Clean up some minor bugs concerning what was inside the main loop

and what wasn't.  Also try to improve the comments so that doesn't happen
again.  Changed SIGPIPE handling to SIG_IGN so that if frontend quits,
we will finish out the current command and return to main loop before
quitting.  This seems much safer than a forced abort mid-command.

Author: tglsfdc

src/backend/tcop/postgres.c

@@ -7,7 +7,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/tcop/postgres.c,v 1.89 1998/09/01 04:32:13 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/tcop/postgres.c,v 1.90 1998/10/02 01:14:14 tgl Exp $
  *
  * NOTES
  *	  this is the "main" module of the postgres backend and
@@ -223,6 +223,7 @@ InteractiveBackend(char *inBuf)
 	 * ----------------
 	 */
 	printf("> ");
+	fflush(stdout);
 
 	for (;;)
 	{
@@ -295,6 +296,7 @@ InteractiveBackend(char *inBuf)
 	 */
 	if (EchoQuery)
 		printf("query: %s\n", inBuf);
+	fflush(stdout);
 
 	return 'Q';
 }
@@ -1398,7 +1400,7 @@ PostgresMain(int argc, char *argv[], int real_argc, char *real_argv[])
 	{
 		PS_INIT_STATUS(real_argc, real_argv, argv[0],
 					   remote_info, userName, DBName);
-		PS_SET_STATUS("idle");
+		PS_SET_STATUS("startup");
 	}
 
 	/* ----------------
@@ -1465,18 +1467,33 @@ PostgresMain(int argc, char *argv[], int real_argc, char *real_argv[])
 		puts("\treset_client_encoding() done.");
 #endif
 
+	/* ----------------
+	 * if stable main memory is assumed (-S(old) flag is set), it is necessary
+	 * to flush all dirty shared buffers before exit
+	 * plai 8/7/90
+	 * this used to be done further down, causing an additional entry in
+	 * the shmem exit list for every error :-( ... tgl 10/1/98
+	 * ----------------
+	 */
+	if (!TransactionFlushEnabled())
+		on_shmem_exit(FlushBufferPool, NULL);
+
 	/* ----------------
 	 *	Set up handler for cancel-request signal, and
 	 *	send this backend's cancellation info to the frontend.
 	 *	This should not be done until we are sure startup is successful.
 	 * ----------------
 	 */
 
-	pqsignal(SIGHUP, read_pg_options);	/* upate pg_options from file */
+	pqsignal(SIGHUP, read_pg_options);	/* update pg_options from file */
 	pqsignal(SIGINT, QueryCancelHandler);		/* cancel current query */
 	pqsignal(SIGQUIT, handle_warn);		/* handle error */
 	pqsignal(SIGTERM, die);
-	pqsignal(SIGPIPE, die);
+	pqsignal(SIGPIPE, SIG_IGN);	/* ignore failure to write to frontend */
+	/* Note: if frontend closes connection, we will notice it and exit cleanly
+	 * when control next returns to outer loop.  This seems safer than forcing
+	 * exit in the midst of output during who-knows-what operation...
+	 */
 	pqsignal(SIGUSR1, quickdie);
 	pqsignal(SIGUSR2, Async_NotifyHandler);		/* flush also sinval cache */
 	pqsignal(SIGCHLD, SIG_IGN); /* ignored, sent by LockOwners */
@@ -1491,7 +1508,15 @@ PostgresMain(int argc, char *argv[], int real_argc, char *real_argv[])
 		/* Need not flush since ReadyForQuery will do it. */
 	}
 
+	if (!IsUnderPostmaster)
+	{
+		puts("\nPOSTGRES backend interactive interface ");
+		puts("$Revision: 1.90 $ $Date: 1998/10/02 01:14:14 $\n");
+	}
+
 	/* ----------------
+	 *	POSTGRES main processing loop begins here
+	 *
 	 *	if an exception is encountered, processing resumes here
 	 *	so we abort the current transaction and start a new one.
 	 *	This must be done after we initialize the slave backends
@@ -1512,52 +1537,41 @@ PostgresMain(int argc, char *argv[], int real_argc, char *real_argv[])
 		if (Verbose)
 			TPRINTF(TRACE_VERBOSE, "AbortCurrentTransaction");
 
