MDEV-32026 lowercase_table2.test failures in 11.3

Also fixes MDEV-32025 Crashes in MDL_key::mdl_key_init with lower-case-table-names=2

Change overview:
- In changes made in MDEV-31948, MDEV-31982 the code path
  which originaly worked only in case of lower-case-table-names==1
  also started to work in case of lower-case-table-names==2 in a mistake.

  Restoring the original check_db_name() compatible behavior
  (but without re-using check_db_name() itself).
- MDEV-31978 erroneously added a wrong DBUG_ASSERT. Removing.

Details:

- In mysql_change_db() the database name should be lower-cased only
  in case of lower_case_table_names==1. It should not be lower-cased
  for lower_case_table_names==2. The problem was caused by MDEV-31948.
  The new code version restored the pre-MDEV-31948 behavior, which
  used check_db_name() behavior.

- Passing lower_case_table_names==1 instead of just lower_case_table_names
  to the "casedn" parameter to DBNameBuffer constructor in sql_parse.cc
  The database name should not be lower-cased for lower_case_table_names==2.
  This restores pre-MDEV-31982 behavioir which used check_db_name() here.

- Adding a new data type Lex_ident_db_normalized, it stores database
  names which are both checked and normalized to lower case
  in case lower_case_table_names==1 and lower_case_table_names==2.

- Changing the data type for the "db" parameter to Lex_ident_db_normalized in
  lock_schema_name(), lock_db_routines(), find_db_tables_and_rm_known_files().

  This is to avoid incorrectly passing a non-normalized name in the future.

- Restoring the database name normalization in mysql_create_db_internal()
  and mysql_rm_db_internal() before calling lock_schema_name().
  The problem was caused MDEV-31982.

- Adding database name normalization in mysql_alter_db_internal()
  and mysql_upgrade_db(). This fixes MDEV-32026.

- Removing a wrong assert in Create_sp_func::create_with_db() was incorrect:

    DBUG_ASSERT(Lex_ident_fs(*db).ok_for_lower_case_names());

  The database name comes to here checked, but not normalized
  to lower case with lower-case-table-names=2.
  The assert was erroneously added by MDEV-31978.

- Recording lowercase_tables2.results and lowercase_tables4.results
  according to
    MDEV-29446 Change SHOW CREATE TABLE to display default collations
  These tests are skipped on buildbot on all platforms, so this change
  was forgotten in the patch for MDEV-29446.

