streamutil.c

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/*-------------------------------------------------------------------------
 *
 * streamutil.c - utility functions for pg_basebackup, pg_receivewal and
 *                  pg_recvlogical
 *
 * Author: Magnus Hagander <magnus@hagander.net>
 *
 * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
 *
 * IDENTIFICATION
 *        src/bin/pg_basebackup/streamutil.c
 *-------------------------------------------------------------------------
 */
 
#include "postgres_fe.h"
 
#include <sys/time.h>
#include <unistd.h>
 
#include "access/xlog_internal.h"
#include "common/connect.h"
#include "common/file_perm.h"
#include "common/logging.h"
#include "common/string.h"
#include "datatype/timestamp.h"
#include "port/pg_bswap.h"
#include "pqexpbuffer.h"
#include "streamutil.h"
 
#define ERRCODE_DUPLICATE_OBJECT  "42710"
 
int         WalSegSz;
 
static bool RetrieveDataDirCreatePerm(PGconn *conn);
static char *FindDbnameInConnParams(PQconninfoOption *conn_opts);
 
/* SHOW command for replication connection was introduced in version 10 */
#define MINIMUM_VERSION_FOR_SHOW_CMD 100000
 
/*
 * Group access is supported from version 11.
 */
#define MINIMUM_VERSION_FOR_GROUP_ACCESS 110000
 
const char *progname;
char       *connection_string = NULL;
char       *dbhost = NULL;
char       *dbuser = NULL;
char       *dbport = NULL;
char       *dbname = NULL;
int         dbgetpassword = 0;  /* 0=auto, -1=never, 1=always */
static char *password = NULL;
PGconn     *conn = NULL;
 
/*
 * Connect to the server. Returns a valid PGconn pointer if connected,
 * or NULL on non-permanent error. On permanent error, the function will
 * call exit(1) directly.
 */
PGconn *
GetConnection(void)
{
    PGconn     *tmpconn;
    int         argcount = 7;   /* dbname, replication, fallback_app_name,
                                 * host, user, port, password */
    int         i;
    const char **keywords;
    const char **values;
    const char *tmpparam;
    bool        need_password;
    PQconninfoOption *conn_opts = NULL;
    PQconninfoOption *conn_opt;
    char       *err_msg = NULL;
 
    /*
     * pg_recvlogical uses dbname only; others use connection_string only.
     * (Note: both variables will be NULL if there's no command line options.)
     */
    Assert(dbname == NULL || connection_string == NULL);
 
    /*
     * Merge the connection info inputs given in form of connection string,
     * options and default values (dbname=replication, replication=true, etc.)
     */
    i = 0;
    if (connection_string)
    {
        conn_opts = PQconninfoParse(connection_string, &err_msg);
        if (conn_opts == NULL)
            pg_fatal("%s", err_msg);
 
        for (conn_opt = conn_opts; conn_opt->keyword != NULL; conn_opt++)
        {
            if (conn_opt->val != NULL && conn_opt->val[0] != '\0')
                argcount++;
        }
 
        keywords = pg_malloc0((argcount + 1) * sizeof(*keywords));
        values = pg_malloc0((argcount + 1) * sizeof(*values));
 
        /*
         * Set dbname here already, so it can be overridden by a dbname in the
         * connection string.
         */
        keywords[i] = "dbname";
        values[i] = "replication";
        i++;
 
        for (conn_opt = conn_opts; conn_opt->keyword != NULL; conn_opt++)
        {
            if (conn_opt->val != NULL && conn_opt->val[0] != '\0')
            {
                keywords[i] = conn_opt->keyword;
                values[i] = conn_opt->val;
                i++;
            }
        }
    }
    else
    {
        keywords = pg_malloc0((argcount + 1) * sizeof(*keywords));
        values = pg_malloc0((argcount + 1) * sizeof(*values));
        keywords[i] = "dbname";
        values[i] = (dbname == NULL) ? "replication" : dbname;
        i++;
    }
 
    keywords[i] = "replication";
    values[i] = (dbname == NULL) ? "true" : "database";
    i++;
    keywords[i] = "fallback_application_name";
    values[i] = progname;
    i++;
 
    if (dbhost)
    {
        keywords[i] = "host";
        values[i] = dbhost;
        i++;
    }
    if (dbuser)
    {
        keywords[i] = "user";
        values[i] = dbuser;
        i++;
    }
    if (dbport)
    {
        keywords[i] = "port";
        values[i] = dbport;
        i++;
    }
 
