Patch: Allow formatting in log_line_prefix

diff -u -r b/doc/src/sgml/config.sgml a/doc/src/sgml/config.sgml
--- b/doc/src/sgml/config.sgml	2013-08-25 07:14:17.000000000 +1200
+++ a/doc/src/sgml/config.sgml	2013-08-26 00:33:31.158147304 +1200
@@ -3942,7 +3942,13 @@
          Unrecognized escapes are ignored. Other
          characters are copied straight to the log line. Some escapes are
          only recognized by session processes, and are ignored by
-         background processes such as the main server process.
+         background processes such as the main server process. Status
+         information may be aligned either left or right by specifying a
+         numeric literal after the % and before the option. A negative
+         padding will cause the status information to be padded on the
+         right with spaces to give it a minimum width. Whereas a positive
+         padding will pad on the left. Padding can be useful keep log 
+         files more human readable.
          This parameter can only be set in the <filename>postgresql.conf</>
          file or on the server command line. The default is an empty string.
 
Only in a/doc/src/sgml: config.sgml~
Only in a/doc/src/sgml: html
Only in a: .git
Only in a/src/backend/bootstrap: bootparse.c
Only in a/src/backend/bootstrap: bootscanner.c
Only in a/src/backend/catalog: postgres.bki
Only in a/src/backend/catalog: postgres.description
Only in a/src/backend/catalog: postgres.shdescription
Only in a/src/backend/catalog: schemapg.h
Only in a/src/backend/parser: gram.c
Only in a/src/backend/parser: gram.h
Only in a/src/backend/parser: scan.c
Only in a/src/backend/replication: repl_gram.c
Only in a/src/backend/replication: repl_scanner.c
Only in a/src/backend/utils: errcodes.h
diff -u -r b/src/backend/utils/error/elog.c a/src/backend/utils/error/elog.c
--- b/src/backend/utils/error/elog.c	2013-08-25 07:14:17.000000000 +1200
+++ a/src/backend/utils/error/elog.c	2013-08-27 00:18:50.852641499 +1200
@@ -167,6 +167,7 @@
 	} while (0)
 
 
+static const char *process_log_prefix_padding(const char *p, int *padding);
 static void log_line_prefix(StringInfo buf, ErrorData *edata);
 static void send_message_to_server_log(ErrorData *edata);
 static void send_message_to_frontend(ErrorData *edata);
@@ -2120,6 +2121,41 @@
 }
 
 /*
+ * helper function for processing the format string in
+ * log_line_prefix()
+ */
+static const char
+*process_log_prefix_padding(const char *p, int *ppadding)
+{
+	int	paddingsign = 1;
+	int	padding = 0;	
+	
+	if (*p == '-')
+	{
+		p++;
+
+		if (*p == '\0')		/* Did the buf end in %- ? */
+			return NULL;
+		paddingsign = -1;
+	}
+	
+
+	/* generate an int version of the numerical string */
+	while (*p >= '0' && *p <= '9')
+		padding = padding * 10 + (*p++ - '0');
+
+	/* Format is invalid if it ends with the padding number */
+	if (*p == '\0')
+		return NULL;
+
+	padding *= paddingsign;
+	*ppadding = padding;
+	return p;
+
+}
+
+
+/*
  * Format tag info for log lines; append to the provided buffer.
  */
 static void
@@ -2129,10 +2165,9 @@
 	static long log_line_number = 0;
 
 	/* has counter been reset in current process? */
-	static int	log_my_pid = 0;
-
-	int			format_len;
-	int			i;
+	static int		log_my_pid = 0;
+	int			padding;
+	const char		*p;	
 
 	/*
 	 * This is one of the few places where we'd rather not inherit a static
@@ -2151,23 +2186,43 @@
 	if (Log_line_prefix == NULL)
 		return;					/* in case guc hasn't run yet */
 
