Age         Owner                  TLA  Line data    Source code

                                  1                 : /*-------------------------------------------------------------------------
                                  2                 :  *
                                  3                 :  * bufmask.c
                                  4                 :  *    Routines for buffer masking. Used to mask certain bits
                                  5                 :  *    in a page which can be different when the WAL is generated
                                  6                 :  *    and when the WAL is applied.
                                  7                 :  *
                                  8                 :  * Portions Copyright (c) 2016-2023, PostgreSQL Global Development Group
                                  9                 :  *
                                 10                 :  * Contains common routines required for masking a page.
                                 11                 :  *
                                 12                 :  * IDENTIFICATION
                                 13                 :  *    src/backend/access/common/bufmask.c
                                 14                 :  *
                                 15                 :  *-------------------------------------------------------------------------
                                 16                 :  */
                                 17                 : 
                                 18                 : #include "postgres.h"
                                 19                 : 
                                 20                 : #include "access/bufmask.h"
                                 21                 : 
                                 22                 : /*
                                 23                 :  * mask_page_lsn_and_checksum
                                 24                 :  *
                                 25                 :  * In consistency checks, the LSN of the two pages compared will likely be
                                 26                 :  * different because of concurrent operations when the WAL is generated and
                                 27                 :  * the state of the page when WAL is applied. Also, mask out checksum as
                                 28                 :  * masking anything else on page means checksum is not going to match as well.
                                 29                 :  */
                                 30                 : void
 2025 rhaas                      31 UBC           0 : mask_page_lsn_and_checksum(Page page)
                                 32                 : {
 2251                            33               0 :     PageHeader  phdr = (PageHeader) page;
                                 34                 : 
                                 35               0 :     PageXLogRecPtrSet(phdr->pd_lsn, (uint64) MASK_MARKER);
 2025                            36               0 :     phdr->pd_checksum = MASK_MARKER;
 2251                            37               0 : }
                                 38                 : 
                                 39                 : /*
                                 40                 :  * mask_page_hint_bits
                                 41                 :  *
                                 42                 :  * Mask hint bits in PageHeader. We want to ignore differences in hint bits,
                                 43                 :  * since they can be set without emitting any WAL.
                                 44                 :  */
                                 45                 : void
                                 46               0 : mask_page_hint_bits(Page page)
                                 47                 : {
                                 48               0 :     PageHeader  phdr = (PageHeader) page;
                                 49                 : 
                                 50                 :     /* Ignore prune_xid (it's like a hint-bit) */
                                 51               0 :     phdr->pd_prune_xid = MASK_MARKER;
                                 52                 : 
                                 53                 :     /* Ignore PD_PAGE_FULL and PD_HAS_FREE_LINES flags, they are just hints. */
                                 54               0 :     PageClearFull(page);
                                 55               0 :     PageClearHasFreeLinePointers(page);
                                 56                 : 
                                 57                 :     /*
                                 58                 :      * During replay, if the page LSN has advanced past our XLOG record's LSN,
                                 59                 :      * we don't mark the page all-visible. See heap_xlog_visible() for
                                 60                 :      * details.
                                 61                 :      */
                                 62               0 :     PageClearAllVisible(page);
                                 63               0 : }
                                 64                 : 
                                 65                 : /*
                                 66                 :  * mask_unused_space
                                 67                 :  *
                                 68                 :  * Mask the unused space of a page between pd_lower and pd_upper.
                                 69                 :  */
                                 70                 : void
                                 71               0 : mask_unused_space(Page page)
                                 72                 : {
                                 73               0 :     int         pd_lower = ((PageHeader) page)->pd_lower;
                                 74               0 :     int         pd_upper = ((PageHeader) page)->pd_upper;
                                 75               0 :     int         pd_special = ((PageHeader) page)->pd_special;
                                 76                 : 
                                 77                 :     /* Sanity check */
                                 78               0 :     if (pd_lower > pd_upper || pd_special < pd_upper ||
                                 79               0 :         pd_lower < SizeOfPageHeaderData || pd_special > BLCKSZ)
                                 80                 :     {
   96 michael                    81               0 :         elog(ERROR, "invalid page pd_lower %u pd_upper %u pd_special %u",
                                 82                 :              pd_lower, pd_upper, pd_special);
                                 83                 :     }
                                 84                 : 
 2251 rhaas                      85               0 :     memset(page + pd_lower, MASK_MARKER, pd_upper - pd_lower);
                                 86               0 : }
                                 87                 : 
                                 88                 : /*
                                 89                 :  * mask_lp_flags
                                 90                 :  *
                                 91                 :  * In some index AMs, line pointer flags can be modified on the primary
                                 92                 :  * without emitting any WAL record.
                                 93                 :  */
                                 94                 : void
                                 95               0 : mask_lp_flags(Page page)
                                 96                 : {
                                 97                 :     OffsetNumber offnum,
                                 98                 :                 maxoff;
                                 99                 : 
                                100               0 :     maxoff = PageGetMaxOffsetNumber(page);
                                101               0 :     for (offnum = FirstOffsetNumber;
                                102               0 :          offnum <= maxoff;
                                103               0 :          offnum = OffsetNumberNext(offnum))
                                104                 :     {
                                105               0 :         ItemId      itemId = PageGetItemId(page, offnum);
                                106                 : 
                                107               0 :         if (ItemIdIsUsed(itemId))
                                108               0 :             itemId->lp_flags = LP_UNUSED;
                                109                 :     }
                                110               0 : }
                                111                 : 
                                112                 : /*
                                113                 :  * mask_page_content
                                114                 :  *
                                115                 :  * In some index AMs, the contents of deleted pages need to be almost
                                116                 :  * completely ignored.
                                117                 :  */
                                118                 : void
                                119               0 : mask_page_content(Page page)
                                120                 : {
                                121                 :     /* Mask Page Content */
                                122               0 :     memset(page + SizeOfPageHeaderData, MASK_MARKER,
                                123                 :            BLCKSZ - SizeOfPageHeaderData);
                                124                 : 
                                125                 :     /* Mask pd_lower and pd_upper */
                                126               0 :     memset(&((PageHeader) page)->pd_lower, MASK_MARKER,
                                127                 :            sizeof(uint16));
                                128               0 :     memset(&((PageHeader) page)->pd_upper, MASK_MARKER,
                                129                 :            sizeof(uint16));
                                130               0 : }