diff --git a/contrib/pg_xlogdump/pg_xlogdump.c b/contrib/pg_xlogdump/pg_xlogdump.c
index c1bfbc2..3ebaac6 100644
--- a/contrib/pg_xlogdump/pg_xlogdump.c
+++ b/contrib/pg_xlogdump/pg_xlogdump.c
@@ -363,14 +363,14 @@ XLogDumpCountRecord(XLogDumpConfig *config, XLogDumpStats *stats,
* takes up BLCKSZ bytes, minus the "hole" length.
*
* XXX: We peek into xlogreader's private decoded backup blocks for the
- * hole_length. It doesn't seem worth it to add an accessor macro for
+ * length of block. It doesn't seem worth it to add an accessor macro for
* this.
*/
fpi_len = 0;
for (block_id = 0; block_id <= record->max_block_id; block_id++)
{
if (XLogRecHasBlockImage(record, block_id))
- fpi_len += BLCKSZ - record->blocks[block_id].hole_length;
+ fpi_len += record->blocks[block_id].bkp_len;
}
/* Update per-rmgr statistics */
@@ -465,9 +465,16 @@ XLogDumpDisplayRecord(XLogDumpConfig *config, XLogReaderState *record)
blk);
if (XLogRecHasBlockImage(record, block_id))
{
- printf(" (FPW); hole: offset: %u, length: %u\n",
- record->blocks[block_id].hole_offset,
- record->blocks[block_id].hole_length);
+ if (record->blocks[block_id].is_compressed)
+ printf(" (FPW compressed); hole offset: %u, "
+ "compressed length: %u, original length: %u\n",
+ record->blocks[block_id].hole_offset,
+ record->blocks[block_id].bkp_len,
+ record->blocks[block_id].bkp_uncompress_len);
+ else
+ printf(" (FPW); hole offset: %u, length: %u\n",
+ record->blocks[block_id].hole_offset,
+ record->blocks[block_id].bkp_len);
}
putchar('\n');
}
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 9261e7f..1e5d4ea 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -2282,6 +2282,35 @@ include_dir 'conf.d'
+
+ wal_compression (boolean)
+
+ wal_compression configuration parameter
+
+
+
+
+ When this parameter is on, the PostgreSQL
+ server compresses the content of full-page writes when necessary and
+ inserts in WAL records with smaller sizes, reducing the amount of
+ WAL stored on disk.
+
+
+
+ Compression has the advantage of reducing the amount of disk I/O when
+ doing WAL-logging, at the cost of some extra CPU to perform the
+ compression of a block image. At WAL replay, compressed block images
+ need extra CPU cycles to perform the decompression of each block
+ image, but it can reduce as well replay time in I/O bounded
+ environments.
+
+
+
+ The default value is off.
+
+
+
+
wal_buffers (integer)
diff --git a/src/backend/access/transam/xlog.c b/src/backend/access/transam/xlog.c
index a28155f..b0d401d 100644
--- a/src/backend/access/transam/xlog.c
+++ b/src/backend/access/transam/xlog.c
@@ -89,6 +89,7 @@ char *XLogArchiveCommand = NULL;
bool EnableHotStandby = false;
bool fullPageWrites = true;
bool wal_log_hints = false;
+bool wal_compression = false;
bool log_checkpoints = false;
int sync_method = DEFAULT_SYNC_METHOD;
int wal_level = WAL_LEVEL_MINIMAL;
@@ -4671,7 +4672,7 @@ BootStrapXLOG(void)
record->xl_rmid = RM_XLOG_ID;
recptr += SizeOfXLogRecord;
/* fill the XLogRecordDataHeaderShort struct */
- *(recptr++) = XLR_BLOCK_ID_DATA_SHORT;
+ *(recptr++) = XLR_CHUNK_ID_DATA_SHORT;
*(recptr++) = sizeof(checkPoint);
memcpy(recptr, &checkPoint, sizeof(checkPoint));
recptr += sizeof(checkPoint);
diff --git a/src/backend/access/transam/xloginsert.c b/src/backend/access/transam/xloginsert.c
index a1e2eb8..68ec8f1 100644
--- a/src/backend/access/transam/xloginsert.c
+++ b/src/backend/access/transam/xloginsert.c
@@ -24,12 +24,16 @@
#include "access/xlog_internal.h"
#include "access/xloginsert.h"
#include "catalog/pg_control.h"
+#include "common/pg_lzcompress.h"
#include "miscadmin.h"
#include "storage/bufmgr.h"
#include "storage/proc.h"
#include "utils/memutils.h"
#include "pg_trace.h"
+/* maximum size for compression buffer of block image */
+#define PGLZ_MAX_BLCKSZ PGLZ_MAX_OUTPUT(BLCKSZ)
+
/*
* For each block reference registered with XLogRegisterBuffer, we fill in
* a registered_buffer struct.
@@ -50,6 +54,8 @@ typedef struct
XLogRecData bkp_rdatas[2]; /* temporary rdatas used to hold references to
* backup block data in XLogRecordAssemble() */
+ char compressed_page[PGLZ_MAX_BLCKSZ]; /* recipient for compressed
+ * page */
} registered_buffer;
static registered_buffer *registered_buffers;
@@ -81,6 +87,9 @@ static char *hdr_scratch = NULL;
MaxSizeOfXLogRecordBlockHeader * (XLR_MAX_BLOCK_ID + 1) + \
SizeOfXLogRecordDataHeaderLong)
+/* Scratch buffer holding block image data to be compressed */
+static char *compression_scratch = NULL;
+
/*
* An array of XLogRecData structs, to hold registered data.
