Merge pull request #3461 from sysown/v2.x-3460

Closes #3460: Fix failing test 'set_character_set'

test/tap/tests/set_character_set-t.cpp

@@ -1,3 +1,35 @@
+/**
+ * @file set_character_set-t.cpp
+ * @brief This test checks the proper behavior for 'SET CHARACTER SET'.
+ * @details The test performs several 'SET' operations in sequence for testing the correct behavior
+ *   for 'SET CHARACTER SET', this are:
+ *
+ *   1. SET NAMES 'utf8'.
+ *   2. SET CHARACTER SET 'latin1'.
+ *   3. SET NAMES 'latin1'.
+ *
+ *   After each of the operations several checks are performed for the following variables:
+ *
+ *   * character_set_client
+ *   * character_set_connection
+ *   * character_set_results
+ *   * character_set_database
+ *
+ *   This checks are performed by means of the query:
+ *
+ *   ```
+ *   SELECT variable_value FROM global_variables WHERE variable_name='%s'
+ *   ```
+ *
+ *   For checking that this variables has changed or keep their values properly.
+ *
+ *   NOTE: After "SET CHARACTER SET 'latin1'" has been issued, no checks are performed for
+ *   'character_set_connection' since, due to multiplexing and ProxySQL explicitely forgetting
+ *   the value for 'character_set_connection' and 'collation_connection' (for more context
+ *   see MySQL_Variables::client_set_value),the value for it is **unknown** and depends entirely
+ *   of the backend connection selected. For more context see #3460.
+ */
+
 #include <cstdlib>
 #include <cstdio>
 #include <cstring>
@@ -16,13 +48,13 @@ int main(int argc, char** argv) {
 	if(cl.getEnv())
 		return exit_status();
 
-	plan(12);
+	plan(11);
 	diag("Testing SET CHARACTER SET");
 
 	MYSQL* mysql = mysql_init(NULL);
 	if (!mysql)
 		return exit_status();
-	
+
 	if (mysql_options(mysql, MYSQL_SET_CHARSET_NAME, "utf8")) {
 		fprintf(stderr, "File %s, line %d, Error: %s\n",
 				__FILE__, __LINE__, mysql_error(mysql));
@@ -92,11 +124,16 @@ int main(int argc, char** argv) {
 	show_variable(mysql, var_charset_database, var_value);
 	ok(var_value.compare("utf8") == 0, "Database character set is not changed. Actual %s", var_value.c_str()); // ok_6
 
-	show_variable(mysql, var_charset_connection, var_value);
-	ok(var_value.compare(db_charset_value) == 0, "Connection character set same as database charset. Actual %s", var_value.c_str()); // ok_7
+	/*
+	 * NOTE: This check was disabled because trying to check 'character_set_connection' after issuing 'SET CHARACTER SET',
+	 * when multiplexing is enabled is invalid, since the value is unknown. Check file top for more details.
+	 *
+	 * show_variable(mysql, var_charset_connection, var_value);
+	 * ok(var_value.compare(db_charset_value) == 0, "Connection character set same as database charset. Actual %s", var_value.c_str()); // ok_
+	 */
 
 	show_variable(mysql, var_charset_results, var_value);
-	ok(var_value.compare("latin1") == 0, "Results character set is changed. Actual %s", var_value.c_str()); // ok_8
+	ok(var_value.compare("latin1") == 0, "Results character set is changed. Actual %s", var_value.c_str()); // ok_7
 
 	if (mysql_query(mysql, "set names latin1")) {
 		fprintf(stderr, "SET NAMES : Error: %s\n",
@@ -105,16 +142,16 @@ int main(int argc, char** argv) {
 	}
 
 	show_variable(mysql, var_charset_client, var_value);
-	ok(var_value.compare("latin1") == 0, "Client character set is correct. Actual %s", var_value.c_str()); // ok_9
+	ok(var_value.compare("latin1") == 0, "Client character set is correct. Actual %s", var_value.c_str()); // ok_8
 
 	show_variable(mysql, var_charset_connection, var_value);
-	ok(var_value.compare("latin1") == 0, "Set names changed connection character set. Actual %s", var_value.c_str()); // ok_10
+	ok(var_value.compare("latin1") == 0, "Set names changed connection character set. Actual %s", var_value.c_str()); // ok_9
 
 	show_variable(mysql, var_charset_results, var_value);
-	ok(var_value.compare("latin1") == 0, "Results character set is correct. Actual %s", var_value.c_str()); // ok_11
+	ok(var_value.compare("latin1") == 0, "Results character set is correct. Actual %s", var_value.c_str()); // ok_10
 
 	show_variable(mysql, var_charset_database, var_value);
-	ok(var_value.compare("utf8") == 0, "Database character set is not changed by set names. Actual %s", var_value.c_str()); // ok_12
+	ok(var_value.compare("utf8") == 0, "Database character set is not changed by set names. Actual %s", var_value.c_str()); // ok_11
 
 	mysql_close(mysql);