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/*
* Constraint.java
*
* Created on March 3, 2000
*
*/
package com.sun.jdo.spi.persistence.support.sqlstore.sql.constraint;
import com.sun.jdo.spi.persistence.support.sqlstore.ActionDesc;
import com.sun.jdo.spi.persistence.support.sqlstore.model.LocalFieldDesc;
import com.sun.jdo.spi.persistence.support.sqlstore.sql.generator.QueryPlan;
import java.util.ArrayList;
import java.util.List;
/**
*/
public class Constraint extends Object {
/**
* The stack that contains all constraints beside join constraints.
* Join constraints are handled by a separate stack.
*/
public List stack;
/**
* The stack that contains outer join constraints. All the elements of this stack
* are instance of {@link ConstraintJoin}. Outer join constraints can be appended
* to the query w/o changing the semantic.
*/
private List outerJoinStack;
/**
* The stack that contains order by constraints. We would like to
* separate Order By constraints from the main stack, but they must
* be merged with all other constraints to preserve the order of
* constraints from different stacks. E.g.
* "order by firstname ascending, department.name ascending"
*
* @see #isEmptyOrOrderBy
*/
// private List orderByStack;
/**
* Adds a field to the constraint stack.
*
* AddField creates a ConstraintField node for the indicated
* named field, optionally including an operation descriptor
* and adds it to the constraint stack.
*
* @param name
* The name parameter specifies the name of the field to be
* added to the constrant stack.
*
* @param desc
* The desc parameter specifies an operation descriptor describing
* what is to be done with the field named by the name parameter.
*/
public void addField(String name, ActionDesc desc) {
stack.add(new ConstraintFieldName(name, desc));
}
/**
* Adds a field to the constraint stack.
*
* AddField creates a ConstraintFieldDesc node for the indicated
* field descriptor and adds it to the constraint stack.
*
* @param desc
* The Desc parameter is the field descriptor to be
* added to the constrant stack.
*/
public void addField(LocalFieldDesc desc) {
stack.add(new ConstraintFieldDesc(desc));
}
/**
* Adds a field to the constraint stack.
*
* AddField creates a ConstraintFieldDesc node for the indicated
* field descriptor and adds it to the constraint stack.
*
* @param desc
* The Desc parameter is the field descriptor to be
* added to the constrant stack.
*
* @param plan
* The query plan to which this desc belongs
*/
public void addField(LocalFieldDesc desc, QueryPlan plan) {
stack.add(new ConstraintFieldDesc(desc, plan));
}
public void addField(ConstraintFieldDesc constraintDesc) {
stack.add(constraintDesc);
}
public void addForeignField(String name, ActionDesc desc) {
stack.add(new ConstraintForeignFieldName(name, desc));
}
/**
* Adds an operation to the constraint stack.
*
* AddOperation creates a ConstraintOperation node whose operation is
* operation and adds it to the constraint stack.
*
* @param operation
* The operation parameter specifies the operation to be added to
* the constrant stack.
*/
public void addOperation(int operation) {
stack.add(new ConstraintOperation(operation));
}
/**
* Adds a data value to the constraint stack. Creates a ConstraintValue
* node whose value is value and adds it to the constraint stack.
* @param value The value to be added to the constrant stack.
* @param localField The localField to which this value is bound.
* Please note that localField can be null for values involved in
* complex expressions in a query.
*/
public void addValue(Object value, LocalFieldDesc localField) {
stack.add(new ConstraintValue(value, localField));
}
/**
* Adds a subquery constraint on the stack.
* @param field The field on which subquery constraint is added.
* @param rd Retrieve descriptor corresponding to the subquery.
*/
public void addConstraintFieldSubQuery(String field, ActionDesc rd) {
stack.add(new ConstraintFieldNameSubQuery(field, rd));
}
/**
* Adds the index of a parameter to the stack.
* @param index the parameter index.
* @param enumType the type for this parameter.
* @param localField the localField to which this parameter is bound.
*/
public void addParamIndex(int index, int enumType,
LocalFieldDesc localField) {
stack.add(new ConstraintParamIndex(index,enumType, localField));
}
/**
* Adds specified join constraint. Equi joins are added to the
* constraint stack, outer joins are added to a separate stack, the
* <code>outerJoinStack</code>.