*/
@@ -97,6 +106,9 @@ static XLogRecData *XLogRecordAssemble(RmgrId rmid, uint8 info,
XLogRecPtr RedoRecPtr, bool doPageWrites,
XLogRecPtr *fpw_lsn);
+static bool XLogCompressBackupBlock(char *page, uint16 hole_offset,
+ uint16 hole_length, char *dest, uint16 *len);
+
/*
* Begin constructing a WAL record. This must be called before the
* XLogRegister* functions and XLogInsert().
@@ -482,7 +494,12 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
bool needs_data;
XLogRecordBlockHeader bkpb;
XLogRecordBlockImageHeader bimg;
+ XLogRecordBlockImageCompressionInfo cbimg;
bool samerel;
+ bool is_compressed = false;
+ bool with_hole = false;
+ uint8 chunk_id = 0;
+ chunk_id |= XLR_CHUNK_BLOCK_REFERENCE;
if (!regbuf->in_use)
continue;
@@ -529,9 +546,13 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
if (needs_backup)
{
Page page = regbuf->page;
+ uint16 hole_length;
+ uint16 hole_offset;
+ uint16 compress_len = 0;
/*
- * The page needs to be backed up, so set up *bimg
+ * The page needs to be backed up, so calculate its hole length
+ * and offset.
*/
if (regbuf->flags & REGBUF_STANDARD)
{
@@ -543,50 +564,98 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
upper > lower &&
upper <= BLCKSZ)
{
- bimg.hole_offset = lower;
- bimg.hole_length = upper - lower;
+ hole_offset = lower;
+ hole_length = upper - lower;
}
else
{
/* No "hole" to compress out */
- bimg.hole_offset = 0;
- bimg.hole_length = 0;
+ hole_offset = 0;
+ hole_length = 0;
}
}
else
{
/* Not a standard page header, don't try to eliminate "hole" */
- bimg.hole_offset = 0;
- bimg.hole_length = 0;
+ hole_offset = 0;
+ hole_length = 0;
}
- /* Fill in the remaining fields in the XLogRecordBlockData struct */
- bkpb.fork_flags |= BKPBLOCK_HAS_IMAGE;
+ /*
+ * First try to compress block without its hole to improve the
+ * compression of the whole. If the block is considered as
+ * not compressible, complete the block header information
+ * accordingly.
+ */
+ if (wal_compression)
+ {
+
+ /* Perform compression of block */
+ if (XLogCompressBackupBlock(page,hole_offset,
+ hole_length,
+ regbuf->compressed_page,
+ &compress_len))
+ {
+ /* compression is done, add record */
+ is_compressed = true;
+ }
+ }
- total_len += BLCKSZ - bimg.hole_length;
+ chunk_id |= XLR_CHUNK_BLOCK_HAS_IMAGE;
/*
* Construct XLogRecData entries for the page content.
*/
- rdt_datas_last->next = ®buf->bkp_rdatas[0];
- rdt_datas_last = rdt_datas_last->next;
- if (bimg.hole_length == 0)
+
+ if (is_compressed)
{
- rdt_datas_last->data = page;
- rdt_datas_last->len = BLCKSZ;
+ /* compressed block information */
+ bimg.length = compress_len;
+ bimg.hole_offset = hole_offset;
+ chunk_id |= XLR_CHUNK_BKP_COMPRESSED;
+ if (hole_length != 0)
+ {
+ cbimg.raw_length = BLCKSZ - hole_length;
+ chunk_id |= XLR_CHUNK_BKP_WITH_HOLE;
+ with_hole = true;
+ }
+
+ /* record entry for compressed block */
+ rdt_datas_last->next = ®buf->bkp_rdatas[0];
+ rdt_datas_last = rdt_datas_last->next;
+ rdt_datas_last->data = regbuf->compressed_page;
+ rdt_datas_last->len = compress_len;
}
else
{
- /* must skip the hole */
- rdt_datas_last->data = page;
- rdt_datas_last->len = bimg.hole_offset;
+ /* uncompressed block information */
+ bimg.length = BLCKSZ - hole_length;
+ bimg.hole_offset = hole_offset;
- rdt_datas_last->next = ®buf->bkp_rdatas[1];
+ /* record entries for uncompressed block */
+ rdt_datas_last->next = ®buf->bkp_rdatas[0];
rdt_datas_last = rdt_datas_last->next;
+ if (hole_length == 0)
+ {
+ rdt_datas_last->data = page;
+ rdt_datas_last->len = BLCKSZ;
+ }
+ else
+ {
+ /* must skip the hole */
+ rdt_datas_last->data = page;
+ rdt_datas_last->len = hole_offset;
+
+ rdt_datas_last->next = ®buf->bkp_rdatas[1];
+ rdt_datas_last = rdt_datas_last->next;
- rdt_datas_last->data = page + (bimg.hole_offset + bimg.hole_length);
- rdt_datas_last->len = BLCKSZ - (bimg.hole_offset + bimg.hole_length);
+ rdt_datas_last->data = page + (hole_offset + hole_length);
+ rdt_datas_last->len = BLCKSZ - (hole_offset + hole_length);
+ chunk_id |= XLR_CHUNK_BKP_WITH_HOLE;
+ with_hole = true;
+ }
}
+ total_len += bimg.length;
}
if (needs_data)
@@ -595,7 +664,7 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
* Link the caller-supplied rdata chain for this buffer to the
* overall list.
