pg_backup_directory.c

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/*-------------------------------------------------------------------------
 *
 * 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 (BLOBs) are stored in separate files named "blob_<uid>.dat",
 *  and there's a plain-text TOC file for them called "blobs.toc". 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) 1996-2013, 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 it's use.
 *
 * IDENTIFICATION
 *      src/bin/pg_dump/pg_backup_directory.c
 *
 *-------------------------------------------------------------------------
 */

#include "compress_io.h"
#include "pg_backup_utils.h"
#include "parallel.h"

#include <dirent.h>
#include <sys/stat.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;

    cfp        *dataFH;         /* currently open data file */

    cfp        *blobsTocFH;     /* file handle for blobs.toc */
    ParallelState *pstate;      /* for parallel backup / restore */
} lclContext;

typedef struct
{
    char       *filename;       /* filename excluding the directory (basename) */
} lclTocEntry;

/* translator: this is a module name */
static const char *modulename = gettext_noop("directory archiver");

/* 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 size_t _WriteData(ArchiveHandle *AH, const void *data, size_t dLen);
static int  _WriteByte(ArchiveHandle *AH, const int i);
static int  _ReadByte(ArchiveHandle *);
static size_t _WriteBuf(ArchiveHandle *AH, const void *buf, size_t len);
static size_t _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, RestoreOptions *ropt);

static void _WriteExtraToc(ArchiveHandle *AH, TocEntry *te);
static void _ReadExtraToc(ArchiveHandle *AH, TocEntry *te);
static void _PrintExtraToc(ArchiveHandle *AH, TocEntry *te);

static void _StartBlobs(ArchiveHandle *AH, TocEntry *te);
static void _StartBlob(ArchiveHandle *AH, TocEntry *te, Oid oid);
static void _EndBlob(ArchiveHandle *AH, TocEntry *te, Oid oid);
static void _EndBlobs(ArchiveHandle *AH, TocEntry *te);
static void _LoadBlobs(ArchiveHandle *AH, RestoreOptions *ropt);

static void _Clone(ArchiveHandle *AH);
static void _DeClone(ArchiveHandle *AH);

static char *_MasterStartParallelItem(ArchiveHandle *AH, TocEntry *te, T_Action act);
static int _MasterEndParallelItem(ArchiveHandle *AH, TocEntry *te,
                       const char *str, T_Action act);
static char *_WorkerJobRestoreDirectory(ArchiveHandle *AH, TocEntry *te);
static char *_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->StartBlobsPtr = _StartBlobs;
    AH->StartBlobPtr = _StartBlob;
    AH->EndBlobPtr = _EndBlob;
    AH->EndBlobsPtr = _EndBlobs;

    AH->ClonePtr = _Clone;
    AH->DeClonePtr = _DeClone;

    AH->WorkerJobRestorePtr = _WorkerJobRestoreDirectory;
    AH->WorkerJobDumpPtr = _WorkerJobDumpDirectory;

    AH->MasterStartParallelItemPtr = _MasterStartParallelItem;
    AH->MasterEndParallelItemPtr = _MasterEndParallelItem;

    /* Set up our private context */
    ctx = (lclContext *) pg_malloc0(sizeof(lclContext));
    AH->formatData = (void *) ctx;

    ctx->dataFH = NULL;
    ctx->blobsTocFH = NULL;

    /* Initialize LO buffering */
    AH->lo_buf_size = LOBBUFSIZE;
    AH->lo_buf = (void *) pg_malloc(LOBBUFSIZE);

    /*
     * Now open the TOC file
     */

    if (!AH->fSpec || strcmp(AH->fSpec, "") == 0)
        exit_horribly(modulename, "no output directory specified\n");

    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 ((d = readdir(dir)))
                {
                    if (strcmp(d->d_name, ".") != 0 && strcmp(d->d_name, "..") != 0)
                    {
                        is_empty = false;
                        break;
                    }
                }
                closedir(dir);
            }
        }

        if (!is_empty && mkdir(ctx->directory, 0700) < 0)
            exit_horribly(modulename, "could not create directory \"%s\": %s\n",
                          ctx->directory, strerror(errno));
    }
    else
    {                           /* Read Mode */
        char        fname[MAXPGPATH];
        cfp        *tocFH;

        setFilePath(AH, fname, "toc.dat");

        tocFH = cfopen_read(fname, PG_BINARY_R);
        if (tocFH == NULL)
            exit_horribly(modulename,
                          "could not open input file \"%s\": %s\n",
                          fname, strerror(errno));

