ProjectMergeRule (Apache Calcite API)

java.lang.Object
- org.apache.calcite.plan.RelOptRule
- - org.apache.calcite.rel.rules.ProjectMergeRule

```
public class ProjectMergeRule
extends RelOptRule
```
ProjectMergeRule merges a Project into another Project, provided the projects aren't projecting identical sets of input references.

Field Summary

Fields
Modifier and Type Field Description

private boolean force
Whether to always merge projects.

static ProjectMergeRule INSTANCE
- Fields inherited from class org.apache.calcite.plan.RelOptRule
  description, operands, relBuilderFactory

Constructor Summary

Constructors
Constructor	Description
`ProjectMergeRule(boolean force, RelFactories.ProjectFactory projectFactory)`	Deprecated.
`ProjectMergeRule(boolean force, RelBuilderFactory relBuilderFactory)`	Creates a ProjectMergeRule, specifying whether to always merge projects.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type Method Description

void onMatch(RelOptRuleCall call)
Receives notification about a rule match.
- Methods inherited from class org.apache.calcite.plan.RelOptRule
  any, convert, convert, convertList, convertOperand, convertOperand, equals, equals, getOperand, getOperands, getOutConvention, getOutTrait, hashCode, matches, none, operand, operand, operand, operand, operand, operandJ, operandJ, some, toString, unordered
- Methods inherited from class java.lang.Object
  clone, finalize, getClass, notify, notifyAll, wait, wait, wait

- Field Detail
  - INSTANCE
```
public static final ProjectMergeRule INSTANCE
```
  - force
```
private final boolean force
```
    Whether to always merge projects.
- Constructor Detail
  - ProjectMergeRule
```
public ProjectMergeRule(boolean force,
                        RelBuilderFactory relBuilderFactory)
```
    Creates a ProjectMergeRule, specifying whether to always merge projects.
    
    Parameters:
    
    force - Whether to always merge projects
  - ProjectMergeRule
```
@Deprecated
public ProjectMergeRule(boolean force,
                        RelFactories.ProjectFactory projectFactory)
```
    Deprecated.
- Method Detail
  - onMatch
```
public void onMatch(RelOptRuleCall call)
```
    Description copied from class: RelOptRule
    
    Receives notification about a rule match. At the time that this method is called, call.rels holds the set of relational expressions which match the operands to the rule; call.rels[0] is the root expression.
    Typically a rule would check that the nodes are valid matches, creates a new expression, then calls back RelOptRuleCall.transformTo(org.apache.calcite.rel.RelNode, java.util.Map<org.apache.calcite.rel.RelNode, org.apache.calcite.rel.RelNode>) to register the expression.
    
    Specified by:
    
    onMatch in class RelOptRule
    
    Parameters:
    
    call - Rule call
    
    See Also:
    
    RelOptRule.matches(RelOptRuleCall)