greenplumn xlogreader 源码
greenplumn xlogreader 代码
文件路径：/src/backend/access/transam/xlogreader.c
/*-------------------------------------------------------------------------
*
* xlogreader.c
* Generic XLog reading facility
*
* Portions Copyright (c) 2013-2019, PostgreSQL Global Development Group
*
* IDENTIFICATION
* src/backend/access/transam/xlogreader.c
*
* NOTES
* See xlogreader.h for more notes on this facility.
*
* This file is compiled as both front-end and backend code, so it
* may not use ereport, server-defined static variables, etc.
*-------------------------------------------------------------------------
*/
#include "postgres.h"
#include "access/transam.h"
#include "access/xlogrecord.h"
#include "access/xlog_internal.h"
#include "access/xlogreader.h"
#include "catalog/pg_control.h"
#include "common/pg_lzcompress.h"
#include "replication/origin.h"
#ifdef USE_ZSTD
/* Zstandard library is provided */
#include <zstd.h>
#endif
#ifndef FRONTEND
#include "utils/memutils.h"
#endif
static bool allocate_recordbuf(XLogReaderState *state, uint32 reclength);
static bool ValidXLogRecordHeader(XLogReaderState *state, XLogRecPtr RecPtr,
XLogRecPtr PrevRecPtr, XLogRecord *record, bool randAccess);
static bool ValidXLogRecord(XLogReaderState *state, XLogRecord *record,
XLogRecPtr recptr);
static int ReadPageInternal(XLogReaderState *state, XLogRecPtr pageptr,
int reqLen);
static void report_invalid_record(XLogReaderState *state, const char *fmt,...) pg_attribute_printf(2, 3);
static void ResetDecoder(XLogReaderState *state);
static bool zstd_decompress_backupblock(const char *source, int32 slen,
char *dest, int32 rawsize,
char *errormessage);
/* size of the buffer allocated for error message. */
#define MAX_ERRORMSG_LEN 1000
/*
* Construct a string in state->errormsg_buf explaining what's wrong with
* the current record being read.
*/
static void
report_invalid_record(XLogReaderState *state, const char *fmt,...)
{
va_list args;
fmt = _(fmt);
va_start(args, fmt);
vsnprintf(state->errormsg_buf, MAX_ERRORMSG_LEN, fmt, args);
va_end(args);
}
/*
* Allocate and initialize a new XLogReader.
*
* Returns NULL if the xlogreader couldn't be allocated.
*/
XLogReaderState *
XLogReaderAllocate(int wal_segment_size, XLogPageReadCB pagereadfunc,
void *private_data)
{
XLogReaderState *state;
state = (XLogReaderState *)
palloc_extended(sizeof(XLogReaderState),
MCXT_ALLOC_NO_OOM | MCXT_ALLOC_ZERO);
if (!state)
return NULL;
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_extended() will provide MAXALIGN'd storage.
*/
state->readBuf = (char *) palloc_extended(XLOG_BLCKSZ,
MCXT_ALLOC_NO_OOM);
if (!state->readBuf)
{
pfree(state);
return NULL;
}
state->wal_segment_size = wal_segment_size;
state->read_page = pagereadfunc;
/* system_identifier initialized to zeroes above */
state->private_data = private_data;
/* ReadRecPtr and EndRecPtr initialized to zeroes above */
/* readSegNo, readOff, readLen, readPageTLI initialized to zeroes above */
state->errormsg_buf = palloc_extended(MAX_ERRORMSG_LEN + 1,
MCXT_ALLOC_NO_OOM);
if (!state->errormsg_buf)
{
pfree(state->readBuf);
pfree(state);
return NULL;
}
state->errormsg_buf[0] = '\0';
/*
* Allocate an initial readRecordBuf of minimal size, which can later be
* enlarged if necessary.
*/
if (!allocate_recordbuf(state, 0))
{
pfree(state->errormsg_buf);
pfree(state->readBuf);
pfree(state);
return NULL;
}
return state;
}
void
XLogReaderFree(XLogReaderState *state)
{
int block_id;
for (block_id = 0; block_id <= XLR_MAX_BLOCK_ID; block_id++)
{
if (state->blocks[block_id].data)
pfree(state->blocks[block_id].data);
}
if (state->main_data)
pfree(state->main_data);
pfree(state->errormsg_buf);
if (state->readRecordBuf)
pfree(state->readRecordBuf);
pfree(state->readBuf);
pfree(state);
}
/*
* Allocate readRecordBuf to fit a record of at least the given length.
* 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
* abort records might need more space.)
*/
static bool
allocate_recordbuf(XLogReaderState *state, uint32 reclength)
{
uint32 newSize = reclength;
newSize += XLOG_BLCKSZ - (newSize % XLOG_BLCKSZ);
newSize = Max(newSize, 5 * Max(BLCKSZ, XLOG_BLCKSZ));
#ifndef FRONTEND
/*
* Note that in much unlucky circumstances, the random data read from a
* recycled segment can cause this routine to be called with a size
* causing a hard failure at allocation. For a standby, this would cause
* the instance to stop suddenly with a hard failure, preventing it to
* retry fetching WAL from one of its sources which could allow it to move
* on with replay without a manual restart. If the data comes from a past
* recycled segment and is still valid, then the allocation may succeed
* but record checks are going to fail so this would be short-lived. If
* the allocation fails because of a memory shortage, then this is not a
* hard failure either per the guarantee given by MCXT_ALLOC_NO_OOM.