*/
- bkpb.fork_flags |= BKPBLOCK_HAS_DATA;
+ chunk_id |= XLR_CHUNK_BLOCK_HAS_DATA;
bkpb.data_length = regbuf->rdata_len;
total_len += regbuf->rdata_len;
@@ -613,12 +682,22 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
samerel = false;
/* Ok, copy the header to the scratch buffer */
+
+ /* chunk_id to identify block reference */
+ *(scratch++) = (uint8) chunk_id;
+
memcpy(scratch, &bkpb, SizeOfXLogRecordBlockHeader);
scratch += SizeOfXLogRecordBlockHeader;
if (needs_backup)
{
memcpy(scratch, &bimg, SizeOfXLogRecordBlockImageHeader);
scratch += SizeOfXLogRecordBlockImageHeader;
+ if (is_compressed && with_hole)
+ {
+ memcpy(scratch, &cbimg,
+ SizeOfXLogRecordBlockImageCompressionInfo);
+ scratch += SizeOfXLogRecordBlockImageCompressionInfo;
+ }
}
if (!samerel)
{
@@ -634,13 +713,13 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
{
if (mainrdata_len > 255)
{
- *(scratch++) = XLR_BLOCK_ID_DATA_LONG;
+ *(scratch++) = XLR_CHUNK_ID_DATA_LONG;
memcpy(scratch, &mainrdata_len, sizeof(uint32));
scratch += sizeof(uint32);
}
else
{
- *(scratch++) = XLR_BLOCK_ID_DATA_SHORT;
+ *(scratch++) = XLR_CHUNK_ID_DATA_SHORT;
*(scratch++) = (uint8) mainrdata_len;
}
rdt_datas_last->next = mainrdata_head;
@@ -681,6 +760,51 @@ XLogRecordAssemble(RmgrId rmid, uint8 info,
}
/*
+ * Create a compressed version of a backup block. If successful, return
+ * true and set 'len' to its length. If block cannot be compressed or if
+ * compression failed return false.
+ */
+static bool
+XLogCompressBackupBlock(char *page, uint16 hole_offset, uint16 hole_length,
+ char *dest, uint16 *len)
+{
+ int orig_len = BLCKSZ - hole_length;
+ char *scratch_buf;
+ int32 compressed_len;
+
+ if (hole_length != 0)
+ {
+ scratch_buf = compression_scratch;
+ memcpy(scratch_buf, page, hole_offset);
+ memcpy(scratch_buf + hole_offset,
+ page + (hole_offset + hole_length),
+ BLCKSZ - (hole_length + hole_offset));
+ }
+ else
+ scratch_buf = page;
+
+ /* run compression */
+ compressed_len = pglz_compress(scratch_buf, orig_len, dest,
+ PGLZ_strategy_default);
+
+ /* leave if data cannot be compressed */
+ if (compressed_len < 0)
+ return false;
+
+ /*
+ * We recheck the actual size even if pglz_compress() reports success and
+ * see if at least 2 bytes of length have been saved, as this corresponds
+ * to the additional amount of data stored in WAL record for a compressed
+ * block via raw_length when block contains hole.
+ */
+ *len = (uint16) compressed_len;
+ if ((hole_length != 0) &&
+ (*len >= orig_len - SizeOfXLogRecordBlockImageCompressionInfo))
+ return false;
+ return true;
+}
+
+/*
* Determine whether the buffer referenced has to be backed up.
*
* Since we don't yet have the insert lock, fullPageWrites and forcePageWrites
@@ -893,4 +1017,9 @@ InitXLogInsert(void)
if (hdr_scratch == NULL)
hdr_scratch = MemoryContextAllocZero(xloginsert_cxt,
HEADER_SCRATCH_SIZE);
+
+ /* allocate scratch buffer used for compression of block images */
+ if (compression_scratch == NULL)
+ compression_scratch = MemoryContextAllocZero(xloginsert_cxt,
+ BLCKSZ);
}
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c
index 60470b5..37693df 100644
--- a/src/backend/access/transam/xlogreader.c
+++ b/src/backend/access/transam/xlogreader.c
@@ -20,6 +20,7 @@
#include "access/xlog_internal.h"
#include "access/xlogreader.h"
#include "catalog/pg_control.h"
+#include "common/pg_lzcompress.h"
static bool allocate_recordbuf(XLogReaderState *state, uint32 reclength);
@@ -74,13 +75,15 @@ XLogReaderAllocate(XLogPageReadCB pagereadfunc, void *private_data)
state->max_block_id = -1;
/*
- * Permanently allocate readBuf. We do it this way, rather than just
- * making a static array, for two reasons: (1) no need to waste the
- * storage in most instantiations of the backend; (2) a static char array
- * isn't guaranteed to have any particular alignment, whereas palloc()
- * will provide MAXALIGN'd storage.
