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Unify buffer sizes in pg_dump compression API 

Prior to the introduction of the compression API in e9960732a9, pg_dump
would use the ZLIB_IN_SIZE/ZLIB_OUT_SIZE to size input/output buffers.
Commit 0da243fed0 introduced similar constants for LZ4, but while gzip
defined both buffers to be 4kB, LZ4 used 4kB and 16kB without any clear
reasoning why that's desirable.

Furthermore, parts of the code unaware of which compression is used
(e.g. pg_backup_directory.c) continued to use ZLIB_OUT_SIZE directly.

Simplify by replacing the various constants with DEFAULT_IO_BUFFER_SIZE,
set to 4kB. The compression implementations still have an option to use
a custom value, but considering 4kB was fine for 20+ years, I find that
unlikely (and we'd probably just increase the default buffer size).

Author: Georgios Kokolatos
Reviewed-by: Tomas Vondra, Justin Pryzby
Discussion: https://postgr.es/m/33496f7c-3449-1426-d568-63f6bca2ac1f@gmail.com
This commit is contained in:
Tomas Vondra 2023-03-23 17:52:32 +01:00
parent d3b57755e6
commit f081a48f9a
5 changed files with 21 additions and 25 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
src/bin/pg_dump/compress_gzip.c
View File

@ -120,8 +120,8 @@ WriteDataToArchiveGzip(ArchiveHandle *AH, CompressorState *cs,
* actually allocate one extra byte because some routines want to
* append a trailing zero byte to the zlib output.
*/
gzipcs->outbuf = pg_malloc(ZLIB_OUT_SIZE + 1);
gzipcs->outsize = ZLIB_OUT_SIZE;
gzipcs->outsize = DEFAULT_IO_BUFFER_SIZE;
gzipcs->outbuf = pg_malloc(gzipcs->outsize + 1);
/*
* A level of zero simply copies the input one block at the time. This
@ -158,10 +158,10 @@ ReadDataFromArchiveGzip(ArchiveHandle *AH, CompressorState *cs)
zp->zfree = Z_NULL;
zp->opaque = Z_NULL;
buf = pg_malloc(ZLIB_IN_SIZE);
buflen = ZLIB_IN_SIZE;
buflen = DEFAULT_IO_BUFFER_SIZE;
buf = pg_malloc(buflen);
out = pg_malloc(ZLIB_OUT_SIZE + 1);
out = pg_malloc(DEFAULT_IO_BUFFER_SIZE + 1);
if (inflateInit(zp) != Z_OK)
pg_fatal("could not initialize compression library: %s",
@ -176,14 +176,14 @@ ReadDataFromArchiveGzip(ArchiveHandle *AH, CompressorState *cs)
while (zp->avail_in > 0)
{
zp->next_out = (void *) out;
zp->avail_out = ZLIB_OUT_SIZE;
zp->avail_out = DEFAULT_IO_BUFFER_SIZE;
res = inflate(zp, 0);
if (res != Z_OK && res != Z_STREAM_END)
pg_fatal("could not uncompress data: %s", zp->msg);
out[ZLIB_OUT_SIZE - zp->avail_out] = '\0';
ahwrite(out, 1, ZLIB_OUT_SIZE - zp->avail_out, AH);
out[DEFAULT_IO_BUFFER_SIZE - zp->avail_out] = '\0';
ahwrite(out, 1, DEFAULT_IO_BUFFER_SIZE - zp->avail_out, AH);
}
}
@ -192,13 +192,13 @@ ReadDataFromArchiveGzip(ArchiveHandle *AH, CompressorState *cs)
while (res != Z_STREAM_END)
{
zp->next_out = (void *) out;
zp->avail_out = ZLIB_OUT_SIZE;
zp->avail_out = DEFAULT_IO_BUFFER_SIZE;
res = inflate(zp, 0);
if (res != Z_OK && res != Z_STREAM_END)
pg_fatal("could not uncompress data: %s", zp->msg);
out[ZLIB_OUT_SIZE - zp->avail_out] = '\0';
ahwrite(out, 1, ZLIB_OUT_SIZE - zp->avail_out, AH);
out[DEFAULT_IO_BUFFER_SIZE - zp->avail_out] = '\0';
ahwrite(out, 1, DEFAULT_IO_BUFFER_SIZE - zp->avail_out, AH);
}
if (inflateEnd(zp) != Z_OK)

