# MetaTableRelation.java

    /*
    ** Module   : MetaTableRelation.java
    ** Abstract : Representation of a database relation between two metaschema tables
    **
    ** Copyright (c) 2013-2017, Golden Code Development Corporation.
    **
    ** -#- -I- --Date-- --------------------------------Description----------------------------------
    ** 001 ECF 20131215 Created initial version.
    */
    /*
    ** This program is free software: you can redistribute it and/or modify
    ** it under the terms of the GNU Affero General Public License as
    ** published by the Free Software Foundation, either version 3 of the
    ** License, or (at your option) any later version.
    **
    ** 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 Affero General Public License for more details.
    **
    ** You may find a copy of the GNU Affero GPL version 3 at the following
    ** location: https://www.gnu.org/licenses/agpl-3.0.en.html
    **
    ** Additional terms under GNU Affero GPL version 3 section 7:
    **
    **   Under Section 7 of the GNU Affero GPL version 3, the following additional
    **   terms apply to the works covered under the License.  These additional terms
    **   are non-permissive additional terms allowed under Section 7 of the GNU
    **   Affero GPL version 3 and may not be removed by you.
    **
    **   0. Attribution Requirement.
    **
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    **     work or Appropriate Legal Notices displayed by works containing the covered
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    **
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    **
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    */

    package com.goldencode.p2j.schema;

    import java.util.*;
    import com.goldencode.ast.*;

    /**
     * A representation of a <em>primary-foreign key relation</em> between two Progress metaschema
     * tables. Relations between metaschema tables differ from relations between regular Progress
     * tables, in that traditional foreign keys are used.
     */
    class MetaTableRelation
    extends TableRelation
    {
       /**
        * Constructor.
        *
        * @param   left
        *          Left table. May not be <code>null</code>.
        * @param   right
        *          Right table. May not be <code>null</code>.
        * @param   key
        *          Set of names of the fields which comprise the join. In this case, the set will
        *          only contain a single value -- the name of the foreign key field.
        */
       public MetaTableRelation(Aast left, Aast right, Set<String> key)
       {
          super(left, right, right, key, MANY_TO_ONE);
       }

       /**
        * Get the database schema name for the given table AST.
        * <p>
        * This version override's the parent class to return the standard database qualifier for
        * metaschema tables:  <code>_meta</code>.
        *
        * @param   table
        *          Target table AST.
        *
        * @return  Name of the table's database schema.
        */
       @Override
       protected String getDatabase(Aast table)
       {
          return "_meta";
       }

       /**
        * Indicates whether this relation uses a real foreign key join (vs. a Progress-style, natural
        * join).
        *
        * @return  <code>true</code>.
        */
       @Override
       protected boolean hasRealForeignKey()
       {
          return true;
       }
    }