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diff --git a/sql/sql_schema.h b/sql/sql_schema.h
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+++ b/sql/sql_schema.h
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+#ifndef SQL_SCHEMA_H_INCLUDED
+#define SQL_SCHEMA_H_INCLUDED
+/*
+ Copyright (c) 2020, MariaDB Corporation.
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; version 2 of the License.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to the Free Software
+ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1335  USA */
+
+#include "mysqld.h"
+#include "lex_string.h"
+
+class Schema
+{
+  LEX_CSTRING m_name;
+public:
+  Schema(const LEX_CSTRING &name)
+   :m_name(name)
+  { }
+  virtual ~Schema() = default;
+  const LEX_CSTRING &name() const { return m_name; }
+  virtual const Type_handler *map_data_type(THD *thd, const Type_handler *src)
+                                            const
+  {
+    return src;
+  }
+
+  // Builders for native SQL function with a special syntax in sql_yacc.yy
+  virtual Item *make_item_func_replace(THD *thd,
+                                       Item *subj,
+                                       Item *find,
+                                       Item *replace) const;
+  virtual Item *make_item_func_substr(THD *thd,
+                                      const Lex_substring_spec_st &spec) const;
+
+  virtual Item *make_item_func_trim(THD *thd, const Lex_trim_st &spec) const;
+
+  /*
+    For now we have *hard-coded* compatibility schemas:
+      schema_mariadb, schema_oracle, schema_maxdb.
+    But eventually we'll turn then into real databases on disk.
+    So the code below compares names according to the filesystem
+    case sensitivity, like it is done for regular databases.
+
+    Note, this is different to information_schema, whose name
+    is always case insensitive. This is intentional!
+    The assymetry will be gone when we'll implement SQL standard
+    regular and delimited identifiers.
+  */
+  bool eq_name(const LEX_CSTRING &name) const
+  {
+    return !table_alias_charset->strnncoll(m_name.str, m_name.length,
+                                           name.str, name.length);
+  }
+  static Schema *find_by_name(const LEX_CSTRING &name);
+  static Schema *find_implied(THD *thd);
+};
+
+
+extern Schema mariadb_schema;
+
+#endif // SQL_SCHEMA_H_INCLUDED