controldata.c

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/*
 *  controldata.c
 *
 *  controldata functions
 *
 *  Copyright (c) 2010-2026, PostgreSQL Global Development Group
 *  src/bin/pg_upgrade/controldata.c
 */
 
#include "postgres_fe.h"
 
#include <ctype.h>
#include <limits.h>             /* for CHAR_MIN */
 
#include "access/xlog_internal.h"
#include "common/string.h"
#include "pg_upgrade.h"
#include "storage/checksum.h"
 
 
/*
 * get_control_data()
 *
 * gets pg_control information in "ctrl". Assumes that bindir and
 * datadir are valid absolute paths to postgresql bin and pgdata
 * directories respectively *and* pg_resetwal is version compatible
 * with datadir. The main purpose of this function is to get pg_control
 * data in a version independent manner.
 *
 * The approach taken here is to invoke pg_resetwal with -n option
 * and then pipe its output. With little string parsing we get the
 * pg_control data.  pg_resetwal cannot be run while the server is running
 * so we use pg_controldata;  pg_controldata doesn't provide all the fields
 * we need to actually perform the upgrade, but it provides enough for
 * check mode.  We do not implement pg_resetwal -n because it is hard to
 * return valid xid data for a running server.
 */
void
get_control_data(ClusterInfo *cluster)
{
    char        cmd[MAXPGPATH];
    char        bufin[MAX_STRING];
    FILE       *output;
    char       *p;
    bool        got_xid = false;
    bool        got_oid = false;
    bool        got_multi = false;
    bool        got_oldestmulti = false;
    bool        got_oldestxid = false;
    bool        got_mxoff = false;
    bool        got_nextxlogfile = false;
    bool        got_float8_pass_by_value = false;
    bool        got_align = false;
    bool        got_blocksz = false;
    bool        got_largesz = false;
    bool        got_walsz = false;
    bool        got_walseg = false;
    bool        got_ident = false;
    bool        got_index = false;
    bool        got_toast = false;
    bool        got_large_object = false;
    bool        got_date_is_int = false;
    bool        got_data_checksum_version = false;
    bool        got_cluster_state = false;
    bool        got_default_char_signedness = false;
    char       *lc_collate = NULL;
    char       *lc_ctype = NULL;
    char       *lc_monetary = NULL;
    char       *lc_numeric = NULL;
    char       *lc_time = NULL;
    char       *lang = NULL;
    char       *language = NULL;
    char       *lc_all = NULL;
    char       *lc_messages = NULL;
    int         rc;
    bool        live_check = (cluster == &old_cluster && user_opts.live_check);
 
    /*
     * Because we test the pg_resetwal output as strings, it has to be in
     * English.  Copied from pg_regress.c.
     */
    if (getenv("LC_COLLATE"))
        lc_collate = pg_strdup(getenv("LC_COLLATE"));
    if (getenv("LC_CTYPE"))
        lc_ctype = pg_strdup(getenv("LC_CTYPE"));
    if (getenv("LC_MONETARY"))
        lc_monetary = pg_strdup(getenv("LC_MONETARY"));
    if (getenv("LC_NUMERIC"))
        lc_numeric = pg_strdup(getenv("LC_NUMERIC"));
    if (getenv("LC_TIME"))
        lc_time = pg_strdup(getenv("LC_TIME"));
    if (getenv("LANG"))
        lang = pg_strdup(getenv("LANG"));
    if (getenv("LANGUAGE"))
        language = pg_strdup(getenv("LANGUAGE"));
    if (getenv("LC_ALL"))
        lc_all = pg_strdup(getenv("LC_ALL"));
    if (getenv("LC_MESSAGES"))
        lc_messages = pg_strdup(getenv("LC_MESSAGES"));
 
    unsetenv("LC_COLLATE");
    unsetenv("LC_CTYPE");
    unsetenv("LC_MONETARY");
    unsetenv("LC_NUMERIC");
    unsetenv("LC_TIME");
#ifndef WIN32
    unsetenv("LANG");
#else
    /* On Windows the default locale may not be English, so force it */
    setenv("LANG", "en", 1);
#endif
    unsetenv("LANGUAGE");
    unsetenv("LC_ALL");
    setenv("LC_MESSAGES", "C", 1);
 
    /*
     * Check for clean shutdown
     */
    if (!live_check || cluster == &new_cluster)
    {
        /* only pg_controldata outputs the cluster state */
        snprintf(cmd, sizeof(cmd), "\"%s/pg_controldata\" \"%s\"",
                 cluster->bindir, cluster->pgdata);
        fflush(NULL);
 
        if ((output = popen(cmd, "r")) == NULL)
            pg_fatal("could not get control data using %s: %m", cmd);
 
