diff options
Diffstat (limited to 'src/backend/access/transam/xlogreader.c')
| -rw-r--r-- | src/backend/access/transam/xlogreader.c | 2165 |
1 files changed, 2165 insertions, 0 deletions
diff --git a/src/backend/access/transam/xlogreader.c b/src/backend/access/transam/xlogreader.c new file mode 100644 index 0000000..c15da9d --- /dev/null +++ b/src/backend/access/transam/xlogreader.c @@ -0,0 +1,2165 @@ +/*------------------------------------------------------------------------- + * + * xlogreader.c + * Generic XLog reading facility + * + * Portions Copyright (c) 2013-2022, 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 <unistd.h> +#ifdef USE_LZ4 +#include <lz4.h> +#endif +#ifdef USE_ZSTD +#include <zstd.h> +#endif + +#include "access/transam.h" +#include "access/xlog_internal.h" +#include "access/xlogreader.h" +#include "access/xlogrecord.h" +#include "catalog/pg_control.h" +#include "common/pg_lzcompress.h" +#include "replication/origin.h" + +#ifndef FRONTEND +#include "miscadmin.h" +#include "pgstat.h" +#include "utils/memutils.h" +#else +#include "common/logging.h" +#endif + +static void report_invalid_record(XLogReaderState *state, const char *fmt,...) + pg_attribute_printf(2, 3); +static void allocate_recordbuf(XLogReaderState *state, uint32 reclength); +static int ReadPageInternal(XLogReaderState *state, XLogRecPtr pageptr, + int reqLen); +static void XLogReaderInvalReadState(XLogReaderState *state); +static XLogPageReadResult XLogDecodeNextRecord(XLogReaderState *state, bool non_blocking); +static bool ValidXLogRecordHeader(XLogReaderState *state, XLogRecPtr RecPtr, + XLogRecPtr PrevRecPtr, XLogRecord *record, bool randAccess); +static bool ValidXLogRecord(XLogReaderState *state, XLogRecord *record, + XLogRecPtr recptr); +static void ResetDecoder(XLogReaderState *state); +static void WALOpenSegmentInit(WALOpenSegment *seg, WALSegmentContext *segcxt, + int segsize, const char *waldir); + +/* size of the buffer allocated for error message. */ +#define MAX_ERRORMSG_LEN 1000 + +/* + * Default size; large enough that typical users of XLogReader won't often need + * to use the 'oversized' memory allocation code path. + */ +#define DEFAULT_DECODE_BUFFER_SIZE (64 * 1024) + +/* + * 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); + + state->errormsg_deferred = true; +} + +/* + * Set the size of the decoding buffer. A pointer to a caller supplied memory + * region may also be passed in, in which case non-oversized records will be + * decoded there. + */ +void +XLogReaderSetDecodeBuffer(XLogReaderState *state, void *buffer, size_t size) +{ + Assert(state->decode_buffer == NULL); + + state->decode_buffer = buffer; + state->decode_buffer_size = size; + state->decode_buffer_tail = buffer; + state->decode_buffer_head = buffer; +} + +/* + * Allocate and initialize a new XLogReader. + * + * Returns NULL if the xlogreader couldn't be allocated. + */ +XLogReaderState * +XLogReaderAllocate(int wal_segment_size, const char *waldir, + XLogReaderRoutine *routine, void *private_data) +{ + XLogReaderState *state; + + state = (XLogReaderState *) + palloc_extended(sizeof(XLogReaderState), + MCXT_ALLOC_NO_OOM | MCXT_ALLOC_ZERO); + if (!state) + return NULL; + + /* initialize caller-provided support functions */ + state->routine = *routine; + + /* + * 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; + } + + /* Initialize segment info. */ + WALOpenSegmentInit(&state->seg, &state->segcxt, wal_segment_size, + waldir); + + /* system_identifier initialized to zeroes above */ + state->private_data = private_data; + /* ReadRecPtr, EndRecPtr and readLen 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. + */ + allocate_recordbuf(state, 0); + return state; +} + +void +XLogReaderFree(XLogReaderState *state) +{ + if (state->seg.ws_file != -1) + state->routine.segment_close(state); + + if (state->decode_buffer && state->free_decode_buffer) + pfree(state->decode_buffer); + + 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. + * + * 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.) + * + * Note: This routine should *never* be called for xl_tot_len until the header + * of the record has been fully validated. + */ +static void +allocate_recordbuf(XLogReaderState *state, uint32 reclength) +{ + uint32 newSize = reclength; + + newSize += XLOG_BLCKSZ - (newSize % XLOG_BLCKSZ); + newSize = Max(newSize, 5 * Max(BLCKSZ, XLOG_BLCKSZ)); + + if (state->readRecordBuf) + pfree(state->readRecordBuf); + state->readRecordBuf = (char *) palloc(newSize); + state->readRecordBufSize = newSize; +} + +/* + * Initialize the passed segment structs. + */ +static void +WALOpenSegmentInit(WALOpenSegment *seg, WALSegmentContext *segcxt, + int segsize, const char *waldir) +{ + seg->ws_file = -1; + seg->ws_segno = 0; + seg->ws_tli = 0; + + segcxt->ws_segsize = segsize; + if (waldir) + snprintf(segcxt->ws_dir, MAXPGPATH, "%s", waldir); +} + +/* + * Begin reading WAL at 'RecPtr'. + * + * 'RecPtr' should point to the beginning of a valid WAL