Re: Determining client_encoding from client locale

Here's my first attempt at setting client_encoding automatically from
locale.

It adds a new conninfo parameter to libpq, "client_encoding". If set to
"auto", libpq uses the encoding as returned by
pg_get_encoding_from_locale(). Any other value is passed through to the
server as is.

psql is modified to set "client_encoding=auto", unless overridden by
PGCLIENTENCODING.


BTW, I had to modify psql to use PQconnectdb() instead of
PQsetdblogin(), so that it can pass the extra parameter. I found it a
bit laboursome to construct the conninfo string with proper escaping,
just to have libpq parse and split it into components again. Could we
have a version of PQconnectdb() with an API more suited for setting the
params programmatically? The PQsetdbLogin() approach doesn't scale as
parameters are added/removed in future versions, but we could have
something like this:

PGconn *PQconnectParams(const char **params)

Where "params" is an array with an even number of parameters, forming
key/value pairs. Usage example:

char *connparams[] = {
    "dbname", "mydb",
    "user", username,
    NULL /* terminate with NULL */
};
conn = PQconnectParams(connparams);

This is similar to what I did internally in psql in the attached patch.

Another idea is to use an array of PQconninfoOption structs:

PQconn *PQconnectParams(PQconninfoOption *params);

This would be quite natural since that's the format returned by
PQconnDefaults() and PQconninfoParse(), but a bit more cumbersome to use
in applications that don't use those functions, as in the previous example.

-- 
  Heikki Linnakangas
  EnterpriseDB   http://www.enterprisedb.com
commit 24f6d68ddd3725c1f9a98c47f7535b2973ffc492
Author: Heikki Linnakangas 
Date:   Mon Jul 6 16:54:00 2009 +0300

    Add client_encoding conninfo parameter. By specifying special value
    'auto', libpq will determine the encoding from the current locale.
    
    Modify psql to use the 'auto' mode if PGCLIENTENCODING if not set.

diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index 86affb0..a5d45b2 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -236,6 +236,19 @@
          
         
 
+        
+         client_encoding
+         
+         
+          Character encoding to use. This sets the client_encoding
+          configuration option for this connection. In addition to the values
+          accepted by the corresponding server option, you can use 'auto' to
+          determine the right encoding from the current locale in the client
+          (LC_CTYPE environment variable on Unix systems).
+         
+         
+        
+
         
          options
          
@@ -5871,6 +5884,16 @@ myEventProc(PGEventId evtId, void *evtInfo, void *passThrough)
       linkend="libpq-connect-connect-timeout"> connection parameter.
      
     
+
+    
+     
+      
+       PGCLIENTENCODING
+      
+      PGCLIENTENCODING behaves the same as  connection parameter.
+     
+    
    
   
 
@@ -5907,17 +5930,6 @@ myEventProc(PGEventId evtId, void *evtInfo, void *passThrough)
     
      
       
-       PGCLIENTENCODING
-      
-      PGCLIENTENCODING sets the default client character
-      set encoding.  (Equivalent to SET client_encoding TO
-      ....)
-     
-    
-
-    
-     
-      
        PGGEQO
       
       PGGEQO sets the default mode for the genetic query
diff --git a/src/bin/psql/command.c b/src/bin/psql/command.c
index 0955e13..6991e7a 100644
--- a/src/bin/psql/command.c
+++ b/src/bin/psql/command.c
@@ -1239,8 +1239,7 @@ do_connect(char *dbname, char *user, char *host, char *port)
 
 	while (true)
 	{
-		n_conn = PQsetdbLogin(host, port, NULL, NULL,
-							  dbname, user, password);
+		n_conn = PSQLconnect(host, port, dbname, user, password);
 
 		/* We can immediately discard the password -- no longer needed */
 		if (password)
diff --git a/src/bin/psql/common.c b/src/bin/psql/common.c
index 6b2de37..a5a0b0a 100644
--- a/src/bin/psql/common.c
+++ b/src/bin/psql/common.c
@@ -32,6 +32,8 @@ static bool ExecQueryUsingCursor(const char *query, double *elapsed_msec);
 static bool command_no_begin(const char *query);
 static bool is_select_command(const char *query);
 
