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#ifndef Query_block_VISITOR_INCLUDED
#define Query_block_VISITOR_INCLUDED
/* Copyright (c) 2015, 2025, Oracle and/or its affiliates.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License, version 2.0,
as published by the Free Software Foundation.
This program is designed to work with certain software (including
but not limited to OpenSSL) that is licensed under separate terms,
as designated in a particular file or component or in included license
documentation. The authors of MySQL hereby grant you an additional
permission to link the program and your derivative works with the
separately licensed software that they have either included with
the program or referenced in the documentation.
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, version 2.0, 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 02110-1301 USA */
/**
@file select_lex_visitor.h
Visitor interface for parse trees.
*/
class Query_expression;
class Query_block;
class Item;
/**
Abstract base class for traversing the Query_block tree. In order to use it,
a client defines a subclass, overriding the member functions that visit the
objects of interest. If a function returns true, traversal is aborted.
*/
class Select_lex_visitor {
public:
virtual bool visits_in_prefix_order() const { return true; }
bool visit(Query_expression *unit) { return visit_union(unit); }
bool visit(Query_block *query_block) {
return visit_query_block(query_block);
}
/// Called for all nodes of all expression trees (i.e. Item trees).
bool visit(Item *item) { return visit_item(item); }
virtual ~Select_lex_visitor() = 0;
protected:
virtual bool visit_union(Query_expression *) { return false; }
virtual bool visit_query_block(Query_block *) { return false; }
virtual bool visit_item(Item *) { return false; }
};
#endif // Query_block_VISITOR_INCLUDED
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