mysql-test/main/lowercase_table2.result

@@ -14,7 +14,7 @@ SHOW CREATE TABLE T1;
 Table	Create Table
 T1	CREATE TABLE `T1` (
   `a` int(11) DEFAULT NULL
-) ENGINE=MyISAM DEFAULT CHARSET=latin1
+) ENGINE=MyISAM DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
 RENAME TABLE T1 TO T2;
 SHOW TABLES LIKE "T2";
 Tables_in_test (T2)
@@ -70,7 +70,7 @@ SHOW CREATE TABLE T1;
 Table	Create Table
 T1	CREATE TABLE `T1` (
   `a` int(11) DEFAULT NULL
-) ENGINE=InnoDB DEFAULT CHARSET=latin1
+) ENGINE=InnoDB DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
 RENAME TABLE T1 TO T2;
 SHOW TABLES LIKE "T2";
 Tables_in_test (T2)
@@ -319,18 +319,63 @@ Database (mysql_t%)
 mysql_TEST
 show create database mysql_test;
 Database	Create Database
-mysql_test	CREATE DATABASE `mysql_test` /*!40100 DEFAULT CHARACTER SET latin1 */
+mysql_test	CREATE DATABASE `mysql_test` /*!40100 DEFAULT CHARACTER SET latin1 COLLATE latin1_swedish_ci */
 show create database mysql_TEST;
 Database	Create Database
-mysql_TEST	CREATE DATABASE `mysql_TEST` /*!40100 DEFAULT CHARACTER SET latin1 */
+mysql_TEST	CREATE DATABASE `mysql_TEST` /*!40100 DEFAULT CHARACTER SET latin1 COLLATE latin1_swedish_ci */
 show create table mysql_TEST.T1;
 Table	Create Table
 T1	CREATE TABLE `T1` (
   `a` int(11) DEFAULT NULL
-) ENGINE=MyISAM DEFAULT CHARSET=latin1
+) ENGINE=MyISAM DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
 show create table mysql_test.t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
   `a` int(11) DEFAULT NULL
-) ENGINE=MyISAM DEFAULT CHARSET=latin1
+) ENGINE=MyISAM DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
 drop database mysql_TEST;
+#
+# MDEV-32026 lowercase_table2.test failures in 11.3
+#
+CREATE DATABASE Db1;
+SHOW CREATE DATABASE Db1;
+Database	Create Database
+Db1	CREATE DATABASE `Db1` /*!40100 DEFAULT CHARACTER SET latin1 COLLATE latin1_swedish_ci */
+USE Db1;
+SELECT DATABASE();
+DATABASE()
+Db1
+DROP DATABASE Db1;
+CREATE DATABASE Db1;
+CREATE FUNCTION Db1.f1() RETURNS INT RETURN 10;
+CREATE FUNCTION db1.f2() RETURNS INT RETURN 10;
+SELECT db, name FROM mysql.proc WHERE name LIKE '^f[12]';
+db	name
+SELECT Db1.f1();
+Db1.f1()
+10
+SELECT db1.f2();
+db1.f2()
+10
+DROP DATABASE Db1;
+#
+# MDEV-32025 Crashes in MDL_key::mdl_key_init with lower-case-table-names=2
+#
+CREATE DATABASE `#mysql50#D+b1`;
+ALTER DATABASE `#mysql50#D+b1` UPGRADE DATA DIRECTORY NAME;
+SHOW CREATE DATABASE `D+b1`;
+Database	Create Database
+D+b1	CREATE DATABASE `D+b1` /*!40100 DEFAULT CHARACTER SET latin1 COLLATE latin1_swedish_ci */
+SHOW CREATE DATABASE `d+b1`;
+Database	Create Database
+d+b1	CREATE DATABASE `d+b1` /*!40100 DEFAULT CHARACTER SET latin1 COLLATE latin1_swedish_ci */
+DROP DATABASE `D+b1`;
+CREATE DATABASE Db1;
+ALTER DATABASE Db1 DEFAULT CHARACTER SET utf8;
+SHOW CREATE DATABASE Db1;
+Database	Create Database
+Db1	CREATE DATABASE `Db1` /*!40100 DEFAULT CHARACTER SET utf8mb3 COLLATE utf8mb3_general_ci */
+SHOW CREATE DATABASE db1;
+Database	Create Database
+db1	CREATE DATABASE `db1` /*!40100 DEFAULT CHARACTER SET utf8mb3 COLLATE utf8mb3_general_ci */
+DROP DATABASE Db1;

mysql-test/main/lowercase_table2.test

@@ -288,3 +288,38 @@ show create database mysql_TEST;
 show create table mysql_TEST.T1;
 show create table mysql_test.t1;
 drop database mysql_TEST;
+
+--echo #
+--echo # MDEV-32026 lowercase_table2.test failures in 11.3
+--echo #
+
+CREATE DATABASE Db1;
+SHOW CREATE DATABASE Db1;
+USE Db1;
+SELECT DATABASE();
+DROP DATABASE Db1;
+
+CREATE DATABASE Db1;
+CREATE FUNCTION Db1.f1() RETURNS INT RETURN 10;
+CREATE FUNCTION db1.f2() RETURNS INT RETURN 10;
+SELECT db, name FROM mysql.proc WHERE name LIKE '^f[12]';
+SELECT Db1.f1();
+SELECT db1.f2();
+DROP DATABASE Db1;
+
+
+--echo #
+--echo # MDEV-32025 Crashes in MDL_key::mdl_key_init with lower-case-table-names=2
+--echo #
+
+CREATE DATABASE `#mysql50#D+b1`;
+ALTER DATABASE `#mysql50#D+b1` UPGRADE DATA DIRECTORY NAME;
+SHOW CREATE DATABASE `D+b1`;
+SHOW CREATE DATABASE `d+b1`;
+DROP DATABASE `D+b1`;
+
+CREATE DATABASE Db1;
+ALTER DATABASE Db1 DEFAULT CHARACTER SET utf8;
+SHOW CREATE DATABASE Db1;
+SHOW CREATE DATABASE db1;
+DROP DATABASE Db1;