*/
if (!AllocSizeIsValid(newSize))
return false;
#endif
if (state->readRecordBuf)
pfree(state->readRecordBuf);
state->readRecordBuf =
(char *) palloc_extended(newSize, MCXT_ALLOC_NO_OOM);
if (state->readRecordBuf == NULL)
{
state->readRecordBufSize = 0;
return false;
}
state->readRecordBufSize = newSize;
return true;
}
/*
* Attempt to read an XLOG record.
*
* If RecPtr is valid, try to read a record at that position. Otherwise
* try to read a record just after the last one previously read.
*
* If the read_page callback fails to read the requested data, NULL is
* returned. The callback is expected to have reported the error; errormsg
* is set to NULL.
*
* If the reading fails for some other reason, NULL is also returned, and
* *errormsg is set to a string with details of the failure.
*
* The returned pointer (or *errormsg) points to an internal buffer that's
* valid until the next call to XLogReadRecord.
*/
XLogRecord *
XLogReadRecord(XLogReaderState *state, XLogRecPtr RecPtr, char **errormsg)
{
XLogRecord *record;
XLogRecPtr targetPagePtr;
bool randAccess;
uint32 len,
total_len;
uint32 targetRecOff;
uint32 pageHeaderSize;
bool assembled;
bool gotheader;
int readOff;
/*
* randAccess indicates whether to verify the previous-record pointer of
* the record we're reading. We only do this if we're reading
* sequentially, which is what we initially assume.
*/
randAccess = false;
/* reset error state */
*errormsg = NULL;
state->errormsg_buf[0] = '\0';
ResetDecoder(state);
state->abortedRecPtr = InvalidXLogRecPtr;
state->missingContrecPtr = InvalidXLogRecPtr;
if (RecPtr == InvalidXLogRecPtr)
{
/* No explicit start point; read the record after the one we just read */
RecPtr = state->EndRecPtr;
if (state->ReadRecPtr == InvalidXLogRecPtr)
randAccess = true;
/*
* RecPtr is pointing to end+1 of the previous WAL record. If we're
* at a page boundary, no more records can fit on the current page. We
* must skip over the page header, but we can't do that until we've
* read in the page, since the header size is variable.
*/
}
else
{
/*
* Caller supplied a position to start at.
*
* In this case, the passed-in record pointer should already be
* pointing to a valid record starting position.
*/
Assert(XRecOffIsValid(RecPtr));
randAccess = true;
}
restart:
state->currRecPtr = RecPtr;
assembled = false;
targetPagePtr = RecPtr - (RecPtr % XLOG_BLCKSZ);
targetRecOff = RecPtr % XLOG_BLCKSZ;
/*
* Read the page containing the record into state->readBuf. Request enough
* byte to cover the whole record header, or at least the part of it that
* fits on the same page.
*/
readOff = ReadPageInternal(state,
targetPagePtr,
Min(targetRecOff + SizeOfXLogRecord, XLOG_BLCKSZ));
if (readOff < 0)
goto err;
/*
* ReadPageInternal always returns at least the page header, so we can
* examine it now.
*/
pageHeaderSize = XLogPageHeaderSize((XLogPageHeader) state->readBuf);
if (targetRecOff == 0)
{
/*
* At page start, so skip over page header.
*/
RecPtr += pageHeaderSize;
targetRecOff = pageHeaderSize;
}
else if (targetRecOff < pageHeaderSize)
{
report_invalid_record(state, "invalid record offset at %X/%X",
(uint32) (RecPtr >> 32), (uint32) RecPtr);
goto err;
}
if ((((XLogPageHeader) state->readBuf)->xlp_info & XLP_FIRST_IS_CONTRECORD) &&
targetRecOff == pageHeaderSize)
{
report_invalid_record(state, "contrecord is requested by %X/%X",
(uint32) (RecPtr >> 32), (uint32) RecPtr);
goto err;
}
/* ReadPageInternal has verified the page header */
Assert(pageHeaderSize <= readOff);
/*
* Read the record length.
*
* NB: Even though we use an XLogRecord pointer here, the whole record
* header might not fit on this page. xl_tot_len is the first field of the
* struct, so it must be on this page (the records are MAXALIGNed), but we
* cannot access any other fields until we've verified that we got the
* whole header.
*/
record = (XLogRecord *) (state->readBuf + RecPtr % XLOG_BLCKSZ);
total_len = record->xl_tot_len;
/*
* If the whole record header is on this page, validate it immediately.
* Otherwise do just a basic sanity check on xl_tot_len, and validate the
* rest of the header after reading it from the next page. The xl_tot_len
* check is necessary here to ensure that we enter the "Need to reassemble
* record" code path below; otherwise we might fail to apply
* ValidXLogRecordHeader at all.
*/
if (targetRecOff <= XLOG_BLCKSZ - SizeOfXLogRecord)
{
if (!ValidXLogRecordHeader(state, RecPtr, state->ReadRecPtr, record,
randAccess))
goto err;
gotheader = true;
}
else
{
/* XXX: more validation should be done here */
if (total_len < SizeOfXLogRecord)
{
report_invalid_record(state,
"invalid record length at %X/%X: wanted %u, got %u",
(uint32) (RecPtr >> 32), (uint32) RecPtr,
(uint32) SizeOfXLogRecord, total_len);
goto err;
}
gotheader = false;
}
len = XLOG_BLCKSZ - RecPtr % XLOG_BLCKSZ;
if (total_len > len)
{
/* Need to reassemble record */
char *contdata;
XLogPageHeader pageHeader;
char *buffer;
uint32 gotlen;
assembled = true;
/*
* Enlarge readRecordBuf as needed.
*/
if (total_len > state->readRecordBufSize &&
!allocate_recordbuf(state, total_len))
{
/* We treat this as a "bogus data" condition */
report_invalid_record(state, "record length %u at %X/%X too long",
total_len,
(uint32) (RecPtr >> 32), (uint32) RecPtr);
goto err;
}
/* Copy the first fragment of the record from the first page. */
memcpy(state->readRecordBuf,
state->readBuf + RecPtr % XLOG_BLCKSZ, len);
buffer = state->readRecordBuf + len;
gotlen = len;
do
{
/* Calculate pointer to beginning of next page */
targetPagePtr += XLOG_BLCKSZ;
/* Wait for the next page to become available */
readOff = ReadPageInternal(state, targetPagePtr,
Min(total_len - gotlen + SizeOfXLogShortPHD,
XLOG_BLCKSZ));
if (readOff < 0)
goto err;
Assert(SizeOfXLogShortPHD <= readOff);
pageHeader = (XLogPageHeader) state->readBuf;
/*
* If we were expecting a continuation record and got an
* "overwrite contrecord" flag, that means the continuation record
* was overwritten with a different record. Restart the read by
* assuming the address to read is the location where we found
* this flag; but keep track of the LSN of the record we were
* reading, for later verification.
*/
if (pageHeader->xlp_info & XLP_FIRST_IS_OVERWRITE_CONTRECORD)
{
state->overwrittenRecPtr = state->currRecPtr;
ResetDecoder(state);
RecPtr = targetPagePtr;
goto restart;
}
/* Check that the continuation on next page looks valid */
if (!(pageHeader->xlp_info & XLP_FIRST_IS_CONTRECORD))
{
report_invalid_record(state,
"there is no contrecord flag at %X/%X",
(uint32) (RecPtr >> 32), (uint32) RecPtr);
goto err;
}
/*
* Cross-check that xlp_rem_len agrees with how much of the record
* we expect there to be left.
*/
if (pageHeader->xlp_rem_len == 0 ||
total_len != (pageHeader->xlp_rem_len + gotlen))
{
report_invalid_record(state,
"invalid contrecord length %u at %X/%X",
pageHeader->xlp_rem_len,
(uint32) (RecPtr >> 32), (uint32) RecPtr);
goto err;
}
/* Append the continuation from this page to the buffer */
pageHeaderSize = XLogPageHeaderSize(pageHeader);
if (readOff < pageHeaderSize)
readOff = ReadPageInternal(state, targetPagePtr,
pageHeaderSize);
Assert(pageHeaderSize <= readOff);
contdata = (char *) state->readBuf + pageHeaderSize;
len = XLOG_BLCKSZ - pageHeaderSize;
if (pageHeader->xlp_rem_len < len)
len = pageHeader->xlp_rem_len;
if (readOff < pageHeaderSize + len)
readOff = ReadPageInternal(state, targetPagePtr,
pageHeaderSize + len);
memcpy(buffer, (char *) contdata, len);
buffer += len;
gotlen += len;
/* If we just reassembled the record header, validate it. */
if (!gotheader)
{
record = (XLogRecord *) state->readRecordBuf;
if (!ValidXLogRecordHeader(state, RecPtr, state->ReadRecPtr,
record, randAccess))
goto err;
gotheader = true;
}
} while (gotlen < total_len);
Assert(gotheader);
record = (XLogRecord *) state->readRecordBuf;
if (!ValidXLogRecord(state, record, RecPtr))
goto err;
pageHeaderSize = XLogPageHeaderSize((XLogPageHeader) state->readBuf);
state->ReadRecPtr = RecPtr;
state->EndRecPtr = targetPagePtr + pageHeaderSize
+ MAXALIGN(pageHeader->xlp_rem_len);
}
else
{
/* Wait for the record data to become available */
readOff = ReadPageInternal(state, targetPagePtr,
Min(targetRecOff + total_len, XLOG_BLCKSZ));
if (readOff < 0)
goto err;
/* Record does not cross a page boundary */
if (!ValidXLogRecord(state, record, RecPtr))
goto err;
state->EndRecPtr = RecPtr + MAXALIGN(total_len);
state->ReadRecPtr = RecPtr;
}
/*
* Special processing if it's an XLOG SWITCH record
*/
if (record->xl_rmid == RM_XLOG_ID &&
(record->xl_info & ~XLR_INFO_MASK) == XLOG_SWITCH)
{
/* Pretend it extends to end of segment */
state->EndRecPtr += state->wal_segment_size - 1;
state->EndRecPtr -= XLogSegmentOffset(state->EndRecPtr, state->wal_segment_size);
}
if (DecodeXLogRecord(state, record, errormsg))
return record;
else
return NULL;
err:
if (assembled)
{
/*
* We get here when a record that spans multiple pages needs to be
* assembled, but something went wrong -- perhaps a contrecord piece
* was lost. If caller is WAL replay, it will know where the aborted
* record was and where to direct followup WAL to be written, marking
* the next piece with XLP_FIRST_IS_OVERWRITE_CONTRECORD, which will
* in turn signal downstream WAL consumers that the broken WAL record
* is to be ignored.
*/
state->abortedRecPtr = RecPtr;
state->missingContrecPtr = targetPagePtr;
}
/*
* Invalidate the read state. We might read from a different source after
* failure.