record. Pointing at + * the beginning of a page is also OK, if there is a new record right after + * the page header, i.e. not a continuation. + * + * This does not make any attempt to read the WAL yet, and hence cannot fail. + * If the starting address is not correct, the first call to XLogReadRecord() + * will error out. + */ +void +XLogBeginRead(XLogReaderState *state, XLogRecPtr RecPtr) +{ + Assert(!XLogRecPtrIsInvalid(RecPtr)); + + ResetDecoder(state); + + /* Begin at the passed-in record pointer. */ + state->EndRecPtr = RecPtr; + state->NextRecPtr = RecPtr; + state->ReadRecPtr = InvalidXLogRecPtr; + state->DecodeRecPtr = InvalidXLogRecPtr; +} + +/* + * Release the last record that was returned by XLogNextRecord(), if any, to + * free up space. Returns the LSN past the end of the record. + */ +XLogRecPtr +XLogReleasePreviousRecord(XLogReaderState *state) +{ + DecodedXLogRecord *record; + XLogRecPtr next_lsn; + + if (!state->record) + return InvalidXLogRecPtr; + + /* + * Remove it from the decoded record queue. It must be the oldest item + * decoded, decode_queue_head. + */ + record = state->record; + next_lsn = record->next_lsn; + Assert(record == state->decode_queue_head); + state->record = NULL; + state->decode_queue_head = record->next; + + /* It might also be the newest item decoded, decode_queue_tail. */ + if (state->decode_queue_tail == record) + state->decode_queue_tail = NULL; + + /* Release the space. */ + if (unlikely(record->oversized)) + { + /* It's not in the decode buffer, so free it to release space. */ + pfree(record); + } + else + { + /* It must be the head (oldest) record in the decode buffer. */ + Assert(state->decode_buffer_head == (char *) record); + + /* + * We need to update head to point to the next record that is in the + * decode buffer, if any, being careful to skip oversized ones + * (they're not in the decode buffer). + */ + record = record->next; + while (unlikely(record && record->oversized)) + record = record->next; + + if (record) + { + /* Adjust head to release space up to the next record. */ + state->decode_buffer_head = (char *) record; + } + else + { + /* + * Otherwise we might as well just reset head and tail to the + * start of the buffer space, because we're empty. This means + * we'll keep overwriting the same piece of memory if we're not + * doing any prefetching. + */ + state->decode_buffer_head = state->decode_buffer; + state->decode_buffer_tail = state->decode_buffer; + } + } + + return next_lsn; +} + +/* + * Attempt to read an XLOG record. + * + * XLogBeginRead() or XLogFindNextRecord() and then XLogReadAhead() must be + * called before the first call to XLogNextRecord(). This functions returns + * records and errors that were put into an internal queue by XLogReadAhead(). + * + * On success, a record is returned. + * + * The returned record (or *errormsg) points to an internal buffer that's + * valid until the next call to XLogNextRecord. + */ +DecodedXLogRecord * +XLogNextRecord(XLogReaderState *state, char **errormsg) +{ + /* Release the last record returned by XLogNextRecord(). */ + XLogReleasePreviousRecord(state); + + if (state->decode_queue_head == NULL) + { + *errormsg = NULL; + if (state->errormsg_deferred) + { + if (state->errormsg_buf[0] != '\0') + *errormsg = state->errormsg_buf; + state->errormsg_deferred = false; + } + + /* + * state->EndRecPtr is expected to have been set by the last call to + * XLogBeginRead() or XLogNextRecord(), and is the location of the + * error. + */ + Assert(!XLogRecPtrIsInvalid(state->EndRecPtr)); + + return NULL; + } + + /* + * Record this as the most recent record returned, so that we'll release + * it next time. This also exposes it to the traditional + * XLogRecXXX(xlogreader) macros, which work with the decoder rather than + * the record for historical reasons. + */ + state->record = state->decode_queue_head; + + /* + * Update the pointers to the beginning and one-past-the-end of this + * record, again for the benefit of historical code that expected the + * decoder to track this rather than accessing these fields of the record + * itself. + */ + state->ReadRecPtr = state->record->lsn; + state->EndRecPtr = state->record->next_lsn; + + *errormsg = NULL; + + return state->record; +} + +/* + * Attempt to read an XLOG record. + * + * XLogBeginRead() or XLogFindNextRecord() must be called before the first call + * to XLogReadRecord(). + * + * If the page_read 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, char **errormsg) +{ + DecodedXLogRecord *decoded; + + /* + * Release last returned record, if there is one. We need to do this so + * that we can check for empty decode queue accurately. + */ + XLogReleasePreviousRecord(state); + + /* + * Call XLogReadAhead() in blocking mode to make sure there is something + * in the queue, though we don't use the result. + */ + if (!XLogReaderHasQueuedRecordOrError(state)) + XLogReadAhead(state, false /* nonblocking */ ); + + /* Consume the head record or error. */ + decoded = XLogNextRecord(state, errormsg); + if (decoded) + { + /* + * This function returns a pointer to the record's header, not the + * actual decoded record. The caller will access the decoded record + * through the XLogRecGetXXX() macros, which reach the decoded + * recorded as xlogreader->record. + */ + Assert(state->record == decoded); + return &decoded->header; + } + + return NULL; +} + +/* + * Allocate space for a decoded record. The only member of the returned + * object that is initialized is the 'oversized' flag, indicating that the + * decoded record wouldn't fit in the decode buffer and must eventually be + * freed explicitly. + * + * The caller is responsible for adjusting decode_buffer_tail with the real + * size after successfully decoding a record into this space. This way, if + * decoding fails, then there is nothing to undo unless the 'oversized' flag + * was set and pfree() must be called. + * + * Return NULL if there is no space in the decode buffer and allow_oversized + * is false, or if memory allocation fails for an oversized buffer. + */ +static DecodedXLogRecord * +XLogReadRecordAlloc(XLogReaderState *state, size_t xl_tot_len, bool allow_oversized) +{ + size_t required_space = DecodeXLogRecordRequiredSpace(xl_tot_len); + DecodedXLogRecord *decoded = NULL; + + /* Allocate a circular decode buffer if we don't have one already. */ + if (unlikely(state->decode_buffer == NULL)) + { + if (state->decode_buffer_size == 0) + state->decode_buffer_size = DEFAULT_DECODE_BUFFER_SIZE; + state->decode_buffer = palloc(state->decode_buffer_size); + state->decode_buffer_head = state->decode_buffer; + state->decode_buffer_tail = state->decode_buffer; + state->free_decode_buffer = true; + } + + /* Try to allocate space in the circular decode buffer. */ + if (state->decode_buffer_tail >= state->decode_buffer_head) + { + /* Empty, or tail is to the right of head. */ + if (state->decode_buffer_tail + required_space <= + state->decode_buffer + state->decode_buffer_size) + { + /* There is space between tail and end. */ + decoded = (DecodedXLogRecord *) state->decode_buffer_tail; + decoded->oversized = false; + return decoded; + } + else if (state->decode_buffer + required_space < + state->decode_buffer_head) + { + /* There is space between start and head. */ + decoded = (DecodedXLogRecord *) state->decode_buffer; + decoded->oversized = false; + return decoded; + } + } + else + { + /* Tail is to the left of head. */ + if (state->decode_buffer_tail + required_space < + state->decode_buffer_head) + { + /* There is space between tail and head. */ + decoded = (DecodedXLogRecord *) state->decode_buffer_tail; + decoded->oversized = false; + return decoded; + } + } + + /* Not enough space in the decode buffer. Are we allowed to allocate? */ + if (allow_oversized) + { + decoded = palloc(required_space); + decoded->oversized = true; + return decoded; + } + + return NULL; +} + +static XLogPageReadResult +XLogDecodeNextRecord(XLogReaderState *state, bool nonblocking) +{ + XLogRecPtr RecPtr; + XLogRecord *record; + XLogRecPtr targetPagePtr; + bool randAccess; + uint32 len, + total_len; + uint32 targetRecOff; + uint32 pageHeaderSize; + bool assembled; + bool gotheader; + int readOff; + DecodedXLogRecord *decoded; + char *errormsg; /* not used */ + + /* + * 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 */ + state->errormsg_buf[0] = '\0'; + decoded = NULL; + + state->abortedRecPtr = InvalidXLogRecPtr; + state->missingContrecPtr = InvalidXLogRecPtr; + + RecPtr = state->NextRecPtr; + + if (state->DecodeRecPtr != InvalidXLogRecPtr) + { + /* read the record after the one we just read */ + + /* + * NextRecPtr 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, NextRecPtr should already be pointing to a valid + * record starting position. + */ + Assert(XRecOffIsValid(RecPtr)); + randAccess = true; + } + +restart: + state->nonblocking = nonblocking; + 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 == XLREAD_WOULDBLOCK) + return XLREAD_WOULDBLOCK; + else 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", + LSN_FORMAT_ARGS(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", + LSN_FORMAT_ARGS(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->DecodeRecPtr, record, + randAccess)) + goto err; + gotheader = true; + } + else + { + /* There may be no next page if it's too small. */ + if (total_len < SizeOfXLogRecord) + { + report_invalid_record(state, + "invalid record length at %X/%X: wanted %u, got %u", + LSN_FORMAT_ARGS(RecPtr), + (uint32) SizeOfXLogRecord, total_len); + goto err; + } + /* We'll validate the header once we have the next page. */ + gotheader = false; + } + + /* + * Try to find space to decode this record, if we can do so without + * calling palloc. If we can't, we'll try again below after we've + * validated that total_len isn't garbage bytes from a recycled WAL page. + */ + decoded = XLogReadRecordAlloc(state, + total_len, + false /* allow_oversized */ ); + if (decoded == NULL && nonblocking) + { + /* + * There is no space in the circular decode buffer, and the caller is + * only reading ahead. The caller should consume existing records to + * make space. + */ + return XLREAD_WOULDBLOCK; + } + + len = XLOG_BLCKSZ - RecPtr % XLOG_BLCKSZ; + if (total_len > len) + { + /* Need to reassemble record */ + char *contdata; + XLogPageHeader pageHeader; + char *buffer; + uint32 gotlen; + + assembled = true; + + /* + * We always have space for a couple of pages, enough to validate a + * boundary-spanning record header. + */ + Assert(state->readRecordBufSize >= XLOG_BLCKSZ * 2); + Assert(state->readRecordBufSize >= len); + + /* 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 == XLREAD_WOULDBLOCK) + return XLREAD_WOULDBLOCK; + else 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 = RecPtr; + 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", + LSN_FORMAT_ARGS(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 (expected %lld) at %X/%X", + pageHeader->xlp_rem_len, + ((long long) total_len) - gotlen, + LSN_FORMAT_ARGS(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->DecodeRecPtr, + record, randAccess)) + goto err; + gotheader = true; + } + + /* + * We might need a bigger buffer. We have validated the record + * header, in the case that it split over a page boundary. We've + * also cross-checked total_len against xlp_rem_len on the second + * page, and verified xlp_pageaddr on both. + */ + if (total_len > state->readRecordBufSize) + { + char save_copy[XLOG_BLCKSZ * 2]; + + /* + * Save and restore the data we already had. It can't be more + * than two pages. + */ + Assert(gotlen <= lengthof(save_copy)); + Assert(gotlen <= state->readRecordBufSize); + memcpy(save_copy, state->readRecordBuf, gotlen); + allocate_recordbuf(state, total_len); + memcpy(state->readRecordBuf, save_copy, gotlen); + buffer = state->readRecordBuf + gotlen; + } + } while (gotlen < total_len); + Assert(gotheader); + + record = (XLogRecord *) state->readRecordBuf; + if (!ValidXLogRecord(state, record, RecPtr)) + goto err; + + pageHeaderSize = XLogPageHeaderSize((XLogPageHeader) state->readBuf); + state->DecodeRecPtr = RecPtr; + state->NextRecPtr = 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 == XLREAD_WOULDBLOCK) + return XLREAD_WOULDBLOCK; + else if (readOff < 0) + goto err; + + /* Record does not cross a page boundary */ + if (!ValidXLogRecord(state, record, RecPtr)) + goto err; + + state->NextRecPtr = RecPtr + MAXALIGN(total_len); + + state->DecodeRecPtr = 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->NextRecPtr += state->segcxt.ws_segsize - 1; + state->NextRecPtr -= XLogSegmentOffset(state->NextRecPtr, state->segcxt.ws_segsize); + } + + /* + * If we got here without a DecodedXLogRecord, it means we needed to + * validate total_len before trusting it, but by now now we've done that. + */ + if (decoded == NULL) + { + Assert(!nonblocking); + decoded = XLogReadRecordAlloc(state, + total_len, + true /* allow_oversized */ ); + /* allocation should always happen under allow_oversized */ + Assert(decoded != NULL); + } + + if (DecodeXLogRecord(state, decoded, record, RecPtr, &errormsg)) + { + /* Record the location of the next record. */ + decoded->next_lsn = state->NextRecPtr; + + /* + * If it's in the decode buffer, mark the decode buffer space as + * occupied. + */ + if (!decoded->oversized) + { + /* The new decode buffer head must be MAXALIGNed. */ + Assert(decoded->size == MAXALIGN(decoded->size)); + if ((char *) decoded == state->decode_buffer) + state->decode_buffer_tail = state->decode_buffer + decoded->size; + else + state->decode_buffer_tail += decoded->size; + } + + /* Insert it into the queue of decoded records. */ + Assert(state->decode_queue_tail != decoded); + if (state->decode_queue_tail) + state->decode_queue_tail->next = decoded; + state->decode_queue_tail = decoded; + if (!state->decode_queue_head) + state->decode_queue_head = decoded; + return XLREAD_SUCCESS; + } + +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; + + /* + * If we got here without reporting an error, make sure an error is + * queued so that XLogPrefetcherReadRecord() doesn't bring us back a + * second time and clobber the above state. + */ + state->errormsg_deferred = true; + } + + if (decoded && decoded->oversized) + pfree(decoded); + + /* + * Invalidate the read state. We might read from a different source after + * failure. + */ + XLogReaderInvalReadState(state); + + /* + * If an error was written to errmsg_buf, it'll be returned to the caller + * of XLogReadRecord() after all successfully decoded records from the + * read queue. + */ + + return XLREAD_FAIL; +} + +/* + * Try to decode the next available record, and return it. The record will + * also be returned to XLogNextRecord(), which must be called to 'consume' + * each record. + * + * If nonblocking is true, may return NULL due to lack of data or WAL decoding + * space. + */ +DecodedXLogRecord * +XLogReadAhead(XLogReaderState *state, bool nonblocking) +{ + XLogPageReadResult result; + + if (state->errormsg_deferred) + return NULL; + + result = XLogDecodeNextRecord(state, nonblocking); + if (result == XLREAD_SUCCESS) + { + Assert(state->decode_queue_tail != NULL); + return state->decode_queue_tail; + } + + return NULL; +} + +/* + * Read a single xlog page including at least [pageptr, reqLen] of valid data + * via the page_read() callback. + * + * Returns XLREAD_FAIL if the required page cannot be read for some + * reason; errormsg_buf is set in that case (unless the error occurs in the + * page_read callback). + * + * Returns XLREAD_WOULDBLOCK if the requested data can't be read without + * waiting. This can be returned only if the installed page_read callback + * respects the state->nonblocking flag, and cannot read the requested data + * immediately. + * + * 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->segcxt.ws_segsize); + targetPageOff = XLogSegmentOffset(pageptr, state->segcxt.ws_segsize); + + /* check whether we have all the requested data already */ + if (targetSegNo == state->seg.ws_segno && + targetPageOff == state->segoff && reqLen <= state->readLen) + return state->readLen; + + /* + * Invalidate contents of internal buffer before read attempt. Just set + * the length to 0, rather than a full XLogReaderInvalReadState(), so we + * don't forget the segment we last successfully read. + */ + state->readLen = 0; + + /* + * Data is not in our buffer. + * + * Every time we actually read the segment, even if we looked at parts of + * it before, we need to do verification as the page_read 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->seg.ws_segno && targetPageOff != 0) + { + XLogRecPtr targetSegmentPtr = pageptr - targetPageOff; + + readLen = state->routine.page_read(state, targetSegmentPtr, XLOG_BLCKSZ, + state->currRecPtr, + state->readBuf); + if (readLen == XLREAD_WOULDBLOCK) + return XLREAD_WOULDBLOCK; + else 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->routine.page_read(state, pageptr, Max(reqLen, SizeOfXLogShortPHD), + state->currRecPtr, + state->readBuf); + if (readLen == XLREAD_WOULDBLOCK) + return XLREAD_WOULDBLOCK; + else 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->routine.page_read(state, pageptr, XLogPageHeaderSize(hdr), + state->currRecPtr, + state->readBuf); + if (readLen == XLREAD_WOULDBLOCK) + return XLREAD_WOULDBLOCK; + else 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->seg.ws_segno = targetSegNo; + state->segoff = targetPageOff; + state->readLen = readLen; + + return readLen; + +err: + XLogReaderInvalReadState(state); + + return XLREAD_FAIL; +} + +/* + * Invalidate the xlogreader's read state to force a re-read. + */ +static void +XLogReaderInvalReadState(XLogReaderState *state) +{ + state->seg.ws_segno = 0; + state->segoff = 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", + LSN_FORMAT_ARGS(RecPtr), + (uint32) SizeOfXLogRecord, record->xl_tot_len); + return false; + } + if (!RmgrIdIsValid(record->xl_rmid)) + { + report_invalid_record(state, + "invalid resource manager ID %u at %X/%X", + record->xl_rmid, LSN_FORMAT_ARGS(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", + LSN_FORMAT_ARGS(record->xl_prev), + LSN_FORMAT_ARGS(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", + LSN_FORMAT_ARGS(record->xl_prev), + LSN_FORMAT_ARGS(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; + + Assert(record->xl_tot_len >= SizeOfXLogRecord); + + /* 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", + LSN_FORMAT_ARGS(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->segcxt.ws_segsize); + offset = XLogSegmentOffset(recptr, state->segcxt.ws_segsize); + + XLogSegNoOffsetToRecPtr(segno, offset, state->segcxt.ws_segsize, recaddr); + + if (hdr->xlp_magic != XLOG_PAGE_MAGIC) + { + char fname[MAXFNAMELEN]; + + XLogFileName(fname, state->seg.ws_tli, segno, state->segcxt.ws_segsize); + + 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->seg.ws_tli, segno, state->segcxt.ws_segsize); + + 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) + { + report_invalid_record(state, + "WAL file is from different database system: WAL file database system identifier is %llu, pg_control database system identifier is %llu", + (unsigned long long) longhdr->xlp_sysid, + (unsigned long long) state->system_identifier); + return false; + } + else if (longhdr->xlp_seg_size != state->segcxt.ws_segsize) + { + 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->seg.ws_tli, segno, state->segcxt.ws_segsize); + + /* 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->seg.ws_tli, segno, state->segcxt.ws_segsize); + + report_invalid_record(state, + "unexpected pageaddr %X/%X in log segment %s, offset %u", + LSN_FORMAT_ARGS(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->seg.ws_tli, segno, state->segcxt.ws_segsize); + + 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; +} + +/* + * Forget about an error produced by XLogReaderValidatePageHeader(). + */ +void +XLogReaderResetError(XLogReaderState *state) +{ + state->errormsg_buf[0] = '\0'; + state->errormsg_deferred = false; +} + +/* + * Find the first record with an lsn >= RecPtr. + * + * This is different from XLogBeginRead() in that RecPtr doesn't need to point + * to a valid record boundary. 