    /* If -W was given, force prompt for password, but only the first time */
    need_password = (dbgetpassword == 1 && !password);
 
    do
    {
        /* Get a new password if appropriate */
        if (need_password)
        {
            free(password);
            password = simple_prompt("Password: ", false);
            need_password = false;
        }
 
        /* Use (or reuse, on a subsequent connection) password if we have it */
        if (password)
        {
            keywords[i] = "password";
            values[i] = password;
        }
        else
        {
            keywords[i] = NULL;
            values[i] = NULL;
        }
 
        /*
         * Only expand dbname when we did not already parse the argument as a
         * connection string ourselves.
         */
        tmpconn = PQconnectdbParams(keywords, values, !connection_string);
 
        /*
         * If there is too little memory even to allocate the PGconn object
         * and PQconnectdbParams returns NULL, we call exit(1) directly.
         */
        if (!tmpconn)
            pg_fatal("could not connect to server");
 
        /* If we need a password and -w wasn't given, loop back and get one */
        if (PQstatus(tmpconn) == CONNECTION_BAD &&
            PQconnectionNeedsPassword(tmpconn) &&
            dbgetpassword != -1)
        {
            PQfinish(tmpconn);
            need_password = true;
        }
    }
    while (need_password);
 
    if (PQstatus(tmpconn) != CONNECTION_OK)
    {
        pg_log_error("%s", PQerrorMessage(tmpconn));
        PQfinish(tmpconn);
        free(values);
        free(keywords);
        PQconninfoFree(conn_opts);
        return NULL;
    }
 
    /* Connection ok! */
    free(values);
    free(keywords);
    PQconninfoFree(conn_opts);
 
    /*
     * Set always-secure search path, so malicious users can't get control.
     * The capacity to run normal SQL queries was added in PostgreSQL 10, so
     * the search path cannot be changed (by us or attackers) on earlier
     * versions.
     */
    if (dbname != NULL && PQserverVersion(tmpconn) >= 100000)
    {
        PGresult   *res;
 
        res = PQexec(tmpconn, ALWAYS_SECURE_SEARCH_PATH_SQL);
        if (PQresultStatus(res) != PGRES_TUPLES_OK)
        {
            pg_log_error("could not clear \"search_path\": %s",
                         PQerrorMessage(tmpconn));
            PQclear(res);
            PQfinish(tmpconn);
            exit(1);
        }
        PQclear(res);
    }
 
    /*
     * Ensure we have the same value of integer_datetimes (now always "on") as
     * the server we are connecting to.
     */
    tmpparam = PQparameterStatus(tmpconn, "integer_datetimes");
    if (!tmpparam)
    {
        pg_log_error("could not determine server setting for \"integer_datetimes\"");
        PQfinish(tmpconn);
        exit(1);
    }
 
    if (strcmp(tmpparam, "on") != 0)
    {
        pg_log_error("\"integer_datetimes\" compile flag does not match server");
        PQfinish(tmpconn);
        exit(1);
    }
 
    /*
     * Retrieve the source data directory mode and use it to construct a umask
     * for creating directories and files.
     */
    if (!RetrieveDataDirCreatePerm(tmpconn))
    {
        PQfinish(tmpconn);
        exit(1);
    }
 
    return tmpconn;
}
 
/*
 * FindDbnameInConnParams
 *
 * This is a helper function for GetDbnameFromConnectionOptions(). Extract
 * the value of dbname from PQconninfoOption parameters, if it's present.
 * Returns a strdup'd result or NULL.
 */
static char *
FindDbnameInConnParams(PQconninfoOption *conn_opts)
{
    PQconninfoOption *conn_opt;
 
    for (conn_opt = conn_opts; conn_opt->keyword != NULL; conn_opt++)
    {
        if (strcmp(conn_opt->keyword, "dbname") == 0 &&
            conn_opt->val != NULL && conn_opt->val[0] != '\0')
            return pg_strdup(conn_opt->val);
    }
    return NULL;
}
 
