESSION_LZ4)
                strlcat(fname, ".lz4", sizeof(fname));
            else if (AH->compression_spec.algorithm == PG_COMPRESSION_ZSTD)
                strlcat(fname, ".zst", sizeof(fname));
 
            if (stat(fname, &st) == 0)
                te->dataLength = st.st_size;
        }
 
        /*
         * If this is a BLOBS entry, what we stat'd was blobs_NNN.toc, which
         * most likely is a lot smaller than the actual blob data.  We don't
         * have a cheap way to estimate how much smaller, but fortunately it
         * doesn't matter too much as long as we get the LOs processed
         * reasonably early.  Arbitrarily scale up by a factor of 1K.
         */
        if (strcmp(te->desc, "BLOBS") == 0)
            te->dataLength *= 1024;
    }
}
 
/*
 * Clone format-specific fields during parallel restoration.
 */
static void
_Clone(ArchiveHandle *AH)
{
    lclContext *ctx = (lclContext *) AH->formatData;
 
    AH->formatData = (lclContext *) pg_malloc(sizeof(lclContext));
    memcpy(AH->formatData, ctx, sizeof(lclContext));
    ctx = (lclContext *) AH->formatData;
 
    /*
     * TOC-entry-local state isn't an issue because any one TOC entry is
     * touched by just one worker child.
     */
 
    /*
     * We also don't copy the ParallelState pointer (pstate), only the leader
     * process ever writes to it.
     */
}
 
static void
_DeClone(ArchiveHandle *AH)
{
    lclContext *ctx = (lclContext *) AH->formatData;
 
    free(ctx);
}
 
/*
 * This function is executed in the child of a parallel backup for a
 * directory-format archive and dumps the actual data for one TOC entry.
 */
static int
_WorkerJobDumpDirectory(ArchiveHandle *AH, TocEntry *te)
{
    /*
     * This function returns void. We either fail and die horribly or
     * succeed... A failure will be detected by the parent when the child dies
     * unexpectedly.
     */
    WriteDataChunksForTocEntry(AH, te);
 
    return 0;
}
 
/*
 * This function is executed in the child of a parallel restore from a
 * directory-format archive and restores the actual data for one TOC entry.
 */
static int
_WorkerJobRestoreDirectory(ArchiveHandle *AH, TocEntry *te)
{
    return parallel_restore(AH, te);
}