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79fed072ba
Getting from get_raw_page() an all-zero page is considered as a valid case by the buffer manager and it can happen for example when finding a corrupted page with zero_damaged_pages enabled (using zero_damaged_pages to look at corrupted pages happens), or after a crash when a relation file is extended before any WAL for its new data is generated (before a vacuum or autovacuum job comes in to do some cleanup). However, all the functions of pageinspect, as of the index AMs (except hash that has its own idea of new pages), heap, the FSM or the page header have never worked with all-zero pages, causing various crashes when going through the page internals. This commit changes all the pageinspect functions to be compliant with all-zero pages, where the choice is made to return NULL or no rows for SRFs when finding a new page. get_raw_page() still works the same way, returning a batch of zeros in the bytea of the page retrieved. A hard error could be used but NULL, while more invasive, is useful when scanning relation files in full to get a batch of results for a single relation in one query. Tests are added for all the code paths impacted. Reported-by: Daria Lepikhova Author: Michael Paquier Discussion: https://postgr.es/m/561e187b-3549-c8d5-03f5-525c14e65bd0@postgrespro.ru Backpatch-through: 10
67 lines
1.6 KiB
C
67 lines
1.6 KiB
C
/*-------------------------------------------------------------------------
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*
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* fsmfuncs.c
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* Functions to investigate FSM pages
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*
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* These functions are restricted to superusers for the fear of introducing
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* security holes if the input checking isn't as water-tight as it should.
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* You'd need to be superuser to obtain a raw page image anyway, so
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* there's hardly any use case for using these without superuser-rights
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* anyway.
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*
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* Copyright (c) 2007-2018, PostgreSQL Global Development Group
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*
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* IDENTIFICATION
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* contrib/pageinspect/fsmfuncs.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 "pageinspect.h"
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#include "funcapi.h"
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#include "lib/stringinfo.h"
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#include "miscadmin.h"
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#include "storage/fsm_internals.h"
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#include "utils/builtins.h"
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/*
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* Dumps the contents of a FSM page.
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*/
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PG_FUNCTION_INFO_V1(fsm_page_contents);
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Datum
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fsm_page_contents(PG_FUNCTION_ARGS)
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{
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bytea *raw_page = PG_GETARG_BYTEA_P(0);
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StringInfoData sinfo;
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Page page;
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FSMPage fsmpage;
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int i;
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if (!superuser())
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ereport(ERROR,
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(errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
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(errmsg("must be superuser to use raw page functions"))));
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page = get_page_from_raw(raw_page);
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if (PageIsNew(page))
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PG_RETURN_NULL();
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fsmpage = (FSMPage) PageGetContents(page);
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initStringInfo(&sinfo);
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for (i = 0; i < NodesPerPage; i++)
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{
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if (fsmpage->fp_nodes[i] != 0)
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appendStringInfo(&sinfo, "%d: %d\n", i, fsmpage->fp_nodes[i]);
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}
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appendStringInfo(&sinfo, "fp_next_slot: %d\n", fsmpage->fp_next_slot);
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PG_RETURN_TEXT_P(cstring_to_text_with_len(sinfo.data, sinfo.len));
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}
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