        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 (cfclose(tocFH) != 0)
            exit_horribly(modulename, "could not close TOC file: %s\n",
                          strerror(errno));
        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 (te->dataDumper)
    {
        snprintf(fn, MAXPGPATH, "%d.dat", te->dumpId);
        tctx->filename = pg_strdup(fn);
    }
    else if (strcmp(te->desc, "BLOBS") == 0)
        tctx->filename = pg_strdup("blobs.toc");
    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 = cfopen_write(fname, PG_BINARY_W, AH->compression);
    if (ctx->dataFH == NULL)
        exit_horribly(modulename, "could not open output file \"%s\": %s\n",
                      fname, strerror(errno));
}

/*
 * Called by archiver when dumper calls WriteData. This routine is
 * called for both BLOB and TABLE data; it is the responsibility of
 * the format to manage each kind of data using StartBlob/StartData.
 *
 * It should only be called from within a DataDumper routine.
 *
 * We write the data to the open data file.
 */
static size_t
_WriteData(ArchiveHandle *AH, const void *data, size_t dLen)
{
    lclContext *ctx = (lclContext *) AH->formatData;

    if (dLen == 0)
        return 0;

    /* Are we aborting? */
    checkAborting(AH);

    return cfwrite(data, dLen, ctx->dataFH);
}

/*
 * 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 */
    cfclose(ctx->dataFH);

    ctx->dataFH = NULL;
}

/*
 * Print data for a given file (can be a BLOB as well)
 */
static void
_PrintFileData(ArchiveHandle *AH, char *filename, RestoreOptions *ropt)
{
    size_t      cnt;
    char       *buf;
    size_t      buflen;
    cfp        *cfp;

    if (!filename)
        return;

    cfp = cfopen_read(filename, PG_BINARY_R);

    if (!cfp)
        exit_horribly(modulename, "could not open input file \"%s\": %s\n",
                      filename, strerror(errno));

    buf = pg_malloc(ZLIB_OUT_SIZE);
    buflen = ZLIB_OUT_SIZE;

    while ((cnt = cfread(buf, buflen, cfp)))
        ahwrite(buf, 1, cnt, AH);

    free(buf);
    if (cfclose(cfp) !=0)
        exit_horribly(modulename, "could not close data file: %s\n",
                      strerror(errno));
}

/*
 * Print data for a given TOC entry
*/
static void
_PrintTocData(ArchiveHandle *AH, TocEntry *te, RestoreOptions *ropt)
{
    lclTocEntry *tctx = (lclTocEntry *) te->formatData;

    if (!tctx->filename)
        return;

    if (strcmp(te->desc, "BLOBS") == 0)
        _LoadBlobs(AH, ropt);
    else
    {
        char        fname[MAXPGPATH];

        setFilePath(AH, fname, tctx->filename);
        _PrintFileData(AH, fname, ropt);
    }
}

static void
_LoadBlobs(ArchiveHandle *AH, RestoreOptions *ropt)
{
    Oid         oid;
    lclContext *ctx = (lclContext *) AH->formatData;
    char        fname[MAXPGPATH];
    char        line[MAXPGPATH];

    StartRestoreBlobs(AH);

    setFilePath(AH, fname, "blobs.toc");

    ctx->blobsTocFH = cfopen_read(fname, PG_BINARY_R);

    if (ctx->blobsTocFH == NULL)
        exit_horribly(modulename, "could not open large object TOC file \"%s\" for input: %s\n",
                      fname, strerror(errno));

    /* Read the blobs TOC file line-by-line, and process each blob */
    while ((cfgets(ctx->blobsTocFH, line, MAXPGPATH)) != NULL)
    {
        char        fname[MAXPGPATH];
        char        path[MAXPGPATH];

        if (sscanf(line, "%u %s\n", &oid, fname) != 2)
            exit_horribly(modulename, "invalid line in large object TOC file \"%s\": \"%s\"\n",
                          fname, line);