+ * Permanently allocate readBuf and uncompressBuf. We do it this way,
+ * rather than just making a static array, for two reasons:
+ * (1) no need to waste the storage in most instantiations of the
+ * backend; (2) a static char array isn't guaranteed to have any
+ * particular alignment, whereas palloc() will provide MAXALIGN'd
+ * storage.
*/
state->readBuf = (char *) palloc(XLOG_BLCKSZ);
+ state->uncompressBuf = (char *) palloc(BLCKSZ);
state->read_page = pagereadfunc;
/* system_identifier initialized to zeroes above */
@@ -98,6 +101,7 @@ XLogReaderAllocate(XLogPageReadCB pagereadfunc, void *private_data)
{
pfree(state->errormsg_buf);
pfree(state->readBuf);
+ pfree(state->uncompressBuf);
pfree(state);
return NULL;
}
@@ -125,6 +129,7 @@ XLogReaderFree(XLogReaderState *state)
if (state->readRecordBuf)
pfree(state->readRecordBuf);
pfree(state->readBuf);
+ pfree(state->uncompressBuf);
pfree(state);
}
@@ -133,7 +138,7 @@ XLogReaderFree(XLogReaderState *state)
* Returns true if successful, false if out of memory.
*
* readRecordBufSize is set to the new buffer size.
- *
+
* To avoid useless small increases, round its size to a multiple of
* XLOG_BLCKSZ, and make sure it's at least 5*Max(BLCKSZ, XLOG_BLCKSZ) to start
* with. (That is enough for all "normal" records, but very large commit or
@@ -922,6 +927,8 @@ ResetDecoder(XLogReaderState *state)
state->blocks[block_id].in_use = false;
state->blocks[block_id].has_image = false;
state->blocks[block_id].has_data = false;
+ state->blocks[block_id].is_compressed = false;
+ state->blocks[block_id].with_hole = false;
}
state->max_block_id = -1;
}
@@ -952,6 +959,7 @@ DecodeXLogRecord(XLogReaderState *state, XLogRecord *record, char **errormsg)
uint32 datatotal;
RelFileNode *rnode = NULL;
uint8 block_id;
+ uint8 chunk_id;
ResetDecoder(state);
@@ -965,9 +973,9 @@ DecodeXLogRecord(XLogReaderState *state, XLogRecord *record, char **errormsg)
datatotal = 0;
while (remaining > datatotal)
{
- COPY_HEADER_FIELD(&block_id, sizeof(uint8));
+ COPY_HEADER_FIELD(&chunk_id, sizeof(uint8));
- if (block_id == XLR_BLOCK_ID_DATA_SHORT)
+ if (chunk_id == XLR_CHUNK_ID_DATA_SHORT)
{
/* XLogRecordDataHeaderShort */
uint8 main_data_len;
@@ -979,7 +987,7 @@ DecodeXLogRecord(XLogReaderState *state, XLogRecord *record, char **errormsg)
break; /* by convention, the main data fragment is
* always last */
}
- else if (block_id == XLR_BLOCK_ID_DATA_LONG)
+ else if (chunk_id == XLR_CHUNK_ID_DATA_LONG)
{
/* XLogRecordDataHeaderLong */
uint32 main_data_len;
@@ -990,81 +998,148 @@ DecodeXLogRecord(XLogReaderState *state, XLogRecord *record, char **errormsg)
break; /* by convention, the main data fragment is
* always last */
}
- else if (block_id <= XLR_MAX_BLOCK_ID)
+ else if ((chunk_id & XLR_CHUNK_BLOCK_REFERENCE) != 0)
{
- /* XLogRecordBlockHeader */
- DecodedBkpBlock *blk;
- uint8 fork_flags;
-
- if (block_id <= state->max_block_id)
+ COPY_HEADER_FIELD(&block_id, sizeof(uint8));
+ if (block_id <= XLR_MAX_BLOCK_ID)
{
- report_invalid_record(state,
- "out-of-order block_id %u at %X/%X",
- block_id,
- (uint32) (state->ReadRecPtr >> 32),
- (uint32) state->ReadRecPtr);
- goto err;
- }
- state->max_block_id = block_id;
+ /* XLogRecordBlockHeader */
+ DecodedBkpBlock *blk;
+ uint8 fork_flags;
- blk = &state->blocks[block_id];
- blk->in_use = true;
+ if (block_id <= state->max_block_id)
+ {
+ report_invalid_record(state,
+ "out-of-order block_id %u at %X/%X",
+ block_id,
+ (uint32) (state->ReadRecPtr >> 32),
+ (uint32) state->ReadRecPtr);
+ goto err;
+ }
+ state->max_block_id = block_id;
- COPY_HEADER_FIELD(&fork_flags, sizeof(uint8));
- blk->forknum = fork_flags & BKPBLOCK_FORK_MASK;
- blk->flags = fork_flags;
- blk->has_image = ((fork_flags & BKPBLOCK_HAS_IMAGE) != 0);
- blk->has_data = ((fork_flags & BKPBLOCK_HAS_DATA) != 0);
+ blk = &state->blocks[block_id];
+ blk->in_use = true;
- COPY_HEADER_FIELD(&blk->data_len, sizeof(uint16));
- /* cross-check that the HAS_DATA flag is set iff data_length > 0 */
- if (blk->has_data && blk->data_len == 0)
- report_invalid_record(state,
- "BKPBLOCK_HAS_DATA set, but no data included at %X/%X",