        /* we have the result of cmd in "output". so parse it line by line now */
        while (fgets(bufin, sizeof(bufin), output))
        {
            if ((p = strstr(bufin, "Database cluster state:")) != NULL)
            {
                p = strchr(p, ':');
 
                if (p == NULL || strlen(p) <= 1)
                    pg_fatal("%d: database cluster state problem", __LINE__);
 
                p++;            /* remove ':' char */
 
                /*
                 * We checked earlier for a postmaster lock file, and if we
                 * found one, we tried to start/stop the server to replay the
                 * WAL.  However, pg_ctl -m immediate doesn't leave a lock
                 * file, but does require WAL replay, so we check here that
                 * the server was shut down cleanly, from the controldata
                 * perspective.
                 */
                /* Remove trailing newline and leading spaces */
                (void) pg_strip_crlf(p);
                while (*p == ' ')
                    p++;
                if (strcmp(p, "shut down in recovery") == 0)
                {
                    if (cluster == &old_cluster)
                        pg_fatal("The source cluster was shut down while in recovery mode.  To upgrade, use \"rsync\" as documented or shut it down as a primary.");
                    else
                        pg_fatal("The target cluster was shut down while in recovery mode.  To upgrade, use \"rsync\" as documented or shut it down as a primary.");
                }
                else if (strcmp(p, "shut down") != 0)
                {
                    if (cluster == &old_cluster)
                        pg_fatal("The source cluster was not shut down cleanly, state reported as: \"%s\"", p);
                    else
                        pg_fatal("The target cluster was not shut down cleanly, state reported as: \"%s\"", p);
                }
                got_cluster_state = true;
            }
        }
 
        rc = pclose(output);
        if (rc != 0)
            pg_fatal("could not get control data using %s: %s",
                     cmd, wait_result_to_str(rc));
 
        if (!got_cluster_state)
        {
            if (cluster == &old_cluster)
                pg_fatal("The source cluster lacks cluster state information:");
            else
                pg_fatal("The target cluster lacks cluster state information:");
        }
    }
 
    snprintf(cmd, sizeof(cmd), "\"%s/%s \"%s\"",
             cluster->bindir,
             live_check ? "pg_controldata\"" : "pg_resetwal\" -n",
             cluster->pgdata);
    fflush(NULL);
 
    if ((output = popen(cmd, "r")) == NULL)
        pg_fatal("could not get control data using %s: %m", cmd);
 
    /* we have the result of cmd in "output". so parse it line by line now */
    while (fgets(bufin, sizeof(bufin), output))
    {
        /* In verbose mode, log each line */
        pg_strip_crlf(bufin);
        pg_log(PG_VERBOSE, "%s", bufin);
 
        if ((p = strstr(bufin, "pg_control version number:")) != NULL)
        {
            p = strchr(p, ':');
 
            if (p == NULL || strlen(p) <= 1)
                pg_fatal("%d: pg_resetwal problem", __LINE__);
 
            p++;                /* remove ':' char */
            cluster->controldata.ctrl_ver = str2uint(p);
        }
        else if ((p = strstr(bufin, "Catalog version number:")) != NULL)
        {
            p = strchr(p, ':');
 
            if (p == NULL || strlen(p) <= 1)
                pg_fatal("%d: controldata retrieval problem", __LINE__);
 
            p++;                /* remove ':' char */
            cluster->controldata.cat_ver = str2uint(p);
        }
        else if ((p = strstr(bufin, "Latest checkpoint's NextXID:")) != NULL)
        {
            p = strchr(p, ':');
 
            if (p == NULL || strlen(p) <= 1)
                pg_fatal("%d: controldata retrieval problem", __LINE__);
 
            p++;                /* remove ':' char */
            cluster->controldata.chkpnt_nxtepoch = str2uint(p);
 
            p = strchr(p, ':');
 
            if (p == NULL || strlen(p) <= 1)
                pg_fatal("%d: controldata retrieval problem", __LINE__);
 
            p++;                /* remove ':' char */
            cluster->controldata.chkpnt_nxtxid = str2uint(p);
            got_xid = true;
        }
        else if ((p = strstr(bufin, "Latest checkpoint's NextOID:")) != NULL)
        {
            p = strchr(p, ':');
 
