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/**
* com.mckoi.database.FunctionDef 07 Sep 2001
*
* Mckoi SQL Database ( http://www.mckoi.com/database )
* Copyright (C) 2000, 2001, 2002 Diehl and Associates, Inc.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* Version 2 as published by the Free Software Foundation.
*
* 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 for more details.
*
* You should have received a copy of the GNU General Public License
* Version 2 along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
*
* Change Log:
*
*
*/
package com.mckoi.database;
/**
* A definition of a function including its name and parameters. A FunctionDef
* can easily be transformed into a Function object via a set of
* FunctionFactory instances.
*
* NOTE: This object is NOT immutable or thread-safe. A FunctionDef should not
* be shared among different threads.
*
* @author Tobias Downer
*/
public final class FunctionDef implements java.io.Serializable, Cloneable {
static final long serialVersionUID = 3339781003247956829L;
/**
* The name of the function.
*/
private String name;
/**
* The list of parameters for the function.
*/
private Expression[] params;
/**
* A cached Function object that was generated when this FunctionDef was
* looked up. Note that the Function object is transient.
*/
private transient Function cached_function;
/**
* Constructs the FunctionDef.
*/
public FunctionDef(String name, Expression[] params) {
this.name = name;
this.params = params;
}
/**
* The name of the function. For example, 'MIN' or 'CONCAT'.
*/
public String getName() {
return name;
}
/**
* The list of parameters that are passed to the function. For example,
* a concat function may have 7 parameters ('There', ' ', 'are', ' ', 10,
* ' ', 'bottles.')
*/
public Expression[] getParameters() {
return params;
}
/**
* Returns true if this function is an aggregate, or the parameters are
* aggregates. It requires a QueryContext object to lookup the function in
* the function factory database.
*/
public boolean isAggregate(QueryContext context) {
FunctionLookup fun_lookup = context.getFunctionLookup();
boolean is_aggregate = fun_lookup.isAggregate(this);
if (is_aggregate) {
return true;
}
// Look at params
Expression[] params = getParameters();
for (int i = 0; i < params.length; ++i) {
is_aggregate = params[i].hasAggregateFunction(context);
if (is_aggregate) {
return true;
}
}
// No
return false;
}
/**
* Returns a Function object from this FunctionDef. Note that two calls to
* this method will produce the same Function object, however the same
* Function object will not be produced over multiple instances of
* FunctionDef even when they represent the same thing.
*/
public Function getFunction(QueryContext context) {
if (cached_function != null) {
return cached_function;
}
else {
FunctionLookup lookup = context.getFunctionLookup();
cached_function = lookup.generateFunction(this);
if (cached_function == null) {
throw new StatementException("Function '" + getName() +
"' doesn't exist.");
}
return cached_function;
}
}
/**
* Performs a deep clone of this object.
*/
public Object clone() throws CloneNotSupportedException {
FunctionDef v = (FunctionDef) super.clone();
// Deep clone the parameters
Expression[] exps = (Expression[]) ((Expression[]) v.params).clone();
// Clone each element of the array
for (int n = 0; n < exps.length; ++n) {
exps[n] = (Expression) exps[n].clone();
}
v.params = exps;
v.cached_function = null;
return v;
}
/**
* Human understandable string, used for the column title.
*/
public String toString() {
StringBuffer buf = new StringBuffer();
buf.append(name);
buf.append('(');
for (int i = 0; i < params.length; ++i) {
buf.append(params[i].text().toString());
if (i < params.length - 1) {
buf.append(',');
}
}
buf.append(')');
return new String(buf);
}
}