org.apache.tajo.plan

Class NamedExprsManager

java.lang.Object

org.apache.tajo.plan.NamedExprsManager

public class NamedExprsManager
extends Object

NamedExprsManager manages an expressions used in a query block. All expressions used in a query block must be added to NamedExprsManager. When an expression is added to NamedExprsManager, NamedExprsManager gives a reference to the expression. If the expression already has an alias name, it gives the alias name as the reference to the expression. If the expression does not have any alias, it gives a generated name as the reference to the expression. Usually, predicates in WHERE clause, expressions in GROUP-BY, ORDER-BY, LIMIT clauses are not given any alias name. Those reference names are used to identify an individual expression. NamedExprsManager only keeps unique expressions. Since expressions in a query block can be duplicated, one or more reference names can point one expressions. Due to this process, it naturally removes duplicated expression. As we mentioned above, one or more reference names can indicate one expression. Primary names are used for representing expressions. A primary name of an expression indicates the reference obtained when the expression is added firstly. All output schemas uses only primary names of expressions. Each expression that NamedExprsManager keeps has an boolean state to indicate whether the expression is evaluated or not. The evaluated state means that upper logical operators can access this expression like a column reference. For it, the reference name is used to access this expression like a column reference, The evaluated state is set with an EvalNode which is an annotated expression. getTarget(String) returns EvalNodes by a reference name.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	NamedExprsManager.UnevaluatedIterator

Constructor Summary

Constructors

Constructor and Description
NamedExprsManager(LogicalPlan plan, LogicalPlan.QueryBlock block)

Method Summary

Methods

Modifier and Type	Method and Description
String	addExpr(Expr expr) Adds an expression and returns a reference name.
String	addExpr(Expr expr, String alias) Adds an expression with an alias name and returns a reference name.
String	addNamedExpr(NamedExpr namedExpr) Adds an expression and returns a reference name.
String[]	addNamedExprArray(Collection<NamedExpr> namedExprs) Adds a list of expressions and returns a list of reference names.
String	checkAndGetIfAliasedColumn(String name) It returns an original column name if it is aliased column reference.
boolean	contains(Expr expr)
boolean	contains(String name)
String	getAlias(String originalName)
Collection<NamedExpr>	getAllNamedExprs()
Iterator<NamedExpr>	getIteratorForUnevaluatedExprs() It returns an iterator for unevaluated NamedExprs.
NamedExpr	getNamedExpr(String name)
String	getOriginalName(String aliasName)
Target	getTarget(String name)
Target	getTarget(String referenceName, boolean unevaluatedForm) get a Target instance.
boolean	isAliased(String name)
boolean	isAliasedName(String aliasName)
boolean	isEvaluated(String name) Check whether the expression corresponding to a given name was evaluated.
void	markAsEvaluated(String referenceName, EvalNode evalNode) It marks the expression identified by the reference name as evaluated.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

NamedExprsManager

public NamedExprsManager(LogicalPlan plan,
                 LogicalPlan.QueryBlock block)

Method Detail

isEvaluated

public boolean isEvaluated(String name)

Check whether the expression corresponding to a given name was evaluated.

Parameters:

name - The name of a certain expression to be checked

Returns:

true if resolved. Otherwise, false.

contains

public boolean contains(String name)

contains

public boolean contains(Expr expr)

getNamedExpr

public NamedExpr getNamedExpr(String name)

isAliased

public boolean isAliased(String name)

getAlias

public String getAlias(String originalName)

isAliasedName

public boolean isAliasedName(String aliasName)

getOriginalName

public String getOriginalName(String aliasName)

addExpr

public String addExpr(Expr expr)
               throws PlanningException

Adds an expression and returns a reference name.

Throws:

PlanningException

addExpr

public String addExpr(Expr expr,
             String alias)
               throws PlanningException

Adds an expression with an alias name and returns a reference name. It specifies the alias as an reference name.

Throws:

PlanningException

addNamedExpr

public String addNamedExpr(NamedExpr namedExpr)
                    throws PlanningException

Adds an expression and returns a reference name. If an alias is given, it specifies the alias as an reference name.

Throws:

PlanningException

addNamedExprArray

public String[] addNamedExprArray(@Nullable
                         Collection<NamedExpr> namedExprs)
                           throws PlanningException

Adds a list of expressions and returns a list of reference names. If some NamedExpr has an alias, NamedExprsManager specifies the alias for the NamedExpr.

Throws:

PlanningException

getAllNamedExprs

public Collection<NamedExpr> getAllNamedExprs()

markAsEvaluated

public void markAsEvaluated(String referenceName,
                   EvalNode evalNode)
                     throws PlanningException

It marks the expression identified by the reference name as evaluated. In addition, it adds an EvanNode for the expression identified by the reference.

Parameters:

referenceName - The reference name to be marked as 'evaluated'.

evalNode - EvalNode to be added.

Throws:

PlanningException

checkAndGetIfAliasedColumn

public String checkAndGetIfAliasedColumn(String name)

It returns an original column name if it is aliased column reference. Otherwise, it will return NULL.

getTarget

public Target getTarget(String name)

getTarget

public Target getTarget(String referenceName,
               boolean unevaluatedForm)

get a Target instance. A target consists of a reference name and an EvalNode corresponding to the reference name. According to evaluation state, it returns different EvalNodes. If the expression corresponding to the reference name is evaluated, it just returns FieldEval (i.e., a column reference). Otherwise, it returns the original EvalNode of the expression.

Parameters:

referenceName - The reference name to get EvalNode

unevaluatedForm - If TRUE, it always return the annotated EvalNode of the expression.

Returns:

toString

public String toString()

Overrides:

toString in class Object

getIteratorForUnevaluatedExprs

public Iterator<NamedExpr> getIteratorForUnevaluatedExprs()

It returns an iterator for unevaluated NamedExprs.