/*
 * GetDbnameFromConnectionOptions
 *
 * This is a special purpose function to retrieve the dbname from either the
 * connection_string specified by the user or from the environment variables.
 *
 * We follow GetConnection() to fetch the dbname from various connection
 * options.
 *
 * Returns NULL, if dbname is not specified by the user in the above
 * mentioned connection options.
 */
char *
GetDbnameFromConnectionOptions(void)
{
    PQconninfoOption *conn_opts;
    char       *err_msg = NULL;
    char       *dbname;
 
    /* First try to get the dbname from connection string. */
    if (connection_string)
    {
        conn_opts = PQconninfoParse(connection_string, &err_msg);
        if (conn_opts == NULL)
            pg_fatal("%s", err_msg);
 
        dbname = FindDbnameInConnParams(conn_opts);
 
        PQconninfoFree(conn_opts);
        if (dbname)
            return dbname;
    }
 
    /*
     * Next try to get the dbname from default values that are available from
     * the environment.
     */
    conn_opts = PQconndefaults();
    if (conn_opts == NULL)
        pg_fatal("out of memory");
 
    dbname = FindDbnameInConnParams(conn_opts);
 
    PQconninfoFree(conn_opts);
    return dbname;
}
 
/*
 * From version 10, explicitly set wal segment size using SHOW wal_segment_size
 * since ControlFile is not accessible here.
 */
bool
RetrieveWalSegSize(PGconn *conn)
{
    PGresult   *res;
    char        xlog_unit[3];
    int         xlog_val,
                multiplier = 1;
 
    /* check connection existence */
    Assert(conn != NULL);
 
    /* for previous versions set the default xlog seg size */
    if (PQserverVersion(conn) < MINIMUM_VERSION_FOR_SHOW_CMD)
    {
        WalSegSz = DEFAULT_XLOG_SEG_SIZE;
        return true;
    }
 
    res = PQexec(conn, "SHOW wal_segment_size");
    if (PQresultStatus(res) != PGRES_TUPLES_OK)
    {
        pg_log_error("could not send replication command \"%s\": %s",
                     "SHOW wal_segment_size", PQerrorMessage(conn));
 
        PQclear(res);
        return false;
    }
    if (PQntuples(res) != 1 || PQnfields(res) < 1)
    {
        pg_log_error("could not fetch WAL segment size: got %d rows and %d fields, expected %d rows and %d or more fields",
                     PQntuples(res), PQnfields(res), 1, 1);
 
        PQclear(res);
        return false;
    }
 
    /* fetch xlog value and unit from the result */
    if (sscanf(PQgetvalue(res, 0, 0), "%d%2s", &xlog_val, xlog_unit) != 2)
    {
        pg_log_error("WAL segment size could not be parsed");
        PQclear(res);
        return false;
    }
 
    PQclear(res);
 
    /* set the multiplier based on unit to convert xlog_val to bytes */
    if (strcmp(xlog_unit, "MB") == 0)
        multiplier = 1024 * 1024;
    else if (strcmp(xlog_unit, "GB") == 0)
        multiplier = 1024 * 1024 * 1024;
 
    /* convert and set WalSegSz */
    WalSegSz = xlog_val * multiplier;
 
    if (!IsValidWalSegSize(WalSegSz))
    {
        pg_log_error(ngettext("remote server reported invalid WAL segment size (%d byte)",
                              "remote server reported invalid WAL segment size (%d bytes)",
                              WalSegSz),
                     WalSegSz);
        pg_log_error_detail("The WAL segment size must be a power of two between 1 MB and 1 GB.");
        return false;
    }
 
    return true;
}
 
/*
 * RetrieveDataDirCreatePerm
 *
 * This function is used to determine the privileges on the server's PG data
 * directory and, based on that, set what the permissions will be for
 * directories and files we create.
 *
 * PG11 added support for (optionally) group read/execute rights to be set on
 * the data directory.  Prior to PG11, only the owner was allowed to have rights
 * on the data directory.
 */
static bool
RetrieveDataDirCreatePerm(PGconn *conn)
{
    PGresult   *res;
    int         data_directory_mode;
 
