</varlistentry>
<varlistentry id="guc-wal-compression" xreflabel="wal_compression">
- <term><varname>wal_compression</varname> (<type>boolean</type>)
+ <term><varname>wal_compression</varname> (<type>enum</type>)
<indexterm>
<primary><varname>wal_compression</varname> configuration parameter</primary>
</indexterm>
</term>
<listitem>
<para>
- When this parameter is <literal>on</literal>, the <productname>PostgreSQL</productname>
+ This parameter enables compression of WAL using the specified
+ compression method.
+ When enabled, the <productname>PostgreSQL</productname>
server compresses full page images written to WAL when
<xref linkend="guc-full-page-writes"/> is on or during a base backup.
A compressed page image will be decompressed during WAL replay.
- The default value is <literal>off</literal>.
- Only superusers can change this setting.
+ The supported methods are <literal>pglz</literal> and
+ <literal>lz4</literal> (if <productname>PostgreSQL</productname> was
+ compiled with <option>--with-lz4</option>). The default value is
+ <literal>off</literal>. Only superusers can change this setting.
</para>
<para>
- Turning this parameter on can reduce the WAL volume without
+ Enabling compression can reduce the WAL volume without
increasing the risk of unrecoverable data corruption,
but at the cost of some extra CPU spent on the compression during
WAL logging and on the decompression during WAL replay.
<term><productname>LZ4</productname></term>
<listitem><para>
Required for supporting <productname>LZ4</productname> compression
- method for compressing the table data. Binaries and source can be
+ method for compressing table or WAL data. Binaries and source can be
downloaded from
<ulink url="https://github.com/lz4/lz4/releases"></ulink>.
</para></listitem>
<para>
You need <productname>LZ4</productname>, if you want to support
compression of data with this method; see
- <xref linkend="guc-default-toast-compression"/>.
+ <xref linkend="guc-default-toast-compression"/> and
+ <xref linkend="guc-wal-compression"/>.
</para>
</listitem>
<para>
Build with <productname>LZ4</productname> compression support.
This allows the use of <productname>LZ4</productname> for
- compression of table data.
+ compression of table and WAL data.
</para>
</listitem>
</varlistentry>
<xsl:text>the configuration parameter default_toast_compression</xsl:text>
</xsl:template>
+<xsl:template match="xref[@linkend='guc-wal-compression']">
+ <xsl:text>the configuration parameter wal_compression</xsl:text>
+</xsl:template>
+
<xsl:template match="xref[@linkend='install-windows']">
<xsl:text>the documentation</xsl:text>
</xsl:template>
bool EnableHotStandby = false;
bool fullPageWrites = true;
bool wal_log_hints = false;
-bool wal_compression = false;
+int wal_compression = WAL_COMPRESSION_NONE;
char *wal_consistency_checking_string = NULL;
bool *wal_consistency_checking = NULL;
bool wal_init_zero = true;
#include "storage/proc.h"
#include "utils/memutils.h"
-/* Buffer size required to store a compressed version of backup block image */
-#define PGLZ_MAX_BLCKSZ PGLZ_MAX_OUTPUT(BLCKSZ)
+/*
+ * Guess the maximum buffer size required to store a compressed version of
+ * backup block image.
