org.eigenbase.rex
Class RexLiteral

java.lang.Object
  org.eigenbase.rex.RexNode
      org.eigenbase.rex.RexLiteral

public class RexLiteral
extends RexNode

Constant value in a row-expression.

There are several methods for creating literals in RexBuilder: RexBuilder.makeLiteral(boolean) and so forth.

How is the value stored? In that respect, the class is somewhat of a black box. There is a getValue() method which returns the value as an object, but the type of that value is implementation detail, and it is best that your code does not depend upon that knowledge. It is better to use task-oriented methods such as getValue2() and toJavaString(java.lang.Comparable, org.eigenbase.sql.type.SqlTypeName).

The allowable types and combinations are:

TypeName	Meaing	Value type
SqlTypeName.NULL	The null value. It has its own special type.	null
SqlTypeName.BOOLEAN	Boolean, namely TRUE, FALSE or UNKNOWN.	Boolean, or null represents the UNKNOWN value
SqlTypeName.DECIMAL	Exact number, for example 0, -.5, 12345.	BigDecimal
SqlTypeName.DOUBLE	Approximate number, for example 6.023E-23.	BigDecimal
SqlTypeName.DATE	Date, for example DATE '1969-04'29'	Calendar
SqlTypeName.TIME	Time, for example TIME '18:37:42.567'	Calendar
SqlTypeName.TIMESTAMP	Timestamp, for example TIMESTAMP '1969-04-29 18:37:42.567'	Calendar
SqlTypeName.CHAR	Character constant, for example 'Hello, world!', '', _N'Bonjour', _ISO-8859-1'It''s superman!' COLLATE SHIFT_JIS$ja_JP$2. These are always CHAR, never VARCHAR.	NlsString
SqlTypeName.BINARY	Binary constant, for example X'7F34'. (The number of hexits must be even; see above.) These constants are always BINARY, never VARBINARY.	ByteBuffer
SqlTypeName.SYMBOL	A symbol is a special type used to make parsing easier; it is not part of the SQL standard, and is not exposed to end-users. It is used to hold a flag, such as the LEADING flag in a call to the function TRIM([LEADING|TRAILING|BOTH] chars FROM string).	A class which implements the Enum14.Value interface

Since:

Nov 24, 2003

Version:

$Id: //open/dev/farrago/src/org/eigenbase/rex/RexLiteral.java#30 $

Author:

jhyde

Field Summary

private RelDataType	type The real type of this literal, as reported by getType().
private SqlTypeName	typeName An indication of the broad type of this literal -- even if its type isn't a SQL type.
private Comparable	value The value of this literal.

Fields inherited from class org.eigenbase.rex.RexNode

digest, EMPTY_ARRAY

Constructor Summary

RexLiteral(Comparable value, RelDataType type, SqlTypeName typeName)
Creates a RexLiteral.

Method Summary

<R> R	accept(RexVisitor<R> visitor) Accepts a visitor, dispatching to the right overloaded visitXxx method.
static boolean	booleanValue(RexNode node)
RexLiteral	clone()
boolean	equals(Object obj)
private static boolean	equals(Object o1, Object o2)
private static Comparable	findValue(RexNode node)
static RexLiteral	fromJdbcString(RelDataType type, SqlTypeName typeName, String literal) Converts a Jdbc string into a RexLiteral.
private static String	getCalendarFormat(SqlTypeName typeName)
RexKind	getKind() Returns the kind of node this is.
RelDataType	getType()
SqlTypeName	getTypeName()
Comparable	getValue() Returns the value of this literal.
Object	getValue2() Returns the value of this literal, in the form that the calculator program builder wants it.
int	hashCode()
static int	intValue(RexNode node)
boolean	isAlwaysTrue() Returns whether this expression always returns true.
static boolean	isNullLiteral(RexNode node)
private static void	printAsJava(Comparable value, PrintWriter pw, SqlTypeName typeName, boolean java) Prints a value as a Java string.
void	printAsJava(PrintWriter pw) Prints the value this literal as a Java string constant.
private static void	printDatetime(PrintWriter pw, ZonelessDatetime datetime, Comparable value)
static String	stringValue(RexNode node)
private static String	toJavaString(Comparable value, SqlTypeName typeName)
static boolean	valueMatchesType(Comparable value, SqlTypeName typeName)