    /* check connection existence */
    Assert(conn != NULL);
 
    /* for previous versions leave the default group access */
    if (PQserverVersion(conn) < MINIMUM_VERSION_FOR_GROUP_ACCESS)
        return true;
 
    res = PQexec(conn, "SHOW data_directory_mode");
    if (PQresultStatus(res) != PGRES_TUPLES_OK)
    {
        pg_log_error("could not send replication command \"%s\": %s",
                     "SHOW data_directory_mode", PQerrorMessage(conn));
 
        PQclear(res);
        return false;
    }
    if (PQntuples(res) != 1 || PQnfields(res) < 1)
    {
        pg_log_error("could not fetch group access flag: got %d rows and %d fields, expected %d rows and %d or more fields",
                     PQntuples(res), PQnfields(res), 1, 1);
 
        PQclear(res);
        return false;
    }
 
    if (sscanf(PQgetvalue(res, 0, 0), "%o", &data_directory_mode) != 1)
    {
        pg_log_error("group access flag could not be parsed: %s",
                     PQgetvalue(res, 0, 0));
 
        PQclear(res);
        return false;
    }
 
    SetDataDirectoryCreatePerm(data_directory_mode);
 
    PQclear(res);
    return true;
}
 
/*
 * Run IDENTIFY_SYSTEM through a given connection and give back to caller
 * some result information if requested:
 * - System identifier
 * - Current timeline ID
 * - Start LSN position
 * - Database name (NULL in servers prior to 9.4)
 */
bool
RunIdentifySystem(PGconn *conn, char **sysid, TimeLineID *starttli,
                  XLogRecPtr *startpos, char **db_name)
{
    PGresult   *res;
    uint32      hi,
                lo;
 
    /* Check connection existence */
    Assert(conn != NULL);
 
    res = PQexec(conn, "IDENTIFY_SYSTEM");
    if (PQresultStatus(res) != PGRES_TUPLES_OK)
    {
        pg_log_error("could not send replication command \"%s\": %s",
                     "IDENTIFY_SYSTEM", PQerrorMessage(conn));
 
        PQclear(res);
        return false;
    }
    if (PQntuples(res) != 1 || PQnfields(res) < 3)
    {
        pg_log_error("could not identify system: got %d rows and %d fields, expected %d rows and %d or more fields",
                     PQntuples(res), PQnfields(res), 1, 3);
 
        PQclear(res);
        return false;
    }
 
    /* Get system identifier */
    if (sysid != NULL)
        *sysid = pg_strdup(PQgetvalue(res, 0, 0));
 
    /* Get timeline ID to start streaming from */
    if (starttli != NULL)
        *starttli = atoi(PQgetvalue(res, 0, 1));
 
    /* Get LSN start position if necessary */
    if (startpos != NULL)
    {
        if (sscanf(PQgetvalue(res, 0, 2), "%X/%X", &hi, &lo) != 2)
        {
            pg_log_error("could not parse write-ahead log location \"%s\"",
                         PQgetvalue(res, 0, 2));
 
            PQclear(res);
            return false;
        }
        *startpos = ((uint64) hi) << 32 | lo;
    }
 
    /* Get database name, only available in 9.4 and newer versions */
    if (db_name != NULL)
    {
        *db_name = NULL;
        if (PQserverVersion(conn) >= 90400)
        {
            if (PQnfields(res) < 4)
            {
                pg_log_error("could not identify system: got %d rows and %d fields, expected %d rows and %d or more fields",
                             PQntuples(res), PQnfields(res), 1, 4);
 
