Clean up some dead code in pg_dump with tar format and gzip compression

Compression with gzip has never been supported in the tar format of
pg_dump since this code has been introduced in c3e18804, as the use of
buffered I/O in gzdopen() changes the file positioning that tar
requires.  The original idea behind the use of compression with the tar
mode is to be able to include compressed data files (named %u.dat.gz)
and blob files (blob_%u.dat.gz) in the tarball generated by the dump,
with toc.dat, that tracks down if compression is used in the dump,
always uncompressed.

Note that this commit removes the dump part of the code as well as the
restore part, removing any dependency to zlib in pg_backup_tar.c.  There
could be an argument behind keeping around the restore part, but this
would require one to change the internals of a tarball previously dumped
so as data and blob files are compressed with toc.dat itself changed to
track down if compression is enabled.  However, the argument about
gzdopen() still holds in the read case with pg_restore.

Removing this code simplifies future additions related to compression in
pg_dump.

Author: Georgios Kokolatos, Rachel Heaton
Discussion: https://postgr.es/m/faUNEOpts9vunEaLnmxmG-DldLSg_ql137OC3JYDmgrOMHm1RvvWY2IdBkv_CRxm5spCCb_OmKNk2T03TMm0fBEWveFF9wA1WizPuAgB7Ss=@protonmail.com

diff --git a/src/bin/pg_dump/pg_backup_tar.c b/src/bin/pg_dump/pg_backup_tar.c
index ccfbe346be9e721ba3c653a4bcf7f36ba8303b92..2491a091b9ea8742e23594c87072dfd7a4c092a9 100644 (file)
--- a/src/bin/pg_dump/pg_backup_tar.c
+++ b/src/bin/pg_dump/pg_backup_tar.c
@@ -65,11 +65,6 @@ static void _EndBlobs(ArchiveHandle *AH, TocEntry *te);
 
 typedef struct
 {
-#ifdef HAVE_LIBZ
-   gzFile      zFH;
-#else
-   FILE       *zFH;
-#endif
    FILE       *nFH;
    FILE       *tarFH;
    FILE       *tmpFH;
@@ -248,14 +243,7 @@ _ArchiveEntry(ArchiveHandle *AH, TocEntry *te)
    ctx = (lclTocEntry *) pg_malloc0(sizeof(lclTocEntry));
    if (te->dataDumper != NULL)
    {
-#ifdef HAVE_LIBZ
-       if (AH->compression == 0)
-           sprintf(fn, "%d.dat", te->dumpId);
-       else
-           sprintf(fn, "%d.dat.gz", te->dumpId);
-#else
-       sprintf(fn, "%d.dat", te->dumpId);
-#endif
+       snprintf(fn, sizeof(fn), "%d.dat", te->dumpId);
        ctx->filename = pg_strdup(fn);
    }
    else
@@ -320,10 +308,6 @@ tarOpen(ArchiveHandle *AH, const char *filename, char mode)
    lclContext *ctx = (lclContext *) AH->formatData;
    TAR_MEMBER *tm;
 
-#ifdef HAVE_LIBZ
-   char        fmode[14];
-#endif
-
    if (mode == 'r')
    {
        tm = _tarPositionTo(AH, filename);
@@ -344,16 +328,10 @@ tarOpen(ArchiveHandle *AH, const char *filename, char mode)
            }
        }
 
-#ifdef HAVE_LIBZ
-
        if (AH->compression == 0)
            tm->nFH = ctx->tarFH;
        else
            fatal("compression is not supported by tar archive format");
-       /* tm->zFH = gzdopen(dup(fileno(ctx->tarFH)), "rb"); */
-#else
-       tm->nFH = ctx->tarFH;
-#endif
    }
    else
    {
@@ -405,21 +383,10 @@ tarOpen(ArchiveHandle *AH, const char *filename, char mode)
 
        umask(old_umask);
 
