QueryPlanNode


1   /**
2    * com.mckoi.database.QueryPlanNode  06 Nov 2001
3    *
4    * Mckoi SQL Database ( http://www.mckoi.com/database )
5    * Copyright (C) 2000, 2001, 2002  Diehl and Associates, Inc.
6    *
7    * This program is free software; you can redistribute it and/or
8    * modify it under the terms of the GNU General Public License
9    * Version 2 as published by the Free Software Foundation.
10   *
11   * This program is distributed in the hope that it will be useful,
12   * but WITHOUT ANY WARRANTY; without even the implied warranty of
13   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
14   * GNU General Public License Version 2 for more details.
15   *
16   * You should have received a copy of the GNU General Public License
17   * Version 2 along with this program; if not, write to the Free Software
18   * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
19   *
20   * Change Log:
21   * 
22   * 
23   */
24  
25  package com.mckoi.database;
26  
27  import java.util.ArrayList  ;
28  
29  /**
30   * A node element of a query plan tree.  A plan of a query is represented as
31   * a tree structure of such nodes.  The design allows for plan nodes to be
32   * easily reorganised for the construction of better plans.
33   *
34   * @author Tobias Downer
35   */
36  
37  public interface QueryPlanNode extends java.io.Serializable  , Cloneable   {
38  
39    /**
40     * Evaluates the node and returns the result as a Table.  The
41     * VariableResolver resolves any outer variables
42     */
43    Table evaluate(QueryContext context);
44  
45    /**
46     * Discovers a list of TableName that represent the sources that this query
47     * requires to complete itself.  For example, if this is a query plan of
48     * two joined table, the fully resolved names of both tables are returned.
49     * <p>
50     * The resultant list will not contain the same table name more than once.
51     * The resultant list contains TableName objects.
52     * <p>
53     * NOTE, if a table is aliased, the unaliased name is returned.
54     */
55    ArrayList   discoverTableNames(ArrayList   list);
56  
57    /**
58     * Discovers all the correlated variables in the plan (and plan children)
59     * that reference a particular layer.  For example, if we wanted to find
60     * all the CorrelatedVariable objects that reference the current layer, we
61     * would typically call 'discoverCorrelatedVariables(0, new ArrayList())'
62     */
63    ArrayList   discoverCorrelatedVariables(int level, ArrayList   list);
64  
65    /**
66     * Deep clones this query plan.
67     */
68    Object   clone() throws CloneNotSupportedException  ;
69  
70    /**
71     * Writes a textural representation of the node to the StringBuffer at the
72     * given indent level.
73     */
74    void debugString(int indent, StringBuffer   buf);
75  
76  }
77
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