- (uint32) (state->ReadRecPtr >> 32), (uint32) state->ReadRecPtr);
- if (!blk->has_data && blk->data_len != 0)
- report_invalid_record(state,
- "BKPBLOCK_HAS_DATA not set, but data length is %u at %X/%X",
- (unsigned int) blk->data_len,
- (uint32) (state->ReadRecPtr >> 32), (uint32) state->ReadRecPtr);
- datatotal += blk->data_len;
+ COPY_HEADER_FIELD(&fork_flags, sizeof(uint8));
+ blk->forknum = fork_flags & BKPBLOCK_FORK_MASK;
+ blk->flags = fork_flags;
+ blk->has_image = ((chunk_id & XLR_CHUNK_BLOCK_HAS_IMAGE) != 0);
+ blk->has_data = ((chunk_id & XLR_CHUNK_BLOCK_HAS_DATA) != 0);
- if (blk->has_image)
- {
- COPY_HEADER_FIELD(&blk->hole_offset, sizeof(uint16));
- COPY_HEADER_FIELD(&blk->hole_length, sizeof(uint16));
- datatotal += BLCKSZ - blk->hole_length;
- }
- if (!(fork_flags & BKPBLOCK_SAME_REL))
- {
- COPY_HEADER_FIELD(&blk->rnode, sizeof(RelFileNode));
- rnode = &blk->rnode;
+ COPY_HEADER_FIELD(&blk->data_len, sizeof(uint16));
+ /* cross-check that the HAS_DATA flag is set iff data_length > 0 */
+ if (blk->has_data && blk->data_len == 0)
+ report_invalid_record(state,
+ "XLR_CHUNK_BLOCK_HAS_DATA set, but no data included at %X/%X",
+ (uint32) (state->ReadRecPtr >> 32), (uint32) state->ReadRecPtr);
+ if (!blk->has_data && blk->data_len != 0)
+ report_invalid_record(state,
+ "XLR_CHUNK_BLOCK_HAS_DATA not set, but data length is %u at %X/%X",
+ (unsigned int) blk->data_len,
+ (uint32) (state->ReadRecPtr >> 32), (uint32) state->ReadRecPtr);
+ datatotal += blk->data_len;
+
+ if (blk->has_image)
+ {
+ XLogRecordBlockImageHeader bkp_info;
+ COPY_HEADER_FIELD(&bkp_info, sizeof(XLogRecordBlockImageHeader));
+ blk->bkp_len = bkp_info.length;
+ blk->hole_offset = bkp_info.hole_offset;
+
+ blk->is_compressed = ((chunk_id & XLR_CHUNK_BKP_COMPRESSED) != 0);
+ blk->with_hole = ((chunk_id & XLR_CHUNK_BKP_WITH_HOLE) != 0);
+
+ if ((blk->with_hole == 0 && blk->hole_offset != 0) ||
+ (blk->with_hole == 1 && blk->hole_offset <= 0))
+ {
+ report_invalid_record(state,
+ "Invalid hole offset in record %X/%X",
+ (uint32) (state->ReadRecPtr >> 32),
+ (uint32) state->ReadRecPtr);
+ goto err;
+ }
+
+ if (blk->is_compressed == 1)
+ {
+ if (blk->with_hole == 1)
+ {
+ COPY_HEADER_FIELD(&blk->bkp_uncompress_len, sizeof(uint16));
+ if (blk->bkp_uncompress_len >= BLCKSZ)
+ {
+ report_invalid_record(state,
+ "Invalid block length in record %X/%X",
+ (uint32) (state->ReadRecPtr >> 32),
+ (uint32) state->ReadRecPtr);
+ goto err;
+ }
+ }
+ else
+ blk->bkp_uncompress_len = BLCKSZ;
+ }
+ else
+ {
+ /*
+ * Length of a block image must be less than BLCKSZ
+ * if the block has hole
+ */
+ if (blk->with_hole == 1 && blk->bkp_len >= BLCKSZ)
+ report_invalid_record(state,
+ "Invalid block length in record %X/%X",
+ (uint32) (state->ReadRecPtr >> 32),
+ (uint32) state->ReadRecPtr);
+
+ /*
+ * Length of a block image must be equal to BLCKSZ
+ * if the block does not have hole
+ */
+ if (blk->with_hole == 0 && blk->bkp_len != BLCKSZ)
+ report_invalid_record(state,
+ "Invalid block length in record %X/%X",
+ (uint32) (state->ReadRecPtr >> 32),
+ (uint32) state->ReadRecPtr);
+ }
+ datatotal += blk->bkp_len;
+ }
+ if (!(fork_flags & BKPBLOCK_SAME_REL))
+ {
+ COPY_HEADER_FIELD(&blk->rnode, sizeof(RelFileNode));
+ rnode = &blk->rnode;
+ }
+ else
+ {
+ if (rnode == NULL)
+ {
+ report_invalid_record(state,
+ "BKPBLOCK_SAME_REL set but no previous rel at %X/%X",
+ (uint32) (state->ReadRecPtr >> 32), (uint32) state->ReadRecPtr);
+ goto err;
+ }
+
+ blk->rnode = *rnode;
+ }
+ COPY_HEADER_FIELD(&blk->blkno, sizeof(BlockNumber));
}
else
{
- if (rnode == NULL)
- {
- report_invalid_record(state,
- "BKPBLOCK_SAME_REL set but no previous rel at %X/%X",
- (uint32) (state->ReadRecPtr >> 32), (uint32) state->ReadRecPtr);
- goto err;
- }
-
- blk->rnode = *rnode;
+ report_invalid_record(state,
+ "invalid block_id %u at %X/%X",
+ block_id,
+ (uint32) (state->ReadRecPtr >> 32),
+ (uint32) state->ReadRecPtr);
+ goto err;
}
- COPY_HEADER_FIELD(&blk->blkno, sizeof(BlockNumber));
}
else
{
report_invalid_record(state,
- "invalid block_id %u at %X/%X",