+static char *construct_conninfo(const char * const *optarray);
+
 /*
  * "Safe" wrapper around strdup()
  */
@@ -1538,3 +1540,75 @@ expand_tilde(char **filename)
 
 	return *filename;
 }
+
+/*
+ * Establish a connection. This has an API similar to libpq's PQsetdblogin(),
+ * but we set "client_encoding=auto" if PGCLIENTENCODING environment variable
+ * is not set.
+ */
+PGconn *
+PSQLconnect(const char *host,
+			const char *port,
+			const char *dbname,
+			const char *user,
+			const char *password)
+{
+	char *conninfo;
+	PGconn *ret;
+
+	const char *opts[] = {
+		"host", host,
+		"port", port,
+		"dbname", dbname,
+		"user", user,
+		"password", password,
+		"client_encoding", getenv("PGCLIENTENCODING") ? NULL : "auto",
+		NULL, NULL
+	};
+
+	conninfo = construct_conninfo(opts);
+	ret = PQconnectdb(conninfo);
+	free(conninfo);
+
+	return ret;
+}
+
+
+/*
+ * Given an array of connection option name/value pairs, construct a
+ * conninfo string suitable for PQconnectdb(). The array must be terminated
+ * by a NULL pointer.
+ */
+static char *
+construct_conninfo(const char * const *optarray)
+{
+	PQExpBufferData buf;
+
+	initPQExpBuffer(&buf);
+
+	while(*optarray)
+	{
+		const char *option = optarray[0];
+		const char *value = optarray[1];
+
+		if (value != NULL)
+		{
+			/* write option name */
+			appendPQExpBuffer(&buf, "%s = '", option);
+
+			/* write value, escaping single quotes and backslashes */
+			while(*value)
+			{
+				if (*value == '\'' || *value == '\\')
+					appendPQExpBufferChar(&buf, '\\');
+				appendPQExpBufferChar(&buf, *(value++));
+			}
+
+			appendPQExpBufferStr(&buf, "' ");
+		}
+
+		optarray+=2;
+	}
+
+	return buf.data;
+}
diff --git a/src/bin/psql/common.h b/src/bin/psql/common.h
index edcb2e5..e962164 100644
--- a/src/bin/psql/common.h
+++ b/src/bin/psql/common.h
@@ -57,6 +57,12 @@ extern PGresult *PSQLexec(const char *query, bool start_xact);
 
 extern bool SendQuery(const char *query);
 
+extern PGconn *PSQLconnect(const char *host,
+						   const char *port,
+						   const char *dbname,
+						   const char *user,
+						   const char *password);
+
 extern bool is_superuser(void);
 extern bool standard_strings(void);
 extern const char *session_username(void);
diff --git a/src/bin/psql/startup.c b/src/bin/psql/startup.c
index 429e5d9..cf65a76 100644
--- a/src/bin/psql/startup.c
+++ b/src/bin/psql/startup.c
@@ -172,7 +172,7 @@ main(int argc, char *argv[])
 	do
 	{
 		new_pass = false;
-		pset.db = PQsetdbLogin(options.host, options.port, NULL, NULL,
+		pset.db = PSQLconnect(options.host, options.port,
 					options.action == ACT_LIST_DB && options.dbname == NULL ?
 							   "postgres" : options.dbname,
 							   options.username, password);
diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 70dfd90..c92fbe6 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -154,6 +154,9 @@ static const PQconninfoOption PQconninfoOptions[] = {
 	{"port", "PGPORT", DEF_PGPORT_STR, NULL,
 	"Database-Port", "", 6},
 
