private void bindDeferred(JavaFrame frame, final RelNode rel) {
final StatementList statementList = getStatementList();
if (frame.bind == null) {
// this relational expression has not bound itself, so we presume
// that we can call its implementSelf() method
if (!(rel instanceof JavaSelfRel)) {
throw Util.newInternal(
"In order to bind-deferred, a "
+ "relational expression must implement JavaSelfRel: "
+ rel);
}
final JavaSelfRel selfRel = (JavaSelfRel) rel;
LazyBind lazyBind =
new LazyBind(
newVariable(),
statementList,
getTypeFactory(),
rel.getRowType(),
new VariableInitializerThunk() {
public VariableInitializer getInitializer() {
return selfRel.implementSelf(JavaRelImplementor.this);
}
});
bind(rel, lazyBind);
} else if ((frame.bind instanceof LazyBind)
&& (((LazyBind) frame.bind).statementList != statementList)) {
// Frame is already bound, but to a variable declared in a different
// scope. Re-bind it.
final LazyBind lazyBind = (LazyBind) frame.bind;
lazyBind.statementList = statementList;
lazyBind.bound = false;
}
}
/**
* Declares a variable, and binds it lazily, so it only gets initialized if it is actually used.
*
* @return the Variable so declared
*/
public Variable bind(
RelNode rel, StatementList statementList, final VariableInitializer initializer) {
VariableInitializerThunk thunk =
new VariableInitializerThunk() {
public VariableInitializer getInitializer() {
return initializer;
}
};
Variable variable = newVariable();
LazyBind bind =
new LazyBind(variable, statementList, getTypeFactory(), rel.getRowType(), thunk);
bind(rel, bind);
return bind.getVariable();
}