+ */
+#ifdef USE_LZ4
+#include <lz4.h>
+#define LZ4_MAX_BLCKSZ LZ4_COMPRESSBOUND(BLCKSZ)
+#else
+#define LZ4_MAX_BLCKSZ 0
+#endif
+
+#define PGLZ_MAX_BLCKSZ PGLZ_MAX_OUTPUT(BLCKSZ)
+
+#define COMPRESS_BUFSIZE Max(PGLZ_MAX_BLCKSZ, LZ4_MAX_BLCKSZ)
/*
* For each block reference registered with XLogRegisterBuffer, we fill in
* backup block data in XLogRecordAssemble() */
/* buffer to store a compressed version of backup block image */
- char compressed_page[PGLZ_MAX_BLCKSZ];
+ char compressed_page[COMPRESS_BUFSIZE];
} registered_buffer;
static registered_buffer *registered_buffers;
/*
* Try to compress a block image if wal_compression is enabled
*/
- if (wal_compression)
+ if (wal_compression != WAL_COMPRESSION_NONE)
{
is_compressed =
XLogCompressBackupBlock(page, bimg.hole_offset,
if (is_compressed)
{
+ /* The current compression is stored in the WAL record */
bimg.length = compressed_len;
- bimg.bimg_info |= BKPIMAGE_IS_COMPRESSED;
+
+ /* Set the compression method used for this block */
+ switch ((WalCompression) wal_compression)
+ {
+ case WAL_COMPRESSION_PGLZ:
+ bimg.bimg_info |= BKPIMAGE_COMPRESS_PGLZ;
+ break;
+
+ case WAL_COMPRESSION_LZ4:
+#ifdef USE_LZ4
+ bimg.bimg_info |= BKPIMAGE_COMPRESS_LZ4;
+#else
+ elog(ERROR, "LZ4 is not supported by this build");
+#endif
+ break;
+
+ case WAL_COMPRESSION_NONE:
+ Assert(false); /* cannot happen */
+ break;
+ /* no default case, so that compiler will warn */
+ }
rdt_datas_last->data = regbuf->compressed_page;
rdt_datas_last->len = compressed_len;
else
source = page;
+ switch ((WalCompression) wal_compression)
+ {
+ case WAL_COMPRESSION_PGLZ:
+ len = pglz_compress(source, orig_len, dest, PGLZ_strategy_default);
+ break;
+
+ case WAL_COMPRESSION_LZ4:
+#ifdef USE_LZ4
+ len = LZ4_compress_default(source, dest, orig_len,
+ COMPRESS_BUFSIZE);
+ if (len <= 0)
+ len = -1; /* failure */
+#else
+ elog(ERROR, "LZ4 is not supported by this build");
+#endif
+ break;
+
+ case WAL_COMPRESSION_NONE:
+ Assert(false); /* cannot happen */
+ break;
+ /* no default case, so that compiler will warn */
+ }
+
/*
- * We recheck the actual size even if pglz_compress() reports success and
- * see if the number of bytes saved by compression is larger than the
- * length of extra data needed for the compressed version of block image.
+ * We recheck the actual size even if compression reports success and see
+ * if the number of bytes saved by compression is larger than the length
+ * of extra data needed for the compressed version of block image.
*/
- len = pglz_compress(source, orig_len, dest, PGLZ_strategy_default);
if (len >= 0 &&
len + extra_bytes < orig_len)
{
#include "postgres.h"
#include <unistd.h>
+#ifdef USE_LZ4
+#include <lz4.h>
+#endif
#include "access/transam.h"
#include "access/xlog_internal.h"
blk->apply_image = ((blk->bimg_info & BKPIMAGE_APPLY) != 0);
- if (blk->bimg_info & BKPIMAGE_IS_COMPRESSED)
+ if (BKPIMAGE_COMPRESSED(blk->bimg_info))
{
if (blk->bimg_info & BKPIMAGE_HAS_HOLE)
COPY_HEADER_FIELD(&blk->hole_length, sizeof(uint16));
}
/*
- * cross-check that bimg_len < BLCKSZ if the IS_COMPRESSED
- * flag is set.
+ * Cross-check that bimg_len < BLCKSZ if it is compressed.
*/
- if ((blk->bimg_info & BKPIMAGE_IS_COMPRESSED) &&
+ if (BKPIMAGE_COMPRESSED(blk->bimg_info) &&
blk->bimg_len == BLCKSZ)
{
report_invalid_record(state,
- "BKPIMAGE_IS_COMPRESSED set, but block image length %u at %X/%X",
+ "BKPIMAGE_COMPRESSED set, but block image length %u at %X/%X",
(unsigned int) blk->bimg_len,
LSN_FORMAT_ARGS(state->ReadRecPtr));
goto err;
}
/*
- * cross-check that bimg_len = BLCKSZ if neither HAS_HOLE nor
- * IS_COMPRESSED flag is set.
+ * cross-check that bimg_len = BLCKSZ if neither HAS_HOLE is
+ * set nor COMPRESSED().