            if (p == NULL || strlen(p) <= 1)
                pg_fatal("%d: controldata retrieval problem", __LINE__);
 
            p++;                /* remove ':' char */
            cluster->controldata.chkpnt_nxtoid = str2uint(p);
            got_oid = true;
        }
        else if ((p = strstr(bufin, "Latest checkpoint's NextMultiXactId:")) != NULL)
        {
            p = strchr(p, ':');
 
            if (p == NULL || strlen(p) <= 1)
                pg_fatal("%d: controldata retrieval problem", __LINE__);
 
            p++;                /* remove ':' char */
            cluster->controldata.chkpnt_nxtmulti = str2uint(p);
            got_multi = true;
        }
        else if ((p = strstr(bufin, "Latest checkpoint's oldestXID:")) != NULL)
        {
            p = strchr(p, ':');
 
            if (p == NULL || strlen(p) <= 1)
                pg_fatal("%d: controldata retrieval problem", __LINE__);
 
            p++;                /* remove ':' char */
            cluster->controldata.chkpnt_oldstxid = str2uint(p);
            got_oldestxid = true;
        }
        else if ((p = strstr(bufin, "Latest checkpoint's oldestMultiXid:")) != NULL)
        {
            p = strchr(p, ':');
 
            if (p == NULL || strlen(p) <= 1)
                pg_fatal("%d: controldata retrieval problem", __LINE__);
 
            p++;                /* remove ':' char */
            cluster->controldata.chkpnt_oldstMulti = str2uint(p);
            got_oldestmulti = true;
        }
        else if ((p = strstr(bufin, "Latest checkpoint's NextMultiOffset:")) != NULL)
        {
            p = strchr(p, ':');
 
            if (p == NULL || strlen(p) <= 1)
                pg_fatal("%d: controldata retrieval problem", __LINE__);
 
            p++;                /* remove ':' char */
            cluster->controldata.chkpnt_nxtmxoff = str2uint(p);
            got_mxoff = true;
        }
        else if ((p = strstr(bufin, "First log segment after reset:")) != NULL)
        {
            /* Skip the colon and any whitespace after it */
            p = strchr(p, ':');
            if (p == NULL || strlen(p) <= 1)
                pg_fatal("%d: controldata retrieval problem", __LINE__);
            p = strpbrk(p, "0123456789ABCDEF");
            if (p == NULL || strlen(p) <= 1)
                pg_fatal("%d: controldata retrieval problem", __LINE__);
 
            /* Make sure it looks like a valid WAL file name */
            if (strspn(p, "0123456789ABCDEF") != 24)
                pg_fatal("%d: controldata retrieval problem", __LINE__);
 
            strlcpy(cluster->controldata.nextxlogfile, p, 25);
            got_nextxlogfile = true;
        }
        else if ((p = strstr(bufin, "Float8 argument passing:")) != NULL)
        {
            p = strchr(p, ':');
 
            if (p == NULL || strlen(p) <= 1)
                pg_fatal("%d: controldata retrieval problem", __LINE__);
 
            p++;                /* remove ':' char */
            /* used later for contrib check */
            cluster->controldata.float8_pass_by_value = strstr(p, "by value") != NULL;
            got_float8_pass_by_value = true;
        }
        else if ((p = strstr(bufin, "Maximum data alignment:")) != NULL)
        {
            p = strchr(p, ':');
 
            if (p == NULL || strlen(p) <= 1)
                pg_fatal("%d: controldata retrieval problem", __LINE__);
 
            p++;                /* remove ':' char */
            cluster->controldata.align = str2uint(p);
            got_align = true;
        }
        else if ((p = strstr(bufin, "Database block size:")) != NULL)
        {
            p = strchr(p, ':');
 
            if (p == NULL || strlen(p) <= 1)
                pg_fatal("%d: controldata retrieval problem", __LINE__);
 
            p++;                /* remove ':' char */
            cluster->controldata.blocksz = str2uint(p);
            got_blocksz = true;
        }
        else if ((p = strstr(bufin, "Blocks per segment of large relation:")) != NULL)
        {
            p = strchr(p, ':');
 
            if (p == NULL || strlen(p) <= 1)
                pg_fatal("%d: controldata retrieval problem", __LINE__);
 
            p++;                /* remove ':' char */
            cluster->controldata.largesz = str2uint(p);
            got_largesz = true;
        }
        else if ((p = strstr(bufin, "WAL block size:")) != NULL)
        {
            p = strchr(p, ':');
 