-	format_len = strlen(Log_line_prefix);
-
-	for (i = 0; i < format_len; i++)
+	/*
+	 * The Log_line_prefix also supports optional space padding similar
+	 * to printf(). e.g. %-10u will pad the right side of the username
+	 * to make it at least 10 chars wide. %10u would pad the left side.
+	 */
+	for (p = Log_line_prefix; *p != '\0'; p++)
 	{
-		if (Log_line_prefix[i] != '%')
+		if (*p != '%')
 		{
 			/* literal char, just copy */
-			appendStringInfoChar(buf, Log_line_prefix[i]);
+			appendStringInfoChar(buf, *p);
 			continue;
 		}
-		/* go to char after '%' */
-		i++;
-		if (i >= format_len)
+
+		/* must be a '%', so skip to the next char */
+		p++;
+		if (*p == '\0')
 			break;				/* format error - ignore it */
+		else if (*p == '%')
+		{
+			/* string contains %% */
+			appendStringInfoChar(buf, '%');
+			continue;
+		}
+
+
+		/*
+		 * Process any formatting which may exist after the '%'.
+		 * Note that this moves p passed the padding number
+		 * if it exists.
+		 */
+		if ((p = process_log_prefix_padding(p, &padding)) == NULL)
+			break;
+
 
 		/* process the option */
-		switch (Log_line_prefix[i])
+		switch (*p)
 		{
 			case 'a':
 				if (MyProcPort)
@@ -2176,8 +2231,13 @@
 
 					if (appname == NULL || *appname == '\0')
 						appname = _("[unknown]");
-					appendStringInfoString(buf, appname);
+					appendStringInfo(buf, "%*s", padding, appname);
+				}
+				else 
+				{
+					appendStringInfoSpaces(buf, padding);
 				}
+
 				break;
 			case 'u':
 				if (MyProcPort)
@@ -2186,7 +2246,11 @@
 
 					if (username == NULL || *username == '\0')
 						username = _("[unknown]");
-					appendStringInfoString(buf, username);
+					appendStringInfo(buf, "%*s", padding, username);
+				}
+				else 
+				{
+					appendStringInfoSpaces(buf, padding);
 				}
 				break;
 			case 'd':
@@ -2196,21 +2260,30 @@
 
 					if (dbname == NULL || *dbname == '\0')
 						dbname = _("[unknown]");
-					appendStringInfoString(buf, dbname);
+					appendStringInfo(buf, "%*s", padding, dbname);
+				}
+				else 
+				{
+					appendStringInfoSpaces(buf, padding);
 				}
 				break;
 			case 'c':
-				appendStringInfo(buf, "%lx.%x", (long) (MyStartTime), MyProcPid);
+				{
+					char strfbuf[128];
+					snprintf(strfbuf, sizeof(strfbuf) - 1, "%lx.%x", 
+						(long) (MyStartTime), MyProcPid);
+					appendStringInfo(buf, "%*s", padding, strfbuf);
+				}
 				break;
 			case 'p':
-				appendStringInfo(buf, "%d", MyProcPid);
+				appendStringInfo(buf, "%*d", padding, MyProcPid);
 				break;
 			case 'l':
-				appendStringInfo(buf, "%ld", log_line_number);
+				appendStringInfo(buf, "%*ld", padding, log_line_number);
 				break;
 			case 'm':
 				setup_formatted_log_time();
-				appendStringInfoString(buf, formatted_log_time);
+				appendStringInfo(buf, "%*s", padding, formatted_log_time);
 				break;
 			case 't':
 				{
@@ -2220,13 +2293,13 @@
 					pg_strftime(strfbuf, sizeof(strfbuf),
 								"%Y-%m-%d %H:%M:%S %Z",
 								pg_localtime(&stamp_time, log_timezone));
-					appendStringInfoString(buf, strfbuf);
+					appendStringInfo(buf, "%*s", padding, strfbuf);
 				}
 				break;
 			case 's':
 				if (formatted_start_time[0] == '\0')
 					setup_formatted_start_time();
-				appendStringInfoString(buf, formatted_start_time);
+				appendStringInfo(buf, "%*s", padding, formatted_start_time);
 				break;
 			case 'i':
 				if (MyProcPort)
@@ -2235,43 +2308,70 @@
 					int			displen;
 
