src/bin/pg_basebackup/streamutil.c - cloudberry - Git at Google

 /*-------------------------------------------------------------------------
  *
  * streamutil.c - utility functions for pg_basebackup, pg_receivewal and
  *					pg_recvlogical
  *
  * Author: Magnus Hagander <magnus@hagander.net>
  *
  * Portions Copyright (c) 1996-2021, 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/fe_memutils.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 "receivelog.h"
 #include "streamutil.h"

 #define ERRCODE_DUPLICATE_OBJECT  "42710"

 uint32		WalSegSz;

 static bool RetrieveDataDirCreatePerm(PGconn *conn);

 /* 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. */
 	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.)
 	 * Explicitly discard any dbname value in the connection string;
 	 * otherwise, PQconnectdbParams() would interpret that value as being
 	 * itself a connection string.
 	 */
 	i = 0;
 	if (connection_string)
 	{
 		conn_opts = PQconninfoParse(connection_string, &err_msg);
 		if (conn_opts == NULL)
 		{
 			pg_log_error("%s", err_msg);
 			exit(1);
 		}

 		for (conn_opt = conn_opts; conn_opt->keyword != NULL; conn_opt++)
 		{
 			if (conn_opt->val != NULL && conn_opt->val[0] != '\0' &&
 				strcmp(conn_opt->keyword, "dbname") != 0)
 				argcount++;
 		}

 		keywords = pg_malloc0((argcount + 1) * sizeof(*keywords));
 		values = pg_malloc0((argcount + 1) * sizeof(*values));

 		for (conn_opt = conn_opts; conn_opt->keyword != NULL; conn_opt++)
 		{
 			if (conn_opt->val != NULL && conn_opt->val[0] != '\0' &&
 				strcmp(conn_opt->keyword, "dbname") != 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)
 		{
 			if (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;
 		}

 		tmpconn = PQconnectdbParams(keywords, values, true);

 		/*
 		 * If there is too little memory even to allocate the PGconn object
 		 * and PQconnectdbParams returns NULL, we call exit(1) directly.
 		 */
 		if (!tmpconn)
 		{
 			pg_log_error("could not connect to server");
 			exit(1);
 		}

 		/* 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);
 		if (conn_opts)
 			PQconninfoFree(conn_opts);
 		return NULL;
 	}

 	/* Connection ok! */
 	free(values);
 	free(keywords);
 	if (conn_opts)
 		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;
 }

 /*
  * 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("WAL segment size must be a power of two between 1 MB and 1 GB, but the remote server reported a value of %d byte",
 							  "WAL segment size must be a power of two between 1 MB and 1 GB, but the remote server reported a value of %d bytes",
 							  WalSegSz),
 					 WalSegSz);
 		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;
 }

 /*
  * 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)
 {
 	PQExpBuffer query;
 	PGresult   *res;

 	query = createPQExpBuffer();

 	Assert((is_physical && plugin == NULL) ||
 		   (!is_physical && plugin != NULL));
 	Assert(slot_name != NULL);

 	/* Build query */
 	appendPQExpBuffer(query, "CREATE_REPLICATION_SLOT \"%s\"", slot_name);
 	if (is_temporary)
 		appendPQExpBufferStr(query, " TEMPORARY");
 	if (is_physical)
 	{
 		appendPQExpBufferStr(query, " PHYSICAL");
 		if (reserve_wal)
 			appendPQExpBufferStr(query, " RESERVE_WAL");
 	}
 	else
 	{
 		appendPQExpBuffer(query, " LOGICAL \"%s\"", plugin);
 		if (PQserverVersion(conn) >= 100000)
 			/* pg_recvlogical doesn't use an exported snapshot, so suppress */
 			appendPQExpBufferStr(query, " NOEXPORT_SNAPSHOT");
 	}

 	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;
 }


 /*
  * 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);
 }
	/*-------------------------------------------------------------------------
	*
	* streamutil.c - utility functions for pg_basebackup, pg_receivewal and
	* pg_recvlogical
	*
	* Author: Magnus Hagander <magnus@hagander.net>
	*
	* Portions Copyright (c) 1996-2021, 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/fe_memutils.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 "receivelog.h"
	#include "streamutil.h"

	#define ERRCODE_DUPLICATE_OBJECT "42710"

	uint32 WalSegSz;

	static bool RetrieveDataDirCreatePerm(PGconn *conn);

	/* 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. */
	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.)
	* Explicitly discard any dbname value in the connection string;
	* otherwise, PQconnectdbParams() would interpret that value as being
	* itself a connection string.
	*/
	i = 0;
	if (connection_string)
	{
	conn_opts = PQconninfoParse(connection_string, &err_msg);
	if (conn_opts == NULL)
	{
	pg_log_error("%s", err_msg);
	exit(1);
	}

	for (conn_opt = conn_opts; conn_opt->keyword != NULL; conn_opt++)
	{
	if (conn_opt->val != NULL && conn_opt->val[0] != '\0' &&
	strcmp(conn_opt->keyword, "dbname") != 0)
	argcount++;
	}

	keywords = pg_malloc0((argcount + 1) * sizeof(*keywords));
	values = pg_malloc0((argcount + 1) * sizeof(*values));

	for (conn_opt = conn_opts; conn_opt->keyword != NULL; conn_opt++)
	{
	if (conn_opt->val != NULL && conn_opt->val[0] != '\0' &&
	strcmp(conn_opt->keyword, "dbname") != 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)
	{
	if (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;
	}

	tmpconn = PQconnectdbParams(keywords, values, true);

	/*
	* If there is too little memory even to allocate the PGconn object
	* and PQconnectdbParams returns NULL, we call exit(1) directly.
	*/
	if (!tmpconn)
	{
	pg_log_error("could not connect to server");
	exit(1);
	}

	/* 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);
	if (conn_opts)
	PQconninfoFree(conn_opts);
	return NULL;
	}

	/* Connection ok! */
	free(values);
	free(keywords);
	if (conn_opts)
	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;
	}

	/*
	* 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("WAL segment size must be a power of two between 1 MB and 1 GB, but the remote server reported a value of %d byte",
	"WAL segment size must be a power of two between 1 MB and 1 GB, but the remote server reported a value of %d bytes",
	WalSegSz),
	WalSegSz);
	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;
	}

	/*
	* 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)
	{
	PQExpBuffer query;
	PGresult *res;

	query = createPQExpBuffer();

	Assert((is_physical && plugin == NULL) \|\|
	(!is_physical && plugin != NULL));
	Assert(slot_name != NULL);

	/* Build query */
	appendPQExpBuffer(query, "CREATE_REPLICATION_SLOT \"%s\"", slot_name);
	if (is_temporary)
	appendPQExpBufferStr(query, " TEMPORARY");
	if (is_physical)
	{
	appendPQExpBufferStr(query, " PHYSICAL");
	if (reserve_wal)
	appendPQExpBufferStr(query, " RESERVE_WAL");
	}
	else
	{
	appendPQExpBuffer(query, " LOGICAL \"%s\"", plugin);
	if (PQserverVersion(conn) >= 100000)
	/* pg_recvlogical doesn't use an exported snapshot, so suppress */
	appendPQExpBufferStr(query, " NOEXPORT_SNAPSHOT");
	}

	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;
	}


	/*
	* 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);
	}