            if (p == NULL || strlen(p) <= 1)
                pg_fatal("%d: controldata retrieval problem", __LINE__);
 
            p++;                /* remove ':' char */
            cluster->controldata.walsz = str2uint(p);
            got_walsz = true;
        }
        else if ((p = strstr(bufin, "Bytes per WAL segment:")) != NULL)
        {
            p = strchr(p, ':');
 
            if (p == NULL || strlen(p) <= 1)
                pg_fatal("%d: controldata retrieval problem", __LINE__);
 
            p++;                /* remove ':' char */
            cluster->controldata.walseg = str2uint(p);
            got_walseg = true;
        }
        else if ((p = strstr(bufin, "Maximum length of identifiers:")) != NULL)
        {
            p = strchr(p, ':');
 
            if (p == NULL || strlen(p) <= 1)
                pg_fatal("%d: controldata retrieval problem", __LINE__);
 
            p++;                /* remove ':' char */
            cluster->controldata.ident = str2uint(p);
            got_ident = true;
        }
        else if ((p = strstr(bufin, "Maximum columns in an index:")) != NULL)
        {
            p = strchr(p, ':');
 
            if (p == NULL || strlen(p) <= 1)
                pg_fatal("%d: controldata retrieval problem", __LINE__);
 
            p++;                /* remove ':' char */
            cluster->controldata.index = str2uint(p);
            got_index = true;
        }
        else if ((p = strstr(bufin, "Maximum size of a TOAST chunk:")) != NULL)
        {
            p = strchr(p, ':');
 
            if (p == NULL || strlen(p) <= 1)
                pg_fatal("%d: controldata retrieval problem", __LINE__);
 
            p++;                /* remove ':' char */
            cluster->controldata.toast = str2uint(p);
            got_toast = true;
        }
        else if ((p = strstr(bufin, "Size of a large-object chunk:")) != NULL)
        {
            p = strchr(p, ':');
 
            if (p == NULL || strlen(p) <= 1)
                pg_fatal("%d: controldata retrieval problem", __LINE__);
 
            p++;                /* remove ':' char */
            cluster->controldata.large_object = str2uint(p);
            got_large_object = true;
        }
        else if ((p = strstr(bufin, "Date/time type storage:")) != NULL)
        {
            p = strchr(p, ':');
 
            if (p == NULL || strlen(p) <= 1)
                pg_fatal("%d: controldata retrieval problem", __LINE__);
 
            p++;                /* remove ':' char */
            cluster->controldata.date_is_int = strstr(p, "64-bit integers") != NULL;
            got_date_is_int = true;
        }
        else if ((p = strstr(bufin, "checksum")) != NULL)
        {
            p = strchr(p, ':');
 
            if (p == NULL || strlen(p) <= 1)
                pg_fatal("%d: controldata retrieval problem", __LINE__);
 
            p++;                /* remove ':' char */
            cluster->controldata.data_checksum_version = str2uint(p);
            got_data_checksum_version = true;
        }
        else if ((p = strstr(bufin, "Default char data signedness:")) != NULL)
        {
            p = strchr(p, ':');
 
            if (p == NULL || strlen(p) <= 1)
                pg_fatal("%d: controldata retrieval problem", __LINE__);
 
            /* Skip the colon and any whitespace after it */
            p++;
            while (isspace((unsigned char) *p))
                p++;
 
            /* The value should be either 'signed' or 'unsigned' */
            if (strcmp(p, "signed") != 0 && strcmp(p, "unsigned") != 0)
                pg_fatal("%d: controldata retrieval problem", __LINE__);
 
            cluster->controldata.default_char_signedness = strcmp(p, "signed") == 0;
            got_default_char_signedness = true;
        }
    }
 
    rc = pclose(output);
    if (rc != 0)
        pg_fatal("could not get control data using %s: %s",
                 cmd, wait_result_to_str(rc));
 
    /*
     * Restore environment variables.  Note all but LANG and LC_MESSAGES were
     * unset above.
     */
    if (lc_collate)
        setenv("LC_COLLATE", lc_collate, 1);
    if (lc_ctype)
        setenv("LC_CTYPE", lc_ctype, 1);
    if (lc_monetary)
        setenv("LC_MONETARY", lc_monetary, 1);
    if (lc_numeric)
        setenv("LC_NUMERIC", lc_numeric, 1);
    if (lc_time)
        setenv("LC_TIME", lc_time, 1);
    if (lang)
        setenv("LANG", lang, 1);
    else
        unsetenv("LANG");
    if (language)
        setenv("LANGUAGE", language, 1);
    if (lc_all)
        setenv("LC_ALL", lc_all, 1);
    if (lc_messages)
        setenv("LC_MESSAGES", lc_messages, 1);
    else
        unsetenv("LC_MESSAGES");
 
    pg_free(lc_collate);
    pg_free(lc_ctype);
    pg_free(lc_monetary);
    pg_free(lc_numeric);
    pg_free(lc_time);
    pg_free(lang);
    pg_free(language);
    pg_free(lc_all);
    pg_free(lc_messages);
 
