net.sf.saffron.oj.xlat
Class OJQueryExpander

java.lang.Object
  |
  +--openjava.ptree.util.ParseTreeVisitor
        |
        +--openjava.ptree.util.EvaluationShuttle
              |
              +--openjava.ptree.util.ScopeHandler
                    |
                    +--openjava.ptree.util.QueryExpander
                          |
                          +--net.sf.saffron.oj.xlat.OJQueryExpander

public class OJQueryExpander

extends QueryExpander

OJQueryExpander passes over a parse tree, and converts relational expressions into regular Java constructs.

Since:

22 September, 2001

Version:

$Id: //open/saffron/src/net/sf/saffron/oj/xlat/OJQueryExpander.java#9 $

Author:

jhyde

Field Summary

private SaffronConnection	connection
private SaffronType	rootRowType

Fields inherited from class openjava.ptree.util.ScopeHandler

Fields inherited from class openjava.ptree.util.EvaluationShuttle

Constructor Summary

OJQueryExpander(Environment env, SaffronConnection connection)

Method Summary

SaffronRel	convertExpToOptimizedRel(Expression exp, boolean eager, CallingConvention convention, Variable variable, StatementList body) Converts an expression to a relational expression according to a particular calling convention, and optimizes it.
SaffronRel	convertExpToUnoptimizedRel(Expression exp, boolean eager, QueryInfo queryInfo, OJClass desiredRowType) Convert an expression to a relation, if it is relational, otherwise return null.
private SaffronRel	convertInsertToRel(InsertExpression insertExp, QueryInfo queryInfo)
private Expression	convertRelToExp(SaffronRel rel)
private Expression	expandExists(Expression exp)
private Expression	expandExpression_(Expression exp, OJClass desiredRowType, CallingConvention convention) Converts an Expression into a java expression which returns an array.
protected Expression	expandExpression(Expression exp) Converts an Expression into a java expression which returns an array.
protected Statement	expandForIn(Variable variable, Expression exp, StatementList body) Converts an Expression of the form for (variable in exp) {body} into a regular java Statement.
private Expression	expandIn(Expression seekExp, Expression queryExp) Translates an expression involving in.
SaffronType	getRootRowType()
private static boolean	isRelational(OJClass clazz) Returns whether an expression clazz can be read as a relation.

Methods inherited from class openjava.ptree.util.QueryExpander

evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, isRelational

Methods inherited from class openjava.ptree.util.ScopeHandler

evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, pop, push, pushClosedEnvironment

Methods inherited from class openjava.ptree.util.EvaluationShuttle

evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, evaluateUp, getEnvironment, setEnvironment, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit, visit

Methods inherited from class openjava.ptree.util.ParseTreeVisitor

visit, visit, visit, visit, visit, visit, visit, visit, visit

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

rootRowType

private SaffronType rootRowType

connection

private final SaffronConnection connection

Constructor Detail

OJQueryExpander

public OJQueryExpander(Environment env,
                       SaffronConnection connection)

Method Detail

getRootRowType

public SaffronType getRootRowType()

Returns:

the row Type for the root relational expression encountered during last expansion, or null if none

convertExpToOptimizedRel

public SaffronRel convertExpToOptimizedRel(Expression exp,
                                           boolean eager,
                                           CallingConvention convention,
                                           Variable variable,
                                           StatementList body)

Converts an expression to a relational expression according to a particular calling convention, and optimizes it.

Parameters:

exp - expression to convert

eager - whether to try to convert expressions which might not be relational, for example arrays

convention - calling convention (see CallingConvention)

variable - iterator variable (for for-loop)

body - statement list to add code to

Returns:

the optimal relational expression

expandExpression

protected Expression expandExpression(Expression exp)

Description copied from class: QueryExpander

Converts an Expression into a java expression which returns an array.

Specified by:

expandExpression in class QueryExpander

expandForIn

protected Statement expandForIn(Variable variable,
                                Expression exp,
                                StatementList body)

Converts an Expression of the form for (variable in exp) {body} into a regular java Statement.

Specified by:

expandForIn in class QueryExpander

convertExpToUnoptimizedRel

public SaffronRel convertExpToUnoptimizedRel(Expression exp,
                                             boolean eager,
                                             QueryInfo queryInfo,
                                             OJClass desiredRowType)

Convert an expression to a relation, if it is relational, otherwise return null. This method only deals with relational expressions which can occur outside a query; joins, in particular, are only dealt with inside queries.

Parameters:

exp - expression to translate

eager - whether to translate expressions which may or may not be (such as references to arrays) into relational expressions

queryInfo - context to convert expressions into results of other queries; null if this expression is not inside a query

desiredRowType - row type required; if this is null, leave the results as they are

Returns:

a relational expression, or null if the expression was not relational

convertInsertToRel

private SaffronRel convertInsertToRel(InsertExpression insertExp,
                                      QueryInfo queryInfo)

convertRelToExp

private Expression convertRelToExp(SaffronRel rel)

expandExists

private Expression expandExists(Expression exp)

expandExpression_

private Expression expandExpression_(Expression exp,
                                     OJClass desiredRowType,
                                     CallingConvention convention)

Converts an Expression into a java expression which returns an array. Examples:

1. Query as expression

   Emp[] femaleEmps = (select emp from emps as emp
                        where emp.gender.equals("F"));

   becomes

   Emp[] femaleEmps = new Object() {
            public Emp[] asArray() {
                Vector v = new Vector();
                for (i in (select emp from emps as emp
                           where emp.gender.equals("F"))) {
                    v.addElement(i);
                }
                Emp[] a = new Emp[v.size()];
                v.copyInto(a);
                return a;
            }
        }.asArray();

Parameters:

desiredRowType - row type required; if this is null, leave the results as they are

convention - calling convention of the result

expandIn

private Expression expandIn(Expression seekExp,
                            Expression queryExp)

Translates an expression involving in. For example,

if ("Fred" in (select name from emps as emp)) {
     yes();
 }

becomes in within a query

if (exists (
         select where "Joe" in (select name from emps as emp))) {
     yes();
 }

isRelational

private static boolean isRelational(OJClass clazz)

Returns whether an expression clazz can be read as a relation.