In the continuing saga of FE/BE protocol revisions, add reporting of

initial values and runtime changes in selected parameters.  This gets
rid of the need for an initial 'select pg_client_encoding()' query in
libpq, bringing us back to one message transmitted in each direction
for a standard connection startup.  To allow server version to be sent
using the same GUC mechanism that handles other parameters, invent the
concept of a never-settable GUC parameter: you can 'show server_version'
but it's not settable by any GUC input source.  Create 'lc_collate' and
'lc_ctype' never-settable parameters so that people can find out these
settings without need for pg_controldata.  (These side ideas were all
discussed some time ago in pgsql-hackers, but not yet implemented.)

3 files changed, 62 insertions, 295 deletions

diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index a31f34d7a98..e2df4de859a 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-connect.c,v 1.236 2003/04/25 01:24:00 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-connect.c,v 1.237 2003/04/25 19:45:09 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -174,8 +174,6 @@ static const struct EnvironmentOptions
 
 static int	connectDBStart(PGconn *conn);
 static int	connectDBComplete(PGconn *conn);
-static bool PQsetenvStart(PGconn *conn);
-static PostgresPollingStatusType PQsetenvPoll(PGconn *conn);
 static PGconn *makeEmptyPGconn(void);
 static void freePGconn(PGconn *conn);
 static void closePGconn(PGconn *conn);
@@ -1207,10 +1205,6 @@ PQconnectPoll(PGconn *conn)
 		case CONNECTION_MADE:
 			break;
 
-		case CONNECTION_SETENV:
-			/* We allow PQsetenvPoll to decide whether to proceed */
-			break;
-
 		default:
 			printfPQExpBuffer(&conn->errorMessage,
 							  libpq_gettext(
@@ -1517,10 +1511,10 @@ keep_going:						/* We will come back to here until there
 				 * message indicates that startup is successful, but we
 				 * might also get an Error message indicating failure.
 				 * (Notice messages indicating nonfatal warnings are also
-				 * allowed by the protocol, as is a BackendKeyData
-				 * message.) Easiest way to handle this is to let
-				 * PQgetResult() read the messages. We just have to fake
-				 * it out about the state of the connection, by setting
+				 * allowed by the protocol, as are ParameterStatus and
+				 * BackendKeyData messages.) Easiest way to handle this is
+				 * to let PQgetResult() read the messages. We just have to
+				 * fake it out about the state of the connection, by setting
 				 * asyncStatus = PGASYNC_BUSY (done above).
 				 */
 
@@ -1554,44 +1548,11 @@ keep_going:						/* We will come back to here until there
 				}
 
 				/*
-				 * Post-connection housekeeping. Prepare to send
-				 * environment variables to server.
+				 * We are open for business!
 				 */
-				if (!PQsetenvStart(conn))
-					goto error_return;
-
-				conn->status = CONNECTION_SETENV;
-
-				goto keep_going;
-			}
-
-		case CONNECTION_SETENV:
-
-			/*
-			 * We pretend that the connection is OK for the duration of
-			 * these queries.
-			 */
-			conn->status = CONNECTION_OK;
-
-			switch (PQsetenvPoll(conn))
-			{
-				case PGRES_POLLING_OK:	/* Success */
-					conn->status = CONNECTION_OK;
-					return PGRES_POLLING_OK;
-
-				case PGRES_POLLING_READING:		/* Still going */
-					conn->status = CONNECTION_SETENV;
-					return PGRES_POLLING_READING;
-
-				case PGRES_POLLING_WRITING:		/* Still going */
-					conn->status = CONNECTION_SETENV;
-					return PGRES_POLLING_WRITING;
-
-				default:
-					conn->status = CONNECTION_SETENV;
-					goto error_return;
+				conn->status = CONNECTION_OK;
+				return PGRES_POLLING_OK;
 			}
-			/* Unreachable */
 
 		default:
 			printfPQExpBuffer(&conn->errorMessage,
@@ -1619,239 +1580,6 @@ error_return:
 