    /*
     * Pre-v18 database clusters don't have the default char signedness
     * information. We use the char signedness of the platform where
     * pg_upgrade was built.
     */
    if (cluster->controldata.cat_ver < DEFAULT_CHAR_SIGNEDNESS_CAT_VER)
    {
        Assert(!got_default_char_signedness);
#if CHAR_MIN != 0
        cluster->controldata.default_char_signedness = true;
#else
        cluster->controldata.default_char_signedness = false;
#endif
    }
 
    /* verify that we got all the mandatory pg_control data */
    if (!got_xid || !got_oid ||
        !got_multi || !got_oldestxid ||
        !got_oldestmulti ||
        !got_mxoff || (!live_check && !got_nextxlogfile) ||
        !got_float8_pass_by_value || !got_align || !got_blocksz ||
        !got_largesz || !got_walsz || !got_walseg || !got_ident ||
        !got_index || !got_toast ||
        !got_large_object ||
        !got_date_is_int || !got_data_checksum_version ||
        (!got_default_char_signedness &&
         cluster->controldata.cat_ver >= DEFAULT_CHAR_SIGNEDNESS_CAT_VER))
    {
        if (cluster == &old_cluster)
            pg_log(PG_REPORT,
                   "The source cluster lacks some required control information:");
        else
            pg_log(PG_REPORT,
                   "The target cluster lacks some required control information:");
 
        if (!got_xid)
            pg_log(PG_REPORT, "  checkpoint next XID");
 
        if (!got_oid)
            pg_log(PG_REPORT, "  latest checkpoint next OID");
 
        if (!got_multi)
            pg_log(PG_REPORT, "  latest checkpoint next MultiXactId");
 
        if (!got_oldestmulti)
            pg_log(PG_REPORT, "  latest checkpoint oldest MultiXactId");
 
        if (!got_oldestxid)
            pg_log(PG_REPORT, "  latest checkpoint oldestXID");
 
        if (!got_mxoff)
            pg_log(PG_REPORT, "  latest checkpoint next MultiXactOffset");
 
        if (!live_check && !got_nextxlogfile)
            pg_log(PG_REPORT, "  first WAL segment after reset");
 
        if (!got_float8_pass_by_value)
            pg_log(PG_REPORT, "  float8 argument passing method");
 
        if (!got_align)
            pg_log(PG_REPORT, "  maximum alignment");
 
        if (!got_blocksz)
            pg_log(PG_REPORT, "  block size");
 
        if (!got_largesz)
            pg_log(PG_REPORT, "  large relation segment size");
 
        if (!got_walsz)
            pg_log(PG_REPORT, "  WAL block size");
 
        if (!got_walseg)
            pg_log(PG_REPORT, "  WAL segment size");
 
        if (!got_ident)
            pg_log(PG_REPORT, "  maximum identifier length");
 
        if (!got_index)
            pg_log(PG_REPORT, "  maximum number of indexed columns");
 
        if (!got_toast)
            pg_log(PG_REPORT, "  maximum TOAST chunk size");
 
        if (!got_large_object)
            pg_log(PG_REPORT, "  large-object chunk size");
 
        if (!got_date_is_int)
            pg_log(PG_REPORT, "  dates/times are integers?");
 
        /* value added in Postgres 9.3 */
        if (!got_data_checksum_version)
            pg_log(PG_REPORT, "  data checksum version");
 
        /* value added in Postgres 18 */
        if (!got_default_char_signedness)
            pg_log(PG_REPORT, "  default char signedness");
 
        pg_fatal("Cannot continue without required control information, terminating");
    }
}
 
