MDEV-12666: CURRENT_ROLE() and DATABASE() does not work in a view

The problem lies in how CURRENT_ROLE is defined. The
Item_func_current_role inherits from Item_func_sysconst, which defines
a safe_charset_converter to be a const_charset_converter.

During view creation, if there is no role previously set, the current_role()
function returns NULL.

This is captured on item instantiation and the
const_charset_converter call subsequently returns an Item_null.
In turn, the function is replaced with Item_null and the view is
then created with an Item_null instead of Item_func_current_role.

Without this patch, the first SHOW CREATE VIEW from the testcase would
have a where clause of WHERE role_name = NULL, while the second SHOW
CREATE VIEW would show a correctly created view.

The same applies for the DATABASE function, as it can change as well.

There is an additional problem with CURRENT_ROLE() when used in a
prepared statement. During prepared statement creation we used to set
the string_value of the function to the current role as well as the
null_value flag. During execution, if CURRENT_ROLE was not null, the
null_value flag was never set to not-null during fix_fields.

Item_func_current_user however can never be NULL so it did not show this
problem in a view before. At the same time, the CURRENT_USER() can not
be changed between prepared statement execution and creation so the
implementation where the value is stored during fix_fields is
sufficient.

Note also that DATABASE() function behaves differently during prepared
statements. See bug 25843 for details or commit
7e0ad09

mysql-test/r/view.result

@@ -5944,6 +5944,68 @@ use_case_id	InitialDeadline
 10	2015-12-18
 drop view v1;
 drop table t1;
+#
+# MDEV-12666: CURRENT_ROLE() and DATABASE() does not work in a view
+#
+# DATABASE() fails only when the initial view creation features a NULL
+# default database.
+#
+# CREATE, USE and DROP database so that we have no "default" database.
+#
+CREATE DATABASE temporary;
+USE temporary;
+DROP DATABASE temporary;
+SELECT DATABASE();
+DATABASE()
+NULL
+CREATE VIEW test.v_no_db AS SELECT DATABASE() = 'temporary_two';
+SHOW CREATE VIEW test.v_no_db;
+View	Create View	character_set_client	collation_connection
+v_no_db	CREATE ALGORITHM=UNDEFINED DEFINER=`root`@`localhost` SQL SECURITY DEFINER VIEW `test`.`v_no_db` AS select (database() = 'temporary_two') AS `DATABASE() = 'temporary_two'`	latin1	latin1_swedish_ci
+PREPARE prepared_no_database FROM "SELECT DATABASE() = 'temporary_two'";
+#
+# All statements should return NULL
+#
+EXECUTE prepared_no_database;
+DATABASE() = 'temporary_two'
+NULL
+SELECT DATABASE() = 'temporary_two';
+DATABASE() = 'temporary_two'
+NULL
+SELECT * FROM test.v_no_db;
+DATABASE() = 'temporary_two'
+NULL
+CREATE DATABASE temporary_two;
+USE temporary_two;
+CREATE VIEW test.v_with_db AS SELECT DATABASE() = 'temporary_two';
+PREPARE prepared_with_database FROM "SELECT DATABASE() = 'temporary_two'";
+#
+# All statements should return 1;
+#
+SELECT DATABASE() = 'temporary_two';
+DATABASE() = 'temporary_two'
+1
+SELECT * FROM test.v_no_db;
+DATABASE() = 'temporary_two'
+1
+SELECT * FROM test.v_with_db;
+DATABASE() = 'temporary_two'
+1
+EXECUTE prepared_with_database;
+DATABASE() = 'temporary_two'
+1
+#
+# Prepared statements maintain default database to be the same
+# during on creation so this should return NULL still.
+# See MySQL bug #25843
+#
+EXECUTE prepared_no_database;
+DATABASE() = 'temporary_two'
+NULL
+DROP DATABASE temporary_two;
+DROP VIEW test.v_no_db;
+DROP VIEW test.v_with_db;
+USE test;
 # -----------------------------------------------------------------
 # -- End of 10.0 tests.
 # -----------------------------------------------------------------

