BlockBuilder (Apache Calcite API)

java.lang.Object
- org.apache.calcite.linq4j.tree.BlockBuilder

```
public class BlockBuilder
extends Object
```
Builder for BlockStatement.
Has methods that help ensure that variable names are unique.

Nested Class Summary

Nested Classes
Modifier and Type	Class and Description
`private static class`	`BlockBuilder.InlineVariableVisitor` Inline Variable Visitor.
`private static class`	`BlockBuilder.Slot` Holds the number of times a declaration was used.
`private static class`	`BlockBuilder.SubstituteVariableVisitor` Substitute Variable Visitor.
`private static class`	`BlockBuilder.UseCounter` Use counter.

Field Summary

Fields
Modifier and Type	Field and Description
`(package private) Map<Expression,DeclarationStatement>`	`expressionForReuse` Contains final-fine-to-reuse-declarations.
`private static Shuttle`	`OPTIMIZE_SHUTTLE`
`private boolean`	`optimizing`
`private BlockBuilder`	`parent`
`(package private) List<Statement>`	`statements`
`(package private) Set<String>`	`variables`

Constructor Summary

Constructors
Constructor and Description
`BlockBuilder()` Creates a non-optimizing BlockBuilder.
`BlockBuilder(boolean optimizing)` Creates a BlockBuilder.
`BlockBuilder(boolean optimizing, BlockBuilder parent)` Creates a BlockBuilder.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`add(Expression expression)`
`void`	`add(Statement statement)`
`protected void`	`addExpressionForReuse(DeclarationStatement decl)`
`private Expression`	`append_(String name, Expression expression, boolean optimize)`
`BlockBuilder`	`append(Expression expression)`
`Expression`	`append(String name, BlockStatement block)` Appends a block to a list of statements and returns an expression (possibly a variable) that represents the result of the newly added block.
`Expression`	`append(String name, BlockStatement block, boolean optimize)` Appends an expression to a list of statements, optionally optimizing it to a variable if it is used more than once.
`Expression`	`append(String name, Expression expression)` Appends an expression to a list of statements, and returns an expression (possibly a variable) that represents the result of the newly added block.
`Expression`	`append(String name, Expression expression, boolean optimize)` Appends an expression to a list of statements, optionally optimizing if the expression is used more than once.
`Expression`	`appendIfNotNull(String name, Expression expression)` Appends an expression to a list of statements, if it is not null.
`void`	`clear()` Clears this BlockBuilder.
`protected Shuttle`	`createFinishingOptimizeShuttle()` Creates a final optimization shuttle.
`protected Shuttle`	`createOptimizeShuttle()` Creates a shuttle that will be used during block optimization.
`DeclarationStatement`	`getComputedExpression(Expression expr)` Returns the reference to ParameterExpression if given expression was already computed and stored to local variable
`boolean`	`hasVariable(String name)`
`private boolean`	`isCostly(DeclarationStatement decl)`
`protected boolean`	`isSafeForReuse(DeclarationStatement decl)`
`protected boolean`	`isSimpleExpression(Expression expr)` Checks if expression is simple enough to always inline at zero cost.
`String`	`newName(String suggestion)` Creates a name for a new variable, unique within this block.
`private String`	`newName(String suggestion, boolean optimize)` Creates a name for a new variable, unique within this block, controlling whether the variable can be inlined later.
`private Expression`	`normalizeDeclaration(DeclarationStatement decl)` Prepares declaration for inlining: adds cast
`private boolean`	`optimize(Shuttle optimizer, boolean performInline)` Optimizes the list of statements.
`BlockStatement`	`toBlock()` Returns a block consisting of the current list of statements.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - statements
```
final List<Statement> statements
```
  - variables
```
final Set<String> variables
```
  - expressionForReuse
```
final Map<Expression,DeclarationStatement> expressionForReuse
```
    Contains final-fine-to-reuse-declarations. An entry to this map is added when adding final declaration of a statement with optimize=true parameter.
  - optimizing
```
private final boolean optimizing
```
  - parent
```
private final BlockBuilder parent
```
  - OPTIMIZE_SHUTTLE
```
private static final Shuttle OPTIMIZE_SHUTTLE
```
- Constructor Detail
  - BlockBuilder
```
public BlockBuilder()
```
    Creates a non-optimizing BlockBuilder.
  - BlockBuilder
```
public BlockBuilder(boolean optimizing)
```
    Creates a BlockBuilder.
    
