net.sf.saffron.opt
Class RelImplementor

java.lang.Object
  |
  +--net.sf.saffron.opt.RelImplementor

public class RelImplementor

extends Object

RelImplementor deals with the nastiness of converting a tree of relational expressions into an implementation, generally an openjava parse tree.

The bind(net.sf.saffron.rel.SaffronRel, openjava.ptree.Variable) method allows relational expressions to register which Java variable holds their row. They can bind 'lazily', so that the variable is only declared and initialized if it is actually used in another expression.

TODO jvs 29-Sept-2003: This class is way too Java-dependent to remain in opt. Most of it needs to be factored out to oj, leaving an interface or abstract base class behind. I intentionally left one macker failure unsuppressed so that this will get some attention.

Nested Class Summary

private static interface	RelImplementor.Bind
private static class	RelImplementor.EagerBind
private static class	RelImplementor.Frame
private static class	RelImplementor.LazyBind
private class	RelImplementor.RelBind Binds a relational expression to whatever another relational expression is currently bound to.
private static class	RelImplementor.Translator Translator is a shuttle used to implement translate(net.sf.saffron.rel.SaffronRel, net.sf.saffron.rex.RexNode).
static interface	RelImplementor.VariableInitializerThunk A VariableInitializerThunk yields a VariableInitializer.

Field Summary

(package private) Statement	exitStatement
(package private) HashMap	mapCorrel2Frame Map String --> Frame such that frame.rel.correlVariable == correlName
(package private) HashMap	mapCorrelNameToVariable
(package private) HashMap	mapRel2Frame
(package private) RexBuilder	rexBuilder
(package private) Stack	stmtListStack

Constructor Summary

RelImplementor(RexBuilder rexBuilder)

Method Summary

private void	bind(SaffronRel rel, RelImplementor.Bind bind) Record the fact that instances of rel are available via bind (which may be eager or lazy).
void	bind(SaffronRel rel, SaffronRel previous) Shares a variable between relations.
Variable	bind(SaffronRel rel, StatementList statementList, VariableInitializer initializer) Declare a variable, and bind it lazily, so it only gets initialized if it is actually used.
void	bind(SaffronRel rel, Variable variable) Record the fact that instances of rel are available in variable.
void	bindCorrel(String correlName, Variable variable) Binds a correlating variable.
private void	bindDeferred(RelImplementor.Frame frame, SaffronRel rel)
private int	computeFieldOffset(SaffronRel rel, int ordinal) Returns the index of the first field in rel which comes from its ordinalth input.
private SaffronRel	findInputRel(SaffronRel rel, int offset)
private SaffronRel	findInputRel(SaffronRel rel, int offset, int[] offsets)
(package private) Variable	findInputVariable(SaffronRel rel) Returns the variable which, in the generated program, will hold the current row of a given relational expression.
SaffronRel	findRel(SaffronRel rel, RexNode expression)
void	generateParentBody(SaffronRel rel, StatementList stmtList) Implements the body of the current expression's parent.
Statement	getExitStatement()
StatementList	getStatementList()
Object	implementChild(SaffronRel parent, int ordinal, SaffronRel child) Implements a relational expression according to a calling convention.
Object	implementRoot(SaffronRel rel) Starts an iteration, by calling SaffronRel.implement(net.sf.saffron.opt.RelImplementor, int) on the root element.
Expression	makeReference(String correlName, SaffronRel rel) Creates an expression which references correlating variable correlName from the context of rel.
Variable	newVariable()
void	popStatementList(StatementList stmtList)
void	pushStatementList(StatementList stmtList)
void	setExitStatement(Statement stmt)
Expression	translate(SaffronRel rel, RexNode exp) Converts an expression in internal form (the input relation is referenced using the variable $input0) to generated form (the input relation is referenced using the bindings in this RelImplementor).
Expression	translateInput(SaffronRel rel, int ordinal) Creates an expression which references the ordinalth input.
Expression	translateInputField(SaffronRel rel, int ordinal, int fieldOrdinal) Creates an expression which references the fieldOrdinalth field of the ordinalth input.
ExpressionList	translateList(SaffronRel rel, RexNode[] exps) Converts an array of expressions in internal into a list of expressions in generated form.