                PQclear(res);
                return false;
            }
            if (!PQgetisnull(res, 0, 3))
                *db_name = pg_strdup(PQgetvalue(res, 0, 3));
        }
    }
 
    PQclear(res);
    return true;
}
 
/*
 * Run READ_REPLICATION_SLOT through a given connection and give back to
 * caller some result information if requested for this slot:
 * - Start LSN position, InvalidXLogRecPtr if unknown.
 * - Current timeline ID, 0 if unknown.
 * Returns false on failure, and true otherwise.
 */
bool
GetSlotInformation(PGconn *conn, const char *slot_name,
                   XLogRecPtr *restart_lsn, TimeLineID *restart_tli)
{
    PGresult   *res;
    PQExpBuffer query;
    XLogRecPtr  lsn_loc = InvalidXLogRecPtr;
    TimeLineID  tli_loc = 0;
 
    if (restart_lsn)
        *restart_lsn = lsn_loc;
    if (restart_tli)
        *restart_tli = tli_loc;
 
    query = createPQExpBuffer();
    appendPQExpBuffer(query, "READ_REPLICATION_SLOT %s", slot_name);
    res = PQexec(conn, query->data);
    destroyPQExpBuffer(query);
 
    if (PQresultStatus(res) != PGRES_TUPLES_OK)
    {
        pg_log_error("could not send replication command \"%s\": %s",
                     "READ_REPLICATION_SLOT", PQerrorMessage(conn));
        PQclear(res);
        return false;
    }
 
    /* The command should always return precisely one tuple and three fields */
    if (PQntuples(res) != 1 || PQnfields(res) != 3)
    {
        pg_log_error("could not read replication slot \"%s\": got %d rows and %d fields, expected %d rows and %d fields",
                     slot_name, PQntuples(res), PQnfields(res), 1, 3);
        PQclear(res);
        return false;
    }
 
    /*
     * When the slot doesn't exist, the command returns a tuple with NULL
     * values.  This checks only the slot type field.
     */
    if (PQgetisnull(res, 0, 0))
    {
        pg_log_error("replication slot \"%s\" does not exist", slot_name);
        PQclear(res);
        return false;
    }
 
    /*
     * Note that this cannot happen as READ_REPLICATION_SLOT supports only
     * physical slots, but play it safe.
     */
    if (strcmp(PQgetvalue(res, 0, 0), "physical") != 0)
    {
        pg_log_error("expected a physical replication slot, got type \"%s\" instead",
                     PQgetvalue(res, 0, 0));
        PQclear(res);
        return false;
    }
 
    /* restart LSN */
    if (!PQgetisnull(res, 0, 1))
    {
        uint32      hi,
                    lo;
 
        if (sscanf(PQgetvalue(res, 0, 1), "%X/%X", &hi, &lo) != 2)
        {
            pg_log_error("could not parse restart_lsn \"%s\" for replication slot \"%s\"",
                         PQgetvalue(res, 0, 1), slot_name);
            PQclear(res);
            return false;
        }
        lsn_loc = ((uint64) hi) << 32 | lo;
    }
 
    /* current TLI */
    if (!PQgetisnull(res, 0, 2))
        tli_loc = (TimeLineID) atoll(PQgetvalue(res, 0, 2));
 
    PQclear(res);
 
    /* Assign results if requested */
    if (restart_lsn)
        *restart_lsn = lsn_loc;
    if (restart_tli)
        *restart_tli = tli_loc;
 
    return true;
}
 
/*
 * Create a replication slot for the given connection. This function
 * returns true in case of success.
 */
bool
CreateReplicationSlot(PGconn *conn, const char *slot_name, const char *plugin,
                      bool is_temporary, bool is_physical, bool reserve_wal,
                      bool slot_exists_ok, bool two_phase)
{
    PQExpBuffer query;
    PGresult   *res;
    bool        use_new_option_syntax = (PQserverVersion(conn) >= 150000);
 
    query = createPQExpBuffer();
 