*/
if (!(blk->bimg_info & BKPIMAGE_HAS_HOLE) &&
- !(blk->bimg_info & BKPIMAGE_IS_COMPRESSED) &&
+ !BKPIMAGE_COMPRESSED(blk->bimg_info) &&
blk->bimg_len != BLCKSZ)
{
report_invalid_record(state,
- "neither BKPIMAGE_HAS_HOLE nor BKPIMAGE_IS_COMPRESSED set, but block image length is %u at %X/%X",
+ "neither BKPIMAGE_HAS_HOLE nor BKPIMAGE_COMPRESSED set, but block image length is %u at %X/%X",
(unsigned int) blk->data_len,
LSN_FORMAT_ARGS(state->ReadRecPtr));
goto err;
bkpb = &record->blocks[block_id];
ptr = bkpb->bkp_image;
- if (bkpb->bimg_info & BKPIMAGE_IS_COMPRESSED)
+ if (BKPIMAGE_COMPRESSED(bkpb->bimg_info))
{
/* If a backup block image is compressed, decompress it */
- if (pglz_decompress(ptr, bkpb->bimg_len, tmp.data,
- BLCKSZ - bkpb->hole_length, true) < 0)
+ bool decomp_success = true;
+
+ if ((bkpb->bimg_info & BKPIMAGE_COMPRESS_PGLZ) != 0)
+ {
+ if (pglz_decompress(ptr, bkpb->bimg_len, tmp.data,
+ BLCKSZ - bkpb->hole_length, true) < 0)
+ decomp_success = false;
+ }
+ else if ((bkpb->bimg_info & BKPIMAGE_COMPRESS_LZ4) != 0)
+ {
+#ifdef USE_LZ4
+ if (LZ4_decompress_safe(ptr, tmp.data,
+ bkpb->bimg_len, BLCKSZ - bkpb->hole_length) <= 0)
+ decomp_success = false;
+#else
+ report_invalid_record(record, "image at %X/%X compressed with %s not supported by build, block %d",
+ (uint32) (record->ReadRecPtr >> 32),
+ (uint32) record->ReadRecPtr,
+ "LZ4",
+ block_id);
+ return false;
+#endif
+ }
+ else
+ {
+ report_invalid_record(record, "image at %X/%X compressed with unknown method, block %d",
+ (uint32) (record->ReadRecPtr >> 32),
+ (uint32) record->ReadRecPtr,
+ block_id);
+ return false;
+ }
+
+ if (!decomp_success)
{
report_invalid_record(record, "invalid compressed image at %X/%X, block %d",
LSN_FORMAT_ARGS(record->ReadRecPtr),
block_id);
return false;
}
+
ptr = tmp.data;
}
{NULL, 0, false}
};
+static const struct config_enum_entry wal_compression_options[] = {
+ {"pglz", WAL_COMPRESSION_PGLZ, false},
+#ifdef USE_LZ4
+ {"lz4", WAL_COMPRESSION_LZ4, false},
+#endif
+ {"on", WAL_COMPRESSION_PGLZ, false},
+ {"off", WAL_COMPRESSION_NONE, false},
+ {"true", WAL_COMPRESSION_PGLZ, true},
+ {"false", WAL_COMPRESSION_NONE, true},
+ {"yes", WAL_COMPRESSION_PGLZ, true},
+ {"no", WAL_COMPRESSION_NONE, true},
+ {"1", WAL_COMPRESSION_PGLZ, true},
+ {"0", WAL_COMPRESSION_NONE, true},
+ {NULL, 0, false}
+};
+
/*
* Options for enum values stored in other modules
*/
NULL, NULL, NULL
},
- {
- {"wal_compression", PGC_SUSET, WAL_SETTINGS,
- gettext_noop("Compresses full-page writes written in WAL file."),
- NULL
- },
- &wal_compression,
- false,
- NULL, NULL, NULL
- },
-
{
{"wal_init_zero", PGC_SUSET, WAL_SETTINGS,
gettext_noop("Writes zeroes to new WAL files before first use."),
NULL, NULL, NULL
},
+ {
+ {"wal_compression", PGC_SUSET, WAL_SETTINGS,
+ gettext_noop("Compresses full-page writes written in WAL file with specified method."),
+ NULL
+ },
+ &wal_compression,
+ WAL_COMPRESSION_NONE, wal_compression_options,
+ NULL, NULL, NULL
+ },
+
{
{"wal_level", PGC_POSTMASTER, WAL_SETTINGS,
gettext_noop("Sets the level of information written to the WAL."),
#full_page_writes = on # recover from partial page writes
#wal_log_hints = off # also do full page writes of non-critical updates