- block_id,
+ "invalid chunk_id %u at %X/%X",
+ chunk_id,
(uint32) (state->ReadRecPtr >> 32),
(uint32) state->ReadRecPtr);
- goto err;
+ goto err;
}
}
-
if (remaining != datatotal)
goto shortdata_err;
@@ -1088,7 +1163,7 @@ DecodeXLogRecord(XLogReaderState *state, XLogRecord *record, char **errormsg)
if (blk->has_image)
{
blk->bkp_image = ptr;
- ptr += BLCKSZ - blk->hole_length;
+ ptr += blk->bkp_len;
}
if (blk->has_data)
{
@@ -1194,6 +1269,8 @@ bool
RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
{
DecodedBkpBlock *bkpb;
+ char *block_image;
+ int hole_length;
if (!record->blocks[block_id].in_use)
return false;
@@ -1201,19 +1278,43 @@ RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
return false;
bkpb = &record->blocks[block_id];
+ block_image = bkpb->bkp_image;
+
+ /*
+ * Fetch page data, with different processing depending on if the
+ * page is compressed or not.
+ */
+ if (bkpb->is_compressed)
+ {
+ if (pglz_decompress(block_image, bkpb->bkp_len, record->uncompressBuf,
+ bkpb->bkp_uncompress_len) < 0)
+ {
+ report_invalid_record(record, "invalid compressed image at %X/%X, block %d",
+ (uint32) (record->ReadRecPtr >> 32),
+ (uint32) record->ReadRecPtr,
+ block_id);
+ return false;
+ }
+
+ block_image = record->uncompressBuf;
+ hole_length = BLCKSZ - bkpb->bkp_uncompress_len;
+ }
+ else
+ hole_length = BLCKSZ - bkpb->bkp_len;
- if (bkpb->hole_length == 0)
+ /* generate page, taking into account hole if necessary */
+ if (hole_length == 0)
{
- memcpy(page, bkpb->bkp_image, BLCKSZ);
+ memcpy(page, block_image, BLCKSZ);
}
else
{
- memcpy(page, bkpb->bkp_image, bkpb->hole_offset);
+ memcpy(page, block_image, bkpb->hole_offset);
/* must zero-fill the hole */
- MemSet(page + bkpb->hole_offset, 0, bkpb->hole_length);
- memcpy(page + (bkpb->hole_offset + bkpb->hole_length),
- bkpb->bkp_image + bkpb->hole_offset,
- BLCKSZ - (bkpb->hole_offset + bkpb->hole_length));
+ MemSet(page + bkpb->hole_offset, 0, hole_length);
+ memcpy(page + (bkpb->hole_offset + hole_length),
+ block_image + bkpb->hole_offset,
+ BLCKSZ - (bkpb->hole_offset + hole_length));
}
return true;
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index d84dba7..130ae74 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -995,6 +995,15 @@ static struct config_bool ConfigureNamesBool[] =
false,
NULL, NULL, NULL
},
+ {
+ {"wal_compression", PGC_USERSET, WAL_SETTINGS,
+ gettext_noop("Compresses full-page writes written in WAL file."),
+ NULL
+ },
+ &wal_compression,
+ false,
+ NULL, NULL, NULL
+ },
{
{"log_checkpoints", PGC_SIGHUP, LOGGING_WHAT,
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index f8f9ce1..7590a6f 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -186,6 +186,7 @@
# fsync_writethrough
# open_sync
#full_page_writes = on # recover from partial page writes
+#wal_compression = off # enable compression of full-page writes
#wal_log_hints = off # also do full page writes of non-critical updates
# (change requires restart)
#wal_buffers = -1 # min 32kB, -1 sets based on shared_buffers
diff --git a/src/bin/pg_resetxlog/pg_resetxlog.c b/src/bin/pg_resetxlog/pg_resetxlog.c
index a16089f..54ab3c9 100644
--- a/src/bin/pg_resetxlog/pg_resetxlog.c
+++ b/src/bin/pg_resetxlog/pg_resetxlog.c
@@ -1089,7 +1089,7 @@ WriteEmptyXLOG(void)
record->xl_info = XLOG_CHECKPOINT_SHUTDOWN;
record->xl_rmid = RM_XLOG_ID;
recptr += SizeOfXLogRecord;
- *(recptr++) = XLR_BLOCK_ID_DATA_SHORT;
+ *(recptr++) = XLR_CHUNK_ID_DATA_SHORT;
*(recptr++) = sizeof(CheckPoint);
memcpy(recptr, &ControlFile.checkPointCopy,
sizeof(CheckPoint));
diff --git a/src/include/access/xlog.h b/src/include/access/xlog.h
index 0e8e587..2b1f423 100644
--- a/src/include/access/xlog.h
+++ b/src/include/access/xlog.h
@@ -100,6 +100,7 @@ extern char *XLogArchiveCommand;
extern bool EnableHotStandby;
extern bool fullPageWrites;
extern bool wal_log_hints;
+extern bool wal_compression;
extern bool log_checkpoints;
extern int CheckPointSegments;
diff --git a/src/include/access/xlogreader.h b/src/include/access/xlogreader.h
index 74bec20..06c35ba 100644
--- a/src/include/access/xlogreader.h
