001 /*
002 // $Id: //open/mondrian/src/main/mondrian/olap/fun/CacheFunDef.java#9 $
003 // This software is subject to the terms of the Common Public License
004 // Agreement, available at the following URL:
005 // http://www.opensource.org/licenses/cpl.html.
006 // Copyright (C) 2005-2007 Julian Hyde and others
007 // All Rights Reserved.
008 // You must accept the terms of that agreement to use this software.
009 */
010 package mondrian.olap.fun;
011
012 import mondrian.olap.*;
013 import mondrian.olap.type.Type;
014 import mondrian.olap.type.SetType;
015 import mondrian.calc.*;
016 import mondrian.calc.impl.GenericCalc;
017 import mondrian.mdx.ResolvedFunCall;
018
019 import java.io.PrintWriter;
020
021 /**
022 * Definition of the <code>Cache</code> system function, which is smart enough
023 * to evaluate its argument only once.
024 *
025 * @author jhyde
026 * @since 2005/8/14
027 * @version $Id: //open/mondrian/src/main/mondrian/olap/fun/CacheFunDef.java#9 $
028 */
029 public class CacheFunDef extends FunDefBase {
030 static final String NAME = "Cache";
031 private static final String SIGNATURE = "Cache(<<Exp>>)";
032 private static final String DESCRIPTION = "Evaluates and returns its sole argument, applying statement-level caching";
033 private static final Syntax SYNTAX = Syntax.Function;
034 static final CacheFunResolver Resolver = new CacheFunResolver();
035
036 CacheFunDef(
037 String name,
038 String signature,
039 String description,
040 Syntax syntax,
041 int category,
042 Type type) {
043 super(name, signature, description, syntax,
044 category, new int[] {category});
045 Util.discard(type);
046 }
047
048 public void unparse(Exp[] args, PrintWriter pw) {
049 args[0].unparse(pw);
050 }
051
052 public Calc compileCall(ResolvedFunCall call, ExpCompiler compiler) {
053 final Exp exp = call.getArg(0);
054 final ExpCacheDescriptor cacheDescriptor =
055 new ExpCacheDescriptor(exp, compiler);
056 return new GenericCalc(call) {
057 public Object evaluate(Evaluator evaluator) {
058 return evaluator.getCachedResult(cacheDescriptor);
059 }
060
061 public Calc[] getCalcs() {
062 return new Calc[] {cacheDescriptor.getCalc()};
063 }
064
065 public ResultStyle getResultStyle() {
066 // cached lists are immutable
067 if (type instanceof SetType) {
068 return ResultStyle.LIST;
069 } else {
070 return ResultStyle.VALUE;
071 }
072 }
073 };
074 }
075
076 public static class CacheFunResolver extends ResolverBase {
077 CacheFunResolver() {
078 super(NAME, SIGNATURE, DESCRIPTION, SYNTAX);
079 }
080
081 public FunDef resolve(
082 Exp[] args, Validator validator, int[] conversionCount) {
083 if (args.length != 1) {
084 return null;
085 }
086 final Exp exp = args[0];
087 final int category = exp.getCategory();
088 final Type type = exp.getType();
089 return new CacheFunDef(NAME, SIGNATURE, DESCRIPTION, SYNTAX,
090 category, type);
091 }
092
093 public boolean requiresExpression(int k) {
094 return false;
095 }
096 }
097 }
098
099 // End CacheFunDef.java