131 lines
3.2 KiB
C
131 lines
3.2 KiB
C
/*-------------------------------------------------------------------------
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*
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* bufmask.c
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* Routines for buffer masking. Used to mask certain bits
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* in a page which can be different when the WAL is generated
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* and when the WAL is applied.
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*
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* Portions Copyright (c) 2016-2020, PostgreSQL Global Development Group
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*
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* Contains common routines required for masking a page.
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*
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* IDENTIFICATION
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* src/backend/access/common/bufmask.c
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*
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*-------------------------------------------------------------------------
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*/
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#include "postgres.h"
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#include "access/bufmask.h"
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/*
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* mask_page_lsn_and_checksum
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*
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* In consistency checks, the LSN of the two pages compared will likely be
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* different because of concurrent operations when the WAL is generated and
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* the state of the page when WAL is applied. Also, mask out checksum as
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* masking anything else on page means checksum is not going to match as well.
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*/
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void
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mask_page_lsn_and_checksum(Page page)
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{
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PageHeader phdr = (PageHeader) page;
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PageXLogRecPtrSet(phdr->pd_lsn, (uint64) MASK_MARKER);
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phdr->pd_checksum = MASK_MARKER;
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}
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/*
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* mask_page_hint_bits
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*
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* Mask hint bits in PageHeader. We want to ignore differences in hint bits,
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* since they can be set without emitting any WAL.
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*/
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void
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mask_page_hint_bits(Page page)
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{
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PageHeader phdr = (PageHeader) page;
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/* Ignore prune_xid (it's like a hint-bit) */
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phdr->pd_prune_xid = MASK_MARKER;
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/* Ignore PD_PAGE_FULL and PD_HAS_FREE_LINES flags, they are just hints. */
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PageClearFull(page);
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PageClearHasFreeLinePointers(page);
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/*
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* During replay, if the page LSN has advanced past our XLOG record's LSN,
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* we don't mark the page all-visible. See heap_xlog_visible() for
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* details.
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*/
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PageClearAllVisible(page);
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}
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/*
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* mask_unused_space
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*
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* Mask the unused space of a page between pd_lower and pd_upper.
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*/
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void
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mask_unused_space(Page page)
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{
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int pd_lower = ((PageHeader) page)->pd_lower;
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int pd_upper = ((PageHeader) page)->pd_upper;
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int pd_special = ((PageHeader) page)->pd_special;
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/* Sanity check */
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if (pd_lower > pd_upper || pd_special < pd_upper ||
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pd_lower < SizeOfPageHeaderData || pd_special > BLCKSZ)
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{
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elog(ERROR, "invalid page pd_lower %u pd_upper %u pd_special %u\n",
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pd_lower, pd_upper, pd_special);
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}
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memset(page + pd_lower, MASK_MARKER, pd_upper - pd_lower);
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}
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/*
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* mask_lp_flags
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*
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* In some index AMs, line pointer flags can be modified in master without
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* emitting any WAL record.
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*/
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void
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mask_lp_flags(Page page)
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{
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OffsetNumber offnum,
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maxoff;
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maxoff = PageGetMaxOffsetNumber(page);
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for (offnum = FirstOffsetNumber;
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offnum <= maxoff;
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offnum = OffsetNumberNext(offnum))
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{
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ItemId itemId = PageGetItemId(page, offnum);
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if (ItemIdIsUsed(itemId))
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itemId->lp_flags = LP_UNUSED;
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}
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}
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/*
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* mask_page_content
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*
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* In some index AMs, the contents of deleted pages need to be almost
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* completely ignored.
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*/
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void
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mask_page_content(Page page)
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{
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/* Mask Page Content */
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memset(page + SizeOfPageHeaderData, MASK_MARKER,
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BLCKSZ - SizeOfPageHeaderData);
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/* Mask pd_lower and pd_upper */
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memset(&((PageHeader) page)->pd_lower, MASK_MARKER,
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sizeof(uint16));
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memset(&((PageHeader) page)->pd_upper, MASK_MARKER,
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sizeof(uint16));
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}
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