Don't call data type input functions in GUC check hooks

Instead of calling pg_lsn_in() in check_recovery_target_lsn and
timestamptz_in() in check_recovery_target_time, reorganize the
respective code so that we don't raise any errors in the check hooks.
The previous code tried to use PG_TRY/PG_CATCH to handle errors in a
way that is not safe, so now the code contains no ereport() calls and
can operate safely within the GUC error handling system.

Moreover, since the interpretation of the recovery_target_time string
may depend on the time zone, we cannot do the final processing of that
string until all the GUC processing is done.  Instead,
check_recovery_target_time() now does some parsing for syntax
checking, but the actual conversion to a timestamptz value is done
later in the recovery code that uses it.
Reported-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Discussion: https://www.postgresql.org/message-id/flat/20190611061115.njjwkagvxp4qujhp%40alap3.anarazel.de

src/backend/access/transam/xlog.c

@@ -272,7 +272,8 @@ RecoveryTargetType recoveryTarget = RECOVERY_TARGET_UNSET;
 bool		recoveryTargetInclusive = true;
 int			recoveryTargetAction = RECOVERY_TARGET_ACTION_PAUSE;
 TransactionId recoveryTargetXid;
-TimestampTz recoveryTargetTime;
+char	   *recovery_target_time_string;
+static TimestampTz recoveryTargetTime;
 const char *recoveryTargetName;
 XLogRecPtr	recoveryTargetLSN;
 int			recovery_min_apply_delay = 0;
@@ -5409,6 +5410,18 @@ validateRecoveryParameters(void)
 		!EnableHotStandby)
 		recoveryTargetAction = RECOVERY_TARGET_ACTION_SHUTDOWN;
 
+	/*
+	 * Final parsing of recovery_target_time string; see also
+	 * check_recovery_target_time().
+	 */
+	if (recoveryTarget == RECOVERY_TARGET_TIME)
+	{
+		recoveryTargetTime = DatumGetTimestampTz(DirectFunctionCall3(timestamptz_in,
+																	 CStringGetDatum(recovery_target_time_string),
+																	 ObjectIdGetDatum(InvalidOid),
+																	 Int32GetDatum(-1)));
+	}
+
 	/*
 	 * If user specified recovery_target_timeline, validate it or compute the
 	 * "latest" value.  We can't do this until after we've gotten the restore

src/backend/utils/adt/pg_lsn.c

@@ -25,10 +25,9 @@
  * Formatting and conversion routines.
  *---------------------------------------------------------*/
 
-Datum
-pg_lsn_in(PG_FUNCTION_ARGS)
+XLogRecPtr
+pg_lsn_in_internal(const char *str, bool *have_error)
 {
-	char	   *str = PG_GETARG_CSTRING(0);
 	int			len1,
 				len2;
 	uint32		id,
@@ -38,16 +37,16 @@ pg_lsn_in(PG_FUNCTION_ARGS)
 	/* Sanity check input format. */
 	len1 = strspn(str, "0123456789abcdefABCDEF");
 	if (len1 < 1 || len1 > MAXPG_LSNCOMPONENT || str[len1] != '/')
-		ereport(ERROR,
-				(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
-				 errmsg("invalid input syntax for type %s: \"%s\"",
-						"pg_lsn", str)));
+	{
+		*have_error = true;
+		return InvalidXLogRecPtr;
+	}
 	len2 = strspn(str + len1 + 1, "0123456789abcdefABCDEF");
 	if (len2 < 1 || len2 > MAXPG_LSNCOMPONENT || str[len1 + 1 + len2] != '\0')
-		ereport(ERROR,
-				(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
-				 errmsg("invalid input syntax for type %s: \"%s\"",
-						"pg_lsn", str)));
+	{
+		*have_error = true;
+		return InvalidXLogRecPtr;
+	}
 
 	/* Decode result. */
 	id = (uint32) strtoul(str, NULL, 16);
@@ -57,6 +56,23 @@ pg_lsn_in(PG_FUNCTION_ARGS)
 	PG_RETURN_LSN(result);
 }
 
+Datum
+pg_lsn_in(PG_FUNCTION_ARGS)
+{
+	char	   *str = PG_GETARG_CSTRING(0);
+	XLogRecPtr	result;
+	bool have_error = false;
+
+	result = pg_lsn_in_internal(str, &have_error);
+	if (have_error)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
+				 errmsg("invalid input syntax for type %s: \"%s\"",
+						"pg_lsn", str)));
+
+	PG_RETURN_LSN(result);
+}
+
 Datum
 pg_lsn_out(PG_FUNCTION_ARGS)
 {

src/backend/utils/misc/guc.c

@@ -579,7 +579,6 @@ static bool assert_enabled;
 static char *recovery_target_timeline_string;
 static char *recovery_target_string;
 static char *recovery_target_xid_string;
-static char *recovery_target_time_string;
 static char *recovery_target_name_string;
 static char *recovery_target_lsn_string;
 
@@ -11572,20 +11571,20 @@ assign_recovery_target_xid(const char *newval, void *extra)
 		recoveryTarget = RECOVERY_TARGET_UNSET;
 }
 