*/
XLogReaderInvalReadState(state);
if (state->errormsg_buf[0] != '\0')
*errormsg = state->errormsg_buf;
return NULL;
}
/*
* Read a single xlog page including at least [pageptr, reqLen] of valid data
* via the read_page() callback.
*
* Returns -1 if the required page cannot be read for some reason; errormsg_buf
* is set in that case (unless the error occurs in the read_page callback).
*
* We fetch the page from a reader-local cache if we know we have the required
* data and if there hasn't been any error since caching the data.
*/
static int
ReadPageInternal(XLogReaderState *state, XLogRecPtr pageptr, int reqLen)
{
int readLen;
uint32 targetPageOff;
XLogSegNo targetSegNo;
XLogPageHeader hdr;
Assert((pageptr % XLOG_BLCKSZ) == 0);
XLByteToSeg(pageptr, targetSegNo, state->wal_segment_size);
targetPageOff = XLogSegmentOffset(pageptr, state->wal_segment_size);
/* check whether we have all the requested data already */
if (targetSegNo == state->readSegNo && targetPageOff == state->readOff &&
reqLen <= state->readLen)
return state->readLen;
/*
* Data is not in our buffer.
*
* Every time we actually read the page, even if we looked at parts of it
* before, we need to do verification as the read_page callback might now
* be rereading data from a different source.
*
* Whenever switching to a new WAL segment, we read the first page of the
* file and validate its header, even if that's not where the target
* record is. This is so that we can check the additional identification
* info that is present in the first page's "long" header.
*/
if (targetSegNo != state->readSegNo && targetPageOff != 0)
{
XLogRecPtr targetSegmentPtr = pageptr - targetPageOff;
readLen = state->read_page(state, targetSegmentPtr, XLOG_BLCKSZ,
state->currRecPtr,
state->readBuf, &state->readPageTLI);
if (readLen < 0)
goto err;
/* we can be sure to have enough WAL available, we scrolled back */
Assert(readLen == XLOG_BLCKSZ);
if (!XLogReaderValidatePageHeader(state, targetSegmentPtr,
state->readBuf))
goto err;
}
/*
* First, read the requested data length, but at least a short page header
* so that we can validate it.
*/
readLen = state->read_page(state, pageptr, Max(reqLen, SizeOfXLogShortPHD),
state->currRecPtr,
state->readBuf, &state->readPageTLI);
if (readLen < 0)
goto err;
Assert(readLen <= XLOG_BLCKSZ);
/* Do we have enough data to check the header length? */
if (readLen <= SizeOfXLogShortPHD)
goto err;
Assert(readLen >= reqLen);
hdr = (XLogPageHeader) state->readBuf;
/* still not enough */
if (readLen < XLogPageHeaderSize(hdr))
{
readLen = state->read_page(state, pageptr, XLogPageHeaderSize(hdr),
state->currRecPtr,
state->readBuf, &state->readPageTLI);
if (readLen < 0)
goto err;
}
/*
* Now that we know we have the full header, validate it.
*/
if (!XLogReaderValidatePageHeader(state, pageptr, (char *) hdr))
goto err;
/* update read state information */
state->readSegNo = targetSegNo;
state->readOff = targetPageOff;
state->readLen = readLen;
return readLen;
err:
XLogReaderInvalReadState(state);
return -1;
}
/*
* Invalidate the xlogreader's read state to force a re-read.
*/
void
XLogReaderInvalReadState(XLogReaderState *state)
{
state->readSegNo = 0;
state->readOff = 0;
state->readLen = 0;
}
/*
* Validate an XLOG record header.
*
* This is just a convenience subroutine to avoid duplicated code in
* XLogReadRecord. It's not intended for use from anywhere else.
*/
static bool
ValidXLogRecordHeader(XLogReaderState *state, XLogRecPtr RecPtr,
XLogRecPtr PrevRecPtr, XLogRecord *record,
bool randAccess)
{
if (record->xl_tot_len < SizeOfXLogRecord)
{
report_invalid_record(state,
"invalid record length at %X/%X: wanted %u, got %u",
(uint32) (RecPtr >> 32), (uint32) RecPtr,
(uint32) SizeOfXLogRecord, record->xl_tot_len);
return false;
}
if (record->xl_rmid > RM_MAX_ID)
{
report_invalid_record(state,
"invalid resource manager ID %u at %X/%X",
record->xl_rmid, (uint32) (RecPtr >> 32),
(uint32) RecPtr);
return false;
}
if (randAccess)
{
/*
* We can't exactly verify the prev-link, but surely it should be less
* than the record's own address.
*/
if (!(record->xl_prev < RecPtr))
{
report_invalid_record(state,
"record with incorrect prev-link %X/%X at %X/%X",
(uint32) (record->xl_prev >> 32),
(uint32) record->xl_prev,
(uint32) (RecPtr >> 32), (uint32) RecPtr);
return false;
}
}
else
{
/*
* Record's prev-link should exactly match our previous location. This
* check guards against torn WAL pages where a stale but valid-looking
* WAL record starts on a sector boundary.
*/
if (record->xl_prev != PrevRecPtr)
{
report_invalid_record(state,
"record with incorrect prev-link %X/%X at %X/%X",
(uint32) (record->xl_prev >> 32),
(uint32) record->xl_prev,
(uint32) (RecPtr >> 32), (uint32) RecPtr);
return false;
}
}
return true;
}
/*
* CRC-check an XLOG record. We do not believe the contents of an XLOG
* record (other than to the minimal extent of computing the amount of
* data to read in) until we've checked the CRCs.
