Allow server-side compression to be used with -Fp.

If you have a low-bandwidth connection between the client and the
server, it's reasonable to want to compress on the server side but
then decompress and extract the backup on the client side. This
commit allows you do to do just that.

Dipesh Pandit, with minor and mostly cosmetic changes by me.

Discussion: http://postgr.es/m/CAN1g5_HiSh8ajUMd4ePtGyCXo89iKZTzaNyzP_qv1eJbi4YHXA@mail.gmail.com

Author: robertmhaas

doc/src/sgml/ref/pg_basebackup.sgml

@@ -428,8 +428,11 @@ PostgreSQL documentation
        </para>
        <para>
         When the tar format is used, the suffix <filename>.gz</filename> will
-        automatically be added to all tar filenames. Compression is not
-        available in plain format.
+        automatically be added to all tar filenames. When the plain format is
+        used, client-side compression may not be specified, but it is
+        still possible to request server-side compression. If this is done,
+        the server will compress the backup for transmission, and the
+        client will decompress and extract it.
        </para>
       </listitem>
      </varlistentry>

src/bin/pg_basebackup/Makefile

@@ -38,6 +38,7 @@ OBJS = \
 BBOBJS = \
 	pg_basebackup.o \
 	bbstreamer_file.o \
+	bbstreamer_gzip.o \
 	bbstreamer_inject.o \
 	bbstreamer_tar.o
 

src/bin/pg_basebackup/bbstreamer.h

@@ -205,6 +205,7 @@ extern bbstreamer *bbstreamer_extractor_new(const char *basepath,
 											const char *(*link_map) (const char *),
 											void (*report_output_file) (const char *));
 
+extern bbstreamer *bbstreamer_gzip_decompressor_new(bbstreamer *next);
 extern bbstreamer *bbstreamer_tar_parser_new(bbstreamer *next);
 extern bbstreamer *bbstreamer_tar_terminator_new(bbstreamer *next);
 extern bbstreamer *bbstreamer_tar_archiver_new(bbstreamer *next);

src/bin/pg_basebackup/bbstreamer_file.c

@@ -11,10 +11,6 @@
 
 #include "postgres_fe.h"
 
-#ifdef HAVE_LIBZ
-#include <zlib.h>
-#endif
-
 #include <unistd.h>
 
 #include "bbstreamer.h"
@@ -30,15 +26,6 @@ typedef struct bbstreamer_plain_writer
 	bool		should_close_file;
 } bbstreamer_plain_writer;
 
-#ifdef HAVE_LIBZ
-typedef struct bbstreamer_gzip_writer
-{
-	bbstreamer	base;
-	char	   *pathname;
-	gzFile		gzfile;
-}			bbstreamer_gzip_writer;
-#endif
-
 typedef struct bbstreamer_extractor
 {
 	bbstreamer	base;
@@ -62,22 +49,6 @@ const bbstreamer_ops bbstreamer_plain_writer_ops = {
 	.free = bbstreamer_plain_writer_free
 };
 
-#ifdef HAVE_LIBZ
-static void bbstreamer_gzip_writer_content(bbstreamer *streamer,
-										   bbstreamer_member *member,
-										   const char *data, int len,
-										   bbstreamer_archive_context context);
-static void bbstreamer_gzip_writer_finalize(bbstreamer *streamer);
-static void bbstreamer_gzip_writer_free(bbstreamer *streamer);
-static const char *get_gz_error(gzFile gzf);
-
-const bbstreamer_ops bbstreamer_gzip_writer_ops = {
-	.content = bbstreamer_gzip_writer_content,
-	.finalize = bbstreamer_gzip_writer_finalize,
-	.free = bbstreamer_gzip_writer_free
-};
-#endif
-
 static void bbstreamer_extractor_content(bbstreamer *streamer,
 										 bbstreamer_member *member,
 										 const char *data, int len,
@@ -195,159 +166,6 @@ bbstreamer_plain_writer_free(bbstreamer *streamer)
 	pfree(mystreamer);
 }
 