+	{"client_encoding", "PGCLIENTENCODING", NULL, NULL,
+	"Client-Encoding", "", 10},
+
 	/*
 	 * "tty" is no longer used either, but keep it present for backwards
 	 * compatibility.
@@ -225,9 +228,6 @@ static const PQEnvironmentOption EnvironmentOptions[] =
 	{
 		"PGTZ", "timezone"
 	},
-	{
-		"PGCLIENTENCODING", "client_encoding"
-	},
 	/* internal performance-related settings */
 	{
 		"PGGEQO", "geqo"
@@ -424,6 +424,8 @@ connectOptions1(PGconn *conn, const char *conninfo)
 	conn->pgpass = tmp ? strdup(tmp) : NULL;
 	tmp = conninfo_getval(connOptions, "connect_timeout");
 	conn->connect_timeout = tmp ? strdup(tmp) : NULL;
+	tmp = conninfo_getval(connOptions, "client_encoding");
+	conn->client_encoding_initial = tmp ? strdup(tmp) : NULL;
 	tmp = conninfo_getval(connOptions, "sslmode");
 	conn->sslmode = tmp ? strdup(tmp) : NULL;
 	tmp = conninfo_getval(connOptions, "sslkey");
@@ -552,6 +554,17 @@ connectOptions2(PGconn *conn)
 		conn->sslmode = strdup(DefaultSSLMode);
 
 	/*
+	 * Resolve 'auto' client_encoding
+	 */
+	if (conn->client_encoding_initial &&
+		strcmp(conn->client_encoding_initial, "auto") == 0)
+	{
+		int encid = pg_get_encoding_from_locale(NULL);
+		free(conn->client_encoding_initial);
+		conn->client_encoding_initial = strdup(pg_encoding_to_char(encid));
+	}
+
+	/*
 	 * Only if we get this far is it appropriate to try to connect. (We need a
 	 * state flag, rather than just the boolean result of this function, in
 	 * case someone tries to PQreset() the PGconn.)
@@ -1843,7 +1856,7 @@ keep_going:						/* We will come back to here until there is
 				if (PG_PROTOCOL_MAJOR(conn->pversion) < 3)
 				{
 					conn->status = CONNECTION_SETENV;
-					conn->setenv_state = SETENV_STATE_OPTION_SEND;
+					conn->setenv_state = SETENV_STATE_CLIENT_ENCODING_SEND;
 					conn->next_eo = EnvironmentOptions;
 					return PGRES_POLLING_WRITING;
 				}
@@ -3649,6 +3662,13 @@ PQsetClientEncoding(PGconn *conn, const char *encoding)
 	if (!encoding)
 		return -1;
 
+	/* resolve special 'auto' value from the locale */
+	if (strcmp(encoding, "auto") == 0)
+	{
+		int encid = pg_get_encoding_from_locale(NULL);
+		encoding = pg_encoding_to_char(encid);
+	}
+
 	/* check query buffer overflow */
 	if (sizeof(qbuf) < (sizeof(query) + strlen(encoding)))
 		return -1;
diff --git a/src/interfaces/libpq/fe-protocol2.c b/src/interfaces/libpq/fe-protocol2.c
index 87ba65b..8d45706 100644
--- a/src/interfaces/libpq/fe-protocol2.c
+++ b/src/interfaces/libpq/fe-protocol2.c
@@ -58,6 +58,7 @@ pqSetenvPoll(PGconn *conn)
 	switch (conn->setenv_state)
 	{
 			/* These are reading states */
+		case SETENV_STATE_CLIENT_ENCODING_WAIT:
 		case SETENV_STATE_OPTION_WAIT:
 		case SETENV_STATE_QUERY1_WAIT:
 		case SETENV_STATE_QUERY2_WAIT:
@@ -74,6 +75,7 @@ pqSetenvPoll(PGconn *conn)
 			}
 