+/*
+ * The interpretation of the recovery_target_time string can depend on the
+ * time zone setting, so we need to wait until after all GUC processing is
+ * done before we can do the final parsing of the string.  This check function
+ * only does a parsing pass to catch syntax errors, but we store the string
+ * and parse it again when we need to use it.
+ */
 static bool
 check_recovery_target_time(char **newval, void **extra, GucSource source)
 {
 	if (strcmp(*newval, "") != 0)
 	{
-		TimestampTz time;
-		TimestampTz *myextra;
-		MemoryContext oldcontext = CurrentMemoryContext;
-
 		/* reject some special values */
-		if (strcmp(*newval, "epoch") == 0 ||
-			strcmp(*newval, "infinity") == 0 ||
-			strcmp(*newval, "-infinity") == 0 ||
-			strcmp(*newval, "now") == 0 ||
+		if (strcmp(*newval, "now") == 0 ||
 			strcmp(*newval, "today") == 0 ||
 			strcmp(*newval, "tomorrow") == 0 ||
 			strcmp(*newval, "yesterday") == 0)
@@ -11593,32 +11592,38 @@ check_recovery_target_time(char **newval, void **extra, GucSource source)
 			return false;
 		}
 
-		PG_TRY();
-		{
-			time = DatumGetTimestampTz(DirectFunctionCall3(timestamptz_in,
-														   CStringGetDatum(*newval),
-														   ObjectIdGetDatum(InvalidOid),
-														   Int32GetDatum(-1)));
-		}
-		PG_CATCH();
-		{
-			ErrorData  *edata;
-
-			/* Save error info */
-			MemoryContextSwitchTo(oldcontext);
-			edata = CopyErrorData();
-			FlushErrorState();
+		/*
+		 * parse timestamp value (see also timestamptz_in())
+		 */
+		{
+			char	   *str = *newval;
+			fsec_t		fsec;
+			struct pg_tm tt,
+					   *tm = &tt;
+			int			tz;
+			int			dtype;
+			int			nf;
+			int			dterr;
+			char	   *field[MAXDATEFIELDS];
+			int			ftype[MAXDATEFIELDS];
+			char		workbuf[MAXDATELEN + MAXDATEFIELDS];
+			TimestampTz timestamp;
+
+			dterr = ParseDateTime(str, workbuf, sizeof(workbuf),
+								  field, ftype, MAXDATEFIELDS, &nf);
+			if (dterr == 0)
+				dterr = DecodeDateTime(field, ftype, nf, &dtype, tm, &fsec, &tz);
+			if (dterr != 0)
+				return false;
+			if (dtype !=  DTK_DATE)
+				return false;
 
-			/* Pass the error message */
-			GUC_check_errdetail("%s", edata->message);
-			FreeErrorData(edata);
+			if (tm2timestamp(tm, fsec, &tz, &timestamp) != 0)
+			{
+				GUC_check_errdetail("timestamp out of range: \"%s\"", str);
 				return false;
 			}
-		PG_END_TRY();
-
-		myextra = (TimestampTz *) guc_malloc(ERROR, sizeof(TimestampTz));
-		*myextra = time;
-		*extra = (void *) myextra;
+		}
 	}
 	return true;
 }
@@ -11631,10 +11636,7 @@ assign_recovery_target_time(const char *newval, void *extra)
 		error_multiple_recovery_targets();
 
 	if (newval && strcmp(newval, "") != 0)
-	{
 		recoveryTarget = RECOVERY_TARGET_TIME;
-		recoveryTargetTime = *((TimestampTz *) extra);
-	}
 	else
 		recoveryTarget = RECOVERY_TARGET_UNSET;
 }
@@ -11675,33 +11677,11 @@ check_recovery_target_lsn(char **newval, void **extra, GucSource source)
 	{
 		XLogRecPtr	lsn;
 		XLogRecPtr *myextra;
-		MemoryContext oldcontext = CurrentMemoryContext;
-
-		/*
-		 * Convert the LSN string given by the user to XLogRecPtr form.
-		 */
-		PG_TRY();
-		{
-			lsn = DatumGetLSN(DirectFunctionCall3(pg_lsn_in,
-												  CStringGetDatum(*newval),
-												  ObjectIdGetDatum(InvalidOid),
-												  Int32GetDatum(-1)));
-		}
-		PG_CATCH();
-		{
-			ErrorData  *edata;
+		bool		have_error = false;
 
-			/* Save error info */
-			MemoryContextSwitchTo(oldcontext);
-			edata = CopyErrorData();
-			FlushErrorState();
-
-			/* Pass the error message */
-			GUC_check_errdetail("%s", edata->message);
-			FreeErrorData(edata);
+		lsn = pg_lsn_in_internal(*newval, &have_error);
+		if (have_error)
 			return false;
-		}
-		PG_END_TRY();
 
 		myextra = (XLogRecPtr *) guc_malloc(ERROR, sizeof(XLogRecPtr));
 		*myextra = lsn;

src/include/access/xlog.h

@@ -132,7 +132,7 @@ extern char *PrimarySlotName;
 
 /* indirectly set via GUC system */
 extern TransactionId recoveryTargetXid;
-extern TimestampTz recoveryTargetTime;
+extern char *recovery_target_time_string;
 extern const char *recoveryTargetName;
 extern XLogRecPtr recoveryTargetLSN;
 extern RecoveryTargetType recoveryTarget;

src/include/utils/pg_lsn.h

@@ -24,4 +24,6 @@
 #define PG_GETARG_LSN(n)	 DatumGetLSN(PG_GETARG_DATUM(n))
 #define PG_RETURN_LSN(x)	 return LSNGetDatum(x)
 
+extern XLogRecPtr pg_lsn_in_internal(const char *str, bool *have_error);
+
 #endif							/* PG_LSN_H */