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. + * + * This positions the reader, like XLogBeginRead(), so that the next call to + * XLogReadRecord() will read the next valid record. + */ +XLogRecPtr +XLogFindNextRecord(XLogReaderState *state, XLogRecPtr RecPtr) +{ + XLogRecPtr tmpRecPtr; + XLogRecPtr found = InvalidXLogRecPtr; + XLogPageHeader header; + char *errormsg; + + Assert(!XLogRecPtrIsInvalid(RecPtr)); + + /* Make sure ReadPageInternal() can't return XLREAD_WOULDBLOCK. */ + state->nonblocking = false; + + /* + * 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. + */ + XLogBeginRead(state, tmpRecPtr); + while (XLogReadRecord(state, &errormsg) != NULL) + { + /* past the record we've found, break out */ + if (RecPtr <= state->ReadRecPtr) + { + /* Rewind the reader to the beginning of the last record. */ + found = state->ReadRecPtr; + XLogBeginRead(state, found); + return found; + } + } + +err: + XLogReaderInvalReadState(state); + + return InvalidXLogRecPtr; +} + +/* + * Helper function to ease writing of XLogRoutine->page_read callbacks. + * If this function is used, caller must supply a segment_open callback in + * 'state', as that is used here. + * + * Read 'count' bytes into 'buf', starting at location 'startptr', from WAL + * fetched from timeline 'tli'. + * + * Returns true if succeeded, false if an error occurs, in which case + * 'errinfo' receives error details. + * + * XXX probably this should be improved to suck data directly from the + * WAL buffers when possible. + */ +bool +WALRead(XLogReaderState *state, + char *buf, XLogRecPtr startptr, Size count, TimeLineID tli, + WALReadError *errinfo) +{ + char *p; + XLogRecPtr recptr; + Size nbytes; + + p = buf; + recptr = startptr; + nbytes = count; + + while (nbytes > 0) + { + uint32 startoff; + int segbytes; + int readbytes; + + startoff = XLogSegmentOffset(recptr, state->segcxt.ws_segsize); + + /* + * If the data we want is not in a segment we have open, close what we + * have (if anything) and open the next one, using the caller's + * provided openSegment callback. + */ + if (state->seg.ws_file < 0 || + !XLByteInSeg(recptr, state->seg.ws_segno, state->segcxt.ws_segsize) || + tli != state->seg.ws_tli) + { + XLogSegNo nextSegNo; + + if (state->seg.ws_file >= 0) + state->routine.segment_close(state); + + XLByteToSeg(recptr, nextSegNo, state->segcxt.ws_segsize); + state->routine.segment_open(state, nextSegNo, &tli); + + /* This shouldn't happen -- indicates a bug in segment_open */ + Assert(state->seg.ws_file >= 0); + + /* Update the current segment info. */ + state->seg.ws_tli = tli; + state->seg.ws_segno = nextSegNo; + } + + /* How many bytes are within this segment? */ + if (nbytes > (state->segcxt.ws_segsize - startoff)) + segbytes = state->segcxt.ws_segsize - startoff; + else + segbytes = nbytes; + +#ifndef FRONTEND + pgstat_report_wait_start(WAIT_EVENT_WAL_READ); +#endif + + /* Reset errno first; eases reporting non-errno-affecting errors */ + errno = 0; + readbytes = pg_pread(state->seg.ws_file, p, segbytes, (off_t) startoff); + +#ifndef FRONTEND + pgstat_report_wait_end(); +#endif + + if (readbytes <= 0) + { + errinfo->wre_errno = errno; + errinfo->wre_req = segbytes; + errinfo->wre_read = readbytes; + errinfo->wre_off = startoff; + errinfo->wre_seg = state->seg; + return false; + } + + /* Update state for read */ + recptr += readbytes; + nbytes -= readbytes; + p += readbytes; + } + + return true; +} + +/* ---------------------------------------- + * Functions for decoding the data and block references in a record. + * ---------------------------------------- + */ + +/* + * Private function to reset the state, forgetting all decoded records, if we + * are asked to move to a new read position. + */ +static void +ResetDecoder(XLogReaderState *state) +{ + DecodedXLogRecord *r; + + /* Reset the decoded record queue, freeing any oversized records. */ + while ((r = state->decode_queue_head) != NULL) + { + state->decode_queue_head = r->next; + if (r->oversized) + pfree(r); + } + state->decode_queue_tail = NULL; + state->decode_queue_head = NULL; + state->record = NULL; + + /* Reset the decode buffer to empty. */ + state->decode_buffer_tail = state->decode_buffer; + state->decode_buffer_head = state->decode_buffer; + + /* Clear error state. */ + state->errormsg_buf[0] = '\0'; + state->errormsg_deferred = false; +} + +/* + * Compute the maximum possible amount of padding that could be required to + * decode a record, given xl_tot_len from the record's header. This is the + * amount of output buffer space that we need to decode a record, though we + * might not finish up using it all. + * + * This computation is pessimistic and assumes the maximum possible number of + * blocks, due