        StartRestoreBlob(AH, oid, ropt->dropSchema);
        snprintf(path, MAXPGPATH, "%s/%s", ctx->directory, fname);
        _PrintFileData(AH, path, ropt);
        EndRestoreBlob(AH, oid);
    }
    if (!cfeof(ctx->blobsTocFH))
        exit_horribly(modulename, "error reading large object TOC file \"%s\"\n",
                      fname);

    if (cfclose(ctx->blobsTocFH) != 0)
        exit_horribly(modulename, "could not close large object TOC file \"%s\": %s\n",
                      fname, strerror(errno));

    ctx->blobsTocFH = NULL;

    EndRestoreBlobs(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;

    if (cfwrite(&c, 1, ctx->dataFH) != 1)
        exit_horribly(modulename, "could not write byte\n");

    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;
    int         res;

    res = cfgetc(ctx->dataFH);
    if (res == EOF)
        exit_horribly(modulename, "unexpected end of file\n");

    return res;
}

/*
 * 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 size_t
_WriteBuf(ArchiveHandle *AH, const void *buf, size_t len)
{
    lclContext *ctx = (lclContext *) AH->formatData;
    size_t      res;

    /* Are we aborting? */
    checkAborting(AH);

    res = cfwrite(buf, len, ctx->dataFH);
    if (res != len)
        exit_horribly(modulename, "could not write to output file: %s\n",
                      strerror(errno));

    return res;
}

/*
 * Read a block of bytes from the archive.
 *
 * Called by the archiver to read a block of bytes from the archive
 */
static size_t
_ReadBuf(ArchiveHandle *AH, void *buf, size_t len)
{
    lclContext *ctx = (lclContext *) AH->formatData;
    size_t      res;

    res = cfread(buf, len, ctx->dataFH);

    return res;
}

/*
 * 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 & BLOBs.
 */
static void
_CloseArchive(ArchiveHandle *AH)
{
    lclContext *ctx = (lclContext *) AH->formatData;

    if (AH->mode == archModeWrite)
    {
        cfp        *tocFH;
        char        fname[MAXPGPATH];

        setFilePath(AH, fname, "toc.dat");

        /* this will actually fork the processes for a parallel backup */
        ctx->pstate = ParallelBackupStart(AH, NULL);

        /* The TOC is always created uncompressed */
        tocFH = cfopen_write(fname, PG_BINARY_W, 0);
        if (tocFH == NULL)
            exit_horribly(modulename, "could not open output file \"%s\": %s\n",
                          fname, strerror(errno));
        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 (cfclose(tocFH) != 0)
            exit_horribly(modulename, "could not close TOC file: %s\n",
                          strerror(errno));
        WriteDataChunks(AH, ctx->pstate);

        ParallelBackupEnd(AH, ctx->pstate);
    }
    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.
     */
}

/*
 * BLOB support
 */

/*
 * Called by the archiver when starting to save all 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 blob.
 */
static void
_StartBlobs(ArchiveHandle *AH, TocEntry *te)
{
    lclContext *ctx = (lclContext *) AH->formatData;
    char        fname[MAXPGPATH];

    setFilePath(AH, fname, "blobs.toc");

    /* The blob TOC file is never compressed */
    ctx->blobsTocFH = cfopen_write(fname, "ab", 0);
    if (ctx->blobsTocFH == NULL)
        exit_horribly(modulename, "could not open output file \"%s\": %s\n",
                      fname, strerror(errno));
}

/*
 * Called by the archiver when we're about to start dumping a blob.
 *
 * We create a file to write the blob to.
 */
static void
_StartBlob(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 = cfopen_write(fname, PG_BINARY_W, AH->compression);

    if (ctx->dataFH == NULL)
        exit_horribly(modulename, "could not open output file \"%s\": %s\n",
                      fname, strerror(errno));
}

/*
 * Called by the archiver when the dumper is finished writing a blob.
 *
 * We close the blob file and write an entry to the blob TOC file for it.
 */
static void
_EndBlob(ArchiveHandle *AH, TocEntry *te, Oid oid)
{
    lclContext *ctx = (lclContext *) AH->formatData;
    char        buf[50];
    int         len;

    /* Close the BLOB data file itself */
    cfclose(ctx->dataFH);
    ctx->dataFH = NULL;

    /* register the blob in blobs.toc */
    len = snprintf(buf, sizeof(buf), "%u blob_%u.dat\n", oid, oid);
    if (cfwrite(buf, len, ctx->blobsTocFH) != len)
        exit_horribly(modulename, "could not write to blobs TOC file\n");
}