mysql-test/main/lowercase_table4.result

@@ -30,7 +30,7 @@ Create Table	CREATE TABLE `Table2` (
   PRIMARY KEY (`c1`),
   KEY `fk1` (`c2`),
   CONSTRAINT `fk1` FOREIGN KEY (`c2`) REFERENCES `Table1` (`c1`)
-) ENGINE=InnoDB DEFAULT CHARSET=latin1
+) ENGINE=InnoDB DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
 SELECT * FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS WHERE CONSTRAINT_SCHEMA='test';
 CONSTRAINT_CATALOG	def
 CONSTRAINT_SCHEMA	test
@@ -75,21 +75,21 @@ Create Table	CREATE TABLE `Product_Order` (
   KEY `Customer_Id` (`Customer_Id`),
   CONSTRAINT `product_order_ibfk_1` FOREIGN KEY (`Product_Category`, `Product_Id`) REFERENCES `Product` (`Category`, `Id`) ON UPDATE CASCADE,
   CONSTRAINT `product_order_ibfk_2` FOREIGN KEY (`Customer_Id`) REFERENCES `Customer` (`Id`)
-) ENGINE=InnoDB DEFAULT CHARSET=latin1
+) ENGINE=InnoDB DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
 SHOW CREATE TABLE Product;
 Table	Product
 Create Table	CREATE TABLE `Product` (
   `Category` int(11) NOT NULL,
   `Id` int(11) NOT NULL,
   `Price` decimal(10,0) DEFAULT NULL,
   PRIMARY KEY (`Category`,`Id`)
-) ENGINE=InnoDB DEFAULT CHARSET=latin1
+) ENGINE=InnoDB DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
 SHOW CREATE TABLE Customer;
 Table	Customer
 Create Table	CREATE TABLE `Customer` (
   `Id` int(11) NOT NULL,
   PRIMARY KEY (`Id`)
-) ENGINE=InnoDB DEFAULT CHARSET=latin1
+) ENGINE=InnoDB DEFAULT CHARSET=latin1 COLLATE=latin1_swedish_ci
 SELECT * FROM INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS WHERE CONSTRAINT_SCHEMA='test';
 CONSTRAINT_CATALOG	def
 CONSTRAINT_SCHEMA	test

sql/item_create.cc

@@ -2768,7 +2768,6 @@ Create_sp_func::create_with_db(THD *thd,
   sp_name *qname;
   const Sp_handler *sph= &sp_handler_function;
   Database_qualified_name pkgname(&null_clex_str, &null_clex_str);
-  DBUG_ASSERT(Lex_ident_fs(*db).ok_for_lower_case_names());
 
   if (unlikely(has_named_parameters(item_list)))
   {

sql/lex_ident.h

@@ -48,9 +48,10 @@ class Lex_ident_fs: public LEX_CSTRING
 
 
 /**
-  A normalized database name identifier.
-  - Converted to lower case if lower_case_table_names say so
-  - Checked to be a valid database name
+  A valid database name identifier,
+  checked with check_db_name().
+  It's not known if it was lower-cased or is
+  in the user typed way.
 */
 class Lex_ident_db: public Lex_ident_fs
 {
@@ -61,12 +62,32 @@ class Lex_ident_db: public Lex_ident_fs
   Lex_ident_db(const char *str, size_t length)
    :Lex_ident_fs(str, length)
   {
-    DBUG_SLOW_ASSERT(ok_for_lower_case_names());
     DBUG_SLOW_ASSERT(!check_db_name());
   }
 };
 
 
+/**
+  A normalized database name:
+  - checked with check_db_name()
+  - lower-cased if lower_case_table_names>0
+*/
+class Lex_ident_db_normalized: public Lex_ident_db
+{
+public:
+  Lex_ident_db_normalized(const char *str, size_t length)
+   :Lex_ident_db(str, length)
+  {
+    DBUG_SLOW_ASSERT(ok_for_lower_case_names());
+  }
+  explicit Lex_ident_db_normalized(const LEX_CSTRING &str)
+   :Lex_ident_db(str.str, str.length)
+  {
+    DBUG_SLOW_ASSERT(ok_for_lower_case_names());
+  }
+};
+
+
 template<size_t buff_sz>
 class IdentBuffer: public CharBuffer<buff_sz>
 {

sql/lock.cc

@@ -881,7 +881,7 @@ MYSQL_LOCK *get_lock_data(THD *thd, TABLE **table_ptr, uint count, uint flags)
                  or this connection was killed.
 */
 