    Assert((is_physical && plugin == NULL) ||
           (!is_physical && plugin != NULL));
    Assert(!(two_phase && is_physical));
    Assert(slot_name != NULL);
 
    /* Build base portion of query */
    appendPQExpBuffer(query, "CREATE_REPLICATION_SLOT \"%s\"", slot_name);
    if (is_temporary)
        appendPQExpBufferStr(query, " TEMPORARY");
    if (is_physical)
        appendPQExpBufferStr(query, " PHYSICAL");
    else
        appendPQExpBuffer(query, " LOGICAL \"%s\"", plugin);
 
    /* Add any requested options */
    if (use_new_option_syntax)
        appendPQExpBufferStr(query, " (");
    if (is_physical)
    {
        if (reserve_wal)
            AppendPlainCommandOption(query, use_new_option_syntax,
                                     "RESERVE_WAL");
    }
    else
    {
        if (two_phase && PQserverVersion(conn) >= 150000)
            AppendPlainCommandOption(query, use_new_option_syntax,
                                     "TWO_PHASE");
 
        if (PQserverVersion(conn) >= 100000)
        {
            /* pg_recvlogical doesn't use an exported snapshot, so suppress */
            if (use_new_option_syntax)
                AppendStringCommandOption(query, use_new_option_syntax,
                                          "SNAPSHOT", "nothing");
            else
                AppendPlainCommandOption(query, use_new_option_syntax,
                                         "NOEXPORT_SNAPSHOT");
        }
    }
    if (use_new_option_syntax)
    {
        /* Suppress option list if it would be empty, otherwise terminate */
        if (query->data[query->len - 1] == '(')
        {
            query->len -= 2;
            query->data[query->len] = '\0';
        }
        else
            appendPQExpBufferChar(query, ')');
    }
 
    /* Now run the query */
    res = PQexec(conn, query->data);
    if (PQresultStatus(res) != PGRES_TUPLES_OK)
    {
        const char *sqlstate = PQresultErrorField(res, PG_DIAG_SQLSTATE);
 
        if (slot_exists_ok &&
            sqlstate &&
            strcmp(sqlstate, ERRCODE_DUPLICATE_OBJECT) == 0)
        {
            destroyPQExpBuffer(query);
            PQclear(res);
            return true;
        }
        else
        {
            pg_log_error("could not send replication command \"%s\": %s",
                         query->data, PQerrorMessage(conn));
 
            destroyPQExpBuffer(query);
            PQclear(res);
            return false;
        }
    }
 
    if (PQntuples(res) != 1 || PQnfields(res) != 4)
    {
        pg_log_error("could not create replication slot \"%s\": got %d rows and %d fields, expected %d rows and %d fields",
                     slot_name,
                     PQntuples(res), PQnfields(res), 1, 4);
 
        destroyPQExpBuffer(query);
        PQclear(res);
        return false;
    }
 
    destroyPQExpBuffer(query);
    PQclear(res);
    return true;
}
 
/*
 * Drop a replication slot for the given connection. This function
 * returns true in case of success.
 */
bool
DropReplicationSlot(PGconn *conn, const char *slot_name)
{
    PQExpBuffer query;
    PGresult   *res;
 
    Assert(slot_name != NULL);
 
    query = createPQExpBuffer();
 
    /* Build query */
    appendPQExpBuffer(query, "DROP_REPLICATION_SLOT \"%s\"",
                      slot_name);
    res = PQexec(conn, query->data);
    if (PQresultStatus(res) != PGRES_COMMAND_OK)
    {
        pg_log_error("could not send replication command \"%s\": %s",
                     query->data, PQerrorMessage(conn));
 
        destroyPQExpBuffer(query);
        PQclear(res);
        return false;
    }
 
    if (PQntuples(res) != 0 || PQnfields(res) != 0)
    {
        pg_log_error("could not drop replication slot \"%s\": got %d rows and %d fields, expected %d rows and %d fields",
                     slot_name,
                     PQntuples(res), PQnfields(res), 0, 0);
 