mysql-test/suite/roles/current_role_view-12666.result

@@ -0,0 +1,103 @@
+CREATE USER has_role@'localhost';
+GRANT ALL PRIVILEGES ON *.* TO has_role@'localhost';
+CREATE ROLE test_role;
+GRANT test_role TO has_role@'localhost';
+CREATE USER no_role@'localhost';
+GRANT ALL PRIVILEGES ON *.* TO no_role@'localhost';
+CREATE TABLE view_role_test (
+id int primary key,
+role_name varchar(50)
+);
+INSERT INTO view_role_test VALUES (1, 'test_role');
+#
+# Use the same logic for stored procedures.
+#
+PREPARE prepared_no_current_role FROM "SELECT * from view_role_test WHERE role_name = CURRENT_ROLE()";
+#
+# Creating a view with no CURRENT_ROLE() set and one with CURRENT_ROLE()
+# set. Both should produce the same SHOW CREATE VIEW output.
+#
+CREATE
+DEFINER = no_role@localhost
+SQL SECURITY INVOKER
+VIEW v_view_role_test_no_current_role
+AS
+SELECT * FROM view_role_test WHERE role_name = CURRENT_ROLE();
+SHOW CREATE VIEW v_view_role_test_no_current_role;
+View	Create View	character_set_client	collation_connection
+v_view_role_test_no_current_role	CREATE ALGORITHM=UNDEFINED DEFINER=`no_role`@`localhost` SQL SECURITY INVOKER VIEW `v_view_role_test_no_current_role` AS select `view_role_test`.`id` AS `id`,`view_role_test`.`role_name` AS `role_name` from `view_role_test` where (`view_role_test`.`role_name` = current_role())	latin1	latin1_swedish_ci
+#
+# No values should be returned
+#
+EXECUTE prepared_no_current_role;
+id	role_name
+SELECT * FROM view_role_test WHERE role_name = CURRENT_ROLE();
+id	role_name
+SELECT * FROM v_view_role_test_no_current_role;
+id	role_name
+#
+# Now let's set the role. Create identical views as before. See if
+# their behaviour is different. It should not be.
+#
+SET ROLE test_role;
+SELECT CURRENT_USER();
+CURRENT_USER()
+root@localhost
+SELECT CURRENT_ROLE();
+CURRENT_ROLE()
+test_role
+#
+# Create the VIEW and prepared Statement with a CURRENT_ROLE() set.
+#
+CREATE
+DEFINER = no_role@localhost
+SQL SECURITY INVOKER
+VIEW v_view_role_test_with_current_role
+AS
+SELECT * FROM view_role_test WHERE role_name = CURRENT_ROLE();
+PREPARE prepared_with_current_role FROM "SELECT * from view_role_test WHERE role_name = CURRENT_ROLE()";
+SHOW CREATE VIEW v_view_role_test_with_current_role;
+View	Create View	character_set_client	collation_connection
+v_view_role_test_with_current_role	CREATE ALGORITHM=UNDEFINED DEFINER=`no_role`@`localhost` SQL SECURITY INVOKER VIEW `v_view_role_test_with_current_role` AS select `view_role_test`.`id` AS `id`,`view_role_test`.`role_name` AS `role_name` from `view_role_test` where (`view_role_test`.`role_name` = current_role())	latin1	latin1_swedish_ci
+#
+# Values should be returned for all select statements as we do have
+# a CURRENT_ROLE() active;
+#
+EXECUTE prepared_no_current_role;
+id	role_name
+1	test_role
+EXECUTE prepared_with_current_role;
+id	role_name
+1	test_role
+SELECT * FROM view_role_test WHERE role_name = CURRENT_ROLE();
+id	role_name
+1	test_role
+SELECT * FROM v_view_role_test_no_current_role;
+id	role_name
+1	test_role
+SELECT * FROM v_view_role_test_with_current_role;
+id	role_name
+1	test_role
+SET ROLE NONE;
+#
+# No values should be returned for all select statements as we do not have
+# a CURRENT_ROLE() active;
+#
+EXECUTE prepared_no_current_role;
+id	role_name
+EXECUTE prepared_with_current_role;
+id	role_name
+SELECT * FROM view_role_test WHERE role_name = CURRENT_ROLE();
+id	role_name
+SELECT * FROM v_view_role_test_no_current_role;
+id	role_name
+SELECT * FROM v_view_role_test_with_current_role;
+id	role_name
+DROP USER has_role@'localhost';
+DROP USER no_role@'localhost';
+DROP ROLE test_role;
+DROP table view_role_test;
+DROP VIEW v_view_role_test_no_current_role;
+DROP VIEW v_view_role_test_with_current_role;
+DROP PREPARE prepared_no_current_role;
+DROP PREPARE prepared_with_current_role;

