Improve user control over truncation of logged bind-parameter values.

This patch replaces the boolean GUC log_parameters_on_error introduced
by commit ba79cb5dc with an integer log_parameter_max_length_on_error,
adding the ability to specify how many bytes to trim each logged
parameter value to.  (The previous coding hard-wired that choice at
64 bytes.)

In addition, add a new parameter log_parameter_max_length that provides
similar control over truncation of query parameters that are logged in
response to statement-logging options, as opposed to errors.  Previous
releases always logged such parameters in full, possibly causing log
bloat.

For backwards compatibility with prior releases,
log_parameter_max_length defaults to -1 (log in full), while
log_parameter_max_length_on_error defaults to 0 (no logging).

Per discussion, log_parameter_max_length is SUSET since the DBA should
control routine logging behavior, but log_parameter_max_length_on_error
is USERSET because it also affects errcontext data sent back to the
client.

Alexey Bashtanov, editorialized a little by me

Discussion: https://postgr.es/m/b10493cc-a399-a03a-67c7-068f2791ee50@imap.cc

src/backend/nodes/params.c

@@ -269,7 +269,7 @@ RestoreParamList(char **start_address)
  * can contain NULLs for any unknown individual values.  NULL can be given if
  * no parameters are known.
  *
- * If maxlen is not zero, that's the maximum number of bytes of any one
+ * If maxlen is >= 0, that's the maximum number of bytes of any one
  * parameter value to be printed; an ellipsis is added if the string is
  * longer.  (Added quotes are not considered in this calculation.)
  */

src/backend/tcop/postgres.c

@@ -1763,7 +1763,7 @@ exec_bind_message(StringInfo input_message)
 	 */
 	if (numParams > 0)
 	{
-		char	  **knownTextValues = NULL;	/* allocate on first use */
+		char	  **knownTextValues = NULL; /* allocate on first use */
 
 		params = makeParamList(numParams);
 
@@ -1833,26 +1833,39 @@ exec_bind_message(StringInfo input_message)
 				pval = OidInputFunctionCall(typinput, pstring, typioparam, -1);
 
 				/*
-				 * Free result of encoding conversion, if any, and save a copy
-				 * for later when logging parameters.
+				 * If we might need to log parameters later, save a copy of
+				 * the converted string in MessageContext; then free the
+				 * result of encoding conversion, if any was done.
 				 */
 				if (pstring)
 				{
-					if (log_parameters_on_error)
+					if (log_parameter_max_length_on_error != 0)
 					{
-						MemoryContext	oldcxt;
+						MemoryContext oldcxt;
 
 						oldcxt = MemoryContextSwitchTo(MessageContext);
+
 						if (knownTextValues == NULL)
 							knownTextValues =
 								palloc0(numParams * sizeof(char *));
-						/*
-						 * Note: must copy at least two more full characters
-						 * than BuildParamLogString wants to see; otherwise it
-						 * might fail to include the ellipsis.
-						 */
-						knownTextValues[paramno] =
-							pnstrdup(pstring, 64 + 2 * MAX_MULTIBYTE_CHAR_LEN);
+
+						if (log_parameter_max_length_on_error < 0)
+							knownTextValues[paramno] = pstrdup(pstring);
+						else
+						{
+							/*
+							 * We can trim the saved string, knowing that we
+							 * won't print all of it.  But we must copy at
+							 * least two more full characters than
+							 * BuildParamLogString wants to use; otherwise it
+							 * might fail to include the trailing ellipsis.
+							 */
+							knownTextValues[paramno] =
+								pnstrdup(pstring,
+										 log_parameter_max_length_on_error
+										 + 2 * MAX_MULTIBYTE_CHAR_LEN);
+						}
+
 						MemoryContextSwitchTo(oldcxt);
 					}
 					if (pstring != pbuf.data)
@@ -1909,13 +1922,15 @@ exec_bind_message(StringInfo input_message)
 		}
 
 		/*
-		 * Once all parameters have been received, prepare for printing them in
-		 * errors, if configured to do so.  (This is saved in the portal, so
-		 * that they'll appear when the query is executed later.)
+		 * Once all parameters have been received, prepare for printing them
+		 * in errors, if configured to do so.  (This is saved in the portal,
+		 * so that they'll appear when the query is executed later.)
 		 */
-		if (log_parameters_on_error)
+		if (log_parameter_max_length_on_error != 0)
 			params->paramValuesStr =
-				BuildParamLogString(params, knownTextValues, 64);
+				BuildParamLogString(params,
+									knownTextValues,
+									log_parameter_max_length_on_error);
 	}
 	else
 		params = NULL;
@@ -2396,15 +2411,17 @@ errdetail_execute(List *raw_parsetree_list)
  * errdetail_params
  *
  * Add an errdetail() line showing bind-parameter data, if available.
+ * Note that this is only used for statement logging, so it is controlled
+ * by log_parameter_max_length not log_parameter_max_length_on_error.
  */
 static int
 errdetail_params(ParamListInfo params)
 {
-	if (params && params->numParams > 0)
+	if (params && params->numParams > 0 && log_parameter_max_length != 0)
 	{
-		char   *str;
+		char	   *str;
 
-		str = BuildParamLogString(params, NULL, 0);
+		str = BuildParamLogString(params, NULL, log_parameter_max_length);
 		if (str && str[0] != '\0')
 			errdetail("parameters: %s", str);
 	}

src/backend/utils/mb/stringinfo_mb.c

@@ -27,7 +27,7 @@
  * appendStringInfoStringQuoted
  *
  * Append up to maxlen bytes from s to str, or the whole input string if
- * maxlen <= 0, adding single quotes around it and doubling all single quotes.
+ * maxlen < 0, adding single quotes around it and doubling all single quotes.
  * Add an ellipsis if the copy is incomplete.
  */
 void
@@ -43,9 +43,9 @@ appendStringInfoStringQuoted(StringInfo str, const char *s, int maxlen)
 	Assert(str != NULL);
 
 	slen = strlen(s);
-	if (maxlen > 0 && maxlen < slen)
+	if (maxlen >= 0 && maxlen < slen)
 	{
-		int		finallen = pg_mbcliplen(s, slen, maxlen);
+		int			finallen = pg_mbcliplen(s, slen, maxlen);
 
 		copy = pnstrdup(s, finallen);
 		chunk_search_start = copy;

src/backend/utils/misc/guc.c

@@ -515,7 +515,6 @@ extern const struct config_enum_entry dynamic_shared_memory_options[];
  * GUC option variables that are exported from this module
  */
 bool		log_duration = false;
-bool		log_parameters_on_error = false;
 bool		Debug_print_plan = false;
 bool		Debug_print_parse = false;
 bool		Debug_print_rewritten = false;
@@ -544,6 +543,8 @@ int			log_min_messages = WARNING;
 int			client_min_messages = NOTICE;
 int			log_min_duration_sample = -1;
 int			log_min_duration_statement = -1;
+int			log_parameter_max_length = -1;
+int			log_parameter_max_length_on_error = 0;
 int			log_temp_files = -1;
 double		log_statement_sample_rate = 1.0;
 double		log_xact_sample_rate = 0;
@@ -1381,15 +1382,6 @@ static struct config_bool ConfigureNamesBool[] =
 		false,
 		NULL, NULL, NULL
 	},
-	{
-		{"log_parameters_on_error", PGC_SUSET, LOGGING_WHAT,
-			gettext_noop("Logs bind parameters of the logged statements where possible."),
-			NULL
-		},
-		&log_parameters_on_error,
-		false,
-		NULL, NULL, NULL
-	},
 	{
 		{"debug_print_parse", PGC_USERSET, LOGGING_WHAT,
 			gettext_noop("Logs each query's parse tree."),
@@ -2855,6 +2847,28 @@ static struct config_int ConfigureNamesInt[] =
 		NULL, NULL, NULL
 	},
 
+	{
+		{"log_parameter_max_length", PGC_SUSET, LOGGING_WHAT,
+			gettext_noop("When logging statements, limit logged parameter values to first N bytes."),
+			gettext_noop("-1 to print values in full."),
+			GUC_UNIT_BYTE
+		},
+		&log_parameter_max_length,
+		-1, -1, INT_MAX / 2,
+		NULL, NULL, NULL
+	},
+
+	{
+		{"log_parameter_max_length_on_error", PGC_USERSET, LOGGING_WHAT,
+			gettext_noop("When reporting an error, limit logged parameter values to first N bytes."),
+			gettext_noop("-1 to print values in full."),
+			GUC_UNIT_BYTE
+		},
+		&log_parameter_max_length_on_error,
+		0, -1, INT_MAX / 2,
+		NULL, NULL, NULL
+	},
+
 	{
 		{"bgwriter_delay", PGC_SIGHUP, RESOURCES_BGWRITER,
 			gettext_noop("Background writer sleep time between rounds."),

src/backend/utils/misc/postgresql.conf.sample

@@ -545,8 +545,13 @@
 					#   %% = '%'
 					# e.g. '<%u%%%d> '
 #log_lock_waits = off			# log lock waits >= deadlock_timeout
+#log_parameter_max_length = -1		# when logging statements, limit logged
+					# bind-parameter values to N bytes;
+					# -1 means print in full, 0 disables
+#log_parameter_max_length_on_error = 0	# when logging an error, limit logged
+					# bind-parameter values to N bytes;
+					# -1 means print in full, 0 disables
 #log_statement = 'none'			# none, ddl, mod, all
-#log_parameters_on_error = off	# on error log statements with bind parameters
 #log_replication_commands = off
 #log_temp_files = -1			# log temporary files equal or larger
 					# than the specified size in kilobytes;

src/bin/pgbench/t/001_pgbench_with_server.pl

@@ -270,8 +270,39 @@ COMMIT;
 }
 	});
 
-# Verify server logging of parameters.
-$node->append_conf('postgresql.conf', "log_parameters_on_error = true");
+# Verify server logging of query parameters.
+# (This doesn't really belong here, but pgbench is a convenient way
+# to issue commands using extended query mode with parameters.)
+
+# 1. Logging neither with errors nor with statements
+$node->append_conf('postgresql.conf',
+				   "log_min_duration_statement = 0\n" .
+				   "log_parameter_max_length = 0\n" .
+				   "log_parameter_max_length_on_error = 0");
+$node->reload;
+pgbench(
+		'-n -t1 -c1 -M prepared',
+		2,
+		[],
+		[
+		qr{ERROR:  invalid input syntax for type json},
+		qr{(?!extended query with parameters)}
+		],
+		'server parameter logging',
+		{
+			'001_param_1' => q[select '{ invalid ' as value \gset
+select $$'Valame Dios!' dijo Sancho; 'no le dije yo a vuestra merced que mirase bien lo que hacia?'$$ as long \gset
+select column1::jsonb from (values (:value), (:long)) as q;
+]
+	});
+my $log = TestLib::slurp_file($node->logfile);
+unlike($log, qr[DETAIL:  parameters: \$1 = '\{ invalid ',], "no parameters logged");
+$log = undef;
+
+# 2. Logging truncated parameters on error, full with statements
+$node->append_conf('postgresql.conf',
+				   "log_parameter_max_length = -1\n" .
+				   "log_parameter_max_length_on_error = 64");
 $node->reload;
 pgbench(
 		'-n -t1 -c1 -M prepared',
@@ -283,7 +314,47 @@ pgbench(
 		],
 		'server parameter logging',
 		{
-			'001_param_1' => q{select '1' as one \gset
+			'001_param_2' => q{select '1' as one \gset
+SELECT 1 / (random() / 2)::int, :one::int, :two::int;
+}
+	});
+pgbench(
+		'-n -t1 -c1 -M prepared',
+		2,
+		[],
+		[
+		qr{ERROR:  invalid input syntax for type json},
+		qr[CONTEXT:  JSON data, line 1: \{ invalid\.\.\.[\r\n]+extended query with parameters: \$1 = '\{ invalid ', \$2 = '''Valame Dios!'' dijo Sancho; ''no le dije yo a vuestra merced que \.\.\.']m
+		],
+		'server parameter logging',
+		{
+			'001_param_3' => q[select '{ invalid ' as value \gset
+select $$'Valame Dios!' dijo Sancho; 'no le dije yo a vuestra merced que mirase bien lo que hacia?'$$ as long \gset
+select column1::jsonb from (values (:value), (:long)) as q;
+]
+	});
+$log = TestLib::slurp_file($node->logfile);
+like($log, qr[DETAIL:  parameters: \$1 = '\{ invalid ', \$2 = '''Valame Dios!'' dijo Sancho; ''no le dije yo a vuestra merced que mirase bien lo que hacia\?'''],
+	 "parameter report does not truncate");
+$log = undef;
+
+# 3. Logging full parameters on error, truncated with statements
+$node->append_conf('postgresql.conf',
+				   "log_min_duration_statement = -1\n" .
+				   "log_parameter_max_length = 7\n" .
+				   "log_parameter_max_length_on_error = -1");
+$node->reload;
+pgbench(
+		'-n -t1 -c1 -M prepared',
+		2,
+		[],
+		[
+		qr{ERROR:  division by zero},
+		qr{CONTEXT:  extended query with parameters: \$1 = '1', \$2 = NULL}
+		],
+		'server parameter logging',
+		{
+			'001_param_4' => q{select '1' as one \gset
 SELECT 1 / (random() / 2)::int, :one::int, :two::int;
 }
 	});
@@ -296,21 +367,25 @@ pgbench(
 		[],
 		[
 		qr{ERROR:  invalid input syntax for type json},
-		qr[CONTEXT:  JSON data, line 1: \{ invalid\.\.\.[\r\n]+extended query with parameters: \$1 = '\{ invalid ', \$2 = '''Valame Dios!'' dijo Sancho; ''no le dije yo a vuestra merced que \.\.\.']m
+		qr[CONTEXT:  JSON data, line 1: \{ invalid\.\.\.[\r\n]+extended query with parameters: \$1 = '\{ invalid ', \$2 = '''Valame Dios!'' dijo Sancho; ''no le dije yo a vuestra merced que mirase bien lo que hacia\?']m
 		],
 		'server parameter logging',
 		{
-			'001_param_2' => q[select '{ invalid ' as value \gset
+			'001_param_5' => q[select '{ invalid ' as value \gset
 select $$'Valame Dios!' dijo Sancho; 'no le dije yo a vuestra merced que mirase bien lo que hacia?'$$ as long \gset
 select column1::jsonb from (values (:value), (:long)) as q;
 ]
 	});
-my $log = TestLib::slurp_file($node->logfile);
-like($log, qr[DETAIL:  parameters: \$1 = '\{ invalid ', \$2 = '''Valame Dios!'' dijo Sancho; ''no le dije yo a vuestra merced que mirase bien lo que hacia\?'''],
-	 "parameter report does not truncate");
+$log = TestLib::slurp_file($node->logfile);
+like($log, qr[DETAIL:  parameters: \$1 = '\{ inval\.\.\.', \$2 = '''Valame\.\.\.'],
+	 "parameter report truncates");
 $log = undef;
 
-$node->append_conf('postgresql.conf', "log_min_duration_statement = -1");
+# Restore default logging config
+$node->append_conf('postgresql.conf',
+				   "log_min_duration_statement = -1\n" .
+				   "log_parameter_max_length_on_error = 0\n" .
+				   "log_parameter_max_length = -1");
 $node->reload;
 
 # test expressions

src/include/utils/guc.h

@@ -233,8 +233,6 @@ typedef enum
 
 
 /* GUC vars that are actually declared in guc.c, rather than elsewhere */
-extern bool log_duration;
-extern bool log_parameters_on_error;
 extern bool Debug_print_plan;
 extern bool Debug_print_parse;
 extern bool Debug_print_rewritten;
@@ -249,6 +247,9 @@ extern bool log_btree_build_stats;
 extern PGDLLIMPORT bool check_function_bodies;
 extern bool session_auth_is_superuser;
 
+extern bool log_duration;
+extern int	log_parameter_max_length;
+extern int	log_parameter_max_length_on_error;
 extern int	log_min_error_statement;
 extern PGDLLIMPORT int log_min_messages;
 extern PGDLLIMPORT int client_min_messages;

src/pl/plpgsql/src/pl_exec.c

@@ -8771,7 +8771,7 @@ format_expr_params(PLpgSQL_execstate *estate,
 										 convert_value_to_string(estate,
 																 paramdatum,
 																 paramtypeid),
-										 0);
+										 -1);
 
 		paramno++;
 	}
@@ -8813,7 +8813,7 @@ format_preparedparamsdata(PLpgSQL_execstate *estate,
 										 convert_value_to_string(estate,
 																 ppd->values[paramno],
 																 ppd->types[paramno]),
-										 0);
+										 -1);
 	}
 
 	MemoryContextSwitchTo(oldcontext);