 
 /*
- *		PQsetenvStart
- *
- * Starts the process of passing the values of a standard set of environment
- * variables to the backend.
- */
-static bool
-PQsetenvStart(PGconn *conn)
-{
-	if (conn == NULL ||
-		conn->status == CONNECTION_BAD ||
-		conn->setenv_state != SETENV_STATE_IDLE)
-		return false;
-
-	conn->setenv_state = SETENV_STATE_ENCODINGS_SEND;
-
-	return true;
-}
-
-/*
- *		PQsetenvPoll
- *
- * Polls the process of passing the values of a standard set of environment
- * variables to the backend.
- */
-static PostgresPollingStatusType
-PQsetenvPoll(PGconn *conn)
-{
-	PGresult   *res;
-
-	if (conn == NULL || conn->status == CONNECTION_BAD)
-		return PGRES_POLLING_FAILED;
-
-	/* Check whether there are any data for us */
-	switch (conn->setenv_state)
-	{
-			/* These are reading states */
-		case SETENV_STATE_ENCODINGS_WAIT:
-			{
-				/* Load waiting data */
-				int			n = pqReadData(conn);
-
-				if (n < 0)
-					goto error_return;
-				if (n == 0)
-					return PGRES_POLLING_READING;
-
-				break;
-			}
-
-			/* These are writing states, so we just proceed. */
-		case SETENV_STATE_ENCODINGS_SEND:
-			break;
-
-			/* Should we raise an error if called when not active? */
-		case SETENV_STATE_IDLE:
-			return PGRES_POLLING_OK;
-
-		default:
-			printfPQExpBuffer(&conn->errorMessage,
-							  libpq_gettext(
-											"invalid setenv state %c, "
-							 "probably indicative of memory corruption\n"
-											),
-							  conn->setenv_state);
-			goto error_return;
-	}
-
-	/* We will loop here until there is nothing left to do in this call. */
-	for (;;)
-	{
-		switch (conn->setenv_state)
-		{
-			case SETENV_STATE_ENCODINGS_SEND:
-				{
-					const char *env = getenv("PGCLIENTENCODING");
-
-					if (!env || *env == '\0')
-					{
-						/*
-						 * PGCLIENTENCODING is not specified, so query
-						 * server for it.  We must use begin/commit in
-						 * case autocommit is off by default.
-						 */
-						if (!PQsendQuery(conn, "begin; select pg_client_encoding(); commit"))
-							goto error_return;
-
-						conn->setenv_state = SETENV_STATE_ENCODINGS_WAIT;
-						return PGRES_POLLING_READING;
-					}
-					else
-					{
-						/* otherwise set client encoding in pg_conn struct */
-						int			encoding = pg_char_to_encoding(env);
-
-						if (encoding < 0)
-						{
-							printfPQExpBuffer(&conn->errorMessage,
-											  libpq_gettext("invalid encoding name in PGCLIENTENCODING: %s\n"),
-											  env);
-							goto error_return;
-						}
-						conn->client_encoding = encoding;
-
-						/* Move on to setting the environment options */
-						conn->setenv_state = SETENV_STATE_IDLE;
-					}
-					break;
-				}
-
-			case SETENV_STATE_ENCODINGS_WAIT:
-				{
-					if (PQisBusy(conn))
-						return PGRES_POLLING_READING;
-
-					res = PQgetResult(conn);
-
-					if (res)
-					{
-						if (PQresultStatus(res) == PGRES_TUPLES_OK)
-						{
-							/* set client encoding in pg_conn struct */
-							char	   *encoding;
-
-							encoding = PQgetvalue(res, 0, 0);
-							if (!encoding)		/* this should not happen */
-								conn->client_encoding = PG_SQL_ASCII;
-							else
-								conn->client_encoding = pg_char_to_encoding(encoding);
-						}
-						else if (PQresultStatus(res) != PGRES_COMMAND_OK)
-						{
-							PQclear(res);
-							goto error_return;
-						}
-						PQclear(res);
-						/* Keep reading until PQgetResult returns NULL */
-					}
-					else
-					{
-						/*
-						 * NULL result indicates that the query is
-						 * finished
-						 */
-						conn->setenv_state = SETENV_STATE_IDLE;
-					}
-					break;
-				}
-
-			case SETENV_STATE_IDLE:
-				return PGRES_POLLING_OK;
-
-			default:
-				printfPQExpBuffer(&conn->errorMessage,
-								  libpq_gettext("invalid state %c, "
-						   "probably indicative of memory corruption\n"),
-								  conn->setenv_state);
-				goto error_return;
-		}
-	}
-
-	/* Unreachable */
-
-error_return:
-	conn->setenv_state = SETENV_STATE_IDLE;
-	return PGRES_POLLING_FAILED;
-}
-
-
-#ifdef NOT_USED
-
-/*
- *		PQsetenv
- *
- * Passes the values of a standard set of environment variables to the
- * backend.
- *
- * Returns true on success, false on failure.
- *
- * This function used to be exported for no particularly good reason.
- * Since it's no longer used by libpq itself, let's try #ifdef'ing it out
- * and see if anyone complains.
- */
-static bool
-PQsetenv(PGconn *conn)
-{
-	PostgresPollingStatusType flag = PGRES_POLLING_WRITING;
-
-	if (!PQsetenvStart(conn))
-		return false;
-
-	for (;;)
-	{
-		/*
-		 * Wait, if necessary.	Note that the initial state (just after
-		 * PQsetenvStart) is to wait for the socket to select for writing.
-		 */
-		switch (flag)
-		{
-			case PGRES_POLLING_OK:
-				return true;	/* success! */
-
-			case PGRES_POLLING_READING:
-				if (pqWait(1, 0, conn))
-				{
-					conn->status = CONNECTION_BAD;
-					return false;
-				}
-				break;
-
-			case PGRES_POLLING_WRITING:
-				if (pqWait(0, 1, conn))
-				{
-					conn->status = CONNECTION_BAD;
-					return false;
-				}
-				break;
-
-			default:
-				/* Just in case we failed to set it in PQsetenvPoll */
-				conn->status = CONNECTION_BAD;
-				return false;
-		}
-
-		/*
-		 * Now try to advance the state machine.
-		 */
-		flag = PQsetenvPoll(conn);
-	}
-}
-#endif   /* NOT_USED */
-
-
-/*
  * makeEmptyPGconn
  *	 - create a PGconn data structure with (as yet) no interesting data
  */
@@ -1869,7 +1597,6 @@ makeEmptyPGconn(void)
 	conn->noticeHook = defaultNoticeProcessor;
 	conn->status = CONNECTION_BAD;
 	conn->asyncStatus = PGASYNC_IDLE;
-	conn->setenv_state = SETENV_STATE_IDLE;
 	conn->notifyList = DLNewList();
 	conn->sock = -1;
 #ifdef USE_SSL
diff --git a/src/interfaces/libpq/fe-exec.c b/src/interfaces/libpq/fe-exec.c
index 84520987812..53c4e288622 100644
--- a/src/interfaces/libpq/fe-exec.c
+++ b/src/interfaces/libpq/fe-exec.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-exec.c,v 1.132 2003/04/25 01:24:00 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/interfaces/libpq/fe-exec.c,v 1.133 2003/04/25 19:45:09 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -21,6 +21,8 @@
 #include "libpq-fe.h"
 #include "libpq-int.h"
 
