fsmfuncs.c

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/*-------------------------------------------------------------------------
 *
 * fsmfuncs.c
 *    Functions to investigate FSM pages
 *
 * These functions are restricted to superusers for the fear of introducing
 * security holes if the input checking isn't as water-tight as it should.
 * You'd need to be superuser to obtain a raw page image anyway, so
 * there's hardly any use case for using these without superuser-rights
 * anyway.
 *
 * Copyright (c) 2007-2025, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *    contrib/pageinspect/fsmfuncs.c
 *
 *-------------------------------------------------------------------------
 */
 
#include "postgres.h"
 
#include "fmgr.h"
#include "lib/stringinfo.h"
#include "miscadmin.h"
#include "pageinspect.h"
#include "storage/fsm_internals.h"
#include "utils/builtins.h"
 
/*
 * Dumps the contents of a FSM page.
 */
PG_FUNCTION_INFO_V1(fsm_page_contents);
 
Datum
fsm_page_contents(PG_FUNCTION_ARGS)
{
    bytea      *raw_page = PG_GETARG_BYTEA_P(0);
    StringInfoData sinfo;
    Page        page;
    FSMPage     fsmpage;
    int         i;
 
    if (!superuser())
        ereport(ERROR,
                (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
                 errmsg("must be superuser to use raw page functions")));
 
    page = get_page_from_raw(raw_page);
 
    if (PageIsNew(page))
        PG_RETURN_NULL();
 
    fsmpage = (FSMPage) PageGetContents(page);
 
    initStringInfo(&sinfo);
 
    for (i = 0; i < NodesPerPage; i++)
    {
        if (fsmpage->fp_nodes[i] != 0)
            appendStringInfo(&sinfo, "%d: %d\n", i, fsmpage->fp_nodes[i]);
    }
    appendStringInfo(&sinfo, "fp_next_slot: %d\n", fsmpage->fp_next_slot);
 
    PG_RETURN_TEXT_P(cstring_to_text_with_len(sinfo.data, sinfo.len));
}