+++ b/src/include/access/xlogreader.h
@@ -52,9 +52,12 @@ typedef struct
/* Information on full-page image, if any */
bool has_image;
+ bool is_compressed;
+ bool with_hole;
char *bkp_image;
+ uint16 bkp_len;
+ uint16 bkp_uncompress_len;
uint16 hole_offset;
- uint16 hole_length;
/* Buffer holding the rmgr-specific data associated with this block */
bool has_data;
@@ -138,6 +141,9 @@ struct XLogReaderState
/* Buffer for currently read page (XLOG_BLCKSZ bytes) */
char *readBuf;
+ /* Scratch buffer used for uncompressed pages */
+ char *uncompressBuf;
+
/* last read segment, segment offset, read length, TLI */
XLogSegNo readSegNo;
uint32 readOff;
diff --git a/src/include/access/xlogrecord.h b/src/include/access/xlogrecord.h
index 25a9265..6dd1900 100644
--- a/src/include/access/xlogrecord.h
+++ b/src/include/access/xlogrecord.h
@@ -35,8 +35,9 @@
* the fields are not aligned.
*
* The XLogRecordBlockHeader, XLogRecordDataHeaderShort and
- * XLogRecordDataHeaderLong structs all begin with a single 'id' byte. It's
- * used to distinguish between block references, and the main data structs.
+ * XLogRecordDataHeaderLong structs all begin with a single 'chunk_id' byte.
+ * It's used to distinguish between different kinds of block references,
+ * and the main data structs.
*/
typedef struct XLogRecord
{
@@ -71,7 +72,8 @@ typedef struct XLogRecord
#define XLR_SPECIAL_REL_UPDATE 0x01
/*
- * Header info for block data appended to an XLOG record.
+ * Header info for block data appended to an XLOG record. chunk_id byte precedes
+ * the header.
*
* 'data_length' is the length of the rmgr-specific payload data associated
* with this block. It does not include the possible full page image, nor
@@ -82,12 +84,14 @@ typedef struct XLogRecord
*/
typedef struct XLogRecordBlockHeader
{
+ /* Chunk ID precedes */
+
uint8 id; /* block reference ID */
uint8 fork_flags; /* fork within the relation, and flags */
uint16 data_length; /* number of payload bytes (not including page
* image) */
- /* If BKPBLOCK_HAS_IMAGE, an XLogRecordBlockImageHeader struct follows */
+ /* If XLR_CHUNK_BLOCK_HAS_IMAGE, an XLogRecordBlockImageHeader struct follows */
/* If !BKPBLOCK_SAME_REL is not set, a RelFileNode follows */
/* BlockNumber follows */
} XLogRecordBlockHeader;
@@ -96,30 +100,57 @@ typedef struct XLogRecordBlockHeader
/*
* Additional header information when a full-page image is included
- * (i.e. when BKPBLOCK_HAS_IMAGE is set).
+ * (i.e. when XLR_CHUNK_BLOCK_HAS_IMAGE is set).
*
- * As a trivial form of data compression, the XLOG code is aware that
- * PG data pages usually contain an unused "hole" in the middle, which
- * contains only zero bytes. If hole_length > 0 then we have removed
- * such a "hole" from the stored data (and it's not counted in the
- * XLOG record's CRC, either). Hence, the amount of block data actually
- * present is BLCKSZ - hole_length bytes.
+ * Block images are able to do several types of compression:
+ * - When wal_compression is off, as a trivial form of compression, the
+ * XLOG code is aware that PG data pages usually contain an unused "hole"
+ * in the middle, which contains only zero bytes. If length < BLCKSZ
+ * then we have removed such a "hole" from the stored data (and it is
+ * not counted in the XLOG record's CRC, either). Hence, the amount
+ * of block data actually present is "length" bytes. The hole "offset"
+ * on page is defined using "hole_offset".
+ * - When wal_compression is on, block images are compressed using a
+ * compression algorithm without their hole to improve compression
+ * process of the page. "length" corresponds in this case to the length
+ * of the compressed block. "hole_offset" is the hole offset of the page,
+ * and the length of the uncompressed block is defined by "raw_length",
+ * whose data is included in the record only when compression is enabled
+ * and block contains hole. If the block has no hole, it is ensured
+ * that the raw size of a compressed block image is equal to BLCKSZ,
+ * hence the contents of XLogRecordBlockImageCompressionInfo
+ * are not necessary.