*
* @param join The join constraint to be added.
*/
public void addJoinConstraint(ConstraintJoin join) {
if (join.operation == ActionDesc.OP_EQUIJOIN) {
stack.add(join);
} else {
// The current logic is written with the assumption that a join
// that is not an equi join is always a left join
assert join.operation == ActionDesc.OP_LEFTJOIN;
outerJoinStack.add(join);
}
}
/**
* Merges the stack with the specified foreign constraint stack.
* @param foreignConstraint The constraint to be merged.
* @param joinOp Join operation as defined in {@link ActionDesc}.
* @return True, if we need to add an additional "AND" constraint.
*/
public boolean mergeConstraint(Constraint foreignConstraint, int joinOp) {
stack.addAll(foreignConstraint.stack);
outerJoinStack.addAll(foreignConstraint.outerJoinStack);
return addAnd(foreignConstraint, joinOp);
}
/**
* Decides, if we need to add an additional "AND" constraint to
* the stack <em>after</em> merging the foreign stack.
*
* @param foreignConstraint Constraint to be joined.
* @param joinOp Join operator.
* @return True, if we need to add an additional "AND" constraint.
*/
private boolean addAnd(Constraint foreignConstraint, int joinOp) {
// Add "AND" constraints for equi-joins only.
// * Don't add an "AND" constraint for outer joins. Outer joins
// don't contribute to the "where"-clause in ANSI-case. In the
// non-ANSI case, outer joins can be appended to the query w/o
// changing the semantic.
// * Don't add an "AND" constaint for non-relationship joins,
// as no additional join constraint is added in this case.
return (joinOp == ActionDesc.OP_EQUIJOIN)
// Never add an "AND" constraint, if the foreign stack is
// empty or contains "ORDER_BY" constraints only, as "ORDER_BY"
// constraints don't contribute to the "where"-clause.
&& !foreignConstraint.isEmptyOrOrderBy();
}
/**
* Checks, if the constraint stack is empty or contains "ORDER_BY"
* constraints only. "ORDER_BY" constraints are recognized as an
* ORDER_BY operation followed by a field name constraint, and
* an optional Value constraint giving the position of the Order
* By constraint.
* <em>NOTE:</em> The value constraints giving the position for
* the order by constraints are currently not generated by the
* query compiler. Order by constraints stay in the correct order
* because of two reasons
* <ul>
* <li>the way, constraints are processed by the query compiler</li>
* <li>the way constraint stacks are joined in
* {@link com.sun.jdo.spi.persistence.support.sqlstore.sql.generator.SelectQueryPlan#processForeignConstraints}.
* </li>
* </ul>
*/
private boolean isEmptyOrOrderBy() {
boolean rc = true;
// Abort the loop at first possible opportunity.
for (int i = stack.size() - 1; i >= 0 && rc; ) {
ConstraintNode node = (ConstraintNode) stack.get(i);
if ((node instanceof ConstraintOperation)
&& ((((ConstraintOperation) node).operation == ActionDesc.OP_ORDERBY) ||
(((ConstraintOperation) node).operation == ActionDesc.OP_ORDERBY_DESC))) {
if ((i > 0) && (
stack.get(i - 1) instanceof ConstraintFieldName ||
stack.get(i - 1) instanceof ConstraintFieldDesc)) {
// Order By constraint.
i--;
if ((i > 0) && (stack.get(i - 1) instanceof ConstraintValue)) {
// Optional Value constraint.
i--;
}
} else {
rc = false;
}
} else {
rc = false;
}
// Check the next constraint if any.
i--;
}
return rc;
}
/**
* Gets the where clause constraints for this Constraint
* @return The where clause constraints for this Constraint
*/
public List getConstraints() {
return stack;
}
/**
* Gets the outer join constraints for this Constraint
* @return The outer join constraints for this Constraint
*/
public List getOuterJoinConstraints() {
return outerJoinStack;
}
public Constraint() {
stack = new ArrayList();
outerJoinStack = new ArrayList();
}
}
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