*
* We assume all of the record (that is, xl_tot_len bytes) has been read
* into memory at *record. Also, ValidXLogRecordHeader() has accepted the
* record's header, which means in particular that xl_tot_len is at least
* SizeOfXlogRecord.
*/
static bool
ValidXLogRecord(XLogReaderState *state, XLogRecord *record, XLogRecPtr recptr)
{
pg_crc32c crc;
/* Calculate the CRC */
INIT_CRC32C(crc);
COMP_CRC32C(crc, ((char *) record) + SizeOfXLogRecord, record->xl_tot_len - SizeOfXLogRecord);
/* include the record header last */
COMP_CRC32C(crc, (char *) record, offsetof(XLogRecord, xl_crc));
FIN_CRC32C(crc);
if (!EQ_CRC32C(record->xl_crc, crc))
{
report_invalid_record(state,
"incorrect resource manager data checksum in record at %X/%X",
(uint32) (recptr >> 32), (uint32) recptr);
return false;
}
return true;
}
/*
* Validate a page header.
*
* Check if 'phdr' is valid as the header of the XLog page at position
* 'recptr'.
*/
bool
XLogReaderValidatePageHeader(XLogReaderState *state, XLogRecPtr recptr,
char *phdr)
{
XLogRecPtr recaddr;
XLogSegNo segno;
int32 offset;
XLogPageHeader hdr = (XLogPageHeader) phdr;
Assert((recptr % XLOG_BLCKSZ) == 0);
XLByteToSeg(recptr, segno, state->wal_segment_size);
offset = XLogSegmentOffset(recptr, state->wal_segment_size);
XLogSegNoOffsetToRecPtr(segno, offset, state->wal_segment_size, recaddr);
if (hdr->xlp_magic != XLOG_PAGE_MAGIC)
{
char fname[MAXFNAMELEN];
XLogFileName(fname, state->readPageTLI, segno, state->wal_segment_size);
report_invalid_record(state,
"invalid magic number %04X in log segment %s, offset %u",
hdr->xlp_magic,
fname,
offset);
return false;
}
if ((hdr->xlp_info & ~XLP_ALL_FLAGS) != 0)
{
char fname[MAXFNAMELEN];
XLogFileName(fname, state->readPageTLI, segno, state->wal_segment_size);
report_invalid_record(state,
"invalid info bits %04X in log segment %s, offset %u",
hdr->xlp_info,
fname,
offset);
return false;
}
if (hdr->xlp_info & XLP_LONG_HEADER)
{
XLogLongPageHeader longhdr = (XLogLongPageHeader) hdr;
if (state->system_identifier &&
longhdr->xlp_sysid != state->system_identifier)
{
char fhdrident_str[32];
char sysident_str[32];
/*
* Format sysids separately to keep platform-dependent format code
* out of the translatable message string.
*/
snprintf(fhdrident_str, sizeof(fhdrident_str), UINT64_FORMAT,
longhdr->xlp_sysid);
snprintf(sysident_str, sizeof(sysident_str), UINT64_FORMAT,
state->system_identifier);
report_invalid_record(state,
"WAL file is from different database system: WAL file database system identifier is %s, pg_control database system identifier is %s",
fhdrident_str, sysident_str);
return false;
}
else if (longhdr->xlp_seg_size != state->wal_segment_size)
{
report_invalid_record(state,
"WAL file is from different database system: incorrect segment size in page header");
return false;
}
else if (longhdr->xlp_xlog_blcksz != XLOG_BLCKSZ)
{
report_invalid_record(state,
"WAL file is from different database system: incorrect XLOG_BLCKSZ in page header");
return false;
}
}
else if (offset == 0)
{
char fname[MAXFNAMELEN];
XLogFileName(fname, state->readPageTLI, segno, state->wal_segment_size);
/* hmm, first page of file doesn't have a long header? */
report_invalid_record(state,
"invalid info bits %04X in log segment %s, offset %u",
hdr->xlp_info,
fname,
offset);
return false;
}
/*
* Check that the address on the page agrees with what we expected. This
* check typically fails when an old WAL segment is recycled, and hasn't
* yet been overwritten with new data yet.
*/
if (hdr->xlp_pageaddr != recaddr)
{
char fname[MAXFNAMELEN];
XLogFileName(fname, state->readPageTLI, segno, state->wal_segment_size);
report_invalid_record(state,
"unexpected pageaddr %X/%X in log segment %s, offset %u",
(uint32) (hdr->xlp_pageaddr >> 32), (uint32) hdr->xlp_pageaddr,
fname,
offset);
return false;
}
/*
* Since child timelines are always assigned a TLI greater than their
* immediate parent's TLI, we should never see TLI go backwards across
* successive pages of a consistent WAL sequence.
*
* Sometimes we re-read a segment that's already been (partially) read. So
* we only verify TLIs for pages that are later than the last remembered
* LSN.
*/
if (recptr > state->latestPagePtr)
{
if (hdr->xlp_tli < state->latestPageTLI)
{
char fname[MAXFNAMELEN];
XLogFileName(fname, state->readPageTLI, segno, state->wal_segment_size);
report_invalid_record(state,
"out-of-sequence timeline ID %u (after %u) in log segment %s, offset %u",
hdr->xlp_tli,
state->latestPageTLI,
fname,
offset);
return false;
}
}
state->latestPagePtr = recptr;
state->latestPageTLI = hdr->xlp_tli;
return true;
}
/*
* In GPDB, this is used in the test in src/test/walrep, so we need it in the
* backend, too.