+#include "mb/pg_wchar.h"
+
 #ifdef WIN32
 #include "win32.h"
 #else
@@ -54,6 +56,7 @@ static void handleSendFailure(PGconn *conn);
 static void handleSyncLoss(PGconn *conn, char id, int msgLength);
 static int	getRowDescriptions(PGconn *conn);
 static int	getAnotherTuple(PGconn *conn, int binary);
+static int	getParameterStatus(PGconn *conn);
 static int	getNotify(PGconn *conn);
 
 /* ---------------
@@ -950,6 +953,11 @@ parseInput(PGconn *conn)
 		 *
 		 * However, if the state is IDLE then we got trouble; we need to deal
 		 * with the unexpected message somehow.
+		 *
+		 * ParameterStatus ('S') messages are a special case: in IDLE state
+		 * we must process 'em (this case could happen if a new value was
+		 * adopted from config file due to SIGHUP), but otherwise we hold
+		 * off until BUSY state.
 		 */
 		if (id == 'A')
 		{
@@ -970,6 +978,7 @@ parseInput(PGconn *conn)
 			/*
 			 * Unexpected message in IDLE state; need to recover somehow.
 			 * ERROR messages are displayed using the notice processor;
+			 * ParameterStatus is handled normally;
 			 * anything else is just dropped on the floor after displaying
 			 * a suitable warning notice.  (An ERROR is very possibly the
 			 * backend telling us why it is about to close the connection,
@@ -980,6 +989,11 @@ parseInput(PGconn *conn)
 				if (pqGetErrorNotice(conn, false /* treat as notice */))
 					return;
 			}
+			else if (id == 'S')
+			{
+				if (getParameterStatus(conn))
+					return;
+			}
 			else
 			{
 				snprintf(noticeWorkspace, sizeof(noticeWorkspace),
@@ -1021,6 +1035,10 @@ parseInput(PGconn *conn)
 													  PGRES_EMPTY_QUERY);
 					conn->asyncStatus = PGASYNC_READY;
 					break;
+				case 'S':		/* parameter status */
+					if (getParameterStatus(conn))
+						return;
+					break;
 				case 'K':		/* secret key data from the backend */
 