mysql-test/suite/roles/current_role_view-12666.test

@@ -0,0 +1,102 @@
+#
+# MDEV-12666 CURRENT_ROLE() does not work in a view
+#
+--source include/not_embedded.inc
+
+CREATE USER has_role@'localhost';
+GRANT ALL PRIVILEGES ON *.* TO has_role@'localhost';
+
+CREATE ROLE test_role;
+GRANT test_role TO has_role@'localhost';
+
+CREATE USER no_role@'localhost';
+GRANT ALL PRIVILEGES ON *.* TO no_role@'localhost';
+
+CREATE TABLE view_role_test (
+        id int primary key,
+        role_name varchar(50)
+        );
+
+INSERT INTO view_role_test VALUES (1, 'test_role');
+
+--echo #
+--echo # Use the same logic for stored procedures.
+--echo #
+PREPARE prepared_no_current_role FROM "SELECT * from view_role_test WHERE role_name = CURRENT_ROLE()";
+
+--echo #
+--echo # Creating a view with no CURRENT_ROLE() set and one with CURRENT_ROLE()
+--echo # set. Both should produce the same SHOW CREATE VIEW output.
+--echo #
+CREATE
+DEFINER = no_role@localhost
+SQL SECURITY INVOKER
+VIEW v_view_role_test_no_current_role
+AS
+SELECT * FROM view_role_test WHERE role_name = CURRENT_ROLE();
+
+SHOW CREATE VIEW v_view_role_test_no_current_role;
+
+
+--echo #
+--echo # No values should be returned
+--echo #
+EXECUTE prepared_no_current_role;
+SELECT * FROM view_role_test WHERE role_name = CURRENT_ROLE();
+SELECT * FROM v_view_role_test_no_current_role;
+
+--echo #
+--echo # Now let's set the role. Create identical views as before. See if
+--echo # their behaviour is different. It should not be.
+--echo #
+SET ROLE test_role;
+
+SELECT CURRENT_USER();
+SELECT CURRENT_ROLE();
+
+--echo #
+--echo # Create the VIEW and prepared Statement with a CURRENT_ROLE() set.
+--echo #
+CREATE
+DEFINER = no_role@localhost
+SQL SECURITY INVOKER
+VIEW v_view_role_test_with_current_role
+AS
+SELECT * FROM view_role_test WHERE role_name = CURRENT_ROLE();
+
+PREPARE prepared_with_current_role FROM "SELECT * from view_role_test WHERE role_name = CURRENT_ROLE()";
+
+SHOW CREATE VIEW v_view_role_test_with_current_role;
+
+
+--echo #
+--echo # Values should be returned for all select statements as we do have
+--echo # a CURRENT_ROLE() active;
+--echo #
+EXECUTE prepared_no_current_role;
+EXECUTE prepared_with_current_role;
+SELECT * FROM view_role_test WHERE role_name = CURRENT_ROLE();
+SELECT * FROM v_view_role_test_no_current_role;
+SELECT * FROM v_view_role_test_with_current_role;
+
+SET ROLE NONE;
+--echo #
+--echo # No values should be returned for all select statements as we do not have
+--echo # a CURRENT_ROLE() active;
+--echo #
+EXECUTE prepared_no_current_role;
+EXECUTE prepared_with_current_role;
+SELECT * FROM view_role_test WHERE role_name = CURRENT_ROLE();
+SELECT * FROM v_view_role_test_no_current_role;
+SELECT * FROM v_view_role_test_with_current_role;
+
+
+DROP USER has_role@'localhost';
+DROP USER no_role@'localhost';
+DROP ROLE test_role;
+
+DROP table view_role_test;
+DROP VIEW v_view_role_test_no_current_role;
+DROP VIEW v_view_role_test_with_current_role;
+DROP PREPARE prepared_no_current_role;
+DROP PREPARE prepared_with_current_role;