    Parameters:
    
    optimizing - Whether to eliminate common sub-expressions
  - BlockBuilder
```
public BlockBuilder(boolean optimizing,
                    BlockBuilder parent)
```
    Creates a BlockBuilder.
    
    Parameters:
    
    optimizing - Whether to eliminate common sub-expressions
- Method Detail
  - clear
```
public void clear()
```
    Clears this BlockBuilder.
  - append
```
public Expression append(String name,
                         BlockStatement block)
```
    Appends a block to a list of statements and returns an expression (possibly a variable) that represents the result of the newly added block.
  - append
```
public Expression append(String name,
                         BlockStatement block,
                         boolean optimize)
```
    Appends an expression to a list of statements, optionally optimizing it to a variable if it is used more than once.
    
    Parameters:
    
    name - Suggested variable name
    
    block - Expression
    
    optimize - Whether to try to optimize by assigning the expression to a variable. Do not do this if the expression has side-effects or a time-dependent value.
  - append
```
public Expression append(String name,
                         Expression expression)
```
    Appends an expression to a list of statements, and returns an expression (possibly a variable) that represents the result of the newly added block.
  - appendIfNotNull
```
public Expression appendIfNotNull(String name,
                                  Expression expression)
```
    Appends an expression to a list of statements, if it is not null.
  - append
```
public Expression append(String name,
                         Expression expression,
                         boolean optimize)
```
    Appends an expression to a list of statements, optionally optimizing if the expression is used more than once.
  - append_
```
private Expression append_(String name,
                           Expression expression,
                           boolean optimize)
```
  - isSimpleExpression
```
protected boolean isSimpleExpression(Expression expr)
```
    Checks if expression is simple enough to always inline at zero cost.
    
    Parameters:
    
    expr - expression to test
    
    Returns:
    
    true when given expression is safe to always inline
  - isSafeForReuse
```
protected boolean isSafeForReuse(DeclarationStatement decl)
```
  - addExpressionForReuse
```
protected void addExpressionForReuse(DeclarationStatement decl)
```
  - isCostly
```
private boolean isCostly(DeclarationStatement decl)
```
  - normalizeDeclaration
```
private Expression normalizeDeclaration(DeclarationStatement decl)
```
    Prepares declaration for inlining: adds cast
    
    Parameters:
    
    decl - inlining candidate
    
    Returns:
    
    normalized expression
  - getComputedExpression
```
public DeclarationStatement getComputedExpression(Expression expr)
```
    Returns the reference to ParameterExpression if given expression was already computed and stored to local variable
    
    Parameters:
    
    expr - expression to test
    
    Returns:
    
    existing ParameterExpression or null
  - add
```
public void add(Statement statement)
```
  - add
```
public void add(Expression expression)
```
  - toBlock
```
public BlockStatement toBlock()
```
    Returns a block consisting of the current list of statements.
  - optimize
```
private boolean optimize(Shuttle optimizer,
                         boolean performInline)
```
    Optimizes the list of statements. If an expression is used only once, it is inlined.
    
    Returns:
    
    whether any optimizations were made
  - createOptimizeShuttle
```
protected Shuttle createOptimizeShuttle()
```
    Creates a shuttle that will be used during block optimization. Sub-classes might provide more specific optimizations (e.g. partial evaluation).
    
    Returns:
    
    shuttle used to optimize the statements when converting to block
  - createFinishingOptimizeShuttle
```
protected Shuttle createFinishingOptimizeShuttle()
```
    Creates a final optimization shuttle. Typically, the visitor will factor out constant expressions.
    
    Returns:
    
    shuttle that is used to finalize the optimization
  - newName
```
private String newName(String suggestion,
                       boolean optimize)
```
    Creates a name for a new variable, unique within this block, controlling whether the variable can be inlined later.
  - newName
```
public String newName(String suggestion)
```
    Creates a name for a new variable, unique within this block.
  - hasVariable
```
public boolean hasVariable(String name)
```
  - append
```
public BlockBuilder append(Expression expression)
```

Class BlockBuilder

Nested Class Summary

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

statements

variables

expressionForReuse

optimizing

parent

OPTIMIZE_SHUTTLE

Constructor Detail

BlockBuilder

BlockBuilder

BlockBuilder

Method Detail

clear

append

append

append

appendIfNotNull

append

append_

isSimpleExpression

isSafeForReuse

addExpressionForReuse

isCostly

normalizeDeclaration

getComputedExpression

add

add

toBlock

optimize

createOptimizeShuttle

createFinishingOptimizeShuttle

newName

newName

hasVariable

append