-bool lock_schema_name(THD *thd, const char *db)
+bool lock_schema_name(THD *thd, const Lex_ident_db_normalized &db)
 {
   MDL_request_list mdl_requests;
   MDL_request global_request;
@@ -898,7 +898,7 @@ bool lock_schema_name(THD *thd, const char *db)
     return TRUE;
   MDL_REQUEST_INIT(&global_request, MDL_key::BACKUP, "", "", MDL_BACKUP_DDL,
                    MDL_STATEMENT);
-  MDL_REQUEST_INIT(&mdl_request, MDL_key::SCHEMA, db, "", MDL_EXCLUSIVE,
+  MDL_REQUEST_INIT(&mdl_request, MDL_key::SCHEMA, db.str, "", MDL_EXCLUSIVE,
                    MDL_TRANSACTION);
 
   mdl_requests.push_front(&mdl_request);

sql/lock.h

@@ -36,7 +36,7 @@ int mysql_lock_remove(THD *thd, MYSQL_LOCK *locked,TABLE *table);
 bool mysql_lock_abort_for_thread(THD *thd, TABLE *table);
 MYSQL_LOCK *mysql_lock_merge(MYSQL_LOCK *a, MYSQL_LOCK *b, THD *thd= NULL);
 /* Lock based on name */
-bool lock_schema_name(THD *thd, const char *db);
+bool lock_schema_name(THD *thd, const Lex_ident_db_normalized &db);
 /* Lock based on stored routine name */
 bool lock_object_name(THD *thd, MDL_key::enum_mdl_namespace mdl_type,
                       const LEX_CSTRING &db, const LEX_CSTRING &name);

sql/rpl_rli.cc

@@ -1685,7 +1685,7 @@ scan_all_gtid_slave_pos_table(THD *thd, int (*cb)(THD *, LEX_CSTRING *, void *),
   MY_DIR *dirp;
 
   thd->reset_for_next_command();
-  if (lock_schema_name(thd, MYSQL_SCHEMA_NAME.str))
+  if (lock_schema_name(thd, Lex_ident_db_normalized(MYSQL_SCHEMA_NAME)))
     return 1;
 
   build_table_filename(path, sizeof(path) - 1, MYSQL_SCHEMA_NAME.str, "", "", 0);

sql/sp.cc

@@ -1795,7 +1795,7 @@ class Lock_db_routines_error_handler : public Internal_error_handler
          cases.
  */
 
-bool lock_db_routines(THD *thd, const LEX_CSTRING &db)
+bool lock_db_routines(THD *thd, const Lex_ident_db_normalized &db)
 {
   TABLE *table;
   uint key_len;

sql/sp.h

@@ -594,7 +594,7 @@ sp_drop_db_routines(THD *thd, const LEX_CSTRING &db);
    @retval  false  Success
    @retval  true   Failure
  */
-bool lock_db_routines(THD *thd, const LEX_CSTRING &db);
+bool lock_db_routines(THD *thd, const Lex_ident_db_normalized &db);
 
 /**
   Structure that represents element in the set of stored routines

sql/sql_db.cc

@@ -55,7 +55,8 @@ const char *del_exts[]= {".BAK", ".opt", NullS};
 static TYPELIB deletable_extensions=
 {array_elements(del_exts)-1,"del_exts", del_exts, NULL};
 
-static bool find_db_tables_and_rm_known_files(THD *, MY_DIR *, const char *,
+static bool find_db_tables_and_rm_known_files(THD *, MY_DIR *,
+                                              const Lex_ident_db_normalized &db,
                                               const char *, TABLE_LIST **);
 
 long mysql_rm_arc_files(THD *thd, MY_DIR *dirp, const char *org_path);
@@ -744,7 +745,10 @@ mysql_create_db_internal(THD *thd, const Lex_ident_db &db,
     DBUG_RETURN(-1);
   }
 
-  if (lock_schema_name(thd, db.str))
+  const DBNameBuffer dbnorm_buffer(db, lower_case_table_names);
+  Lex_ident_db_normalized dbnorm(dbnorm_buffer.to_lex_cstring());
+
+  if (lock_schema_name(thd, dbnorm))
     DBUG_RETURN(-1);
 
   /* Check directory */
@@ -880,7 +884,10 @@ mysql_alter_db_internal(THD *thd, const Lex_ident_db &db,
   int error= 0;
   DBUG_ENTER("mysql_alter_db");
 
-  if (lock_schema_name(thd, db.str))
+  const DBNameBuffer dbnorm_buffer(db, lower_case_table_names);
+  Lex_ident_db_normalized dbnorm(dbnorm_buffer.to_lex_cstring());
+
+  if (lock_schema_name(thd, dbnorm))
     DBUG_RETURN(TRUE);
 
