saffron.rel
Class SaffronQueryExpander

java.lang.Object
  |
  +--openjava.ptree.util.ParseTreeVisitor
        |
        +--openjava.ptree.util.EvaluationShuttle
              |
              +--openjava.ptree.util.ScopeHandler
                    |
                    +--openjava.ptree.util.QueryExpander
                          |
                          +--saffron.rel.SaffronQueryExpander

public class SaffronQueryExpander

extends QueryExpander

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

Since:

22 September, 2001

Version:

$Id: //open/saffron/src/main/saffron/rel/SaffronQueryExpander.java#10 $

Author:

jhyde

Field Summary

private Type

rootRowType

Fields inherited from class openjava.ptree.util.ScopeHandler

Fields inherited from class openjava.ptree.util.EvaluationShuttle

Constructor Summary

SaffronQueryExpander(Environment env)

Method Summary

Rel	convertExpToRel(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.
(package private) Rel	convertExpToRel(Expression exp, boolean eager, QueryInfo queryInfo, OJClass desiredRowType) Convert an expression to a relation, if it is relational, otherwise return null.
private Expression	convertRelToExp(Rel 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.
Type	getRootRowType()

Methods inherited from class openjava.ptree.util.QueryExpander

evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown, evaluateDown

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, 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

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 Type rootRowType

Constructor Detail

SaffronQueryExpander

public SaffronQueryExpander(Environment env)

Method Detail

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

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

getRootRowType

public Type getRootRowType()

Returns:

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

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

convertExpToRel

public Rel convertExpToRel(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

convertExpToRel

Rel convertExpToRel(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

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();
 }

expandExists

private Expression expandExists(Expression exp)

convertRelToExp

private Expression convertRelToExp(Rel rel)