-/*
- * Create a bbstreamer that just compresses data using gzip, and then writes
- * it to a file.
- *
- * As in the case of bbstreamer_plain_writer_new, pathname is always used
- * for error reporting purposes; if file is NULL, it is also the opened and
- * closed so that the data may be written there.
- */
-bbstreamer *
-bbstreamer_gzip_writer_new(char *pathname, FILE *file, int compresslevel)
-{
-#ifdef HAVE_LIBZ
-	bbstreamer_gzip_writer *streamer;
-
-	streamer = palloc0(sizeof(bbstreamer_gzip_writer));
-	*((const bbstreamer_ops **) &streamer->base.bbs_ops) =
-		&bbstreamer_gzip_writer_ops;
-
-	streamer->pathname = pstrdup(pathname);
-
-	if (file == NULL)
-	{
-		streamer->gzfile = gzopen(pathname, "wb");
-		if (streamer->gzfile == NULL)
-		{
-			pg_log_error("could not create compressed file \"%s\": %m",
-						 pathname);
-			exit(1);
-		}
-	}
-	else
-	{
-		int			fd = dup(fileno(file));
-
-		if (fd < 0)
-		{
-			pg_log_error("could not duplicate stdout: %m");
-			exit(1);
-		}
-
-		streamer->gzfile = gzdopen(fd, "wb");
-		if (streamer->gzfile == NULL)
-		{
-			pg_log_error("could not open output file: %m");
-			exit(1);
-		}
-	}
-
-	if (gzsetparams(streamer->gzfile, compresslevel,
-					Z_DEFAULT_STRATEGY) != Z_OK)
-	{
-		pg_log_error("could not set compression level %d: %s",
-					 compresslevel, get_gz_error(streamer->gzfile));
-		exit(1);
-	}
-
-	return &streamer->base;
-#else
-	pg_log_error("this build does not support compression");
-	exit(1);
-#endif
-}
-
-#ifdef HAVE_LIBZ
-/*
- * Write archive content to gzip file.
- */
-static void
-bbstreamer_gzip_writer_content(bbstreamer *streamer,
-							   bbstreamer_member *member, const char *data,
-							   int len, bbstreamer_archive_context context)
-{
-	bbstreamer_gzip_writer *mystreamer;
-
-	mystreamer = (bbstreamer_gzip_writer *) streamer;
-
-	if (len == 0)
-		return;
-
-	errno = 0;
-	if (gzwrite(mystreamer->gzfile, data, len) != len)
-	{
-		/* if write didn't set errno, assume problem is no disk space */
-		if (errno == 0)
-			errno = ENOSPC;
-		pg_log_error("could not write to compressed file \"%s\": %s",
-					 mystreamer->pathname, get_gz_error(mystreamer->gzfile));
-		exit(1);
-	}
-}
-
-/*
- * End-of-archive processing when writing to a gzip file consists of just
- * calling gzclose.
- *
- * It makes no difference whether we opened the file or the caller did it,
- * because libz provides no way of avoiding a close on the underling file
- * handle. Notice, however, that bbstreamer_gzip_writer_new() uses dup() to
- * work around this issue, so that the behavior from the caller's viewpoint
- * is the same as for bbstreamer_plain_writer.
- */
-static void
-bbstreamer_gzip_writer_finalize(bbstreamer *streamer)
-{
-	bbstreamer_gzip_writer *mystreamer;
-
-	mystreamer = (bbstreamer_gzip_writer *) streamer;
-
-	errno = 0;					/* in case gzclose() doesn't set it */
-	if (gzclose(mystreamer->gzfile) != 0)
-	{
-		pg_log_error("could not close compressed file \"%s\": %m",
-					 mystreamer->pathname);
-		exit(1);
-	}
-
-	mystreamer->gzfile = NULL;
-}
-
-/*
- * Free memory associated with this bbstreamer.
- */
-static void
-bbstreamer_gzip_writer_free(bbstreamer *streamer)
-{
-	bbstreamer_gzip_writer *mystreamer;
-
-	mystreamer = (bbstreamer_gzip_writer *) streamer;
-
-	Assert(mystreamer->base.bbs_next == NULL);
-	Assert(mystreamer->gzfile == NULL);
-
-	pfree(mystreamer->pathname);
-	pfree(mystreamer);
-}
-
-/*
- * Helper function for libz error reporting.
- */
-static const char *
-get_gz_error(gzFile gzf)
-{
-	int			errnum;
-	const char *errmsg;
-
-	errmsg = gzerror(gzf, &errnum);
-	if (errnum == Z_ERRNO)
-		return strerror(errno);
-	else
-		return errmsg;
-}
-#endif
-
 /*
  * Create a bbstreamer that extracts an archive.
  *