52 lines
1.8 KiB
C++
52 lines
1.8 KiB
C++
#ifndef SELECT_LEX_VISITOR_INCLUDED
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#define SELECT_LEX_VISITOR_INCLUDED
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/* Copyright (c) 2015, Oracle and/or its affiliates. All rights reserved.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; version 2 of the License.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software Foundation,
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51 Franklin Street, Suite 500, Boston, MA 02110-1335 USA */
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/**
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@file select_lex_visitor.h
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Visitor interface for parse trees.
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*/
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typedef class st_select_lex_unit SELECT_LEX_UNIT;
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typedef class st_select_lex SELECT_LEX;
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class Item;
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/**
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Abstract base class for traversing the SELECT_LEX tree. In order to use it,
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a client defines a subclass, overriding the member functions that visit the
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objects of interest. If a function returns true, traversal is aborted.
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*/
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class Select_lex_visitor
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{
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public:
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virtual bool visits_in_prefix_order() const { return true; }
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bool visit(SELECT_LEX_UNIT *unit) { return visit_union(unit); }
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bool visit(SELECT_LEX *select_lex) { return visit_query_block(select_lex); }
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/// Called for all nodes of all expression trees (i.e. Item trees).
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bool visit(Item *item) { return visit_item(item); }
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virtual ~Select_lex_visitor() = 0;
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protected:
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virtual bool visit_union(SELECT_LEX_UNIT *) { return false; }
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virtual bool visit_query_block(SELECT_LEX *) { return false; }
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virtual bool visit_item(Item *) { return false; }
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};
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#endif // SELECT_LEX_VISITOR_INCLUDED
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