-#ifdef HAVE_LIBZ
-
-       if (AH->compression != 0)
-       {
-           sprintf(fmode, "wb%d", AH->compression);
-           tm->zFH = gzdopen(dup(fileno(tm->tmpFH)), fmode);
-           if (tm->zFH == NULL)
-               fatal("could not open temporary file");
-       }
-       else
+       if (AH->compression == 0)
            tm->nFH = tm->tmpFH;
-#else
-
-       tm->nFH = tm->tmpFH;
-#endif
+       else
+           fatal("compression is not supported by tar archive format");
 
        tm->AH = AH;
        tm->targetFile = pg_strdup(filename);
@@ -434,15 +401,8 @@ tarOpen(ArchiveHandle *AH, const char *filename, char mode)
 static void
 tarClose(ArchiveHandle *AH, TAR_MEMBER *th)
 {
-   /*
-    * Close the GZ file since we dup'd. This will flush the buffers.
-    */
    if (AH->compression != 0)
-   {
-       errno = 0;              /* in case gzclose() doesn't set it */
-       if (GZCLOSE(th->zFH) != 0)
-           fatal("could not close tar member: %m");
-   }
+       fatal("compression is not supported by tar archive format");
 
    if (th->mode == 'w')
        _tarAddFile(AH, th);    /* This will close the temp file */
@@ -456,7 +416,6 @@ tarClose(ArchiveHandle *AH, TAR_MEMBER *th)
        free(th->targetFile);
 
    th->nFH = NULL;
-   th->zFH = NULL;
 }
 
 #ifdef __NOT_USED__
@@ -542,29 +501,9 @@ _tarReadRaw(ArchiveHandle *AH, void *buf, size_t len, TAR_MEMBER *th, FILE *fh)
        }
        else if (th)
        {
-           if (th->zFH)
-           {
-               res = GZREAD(&((char *) buf)[used], 1, len, th->zFH);
-               if (res != len && !GZEOF(th->zFH))
-               {
-#ifdef HAVE_LIBZ
-                   int         errnum;
-                   const char *errmsg = gzerror(th->zFH, &errnum);
-
-                   fatal("could not read from input file: %s",
-                         errnum == Z_ERRNO ? strerror(errno) : errmsg);
-#else
-                   fatal("could not read from input file: %s",
-                         strerror(errno));
-#endif
-               }
-           }
-           else
-           {
-               res = fread(&((char *) buf)[used], 1, len, th->nFH);
-               if (res != len && !feof(th->nFH))
-                   READ_ERROR_EXIT(th->nFH);
-           }
+           res = fread(&((char *) buf)[used], 1, len, th->nFH);
+           if (res != len && !feof(th->nFH))
+               READ_ERROR_EXIT(th->nFH);
        }
    }
 
@@ -596,10 +535,7 @@ tarWrite(const void *buf, size_t len, TAR_MEMBER *th)
 {
    size_t      res;
 
-   if (th->zFH != NULL)
-       res = GZWRITE(buf, 1, len, th->zFH);
-   else
-       res = fwrite(buf, 1, len, th->nFH);
+   res = fwrite(buf, 1, len, th->nFH);
 
    th->pos += res;
    return res;
@@ -949,17 +885,14 @@ _StartBlob(ArchiveHandle *AH, TocEntry *te, Oid oid)
    lclContext *ctx = (lclContext *) AH->formatData;
    lclTocEntry *tctx = (lclTocEntry *) te->formatData;
    char        fname[255];
-   char       *sfx;
 
    if (oid == 0)
        fatal("invalid OID for large object (%u)", oid);
 
    if (AH->compression != 0)
-       sfx = ".gz";
-   else
-       sfx = "";
+       fatal("compression is not supported by tar archive format");
 
-   sprintf(fname, "blob_%u.dat%s", oid, sfx);
+   sprintf(fname, "blob_%u.dat", oid);
 
    tarPrintf(ctx->blobToc, "%u %s\n", oid, fname);