Methods inherited from class java.lang.Object

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

Field Detail

mapCorrel2Frame

final HashMap mapCorrel2Frame

Map String --> Frame such that frame.rel.correlVariable == correlName

mapCorrelNameToVariable

final HashMap mapCorrelNameToVariable

mapRel2Frame

final HashMap mapRel2Frame

stmtListStack

final Stack stmtListStack

exitStatement

Statement exitStatement

rexBuilder

RexBuilder rexBuilder

Constructor Detail

RelImplementor

public RelImplementor(RexBuilder rexBuilder)

Method Detail

setExitStatement

public void setExitStatement(Statement stmt)

getExitStatement

public Statement getExitStatement()

getStatementList

public StatementList getStatementList()

bind

public void bind(SaffronRel rel,
                 Variable variable)

Record the fact that instances of rel are available in variable.

bind

public Variable bind(SaffronRel rel,
                     StatementList statementList,
                     VariableInitializer initializer)

Declare a variable, and bind it lazily, so it only gets initialized if it is actually used.

Returns:

the Variable so declared

bind

public void bind(SaffronRel rel,
                 SaffronRel previous)

Shares a variable between relations. previous already has a variable, and calling this method indicates that rel's output will appear in this variable too.

bindCorrel

public void bindCorrel(String correlName,
                       Variable variable)

Binds a correlating variable. References to correlating variables such as $cor2 will be replaced with java variables such as $Oj14.

findRel

public SaffronRel findRel(SaffronRel rel,
                          RexNode expression)

generateParentBody

public void generateParentBody(SaffronRel rel,
                               StatementList stmtList)

Implements the body of the current expression's parent. If variable is not null, bind the current expression to variable. For example, a nested loops join would generate

 for (int i = 0; i < emps.length; i++) {
   Emp emp = emps[i];
   for (int j = 0; j < depts.length; j++) {
     Dept dept = depts[j];
     if (emp.deptno == dept.deptno) {
       <>
     }
   }
 }
 

which corresponds to

 [emp:iter
   [dept:iter
     [join:body(emp,dept)
       [parent:body]
     ]
   ]
 ]
 

Parameters:

rel - child relation

stmtList - block that child was generating its code into

bindDeferred

private void bindDeferred(RelImplementor.Frame frame,
                          SaffronRel rel)

implementChild

public Object implementChild(SaffronRel parent,
                             int ordinal,
                             SaffronRel child)

Implements a relational expression according to a calling convention.

implementRoot

public Object implementRoot(SaffronRel rel)

Starts an iteration, by calling SaffronRel.implement(net.sf.saffron.opt.RelImplementor, int) on the root element.

makeReference

public Expression makeReference(String correlName,
                                SaffronRel rel)

Creates an expression which references correlating variable correlName from the context of rel. For example, if correlName is set by the 1st child of rel's 2nd child, then this method returns $input2.$input1.

newVariable

public Variable newVariable()

popStatementList

public void popStatementList(StatementList stmtList)

pushStatementList

public void pushStatementList(StatementList stmtList)

translate

public Expression translate(SaffronRel rel,
                            RexNode exp)

Converts an expression in internal form (the input relation is referenced using the variable $input0) to generated form (the input relation is referenced using the bindings in this RelImplementor). Compare this method with QueryInfo.convertExpToInternal(openjava.ptree.Expression), which converts from source form to internal form.

Parameters:

exp - the expression to translate (it is cloned, not modified)

rel - the relational expression which is the context for exp

translateList

public ExpressionList translateList(SaffronRel rel,
                                    RexNode[] exps)

Converts an array of expressions in internal into a list of expressions in generated form.

See Also:

translate(SaffronRel,RexNode)

translateInput

public Expression translateInput(SaffronRel rel,
                                 int ordinal)

Creates an expression which references the ordinal^th input.

computeFieldOffset

private int computeFieldOffset(SaffronRel rel,
                               int ordinal)

Returns the index of the first field in rel which comes from its ordinalth input.

For example, if rel joins T0(A,B,C) to T1(D,E), then countFields(0,rel) yields 0, and countFields(1,rel) yields 3.

translateInputField

public Expression translateInputField(SaffronRel rel,
                                      int ordinal,
                                      int fieldOrdinal)

Creates an expression which references the fieldOrdinal^th field of the ordinal^th input.

(We can potentially optimize the generation process, so we can access field values without actually instantiating the row.)

bind

private void bind(SaffronRel rel,
                  RelImplementor.Bind bind)

Record the fact that instances of rel are available via bind (which may be eager or lazy).

findInputRel

private SaffronRel findInputRel(SaffronRel rel,
                                int offset)

findInputRel

private SaffronRel findInputRel(SaffronRel rel,
                                int offset,
                                int[] offsets)

findInputVariable

Variable findInputVariable(SaffronRel rel)

Returns the variable which, in the generated program, will hold the current row of a given relational expression. This method is only applicable if the relational expression is the current one or an input; if it is an ancestor, there is no current value, and this method returns null.