# (change requires restart)
-#wal_compression = off # enable compression of full-page writes
+#wal_compression = off # enables compression of full-page writes;
+ # off, pglz, lz4, or on
#wal_init_zero = on # zero-fill new WAL files
#wal_recycle = on # recycle WAL files
#wal_buffers = -1 # min 32kB, -1 sets based on shared_buffers
blk);
if (XLogRecHasBlockImage(record, block_id))
{
- if (record->blocks[block_id].bimg_info &
- BKPIMAGE_IS_COMPRESSED)
+ uint8 bimg_info = record->blocks[block_id].bimg_info;
+
+ if (BKPIMAGE_COMPRESSED(bimg_info))
{
+ const char *method;
+
+ if ((bimg_info & BKPIMAGE_COMPRESS_PGLZ) != 0)
+ method = "pglz";
+ else if ((bimg_info & BKPIMAGE_COMPRESS_LZ4) != 0)
+ method = "lz4";
+ else
+ method = "unknown";
+
printf(" (FPW%s); hole: offset: %u, length: %u, "
- "compression saved: %u",
+ "compression saved: %u, method: %s",
XLogRecBlockImageApply(record, block_id) ?
"" : " for WAL verification",
record->blocks[block_id].hole_offset,
record->blocks[block_id].hole_length,
BLCKSZ -
record->blocks[block_id].hole_length -
- record->blocks[block_id].bimg_len);
+ record->blocks[block_id].bimg_len,
+ method);
}
else
{
extern bool EnableHotStandby;
extern bool fullPageWrites;
extern bool wal_log_hints;
-extern bool wal_compression;
+extern int wal_compression;
extern bool wal_init_zero;
extern bool wal_recycle;
extern bool *wal_consistency_checking;
WAL_LEVEL_LOGICAL
} WalLevel;
+/* Compression algorithms for WAL */
+typedef enum WalCompression
+{
+ WAL_COMPRESSION_NONE = 0,
+ WAL_COMPRESSION_PGLZ,
+ WAL_COMPRESSION_LZ4
+} WalCompression;
+
/* Recovery states */
typedef enum RecoveryState
{
* present is (BLCKSZ - <length of "hole" bytes>).
*
* Additionally, when wal_compression is enabled, we will try to compress full
- * page images using the PGLZ compression algorithm, after removing the "hole".
- * This can reduce the WAL volume, but at some extra cost of CPU spent
+ * page images using one of the supported algorithms, after removing the
+ * "hole". This can reduce the WAL volume, but at some extra cost of CPU spent
* on the compression during WAL logging. In this case, since the "hole"
* length cannot be calculated by subtracting the number of page image bytes
* from BLCKSZ, basically it needs to be stored as an extra information.
uint8 bimg_info; /* flag bits, see below */
/*
- * If BKPIMAGE_HAS_HOLE and BKPIMAGE_IS_COMPRESSED, an
+ * If BKPIMAGE_HAS_HOLE and BKPIMAGE_COMPRESSED(), an
* XLogRecordBlockCompressHeader struct follows.
*/
} XLogRecordBlockImageHeader;
/* Information stored in bimg_info */
#define BKPIMAGE_HAS_HOLE 0x01 /* page image has "hole" */
-#define BKPIMAGE_IS_COMPRESSED 0x02 /* page image is compressed */
-#define BKPIMAGE_APPLY 0x04 /* page image should be restored during
- * replay */
+#define BKPIMAGE_APPLY 0x02 /* page image should be restored
+ * during replay */
+/* compression methods supported */
+#define BKPIMAGE_COMPRESS_PGLZ 0x04
+#define BKPIMAGE_COMPRESS_LZ4 0x08
+#define BKPIMAGE_COMPRESSED(info) \
+ ((info & (BKPIMAGE_COMPRESS_PGLZ | BKPIMAGE_COMPRESS_LZ4)) != 0)
/*
* Extra header information used when page image has "hole" and
WaitEventTimeout
WaitPMResult
WalCloseMethod
+WalCompression
WalLevel
WalRcvData
WalRcvExecResult
projects / postgresql.git / commitdiff