to lack of better information. + */ +size_t +DecodeXLogRecordRequiredSpace(size_t xl_tot_len) +{ + size_t size = 0; + + /* Account for the fixed size part of the decoded record struct. */ + size += offsetof(DecodedXLogRecord, blocks[0]); + /* Account for the flexible blocks array of maximum possible size. */ + size += sizeof(DecodedBkpBlock) * (XLR_MAX_BLOCK_ID + 1); + /* Account for all the raw main and block data. */ + size += xl_tot_len; + /* We might insert padding before main_data. */ + size += (MAXIMUM_ALIGNOF - 1); + /* We might insert padding before each block's data. */ + size += (MAXIMUM_ALIGNOF - 1) * (XLR_MAX_BLOCK_ID + 1); + /* We might insert padding at the end. */ + size += (MAXIMUM_ALIGNOF - 1); + + return size; +} + +/* + * Decode a record. "decoded" must point to a MAXALIGNed memory area that has + * space for at least DecodeXLogRecordRequiredSpace(record) bytes. On + * success, decoded->size contains the actual space occupied by the decoded + * record, which may turn out to be less. + * + * Only decoded->oversized member must be initialized already, and will not be + * modified. Other members will be initialized as required. + * + * On error, a human-readable error message is returned in *errormsg, and + * the return value is false. + */ +bool +DecodeXLogRecord(XLogReaderState *state, + DecodedXLogRecord *decoded, + XLogRecord *record, + XLogRecPtr lsn, + 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; + char *out; + uint32 remaining; + uint32 datatotal; + RelFileNode *rnode = NULL; + uint8 block_id; + + decoded->header = *record; + decoded->lsn = lsn; + decoded->next = NULL; + decoded->record_origin = InvalidRepOriginId; + decoded->toplevel_xid = InvalidTransactionId; + decoded->main_data = NULL; + decoded->main_data_len = 0; + decoded->max_block_id = -1; + 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)); + + decoded->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)); + decoded->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(&decoded->record_origin, sizeof(RepOriginId)); + } + else if (block_id == XLR_BLOCK_ID_TOPLEVEL_XID) + { + COPY_HEADER_FIELD(&decoded->toplevel_xid, sizeof(TransactionId)); + } + else if (block_id <= XLR_MAX_BLOCK_ID) + { + /* XLogRecordBlockHeader */ + DecodedBkpBlock *blk; + uint8 fork_flags; + + /* mark any intervening block IDs as not in use */ + for (int i = decoded->max_block_id + 1; i < block_id; ++i) + decoded->blocks[i].in_use = false; + + if (block_id <= decoded->max_block_id) + { + report_invalid_record(state, + "out-of-order block_id %u at %X/%X", + block_id, + LSN_FORMAT_ARGS(state->ReadRecPtr)); + goto err; + } + decoded->max_block_id = block_id; + + blk = &decoded->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); + + blk->prefetch_buffer = InvalidBuffer; + + 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", + LSN_FORMAT_ARGS(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, + LSN_FORMAT_ARGS(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 (BKPIMAGE_COMPRESSED(blk->bimg_info)) + { + 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, + LSN_FORMAT_ARGS(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, + LSN_FORMAT_ARGS(state->ReadRecPtr)); + goto err; + } + + /* + * Cross-check that bimg_len < BLCKSZ if it is compressed. + */ + if (BKPIMAGE_COMPRESSED(blk->bimg_info) && + blk->bimg_len == BLCKSZ) + { + report_invalid_record(state, + "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 is + * set nor COMPRESSED(). + */ + if (!(blk->bimg_info & BKPIMAGE_HAS_HOLE) && + !BKPIMAGE_COMPRESSED(blk->bimg_info) && + blk->bimg_len != BLCKSZ) + { + report_invalid_record(state, + "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; + } + } + 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", + LSN_FORMAT_ARGS(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, LSN_FORMAT_ARGS(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 contiguous space after the + * blocks array, inserting alignment padding before the data fragments so + * they can be cast to struct pointers by REDO routines. + */ + out = ((char *) decoded) + + offsetof(DecodedXLogRecord, blocks) + + sizeof(decoded->blocks[0]) * (decoded->max_block_id + 1); + + /* block data first */ + for (block_id = 0; block_id <= decoded->max_block_id; block_id++) + { + DecodedBkpBlock *blk = &decoded->blocks[block_id]; + + if (!blk->in_use) + continue; + + Assert(blk->has_image || !blk->apply_image); + + if (blk->has_image) + { + /* no need to align image */ + blk->bkp_image = out; + memcpy(out, ptr, blk->bimg_len); + ptr += blk->bimg_len; + out += blk->bimg_len; + } + if (blk->has_data) + { + out = (char *) MAXALIGN(out); + blk->data = out; + memcpy(blk->data, ptr, blk->data_len); + ptr += blk->data_len; + out += blk->data_len; + } + } + + /* and finally, the main data */ + if (decoded->main_data_len > 0) + { + out = (char *) MAXALIGN(out); + decoded->main_data = out; + memcpy(decoded->main_data, ptr, decoded->main_data_len); + ptr += decoded->main_data_len; + out += decoded->main_data_len; + } + + /* Report the actual size we used. */ + decoded->size = MAXALIGN(out - (char *) decoded); + Assert(DecodeXLogRecordRequiredSpace(record->xl_tot_len) >= + decoded->size); + + return true; + +shortdata_err: + report_invalid_record(state, + "record with invalid length at %X/%X", + LSN_FORMAT_ARGS(state->ReadRecPtr)); +err: + *errormsg = state->errormsg_buf; + + return false; +} + +/* + * Returns information about the block that a block reference refers to. + * + * This is like XLogRecGetBlockTagExtended, except that the block reference + * must exist and there's no access to prefetch_buffer. + */ +void +XLogRecGetBlockTag(XLogReaderState *record, uint8 block_id, + RelFileNode *rnode, ForkNumber *forknum, BlockNumber *blknum) +{ + if (!XLogRecGetBlockTagExtended(record, block_id, rnode, forknum, blknum, + NULL)) + { +#ifndef FRONTEND + elog(ERROR, "could not locate backup block with ID %d in WAL record", + block_id); +#else + pg_fatal("could not locate backup block with ID %d in WAL record", + block_id); +#endif + } +} + +/* + * Returns information about the block that a block reference refers to, + * optionally including the buffer that the block may already be in. + * + * If the WAL record contains a block reference with the given ID, *rnode, + * *forknum, *blknum and *prefetch_buffer are filled in (if not NULL), and + * returns true. Otherwise returns false. + */ +bool +XLogRecGetBlockTagExtended(XLogReaderState *record, uint8 block_id, + RelFileNode *rnode, ForkNumber *forknum, + BlockNumber *blknum, + Buffer *prefetch_buffer) +{ + DecodedBkpBlock *bkpb; + + if (!XLogRecHasBlockRef(record, block_id)) + return false; + + bkpb = &record->record->blocks[block_id]; + if (rnode) + *rnode = bkpb->rnode; + if (forknum) + *forknum = bkpb->forknum; + if (blknum) + *blknum = bkpb->blkno; + if (prefetch_buffer) + *prefetch_buffer = bkpb->prefetch_buffer; + 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 (block_id > record->record->max_block_id || + !record->record->blocks[block_id].in_use) + return NULL; + + bkpb = &record->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 true if a full-page image is restored, and false on failure with + * an error to be consumed by the caller. + */ +bool +RestoreBlockImage(XLogReaderState *record, uint8 block_id, char *page) +{ + DecodedBkpBlock *bkpb; + char *ptr; + PGAlignedBlock tmp; + + if (block_id > record->record->max_block_id || + !record->record->blocks[block_id].in_use) + { + report_invalid_record(record, + "could not restore image at %X/%X with invalid block %d specified", + LSN_FORMAT_ARGS(record->ReadRecPtr), + block_id); + return false; + } + if (!record->record->blocks[block_id].has_image) + { + report_invalid_record(record, "could not restore image at %X/%X with invalid state, block %d", + LSN_FORMAT_ARGS(record->ReadRecPtr), + block_id); + return false; + } + + bkpb = &record->record->blocks[block_id]; + ptr = bkpb->bkp_image; + + if (BKPIMAGE_COMPRESSED(bkpb->bimg_info)) + { + /* If a backup block image is compressed, decompress it */ + 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, "could not restore image at %X/%X compressed with %s not supported by build, block %d", + LSN_FORMAT_ARGS(record->ReadRecPtr), + "LZ4", + block_id); + return false; +#endif + } + else if ((bkpb->bimg_info & BKPIMAGE_COMPRESS_ZSTD) != 0) + { +#ifdef USE_ZSTD + size_t decomp_result = ZSTD_decompress(tmp.data, + BLCKSZ - bkpb->hole_length, + ptr, bkpb->bimg_len); + + if (ZSTD_isError(decomp_result)) + decomp_success = false; +#else + report_invalid_record(record, "could not restore image at %X/%X compressed with %s not supported by build, block %d", + LSN_FORMAT_ARGS(record->ReadRecPtr), + "zstd", + block_id); + return false; +#endif + } + else + { + report_invalid_record(record, "could not restore image at %X/%X compressed with unknown method, block %d", + LSN_FORMAT_ARGS(record->ReadRecPtr), + block_id); + return false; + } + + if (!decomp_success) + { + report_invalid_record(record, "could not decompress image at %X/%X, block %d", + LSN_FORMAT_ARGS(record->ReadRecPtr), + block_id); + 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; +} + +#ifndef FRONTEND + +/* + * Extract the FullTransactionId from a WAL record. + */ +FullTransactionId +XLogRecGetFullXid(XLogReaderState *record) +{ + TransactionId xid, + next_xid; + uint32 epoch; + + /* + * This function is only safe during replay, because it depends on the + * replay state. See AdvanceNextFullTransactionIdPastXid() for more. + */ + Assert(AmStartupProcess() || !IsUnderPostmaster); + + xid = XLogRecGetXid(record); + next_xid = XidFromFullTransactionId(ShmemVariableCache->nextXid); + epoch = EpochFromFullTransactionId(ShmemVariableCache->nextXid); + + /* + * If xid is numerically greater than next_xid, it has to be from the last + * epoch. + */ + if (unlikely(xid > next_xid)) + --epoch; + + return FullTransactionIdFromEpochAndXid(epoch, xid); +} + +#endif |