PostgreSQL xlog格式之no backup full page

heap_insert        xl_heap_insert xlrec;        xl_heap_header xlhdr;        XLogRegisterData((char *) &xlrec, SizeOfHeapInsert);->//xl_heap_insert        |--     XLogRecData *rdata;        |       rdata->data = data;        |       rdata->len = len;        |       mainrdata_last->next = rdata;        |       mainrdata_last = rdata;        |--     mainrdata_len += len;        //xl_heap_header+heapup->t_data        XLogRegisterBufData(0, (char *) &xlhdr, SizeOfHeapHeader);->        |--     regbuf = ®istered_buffers[block_id];        |       rdata->data = data;        |       rdata->len = len;        |       regbuf->rdata_tail->next = rdata;        |       regbuf->rdata_tail = rdata;        |--     regbuf->rdata_len += len;        XLogRegisterBufData(0,(char *) heaptup->t_data + SizeofHeapTupleHeader,heaptup->t_len - SizeofHeapTupleHeader);        recptr = XLogInsert(RM_HEAP_ID, info);->        |--     rdt = XLogRecordAssemble(rmid, info, RedoRecPtr, doPageWrites,&fpw_lsn);        |--     EndPos = XLogInsertRecord(rdt, fpw_lsn, curinsert_flags);static XLogRecData hdr_rdt;XLogRecordAssemble:        char       *scratch = hdr_scratch;//hdr_scratch是一个xlog记录的开始位置        rechdr = (XLogRecord *) scratch;        scratch += SizeOfXLogRecord;        hdr_rdt.next = NULL;        rdt_datas_last = &hdr_rdt;//xlog记录链表头        hdr_rdt.data = hdr_scratch;        //hdr_rdt->next=xl_heap_header+heapup->t_data        registered_buffer *regbuf = ®istered_buffers[block_id];        rdt_datas_last->next = regbuf->rdata_head;        dt_datas_last = regbuf->rdata_tail;        //xl_heap_header+heapup->t_data后面紧跟着xl_heap_insert        rdt_datas_last->next = mainrdata_head;        rdt_datas_last = mainrdata_last;