*/
/* #ifdef FRONTEND */
#if 1
/*
* Functions that are currently not needed in the backend, but are better
* implemented inside xlogreader.c because of the internal facilities available
* here.
*/
/*
* Find the first record with an lsn >= RecPtr.
*
* Useful for checking whether RecPtr is a valid xlog address for reading, and
* to find the first valid address after some address when dumping records for
* debugging purposes.
*/
XLogRecPtr
XLogFindNextRecord(XLogReaderState *state, XLogRecPtr RecPtr)
{
XLogReaderState saved_state = *state;
XLogRecPtr tmpRecPtr;
XLogRecPtr found = InvalidXLogRecPtr;
XLogPageHeader header;
char *errormsg;
Assert(!XLogRecPtrIsInvalid(RecPtr));
/*
* skip over potential continuation data, keeping in mind that it may span
* multiple pages
*/
tmpRecPtr = RecPtr;
while (true)
{
XLogRecPtr targetPagePtr;
int targetRecOff;
uint32 pageHeaderSize;
int readLen;
/*
* Compute targetRecOff. It should typically be equal or greater than
* short page-header since a valid record can't start anywhere before
* that, except when caller has explicitly specified the offset that
* falls somewhere there or when we are skipping multi-page
* continuation record. It doesn't matter though because
* ReadPageInternal() is prepared to handle that and will read at
* least short page-header worth of data
*/
targetRecOff = tmpRecPtr % XLOG_BLCKSZ;
/* scroll back to page boundary */
targetPagePtr = tmpRecPtr - targetRecOff;
/* Read the page containing the record */
readLen = ReadPageInternal(state, targetPagePtr, targetRecOff);
if (readLen < 0)
goto err;
header = (XLogPageHeader) state->readBuf;
pageHeaderSize = XLogPageHeaderSize(header);
/* make sure we have enough data for the page header */
readLen = ReadPageInternal(state, targetPagePtr, pageHeaderSize);
if (readLen < 0)
goto err;
/* skip over potential continuation data */
if (header->xlp_info & XLP_FIRST_IS_CONTRECORD)
{
/*
* If the length of the remaining continuation data is more than
* what can fit in this page, the continuation record crosses over
* this page. Read the next page and try again. xlp_rem_len in the
* next page header will contain the remaining length of the
* continuation data
*
* Note that record headers are MAXALIGN'ed
*/
if (MAXALIGN(header->xlp_rem_len) > (XLOG_BLCKSZ - pageHeaderSize))
tmpRecPtr = targetPagePtr + XLOG_BLCKSZ;
else
{
/*
* The previous continuation record ends in this page. Set
* tmpRecPtr to point to the first valid record
*/
tmpRecPtr = targetPagePtr + pageHeaderSize
+ MAXALIGN(header->xlp_rem_len);
break;
}
}
else
{
tmpRecPtr = targetPagePtr + pageHeaderSize;
break;
}
}
/*
* we know now that tmpRecPtr is an address pointing to a valid XLogRecord
* because either we're at the first record after the beginning of a page
* or we just jumped over the remaining data of a continuation.
*/
while (XLogReadRecord(state, tmpRecPtr, &errormsg) != NULL)
{
/* continue after the record */
tmpRecPtr = InvalidXLogRecPtr;
/* past the record we've found, break out */
if (RecPtr <= state->ReadRecPtr)
{
found = state->ReadRecPtr;
goto out;
}
}
err:
out:
/* Reset state to what we had before finding the record */
state->ReadRecPtr = saved_state.ReadRecPtr;
state->EndRecPtr = saved_state.EndRecPtr;
XLogReaderInvalReadState(state);
return found;
}
#endif /* FRONTEND */
/* ----------------------------------------
* Functions for decoding the data and block references in a record.
* ----------------------------------------
*/
/* private function to reset the state between records */
static void
ResetDecoder(XLogReaderState *state)
{
int block_id;
state->decoded_record = NULL;
state->main_data_len = 0;
for (block_id = 0; block_id <= state->max_block_id; block_id++)
{
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].apply_image = false;
}
state->max_block_id = -1;
}
/*
* Decode the previously read record.
*
* On error, a human-readable error message is returned in *errormsg, and
* the return value is false.
*/
bool
DecodeXLogRecord(XLogReaderState *state, XLogRecord *record, char **errormsg)
{
/*
* read next _size bytes from record buffer, but check for overrun first.