*/
typedef struct XLogRecordBlockImageHeader
{
- uint16 hole_offset; /* number of bytes before "hole" */
- uint16 hole_length; /* number of bytes in "hole" */
+ uint16 length; /* length of block data in record */
+ uint16 hole_offset; /* number of bytes before "hole" */
+
+ /* Followed by the data related to compression if block is compressed */
} XLogRecordBlockImageHeader;
#define SizeOfXLogRecordBlockImageHeader sizeof(XLogRecordBlockImageHeader)
/*
+ * Extra header information used when a block is compressed and has a hole.
+ * This state is determined by the previous flags is_compressed and with_hole.
+ */
+typedef struct XLogRecordBlockImageCompressionInfo
+{
+ uint16 raw_length; /* raw length of uncompressed block */
+} XLogRecordBlockImageCompressionInfo;
+
+#define SizeOfXLogRecordBlockImageCompressionInfo \
+ sizeof(XLogRecordBlockImageCompressionInfo)
+
+/*
* Maximum size of the header for a block reference. This is used to size a
* temporary buffer for constructing the header.
*/
#define MaxSizeOfXLogRecordBlockHeader \
(SizeOfXLogRecordBlockHeader + \
SizeOfXLogRecordBlockImageHeader + \
+ SizeOfXLogRecordBlockImageCompressionInfo + \
sizeof(RelFileNode) + \
sizeof(BlockNumber))
@@ -129,8 +160,6 @@ typedef struct XLogRecordBlockImageHeader
*/
#define BKPBLOCK_FORK_MASK 0x0F
#define BKPBLOCK_FLAG_MASK 0xF0
-#define BKPBLOCK_HAS_IMAGE 0x10 /* block data is an XLogRecordBlockImage */
-#define BKPBLOCK_HAS_DATA 0x20
#define BKPBLOCK_WILL_INIT 0x40 /* redo will re-init the page */
#define BKPBLOCK_SAME_REL 0x80 /* RelFileNode omitted, same as previous */
@@ -145,7 +174,7 @@ typedef struct XLogRecordBlockImageHeader
*/
typedef struct XLogRecordDataHeaderShort
{
- uint8 id; /* XLR_BLOCK_ID_DATA_SHORT */
+ uint8 chunk_id; /* XLR_CHUNK_ID_DATA_SHORT */
uint8 data_length; /* number of payload bytes */
} XLogRecordDataHeaderShort;
@@ -153,18 +182,17 @@ typedef struct XLogRecordDataHeaderShort
typedef struct XLogRecordDataHeaderLong
{
- uint8 id; /* XLR_BLOCK_ID_DATA_LONG */
+ uint8 chunk_id; /* XLR_CHUNK_ID_DATA_LONG */
/* followed by uint32 data_length, unaligned */
} XLogRecordDataHeaderLong;
#define SizeOfXLogRecordDataHeaderLong (sizeof(uint8) + sizeof(uint32))
/*
- * Block IDs used to distinguish different kinds of record fragments. Block
+ * Block IDs used to distinguish between different block_references. Block
* references are numbered from 0 to XLR_MAX_BLOCK_ID. A rmgr is free to use
* any ID number in that range (although you should stick to small numbers,
- * because the WAL machinery is optimized for that case). A couple of ID
- * numbers are reserved to denote the "main" data portion of the record.
+ * because the WAL machinery is optimized for that case).
*
* The maximum is currently set at 32, quite arbitrarily. Most records only
* need a handful of block references, but there are a few exceptions that
@@ -172,7 +200,26 @@ typedef struct XLogRecordDataHeaderLong
*/
#define XLR_MAX_BLOCK_ID 32
-#define XLR_BLOCK_ID_DATA_SHORT 255
-#define XLR_BLOCK_ID_DATA_LONG 254
+/*
+ * Chunk IDs are used to distinguish between different kinds of xlog record
+ * fragments. A couple of ID numbers are reserved to denote the "main" data
+ * portion of the record.
+ * XLR_CHUNK_BLOCK_REFERENCE denotes block fragments of the record.
+ * XLR_CHUNK_BLOCK_HAS_IMAGE indicates presence of backup block image in block
+ * reference.
+ * XLR_CHUNK_BLOCK_HAS_DATA indicates presence of data in block reference.
+ * Presence of a compressed block image is determined by XLR_CHUNK_BKP_COMPRESSED
+ * Similarly presence of a hole in block image is determined by
+ * XLR_CHUNK_BKP_WITH_HOLE.
+ */
+
+#define XLR_CHUNK_ID_DATA_SHORT 255
+#define XLR_CHUNK_ID_DATA_LONG 254
+#define XLR_CHUNK_BKP_COMPRESSED 0x01
+#define XLR_CHUNK_BKP_WITH_HOLE 0x02
+#define XLR_CHUNK_BLOCK_REFERENCE 0x10
+#define XLR_CHUNK_BLOCK_HAS_IMAGE 0x04
+#define XLR_CHUNK_BLOCK_HAS_DATA 0x08
+
#endif /* XLOGRECORD_H */