 					/*
@@ -1672,6 +1690,35 @@ fail:
 }
 
 /*
+ * Attempt to read a ParameterStatus message.
+ * This is possible in several places, so we break it out as a subroutine.
+ * Entry: 'S' message type and length have already been consumed.
+ * Exit: returns 0 if successfully consumed message.
+ *		 returns EOF if not enough data.
+ */
+static int
+getParameterStatus(PGconn *conn)
+{
+	/* Get the parameter name */
+	if (pqGets(&conn->workBuffer, conn))
+		return EOF;
+	/* Is it one we care about? */
+	if (strcmp(conn->workBuffer.data, "client_encoding") == 0)
+	{
+		if (pqGets(&conn->workBuffer, conn))
+			return EOF;
+		conn->client_encoding = pg_char_to_encoding(conn->workBuffer.data);
+	}
+	else
+	{
+		/* Uninteresting parameter, ignore it */
+		if (pqGets(&conn->workBuffer, conn))
+			return EOF;
+	}
+	return 0;
+}
+
+/*
  * Attempt to read a Notify response message.
  * This is possible in several places, so we break it out as a subroutine.
  * Entry: 'A' message type and length have already been consumed.
@@ -2249,6 +2296,10 @@ PQfn(PGconn *conn,
 				if (conn->result)
 					return prepareAsyncResult(conn);
 				return PQmakeEmptyPGresult(conn, status);
+			case 'S':			/* parameter status */
+				if (getParameterStatus(conn))
+					continue;
+				break;
 			default:
 				/* The backend violates the protocol. */
 				printfPQExpBuffer(&conn->errorMessage,
diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h
index 4688fbf8f5a..12670f3a0a4 100644
--- a/src/interfaces/libpq/libpq-int.h
+++ b/src/interfaces/libpq/libpq-int.h
@@ -12,7 +12,7 @@
  * Portions Copyright (c) 1996-2002, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: libpq-int.h,v 1.64 2003/04/24 21:16:44 tgl Exp $
+ * $Id: libpq-int.h,v 1.65 2003/04/25 19:45:10 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -56,7 +56,7 @@ typedef int ssize_t;			/* ssize_t doesn't exist in VC (atleast
  * pqcomm.h describe what the backend knows, not what libpq knows.
  */
 
-#define PG_PROTOCOL_LIBPQ	PG_PROTOCOL(3,103) /* XXX temporary value */
+#define PG_PROTOCOL_LIBPQ	PG_PROTOCOL(3,104) /* XXX temporary value */
 
 /*
  * POSTGRES backend dependent Constants.
@@ -194,14 +194,6 @@ typedef enum
 	PGASYNC_COPY_OUT			/* Copy Out data transfer in progress */
 }	PGAsyncStatusType;
 
-/* PGSetenvStatusType defines the state of the PQSetenv state machine */
-typedef enum
-{
-	SETENV_STATE_ENCODINGS_SEND,	/* About to send an "encodings" query */
-	SETENV_STATE_ENCODINGS_WAIT,	/* Waiting for query to complete	  */
-	SETENV_STATE_IDLE
-}	PGSetenvStatusType;
-
 /* large-object-access data ... allocated only if large-object code is used. */
 typedef struct pgLobjfuncs
 {
@@ -293,9 +285,6 @@ struct pg_conn
 	PGresult   *result;			/* result being constructed */
 	PGresAttValue *curTuple;	/* tuple currently being read */
 
-	/* Status for sending environment info.  Used during PQSetenv only. */
-	PGSetenvStatusType setenv_state;
-
 #ifdef USE_SSL
 	bool		allow_ssl_try;	/* Allowed to try SSL negotiation */
 	bool		require_ssl;	/* Require SSL to make connection */