mysql-test/t/view.test

@@ -5814,6 +5814,55 @@ SELECT * FROM v1 where use_case_id = 10;
 drop view v1;
 drop table t1;
 
+--echo #
+--echo # MDEV-12666: CURRENT_ROLE() and DATABASE() does not work in a view
+--echo #
+--echo # DATABASE() fails only when the initial view creation features a NULL
+--echo # default database.
+--echo #
+--echo # CREATE, USE and DROP database so that we have no "default" database.
+--echo #
+CREATE DATABASE temporary;
+USE temporary;
+DROP DATABASE temporary;
+SELECT DATABASE();
+
+CREATE VIEW test.v_no_db AS SELECT DATABASE() = 'temporary_two';
+SHOW CREATE VIEW test.v_no_db;
+PREPARE prepared_no_database FROM "SELECT DATABASE() = 'temporary_two'";
+
+--echo #
+--echo # All statements should return NULL
+--echo #
+EXECUTE prepared_no_database;
+SELECT DATABASE() = 'temporary_two';
+SELECT * FROM test.v_no_db;
+
+CREATE DATABASE temporary_two;
+USE temporary_two;
+CREATE VIEW test.v_with_db AS SELECT DATABASE() = 'temporary_two';
+PREPARE prepared_with_database FROM "SELECT DATABASE() = 'temporary_two'";
+
+--echo #
+--echo # All statements should return 1;
+--echo #
+SELECT DATABASE() = 'temporary_two';
+SELECT * FROM test.v_no_db;
+SELECT * FROM test.v_with_db;
+EXECUTE prepared_with_database;
+
+--echo #
+--echo # Prepared statements maintain default database to be the same
+--echo # during on creation so this should return NULL still.
+--echo # See MySQL bug #25843
+--echo #
+EXECUTE prepared_no_database;
+
+DROP DATABASE temporary_two;
+DROP VIEW test.v_no_db;
+DROP VIEW test.v_with_db;
+USE test;
+
 --echo # -----------------------------------------------------------------
 --echo # -- End of 10.0 tests.
 --echo # -----------------------------------------------------------------

sql/item.cc

@@ -1263,6 +1263,7 @@ Item *Item::const_charset_converter(CHARSET_INFO *tocs,
   DBUG_ASSERT(fixed);
   StringBuffer<64>tmp;
   String *s= val_str(&tmp);
+
   if (!s)
     return new Item_null((char *) func_name, tocs);
 

sql/item.h

@@ -1476,7 +1476,7 @@ class Item {
   virtual Item *expr_cache_insert_transformer(uchar *thd_arg) { return this; }
   virtual bool expr_cache_is_needed(THD *) { return FALSE; }
   virtual Item *safe_charset_converter(CHARSET_INFO *tocs);
-  bool needs_charset_converter(uint32 length, CHARSET_INFO *tocs)
+  bool needs_charset_converter(uint32 length, CHARSET_INFO *tocs) const
   {
     /*
       This will return "true" if conversion happens: