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

1 files changed, 37 insertions, 20 deletions

diff --git a/src/backend/tcop/postgres.c b/src/backend/tcop/postgres.c
index 5b677863b9c..8958ec8103e 100644
--- a/src/backend/tcop/postgres.c
+++ b/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);
 	}