        destroyPQExpBuffer(query);
        PQclear(res);
        return false;
    }
 
    destroyPQExpBuffer(query);
    PQclear(res);
    return true;
}
 
/*
 * Append a "plain" option - one with no value - to a server command that
 * is being constructed.
 *
 * In the old syntax, all options were parser keywords, so you could just
 * write things like SOME_COMMAND OPTION1 OPTION2 'opt2value' OPTION3 42. The
 * new syntax uses a comma-separated list surrounded by parentheses, so the
 * equivalent is SOME_COMMAND (OPTION1, OPTION2 'optvalue', OPTION3 42).
 */
void
AppendPlainCommandOption(PQExpBuffer buf, bool use_new_option_syntax,
                         char *option_name)
{
    if (buf->len > 0 && buf->data[buf->len - 1] != '(')
    {
        if (use_new_option_syntax)
            appendPQExpBufferStr(buf, ", ");
        else
            appendPQExpBufferChar(buf, ' ');
    }
 
    appendPQExpBuffer(buf, " %s", option_name);
}
 
/*
 * Append an option with an associated string value to a server command that
 * is being constructed.
 *
 * See comments for AppendPlainCommandOption, above.
 */
void
AppendStringCommandOption(PQExpBuffer buf, bool use_new_option_syntax,
                          char *option_name, char *option_value)
{
    AppendPlainCommandOption(buf, use_new_option_syntax, option_name);
 
    if (option_value != NULL)
    {
        size_t      length = strlen(option_value);
        char       *escaped_value = palloc(1 + 2 * length);
 
        PQescapeStringConn(conn, escaped_value, option_value, length, NULL);
        appendPQExpBuffer(buf, " '%s'", escaped_value);
        pfree(escaped_value);
    }
}
 
/*
 * Append an option with an associated integer value to a server command
 * is being constructed.
 *
 * See comments for AppendPlainCommandOption, above.
 */
void
AppendIntegerCommandOption(PQExpBuffer buf, bool use_new_option_syntax,
                           char *option_name, int32 option_value)
{
    AppendPlainCommandOption(buf, use_new_option_syntax, option_name);
 
    appendPQExpBuffer(buf, " %d", option_value);
}
 
/*
 * Frontend version of GetCurrentTimestamp(), since we are not linked with
 * backend code.
 */
TimestampTz
feGetCurrentTimestamp(void)
{
    TimestampTz result;
    struct timeval tp;
 
    gettimeofday(&tp, NULL);
 
    result = (TimestampTz) tp.tv_sec -
        ((POSTGRES_EPOCH_JDATE - UNIX_EPOCH_JDATE) * SECS_PER_DAY);
    result = (result * USECS_PER_SEC) + tp.tv_usec;
 
    return result;
}
 
/*
 * Frontend version of TimestampDifference(), since we are not linked with
 * backend code.
 */
void
feTimestampDifference(TimestampTz start_time, TimestampTz stop_time,
                      long *secs, int *microsecs)
{
    TimestampTz diff = stop_time - start_time;
 
    if (diff <= 0)
    {
        *secs = 0;
        *microsecs = 0;
    }
    else
    {
        *secs = (long) (diff / USECS_PER_SEC);
        *microsecs = (int) (diff % USECS_PER_SEC);
    }
}
 
/*
 * Frontend version of TimestampDifferenceExceeds(), since we are not
 * linked with backend code.
 */
bool
feTimestampDifferenceExceeds(TimestampTz start_time,
                             TimestampTz stop_time,
                             int msec)
{
    TimestampTz diff = stop_time - start_time;
 
    return (diff >= msec * INT64CONST(1000));
}
 
/*
 * Converts an int64 to network byte order.
 */
void
fe_sendint64(int64 i, char *buf)
{
    uint64      n64 = pg_hton64(i);
 
    memcpy(buf, &n64, sizeof(n64));
}
 
/*
 * Converts an int64 from network byte order to native format.
 */
int64
fe_recvint64(char *buf)
{
    uint64      n64;
 
    memcpy(&n64, buf, sizeof(n64));
 
    return pg_ntoh64(n64);
}