5
src/bin/pg_dump/compress_io.h
View File

@ -17,9 +17,8 @@
#include "pg_backup_archiver.h"
/* Initial buffer sizes used in zlib compression. */
#define ZLIB_OUT_SIZE 4096
#define ZLIB_IN_SIZE 4096
/* Default size used for IO buffers */
#define DEFAULT_IO_BUFFER_SIZE 4096
extern char *supports_compression(const pg_compress_specification compression_spec);

11
src/bin/pg_dump/compress_lz4.c
View File

@ -20,9 +20,6 @@
#include <lz4.h>
#include <lz4frame.h>
#define LZ4_OUT_SIZE (4 * 1024)
#define LZ4_IN_SIZE (16 * 1024)
/*
* LZ4F_HEADER_SIZE_MAX first appeared in v1.7.5 of the library.
* Redefine it for installations with a lesser version.
@ -57,7 +54,7 @@ ReadDataFromArchiveLZ4(ArchiveHandle *AH, CompressorState *cs)
size_t buflen;
size_t cnt;
buflen = LZ4_IN_SIZE;
buflen = DEFAULT_IO_BUFFER_SIZE;
buf = pg_malloc(buflen);
decbuf = pg_malloc(buflen);
@ -208,7 +205,7 @@ LZ4File_init(LZ4File *fs, int size, bool compressing)
if (fs->compressing)
{
fs->buflen = LZ4F_compressBound(LZ4_IN_SIZE, &fs->prefs);
fs->buflen = LZ4F_compressBound(DEFAULT_IO_BUFFER_SIZE, &fs->prefs);
if (fs->buflen < LZ4F_HEADER_SIZE_MAX)
fs->buflen = LZ4F_HEADER_SIZE_MAX;
@ -244,7 +241,7 @@ LZ4File_init(LZ4File *fs, int size, bool compressing)
return false;
}
fs->buflen = size > LZ4_OUT_SIZE ? size : LZ4_OUT_SIZE;
fs->buflen = Max(size, DEFAULT_IO_BUFFER_SIZE);
fs->buffer = pg_malloc(fs->buflen);
fs->overflowalloclen = fs->buflen;
@ -423,7 +420,7 @@ LZ4File_write(const void *ptr, size_t size, CompressFileHandle *CFH)
while (remaining > 0)
{
int chunk = remaining < LZ4_IN_SIZE ? remaining : LZ4_IN_SIZE;
int chunk = Min(remaining, DEFAULT_IO_BUFFER_SIZE);
remaining -= chunk;

4
src/bin/pg_dump/compress_none.c
View File

@ -33,8 +33,8 @@ ReadDataFromArchiveNone(ArchiveHandle *AH, CompressorState *cs)
char *buf;
size_t buflen;
buf = pg_malloc(ZLIB_OUT_SIZE);
buflen = ZLIB_OUT_SIZE;
buflen = DEFAULT_IO_BUFFER_SIZE;
buf = pg_malloc(buflen);
while ((cnt = cs->readF(AH, &buf, &buflen)))
{

4
src/bin/pg_dump/pg_backup_directory.c
View File

@ -394,8 +394,8 @@ _PrintFileData(ArchiveHandle *AH, char *filename)
if (!CFH)
pg_fatal("could not open input file \"%s\": %m", filename);
buf = pg_malloc(ZLIB_OUT_SIZE);
buflen = ZLIB_OUT_SIZE;
buflen = DEFAULT_IO_BUFFER_SIZE;
buf = pg_malloc(buflen);
while (CFH->read_func(buf, buflen, &cnt, CFH) && cnt > 0)
{