 			/* These are writing states, so we just proceed. */
+		case SETENV_STATE_CLIENT_ENCODING_SEND:
 		case SETENV_STATE_OPTION_SEND:
 		case SETENV_STATE_QUERY1_SEND:
 		case SETENV_STATE_QUERY2_SEND:
@@ -98,6 +100,34 @@ pqSetenvPoll(PGconn *conn)
 	{
 		switch (conn->setenv_state)
 		{
+			case SETENV_STATE_CLIENT_ENCODING_SEND:
+				{
+					char		setQuery[100];	/* note length limit in
+												 * sprintf below */
+					const char *val = conn->client_encoding_initial;
+
+					if (val)
+					{
+						if (pg_strcasecmp(val, "default") == 0)
+							sprintf(setQuery, "SET client_encoding = DEFAULT");
+						else
+							sprintf(setQuery, "SET client_encoding = '%.60s'",
+									val);
+#ifdef CONNECTDEBUG
+						fprintf(stderr,
+								"Sending client_encoding with %s\n",
+								setQuery);
+#endif
+						if (!PQsendQuery(conn, setQuery))
+							goto error_return;
+
+						conn->setenv_state = SETENV_STATE_CLIENT_ENCODING_WAIT;
+					}
+					else
+						conn->setenv_state = SETENV_STATE_OPTION_SEND;
+					break;
+				}
+
 			case SETENV_STATE_OPTION_SEND:
 				{
 					/*
@@ -142,6 +172,31 @@ pqSetenvPoll(PGconn *conn)
 					break;
 				}
 
+			case SETENV_STATE_CLIENT_ENCODING_WAIT:
+				{
+					if (PQisBusy(conn))
+						return PGRES_POLLING_READING;
+
+					res = PQgetResult(conn);
+
+					if (res)
+					{
+						if (PQresultStatus(res) != PGRES_COMMAND_OK)
+						{
+							PQclear(res);
+							goto error_return;
+						}
+						PQclear(res);
+						/* Keep reading until PQgetResult returns NULL */
+					}
+					else
+					{
+						/* Query finished, so send the next option */
+						conn->setenv_state = SETENV_STATE_OPTION_SEND;
+					}
+					break;
+				}
+
 			case SETENV_STATE_OPTION_WAIT:
 				{
 					if (PQisBusy(conn))
diff --git a/src/interfaces/libpq/fe-protocol3.c b/src/interfaces/libpq/fe-protocol3.c
index 9102b61..a01ace7 100644
--- a/src/interfaces/libpq/fe-protocol3.c
+++ b/src/interfaces/libpq/fe-protocol3.c
@@ -1920,6 +1920,15 @@ build_startup_packet(const PGconn *conn, char *packet,
 			strcpy(packet + packet_len, conn->pgoptions);
 		packet_len += strlen(conn->pgoptions) + 1;
 	}
+	if (conn->client_encoding_initial && conn->client_encoding_initial[0])
+	{
+		if (packet)
+			strcpy(packet + packet_len, "client_encoding");
+		packet_len += strlen("client_encoding") + 1;
+		if (packet)
+			strcpy(packet + packet_len, conn->client_encoding_initial);
+		packet_len += strlen(conn->client_encoding_initial) + 1;
+	}
 
 	/* Add any environment-driven GUC settings needed */
 	for (next_eo = options; next_eo->envName; next_eo++)
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index ff9e6b8..1d036ba 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -235,6 +235,8 @@ typedef enum
 /* (this is used only for 2.0-protocol connections) */
 typedef enum
 {
+	SETENV_STATE_CLIENT_ENCODING_SEND,	/* About to send an Environment Option */
+	SETENV_STATE_CLIENT_ENCODING_WAIT,	/* Waiting for above send to complete */
 	SETENV_STATE_OPTION_SEND,	/* About to send an Environment Option */
 	SETENV_STATE_OPTION_WAIT,	/* Waiting for above send to complete */
 	SETENV_STATE_QUERY1_SEND,	/* About to send a status query */
@@ -294,6 +296,7 @@ struct pg_conn
 	char	   *pgtty;			/* tty on which the backend messages is
 								 * displayed (OBSOLETE, NOT USED) */
 	char	   *connect_timeout;	/* connection timeout (numeric string) */
+	char	   *client_encoding_initial; /* encoding to use */
 	char	   *pgoptions;		/* options to start the backend with */
 	char	   *dbName;			/* database name */
 	char	   *pguser;			/* Postgres username and password, if any */