   /* 
@@ -1046,9 +1053,11 @@ mysql_rm_db_internal(THD *thd, const Lex_ident_db &db, bool if_exists,
   Drop_table_error_handler err_handler;
   DBUG_ENTER("mysql_rm_db");
 
+  const DBNameBuffer dbnorm_buffer(db, lower_case_table_names);
+  Lex_ident_db_normalized dbnorm(dbnorm_buffer.to_lex_cstring());
   bzero(&ddl_log_state, sizeof(ddl_log_state));
 
-  if (lock_schema_name(thd, db.str))
+  if (lock_schema_name(thd, dbnorm))
     DBUG_RETURN(true);
 
   path_length= build_table_filename(path, sizeof(path) - 1, db.str, "", "", 0);
@@ -1071,7 +1080,7 @@ mysql_rm_db_internal(THD *thd, const Lex_ident_db &db, bool if_exists,
     }
   }
 
-  if (find_db_tables_and_rm_known_files(thd, dirp, db.str, path, &tables))
+  if (find_db_tables_and_rm_known_files(thd, dirp, dbnorm, path, &tables))
     goto exit;
 
   /*
@@ -1089,7 +1098,7 @@ mysql_rm_db_internal(THD *thd, const Lex_ident_db &db, bool if_exists,
   /* Lock all tables and stored routines about to be dropped. */
   if (lock_table_names(thd, tables, NULL, thd->variables.lock_wait_timeout,
                        0) ||
-      lock_db_routines(thd, db))
+      lock_db_routines(thd, dbnorm))
     goto exit;
 
   if (!rm_mysql_schema)
@@ -1115,15 +1124,15 @@ mysql_rm_db_internal(THD *thd, const Lex_ident_db &db, bool if_exists,
   thd->push_internal_handler(&err_handler);
   if (!thd->killed &&
       !(tables &&
-        mysql_rm_table_no_locks(thd, tables, &db, &ddl_log_state, true, false,
+        mysql_rm_table_no_locks(thd, tables, &dbnorm, &ddl_log_state, true, false,
                                 true, false, true, false)))
   {
     debug_crash_here("ddl_log_drop_after_drop_tables");
 
     LEX_CSTRING cpath{ path, path_length};
-    ddl_log_drop_db(&ddl_log_state, &db, &cpath);
+    ddl_log_drop_db(&ddl_log_state, &dbnorm, &cpath);
 
-    drop_database_objects(thd, &cpath, &db, rm_mysql_schema);
+    drop_database_objects(thd, &cpath, &dbnorm, rm_mysql_schema);
 
     /*
       Now remove the db.opt file.
@@ -1303,12 +1312,11 @@ bool mysql_rm_db(THD *thd, const Lex_ident_db &db, bool if_exists)
 
 
 static bool find_db_tables_and_rm_known_files(THD *thd, MY_DIR *dirp,
-                                              const char *dbname,
+                                              const Lex_ident_db_normalized &db,
                                               const char *path,
                                               TABLE_LIST **tables)
 {
   char filePath[FN_REFLEN];
-  LEX_CSTRING db= { dbname, strlen(dbname) };
   TABLE_LIST *tot_list=0, **tot_list_next_local, **tot_list_next_global;
   DBUG_ENTER("find_db_tables_and_rm_known_files");
   DBUG_PRINT("enter",("path: %s", path));
@@ -1732,7 +1740,7 @@ uint mysql_change_db(THD *thd, const LEX_CSTRING *new_db_name,
     goto done;
   }
 
-  new_db_file_name= lower_case_table_names ?
+  new_db_file_name= lower_case_table_names == 1 ?
                     new_db_buff.copy_casedn(&my_charset_utf8mb3_general_ci,
                                             *new_db_name).to_lex_cstring() :
                     *new_db_name;
@@ -1917,8 +1925,11 @@ bool mysql_upgrade_db(THD *thd, const Lex_ident_db &old_db)
   new_db= Lex_ident_db(old_db.str + MYSQL50_TABLE_NAME_PREFIX_LENGTH,
                        old_db.length - MYSQL50_TABLE_NAME_PREFIX_LENGTH);
 
+  const DBNameBuffer dbnorm_buffer_old(old_db, lower_case_table_names);
+  Lex_ident_db_normalized old_dbnorm(dbnorm_buffer_old.to_lex_cstring());
+
   /* Lock the old name, the new name will be locked by mysql_create_db().*/
-  if (lock_schema_name(thd, old_db.str))
+  if (lock_schema_name(thd, old_dbnorm))
     DBUG_RETURN(1);
 
   /*