/*
 * Called by the archiver when finishing saving all BLOB DATA.
 *
 * We close the blobs TOC file.
 */
static void
_EndBlobs(ArchiveHandle *AH, TocEntry *te)
{
    lclContext *ctx = (lclContext *) AH->formatData;

    cfclose(ctx->blobsTocFH);
    ctx->blobsTocFH = 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)
        exit_horribly(modulename, "file name too long: \"%s\"\n", dname);

    strcpy(buf, dname);
    strcat(buf, "/");
    strcat(buf, relativeFilename);
}

/*
 * 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;

    /*
     * Note: we do not make a local lo_buf because we expect at most one BLOBS
     * entry per archive, so no parallelism is possible.  Likewise,
     * 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 master
     * process ever writes to it.
     */
}

static void
_DeClone(ArchiveHandle *AH)
{
    lclContext *ctx = (lclContext *) AH->formatData;

    free(ctx);
}

/*
 * This function is executed in the parent process. Depending on the desired
 * action (dump or restore) it creates a string that is understood by the
 * _WorkerJobDump /_WorkerJobRestore functions of the dump format.
 */
static char *
_MasterStartParallelItem(ArchiveHandle *AH, TocEntry *te, T_Action act)
{
    /*
     * A static char is okay here, even on Windows because we call this
     * function only from one process (the master).
     */
    static char buf[64];

    if (act == ACT_DUMP)
        snprintf(buf, sizeof(buf), "DUMP %d", te->dumpId);
    else if (act == ACT_RESTORE)
        snprintf(buf, sizeof(buf), "RESTORE %d", te->dumpId);

    return buf;
}

/*
 * This function is executed in the child of a parallel backup for the
 * directory archive and dumps the actual data.
 *
 * We are currently returning only the DumpId so theoretically we could
 * make this function returning an int (or a DumpId). However, to
 * facilitate further enhancements and because sooner or later we need to
 * convert this to a string and send it via a message anyway, we stick with
 * char *. It is parsed on the other side by the _EndMasterParallel()
 * function of the respective dump format.
 */
static char *
_WorkerJobDumpDirectory(ArchiveHandle *AH, TocEntry *te)
{
    /*
     * short fixed-size string + some ID so far, this needs to be malloc'ed
     * instead of static because we work with threads on windows
     */
    const int   buflen = 64;
    char       *buf = (char *) pg_malloc(buflen);
    lclTocEntry *tctx = (lclTocEntry *) te->formatData;

    /* This should never happen */
    if (!tctx)
        exit_horribly(modulename, "Error during backup\n");

    /*
     * 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);

    snprintf(buf, buflen, "OK DUMP %d", te->dumpId);

    return buf;
}

/*
 * This function is executed in the child of a parallel backup for the
 * directory archive and dumps the actual data.
 */
static char *
_WorkerJobRestoreDirectory(ArchiveHandle *AH, TocEntry *te)
{
    /*
     * short fixed-size string + some ID so far, this needs to be malloc'ed
     * instead of static because we work with threads on windows
     */
    const int   buflen = 64;
    char       *buf = (char *) pg_malloc(buflen);
    ParallelArgs pargs;
    int         status;

    pargs.AH = AH;
    pargs.te = te;

    status = parallel_restore(&pargs);

    snprintf(buf, buflen, "OK RESTORE %d %d %d", te->dumpId, status,
             status == WORKER_IGNORED_ERRORS ? AH->public.n_errors : 0);

    return buf;
}

/*
 * This function is executed in the parent process. It analyzes the response of
 * the _WorkerJobDumpDirectory/_WorkerJobRestoreDirectory functions of the
 * respective dump format.
 */
static int
_MasterEndParallelItem(ArchiveHandle *AH, TocEntry *te, const char *str, T_Action act)
{
    DumpId      dumpId;
    int         nBytes,
                n_errors;
    int         status = 0;

    if (act == ACT_DUMP)
    {
        sscanf(str, "%u%n", &dumpId, &nBytes);

        Assert(dumpId == te->dumpId);
        Assert(nBytes == strlen(str));
    }
    else if (act == ACT_RESTORE)
    {
        sscanf(str, "%u %u %u%n", &dumpId, &status, &n_errors, &nBytes);

        Assert(dumpId == te->dumpId);
        Assert(nBytes == strlen(str));

        AH->public.n_errors += n_errors;
    }

    return status;
}