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

michaelpq · michaelpq · commit 8ac4c25a05d1 · 2022-03-31T10:34:10.000+09:00
Compression with gzip has never been supported in the tar format of pg_dump since this code has been introduced in c3e1880, 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
@@ -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);
 