 					psdisp = get_ps_display(&displen);
-					appendBinaryStringInfo(buf, psdisp, displen);
+					appendStringInfo(buf, "%*s", padding, psdisp);
+				}
+				else 
+				{
+					appendStringInfoSpaces(buf, padding);
 				}
 				break;
 			case 'r':
 				if (MyProcPort && MyProcPort->remote_host)
 				{
-					appendStringInfoString(buf, MyProcPort->remote_host);
-					if (MyProcPort->remote_port &&
-						MyProcPort->remote_port[0] != '\0')
-						appendStringInfo(buf, "(%s)",
-										 MyProcPort->remote_port);
+					if (MyProcPort->remote_port && MyProcPort->remote_port[0] != '\0')
+					{
+						/* 
+						 * This option is slightly special as the port number
+	 					 * may be appended onto the end. Here we need to build
+						 * 1 string which contains the remote_host and optionally
+						 * the remote_port (if set) so we can properly align the
+						 * string.
+						 */
+
+						char *hostport;
+						int alloclen = strlen(MyProcPort->remote_host) +
+							 strlen(MyProcPort->remote_port) + 3; 
+						hostport = palloc(alloclen);
+						sprintf(hostport, "%s(%s)", MyProcPort->remote_host, MyProcPort->remote_port);
+						appendStringInfo(buf, "%*s", padding, hostport);
+						pfree(hostport);
+						
+					}
+					else
+					{
+						appendStringInfo(buf, "%*s", padding, MyProcPort->remote_host);
+					}
+				}
+				else 
+				{
+					appendStringInfoSpaces(buf, padding);
 				}
 				break;
 			case 'h':
 				if (MyProcPort && MyProcPort->remote_host)
-					appendStringInfoString(buf, MyProcPort->remote_host);
+					appendStringInfo(buf, "%*s", padding, MyProcPort->remote_host);
+				else
+					appendStringInfoSpaces(buf, padding);
 				break;
 			case 'q':
 				/* in postmaster and friends, stop if %q is seen */
 				/* in a backend, just ignore */
 				if (MyProcPort == NULL)
-					i = format_len;
+					return;
 				break;
 			case 'v':
 				/* keep VXID format in sync with lockfuncs.c */
 				if (MyProc != NULL && MyProc->backendId != InvalidBackendId)
 					appendStringInfo(buf, "%d/%u",
 									 MyProc->backendId, MyProc->lxid);
+				else
+					appendStringInfoSpaces(buf, padding);
 				break;
 			case 'x':
-				appendStringInfo(buf, "%u", GetTopTransactionIdIfAny());
+				appendStringInfo(buf, "%*u", padding, GetTopTransactionIdIfAny());
 				break;
 			case 'e':
-				appendStringInfoString(buf, unpack_sql_state(edata->sqlerrcode));
-				break;
-			case '%':
-				appendStringInfoChar(buf, '%');
+				appendStringInfo(buf, "%*s", padding, unpack_sql_state(edata->sqlerrcode));
 				break;
 			default:
 				/* format error - ignore it */
Only in a/src/backend/utils/error: elog.c~
Only in a/src/backend/utils: fmgroids.h
Only in a/src/backend/utils: fmgrtab.c
Only in a/src/backend/utils/misc: guc-file.c
Only in a/src/backend/utils/sort: qsort_tuple.c
Only in a/src/bin/psql: psqlscan.c
Only in a/src/bin/psql: sql_help.c
Only in a/src/bin/psql: sql_help.h
Only in a/src/interfaces/ecpg/preproc: pgc.c
Only in a/src/interfaces/ecpg/preproc: preproc.c
Only in a/src/interfaces/ecpg/preproc: preproc.h
Only in a/src/interfaces/ecpg/preproc: preproc.y
Only in a/src/pl/plpgsql/src: plerrcodes.h
Only in a/src/pl/plpgsql/src: pl_gram.c
Only in a/src/pl/plpgsql/src: pl_gram.h
Only in a/src/tools/entab: entab
Only in a/src/tools/entab: entab.o
Only in a/src/tools/pgindent: log_line_formatting.patch