-		MemSet(parser_input, 0, MAX_PARSE_BUFFER);
-
 		AbortCurrentTransaction();
-
 	}
 
 	InError = false;
 
-	/* ----------------
-	 *	POSTGRES main processing loop begins here
-	 * ----------------
-	 */
-	if (!IsUnderPostmaster)
-	{
-		puts("\nPOSTGRES backend interactive interface");
-		puts("$Revision: 1.89 $ $Date: 1998/09/01 04:32:13 $");
-	}
-
-	/* ----------------
-	 * if stable main memory is assumed (-S(old) flag is set), it is necessary
-	 * to flush all dirty shared buffers before exit
-	 * plai 8/7/90
-	 * ----------------
+	/*
+	 * Non-error queries loop here.
 	 */
-	if (!TransactionFlushEnabled())
-		on_shmem_exit(FlushBufferPool, NULL);
 
 	for (;;)
 	{
+		PS_SET_STATUS("idle");
+
 		/* ----------------
-		 *	 (0) tell the frontend we're ready for a new query.
+		 *	 (1) tell the frontend we're ready for a new query.
+		 *
+		 *   Note: this includes fflush()'ing the last of the prior output.
 		 * ----------------
 		 */
 		ReadyForQuery(whereToSendOutput);
 
 		/* ----------------
-		 *	 (1) read a command.
+		 *	 (2) read a command.
 		 * ----------------
 		 */
 		MemSet(parser_input, 0, MAX_PARSE_BUFFER);
 
 		firstchar = ReadCommand(parser_input);
 
-		QueryCancel = false;
+		QueryCancel = false;	/* forget any earlier CANCEL signal */
 
-		/* process the command */
+		/* ----------------
+		 *	 (3) process the command.
+		 * ----------------
+		 */
 		switch (firstchar)
 		{
 				/* ----------------
@@ -1571,19 +1585,16 @@ PostgresMain(int argc, char *argv[], int real_argc, char *real_argv[])
 				/* start an xact for this function invocation */
 				if (Verbose)
 					TPRINTF(TRACE_VERBOSE, "StartTransactionCommand");
-
 				StartTransactionCommand();
+
 				HandleFunctionRequest();
-				PS_SET_STATUS("idle");
 				break;
 
 				/* ----------------
 				 *	'Q' indicates a user query
 				 * ----------------
 				 */
 			case 'Q':
-				fflush(stdout);
-
 				if (strspn(parser_input, " \t\n") == strlen(parser_input))
 				{
 					/* ----------------
@@ -1610,8 +1621,6 @@ PostgresMain(int argc, char *argv[], int real_argc, char *real_argv[])
 
 					pg_exec_query(parser_input);
 
-					PS_SET_STATUS("idle");
-
 					if (ShowStats)
 						ShowUsage();
 				}
@@ -1631,7 +1640,7 @@ PostgresMain(int argc, char *argv[], int real_argc, char *real_argv[])
 		}
 
 		/* ----------------
-		 *	 (3) commit the current transaction
+		 *	 (4) commit the current transaction
 		 *
 		 *	 Note: if we had an empty input buffer, then we didn't
 		 *	 call pg_exec_query, so we don't bother to commit this transaction.
@@ -1643,17 +1652,15 @@ PostgresMain(int argc, char *argv[], int real_argc, char *real_argv[])
 				TPRINTF(TRACE_VERBOSE, "CommitTransactionCommand");
 			PS_SET_STATUS("commit");
 			CommitTransactionCommand();
-			PS_SET_STATUS("idle");
-
 		}
 		else
 		{
 			if (IsUnderPostmaster)
 				NullCommand(Remote);
 		}
-
 	}							/* infinite for-loop */
-	proc_exit(0);
+
+	proc_exit(0);				/* shouldn't get here... */
 	return 1;
 }