MDEV-31982 Remove check_db_name() from prepare_db_action()

- Adding a new class Lex_ident_db, to store normalized database names:
  lower-cased if lower-case-table-name says so,
  and checked to be a valid database name using Lex_ident_fs::check_db_name()

- Reusing the new class in parameters to functions:
    prepare_db_action()
    mysql_create_db()
    mysql_alter_db()
    mysql_rm_db()
    mysql_upgrade_db()

This change removed two old-style check_db_name() calls.

Author: abarkov

sql/lex_ident.h

@@ -47,6 +47,26 @@ 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
+*/
+class Lex_ident_db: public Lex_ident_fs
+{
+public:
+  Lex_ident_db()
+   :Lex_ident_fs(NULL, 0)
+  { }
+  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 helper class to store temporary database names in a buffer.
   After constructing it's typically should be checked using
@@ -67,6 +87,13 @@ class DBNameBuffer: public CharBuffer<SAFE_NAME_LEN + MY_CS_MBMAXLEN>
   {
     copy_casedn(&my_charset_utf8mb3_general_ci, db, casedn);
   }
+  Lex_ident_db to_lex_ident_db_with_error() const
+  {
+    LEX_CSTRING tmp= to_lex_cstring();
+    if (Lex_ident_fs(tmp).check_db_name_with_error())
+      return Lex_ident_db();
+    return Lex_ident_db(tmp.str, tmp.length);
+  }
 };
 
 

sql/sql_class.cc

@@ -6078,6 +6078,26 @@ void THD::get_definer(LEX_USER *definer, bool role)
 }
 
 
+bool THD::check_slave_ignored_db_with_error(const Lex_ident_db &db) const
+{
+#ifdef HAVE_REPLICATION
+  if (slave_thread)
+  {
+    Rpl_filter *rpl_filter;
+    rpl_filter= system_thread_info.rpl_sql_info->rpl_filter;
+    if (!rpl_filter->db_ok(db.str) ||
+        !rpl_filter->db_ok_with_wild_table(db.str))
+    {
+      my_message(ER_SLAVE_IGNORED_TABLE,
+                 ER_THD(this, ER_SLAVE_IGNORED_TABLE), MYF(0));
+      return true;
+    }
+  }
+#endif
+  return false;
+}
+
+
 /**
   Mark transaction to rollback and mark error as fatal to a sub-statement.
 

sql/sql_class.h

@@ -5356,6 +5356,8 @@ class THD: public THD_count, /* this must be first */
   bool is_binlog_dump_thread();
 #endif
 
+  bool check_slave_ignored_db_with_error(const Lex_ident_db &db) const;
+
   /*
     Indicates if this thread is suspended due to awaiting an ACK from a
     replica. True if suspended, false otherwise.