*/
#define COPY_HEADER_FIELD(_dst, _size) \
do { \
if (remaining < _size) \
goto shortdata_err; \
memcpy(_dst, ptr, _size); \
ptr += _size; \
remaining -= _size; \
} while(0)
char *ptr;
uint32 remaining;
uint32 datatotal;
RelFileNode *rnode = NULL;
uint8 block_id;
ResetDecoder(state);
state->decoded_record = record;
state->record_origin = InvalidRepOriginId;
ptr = (char *) record;
ptr += SizeOfXLogRecord;
remaining = record->xl_tot_len - SizeOfXLogRecord;
/* Decode the headers */
datatotal = 0;
while (remaining > datatotal)
{
COPY_HEADER_FIELD(&block_id, sizeof(uint8));
if (block_id == XLR_BLOCK_ID_DATA_SHORT)
{
/* XLogRecordDataHeaderShort */
uint8 main_data_len;
COPY_HEADER_FIELD(&main_data_len, sizeof(uint8));
state->main_data_len = main_data_len;
datatotal += main_data_len;
break; /* by convention, the main data fragment is
* always last */
}
else if (block_id == XLR_BLOCK_ID_DATA_LONG)
{
/* XLogRecordDataHeaderLong */
uint32 main_data_len;
COPY_HEADER_FIELD(&main_data_len, sizeof(uint32));
state->main_data_len = main_data_len;
datatotal += main_data_len;
break; /* by convention, the main data fragment is
* always last */
}
else if (block_id == XLR_BLOCK_ID_ORIGIN)
{
COPY_HEADER_FIELD(&state->record_origin, sizeof(RepOriginId));
}
else if (block_id <= XLR_MAX_BLOCK_ID)
{
/* XLogRecordBlockHeader */
DecodedBkpBlock *blk;
uint8 fork_flags;
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;
blk = &state->blocks[block_id];
blk->in_use = true;
blk->apply_image = false;
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);
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);
goto err;
}
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);
goto err;
}
datatotal += blk->data_len;
if (blk->has_image)
{
COPY_HEADER_FIELD(&blk->bimg_len, sizeof(uint16));
COPY_HEADER_FIELD(&blk->hole_offset, sizeof(uint16));
COPY_HEADER_FIELD(&blk->bimg_info, sizeof(uint8));
blk->apply_image = ((blk->bimg_info & BKPIMAGE_APPLY) != 0);
if (blk->bimg_info & BKPIMAGE_IS_COMPRESSED)
{
if (blk->bimg_info & BKPIMAGE_HAS_HOLE)
COPY_HEADER_FIELD(&blk->hole_length, sizeof(uint16));
else
blk->hole_length = 0;
}
else
blk->hole_length = BLCKSZ - blk->bimg_len;
datatotal += blk->bimg_len;
/*
* cross-check that hole_offset > 0, hole_length > 0 and
* bimg_len < BLCKSZ if the HAS_HOLE flag is set.
*/
if ((blk->bimg_info & BKPIMAGE_HAS_HOLE) &&
(blk->hole_offset == 0 ||
blk->hole_length == 0 ||
blk->bimg_len == BLCKSZ))
{
report_invalid_record(state,
"BKPIMAGE_HAS_HOLE set, but hole offset %u length %u block image length %u at %X/%X",
(unsigned int) blk->hole_offset,
(unsigned int) blk->hole_length,
(unsigned int) blk->bimg_len,
(uint32) (state->ReadRecPtr >> 32), (uint32) state->ReadRecPtr);
goto err;
}
/*
* cross-check that hole_offset == 0 and hole_length == 0 if
* the HAS_HOLE flag is not set.
*/
if (!(blk->bimg_info & BKPIMAGE_HAS_HOLE) &&
(blk->hole_offset != 0 || blk->hole_length != 0))
{
report_invalid_record(state,
"BKPIMAGE_HAS_HOLE not set, but hole offset %u length %u at %X/%X",
(unsigned int) blk->hole_offset,
(unsigned int) blk->hole_length,
(uint32) (state->ReadRecPtr >> 32), (uint32) state->ReadRecPtr);
goto err;
}
/*
* cross-check that bimg_len < BLCKSZ if the IS_COMPRESSED
* flag is set.
*/
if ((blk->bimg_info & BKPIMAGE_IS_COMPRESSED) &&
blk->bimg_len == BLCKSZ)
{
report_invalid_record(state,
"BKPIMAGE_IS_COMPRESSED set, but block image length %u at %X/%X",
(unsigned int) blk->bimg_len,
(uint32) (state->ReadRecPtr >> 32), (uint32) state->ReadRecPtr);
goto err;
}
/*
* cross-check that bimg_len = BLCKSZ if neither HAS_HOLE nor
* IS_COMPRESSED flag is set.
*/
if (!(blk->bimg_info & BKPIMAGE_HAS_HOLE) &&
!(blk->bimg_info & BKPIMAGE_IS_COMPRESSED) &&
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",
(unsigned int) blk->data_len,
(uint32) (state->ReadRecPtr >> 32), (uint32) state->ReadRecPtr);
goto err;
}
}
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
{
report_invalid_record(state,
"invalid block_id %u at %X/%X",
block_id,
(uint32) (state->ReadRecPtr >> 32),
(uint32) state->ReadRecPtr);
goto err;
}
}
if (remaining != datatotal)
goto shortdata_err;
/*
* Ok, we've parsed the fragment headers, and verified that the total
* length of the payload in the fragments is equal to the amount of data
* left. Copy the data of each fragment to a separate buffer.
*
* We could just set up pointers into readRecordBuf, but we want to align
* the data for the convenience of the callers. Backup images are not
* copied, however; they don't need alignment.
*/
/* block data first */
for (block_id = 0; block_id <= state->max_block_id; block_id++)
{
DecodedBkpBlock *blk = &state->blocks[block_id];
if (!blk->in_use)
continue;
Assert(blk->has_image || !blk->apply_image);
if (blk->has_image)
{
blk->bkp_image = ptr;
ptr += blk->bimg_len;
}
if (blk->has_data)
{
if (!blk->data || blk->data_len > blk->data_bufsz)
{
if (blk->data)
pfree(blk->data);
/*
* Force the initial request to be BLCKSZ so that we don't
* waste time with lots of trips through this stanza as a
* result of WAL compression.
*/
blk->data_bufsz = MAXALIGN(Max(blk->data_len, BLCKSZ));
blk->data = palloc(blk->data_bufsz);
}
memcpy(blk->data, ptr, blk->data_len);
ptr += blk->data_len;
}
}
/* and finally, the main data */
if (state->main_data_len > 0)
{
if (!state->main_data || state->main_data_len > state->main_data_bufsz)
{
if (state->main_data)
pfree(state->main_data);
/*
* main_data_bufsz must be MAXALIGN'ed. In many xlog record
* types, we omit trailing struct padding on-disk to save a few
* bytes; but compilers may generate accesses to the xlog struct
* that assume that padding bytes are present. If the palloc
* request is not large enough to include such padding bytes then
* we'll get valgrind complaints due to otherwise-harmless fetches
* of the padding bytes.
*
* In addition, force the initial request to be reasonably large
* so that we don't waste time with lots of trips through this
* stanza. BLCKSZ / 2 seems like a good compromise choice.
*/
state->main_data_bufsz = MAXALIGN(Max(state->main_data_len,
BLCKSZ / 2));
state->main_data = palloc(state->main_data_bufsz);
}
memcpy(state->main_data, ptr, state->main_data_len);
ptr += state->main_data_len;
}
return true;
shortdata_err:
report_invalid_record(state,
"record with invalid length at %X/%X",
(uint32) (state->ReadRecPtr >> 32), (uint32) state->ReadRecPtr);
err:
*errormsg = state->errormsg_buf;
return false;
}
/*
* Returns information about the block that a block reference refers to.
*
* If the WAL record contains a block reference with the given ID, *rnode,
* *forknum, and *blknum are filled in (if not NULL), and returns true.
* Otherwise returns false.
*/
bool
XLogRecGetBlockTag(XLogReaderState *record, uint8 block_id,
RelFileNode *rnode, ForkNumber *forknum, BlockNumber *blknum)
{
DecodedBkpBlock *bkpb;
if (!record->blocks[block_id].in_use)
return false;
bkpb = &record->blocks[block_id];
if (rnode)
*rnode = bkpb->rnode;
if (forknum)
*forknum = bkpb->forknum;
if (blknum)
*blknum = bkpb->blkno;
return true;
}
/*
* Returns the data associated with a block reference, or NULL if there is
* no data (e.g. because a full-page image was taken instead). The returned
* pointer points to a MAXALIGNed buffer.
*/
char *
XLogRecGetBlockData(XLogReaderState *record, uint8 block_id, Size *len)
{
DecodedBkpBlock *bkpb;
if (!record->blocks[block_id].in_use)
return NULL;
bkpb = &record->blocks[block_id];
if (!bkpb->has_data)
{
if (len)
*len = 0;
return NULL;
}
else
{
if (len)
*len = bkpb->data_len;
return bkpb->data;
}
}
/*
* Restore a full-page image from a backup block attached to an XLOG record.
*
* Returns the buffer number containing the page.
*/
bool
RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page)
{
DecodedBkpBlock *bkpb;
char *ptr;
PGAlignedBlock tmp;
if (!record->blocks[block_id].in_use)
return false;
if (!record->blocks[block_id].has_image)
return false;
bkpb = &record->blocks[block_id];
ptr = bkpb->bkp_image;
if (bkpb->bimg_info & BKPIMAGE_IS_COMPRESSED)
{
char errormessage[MAX_ERRORMSG_LEN];
/* If a backup block image is compressed, decompress it */
if (!zstd_decompress_backupblock(ptr, bkpb->bimg_len, tmp.data,
BLCKSZ - bkpb->hole_length,
errormessage))
{
report_invalid_record(record, "invalid compressed image at %X/%X, block %d (%s)",
(uint32) (record->ReadRecPtr >> 32),
(uint32) record->ReadRecPtr,
block_id,
errormessage);
return false;
}
ptr = tmp.data;
}
/* generate page, taking into account hole if necessary */
if (bkpb->hole_length == 0)
{
memcpy(page, ptr, BLCKSZ);
}
else
{
memcpy(page, ptr, 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),
ptr + bkpb->hole_offset,
BLCKSZ - (bkpb->hole_offset + bkpb->hole_length));
}
return true;
}
bool
zstd_decompress_backupblock(const char *source, int32 slen, char *dest,
int32 rawsize, char *errormessage)
{
#ifdef USE_ZSTD
unsigned long long uncompressed_size;
int dst_length_used;
static ZSTD_DCtx *cxt = NULL; /* ZSTD decompression context */
if (!cxt)
{
cxt = ZSTD_createDCtx();
if (!cxt)
{
snprintf(errormessage, MAX_ERRORMSG_LEN, "out of memory");
return false;
}
}
uncompressed_size = ZSTD_getFrameContentSize(source, slen);
if (uncompressed_size == ZSTD_CONTENTSIZE_UNKNOWN)
{
snprintf(errormessage, MAX_ERRORMSG_LEN,
"decompressed size not known");
return false;
}
if (uncompressed_size == ZSTD_CONTENTSIZE_ERROR)
{
snprintf(errormessage, MAX_ERRORMSG_LEN,
"error computing decompression size");
return false;
}
if (uncompressed_size > rawsize)
{
snprintf(errormessage, MAX_ERRORMSG_LEN,
"too large ("UINT64_FORMAT") size after decompression",
(uint64) uncompressed_size);
return false;
}
dst_length_used = ZSTD_decompressDCtx(cxt,
dest, rawsize,
source, slen);
if (ZSTD_isError(dst_length_used))
{
snprintf(errormessage, MAX_ERRORMSG_LEN,
"%s error encountered on decompression",
ZSTD_getErrorName(dst_length_used));
return false;
}
Assert(dst_length_used == rawsize);
return true;
#endif
snprintf(errormessage, MAX_ERRORMSG_LEN,
"binary not compiled with ZSTD support");
return false;
}
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