 
/*
 * check_control_data()
 *
 * check to make sure the control data settings are compatible
 */
void
check_control_data(ControlData *oldctrl,
                   ControlData *newctrl)
{
    if (oldctrl->align == 0 || oldctrl->align != newctrl->align)
        pg_fatal("old and new pg_controldata alignments are invalid or do not match.\n"
                 "Likely one cluster is a 32-bit install, the other 64-bit");
 
    if (oldctrl->blocksz == 0 || oldctrl->blocksz != newctrl->blocksz)
        pg_fatal("old and new pg_controldata block sizes are invalid or do not match");
 
    if (oldctrl->largesz == 0 || oldctrl->largesz != newctrl->largesz)
        pg_fatal("old and new pg_controldata maximum relation segment sizes are invalid or do not match");
 
    if (oldctrl->walsz == 0 || oldctrl->walsz != newctrl->walsz)
        pg_fatal("old and new pg_controldata WAL block sizes are invalid or do not match");
 
    if (oldctrl->walseg == 0 || oldctrl->walseg != newctrl->walseg)
        pg_fatal("old and new pg_controldata WAL segment sizes are invalid or do not match");
 
    if (oldctrl->ident == 0 || oldctrl->ident != newctrl->ident)
        pg_fatal("old and new pg_controldata maximum identifier lengths are invalid or do not match");
 
    if (oldctrl->index == 0 || oldctrl->index != newctrl->index)
        pg_fatal("old and new pg_controldata maximum indexed columns are invalid or do not match");
 
    if (oldctrl->toast == 0 || oldctrl->toast != newctrl->toast)
        pg_fatal("old and new pg_controldata maximum TOAST chunk sizes are invalid or do not match");
 
    if (oldctrl->large_object == 0 ||
        oldctrl->large_object != newctrl->large_object)
        pg_fatal("old and new pg_controldata large-object chunk sizes are invalid or do not match");
 
    if (oldctrl->date_is_int != newctrl->date_is_int)
        pg_fatal("old and new pg_controldata date/time storage types do not match");
 
    /*
     * float8_pass_by_value does not need to match, but is used in
     * check_for_isn_and_int8_passing_mismatch().
     */
 
    /*
     * If data checksums are in any in-progress state then disallow the
     * upgrade. The user should either let the process finish, or turn off
     * data checksums, before retrying.
     */
    if (oldctrl->data_checksum_version > PG_DATA_CHECKSUM_VERSION)
        pg_fatal("checksums are being enabled in the old cluster");
 
    /*
     * We might eventually allow upgrades from checksum to no-checksum
     * clusters.
     */
    if (oldctrl->data_checksum_version == PG_DATA_CHECKSUM_OFF &&
        newctrl->data_checksum_version != PG_DATA_CHECKSUM_OFF)
        pg_fatal("old cluster does not use data checksums but the new one does");
    else if (oldctrl->data_checksum_version != PG_DATA_CHECKSUM_OFF &&
             newctrl->data_checksum_version == PG_DATA_CHECKSUM_OFF)
        pg_fatal("old cluster uses data checksums but the new one does not");
    else if (oldctrl->data_checksum_version != newctrl->data_checksum_version)
        pg_fatal("old and new cluster pg_controldata checksum versions do not match");
}
 
 
void
disable_old_cluster(transferMode transfer_mode)
{
    char        old_path[MAXPGPATH],
                new_path[MAXPGPATH];
 
    /* rename pg_control so old server cannot be accidentally started */
    /* translator: %s is the file path of the control file */
    prep_status("Adding \".old\" suffix to old \"%s\"", XLOG_CONTROL_FILE);
 
    snprintf(old_path, sizeof(old_path), "%s/%s", old_cluster.pgdata, XLOG_CONTROL_FILE);
    snprintf(new_path, sizeof(new_path), "%s/%s.old", old_cluster.pgdata, XLOG_CONTROL_FILE);
    if (pg_mv_file(old_path, new_path) != 0)
        pg_fatal("could not rename file \"%s\" to \"%s\": %m",
                 old_path, new_path);
    check_ok();
 
    if (transfer_mode == TRANSFER_MODE_LINK)
        /* translator: %s/%s is the file path of the control file */
        pg_log(PG_REPORT, "\n"
               "If you want to start the old cluster, you will need to remove\n"
               "the \".old\" suffix from \"%s/%s.old\".\n"
               "Because \"link\" mode was used, the old cluster cannot be safely\n"
               "started once the new cluster has been started.",
               old_cluster.pgdata, XLOG_CONTROL_FILE);
    else if (transfer_mode == TRANSFER_MODE_SWAP)
        pg_log(PG_REPORT, "\n"
               "Because \"swap\" mode was used, the old cluster can no longer be\n"
               "safely started.");
    else
        pg_fatal("unrecognized transfer mode");
}