Methods inherited from class org.eigenbase.rex.RexNode

isA, toString

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

value

private final Comparable value

The value of this literal. Must be consistent with its type, as per valueMatchesType(java.lang.Comparable, org.eigenbase.sql.type.SqlTypeName). For example, you can't store an Integer value here just because you feel like it -- all numbers are represented by a BigDecimal. But since this field is private, it doesn't really matter how the values are stored.

type

private final RelDataType type

The real type of this literal, as reported by getType().

typeName

private final SqlTypeName typeName

An indication of the broad type of this literal -- even if its type isn't a SQL type. Sometimes this will be different than the SQL type; for example, all exact numbers, including integers have typeName SqlTypeName.DECIMAL. See valueMatchesType(java.lang.Comparable, org.eigenbase.sql.type.SqlTypeName) for the definitive story.

Constructor Detail

RexLiteral

RexLiteral(Comparable value,
           RelDataType type,
           SqlTypeName typeName)

Creates a RexLiteral.

"Precondition:"

type != null, valueMatchesType(value,typeName), (value == null) == type.isNullable()

Method Detail

valueMatchesType

public static boolean valueMatchesType(Comparable value,
                                       SqlTypeName typeName)

Returns:

whether value is appropriate for its type (we have rules about these things)

toJavaString

private static String toJavaString(Comparable value,
                                   SqlTypeName typeName)

printAsJava

public void printAsJava(PrintWriter pw)

Prints the value this literal as a Java string constant.

printAsJava

private static void printAsJava(Comparable value,
                                PrintWriter pw,
                                SqlTypeName typeName,
                                boolean java)

Prints a value as a Java string. The value must be consistent with the type, as per valueMatchesType(java.lang.Comparable, org.eigenbase.sql.type.SqlTypeName).

Typical return values:

• true
• null
• "Hello, world!"
• 1.25
• 1234ABCD

Parameters:

value - Value

pw - Writer to write to

typeName - Type family

printDatetime

private static void printDatetime(PrintWriter pw,
                                  ZonelessDatetime datetime,
                                  Comparable value)

fromJdbcString

public static RexLiteral fromJdbcString(RelDataType type,
                                        SqlTypeName typeName,
                                        String literal)

Converts a Jdbc string into a RexLiteral. This method accepts a string, as returned by the Jdbc method ResultSet.getString(), and restores the string into an equivalent RexLiteral. It allows one to use Jdbc strings as a common format for data.

If a null literal is provided, then a null pointer will be returned.

Parameters:

type - data type of literal to be read

typeName - type family of literal

literal - the (non-SQL encoded) string representation, as returned by the Jdbc call to return a column as a string

Returns:

a typed RexLiteral, or null

getCalendarFormat

private static String getCalendarFormat(SqlTypeName typeName)

getTypeName

public SqlTypeName getTypeName()

getType

public RelDataType getType()

Specified by:

getType in class RexNode

getKind

public RexKind getKind()

Description copied from class: RexNode

Returns the kind of node this is.

Overrides:

getKind in class RexNode

Returns:

A RexKind value, never null

getValue

public Comparable getValue()

Returns the value of this literal.

"Postcondition:"

valueMatchesType(return, typeName)

getValue2

public Object getValue2()

Returns the value of this literal, in the form that the calculator program builder wants it.

booleanValue

public static boolean booleanValue(RexNode node)

isAlwaysTrue

public boolean isAlwaysTrue()

Description copied from class: RexNode

Returns whether this expression always returns true. (Such as if this expression is equal to the literal TRUE.)

Overrides:

isAlwaysTrue in class RexNode

equals

public boolean equals(Object obj)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

intValue

public static int intValue(RexNode node)

stringValue

public static String stringValue(RexNode node)

findValue

private static Comparable findValue(RexNode node)

isNullLiteral

public static boolean isNullLiteral(RexNode node)

clone

public RexLiteral clone()

Specified by:

clone in class RexNode

equals

private static boolean equals(Object o1,
                              Object o2)

accept

public <R> R accept(RexVisitor<R> visitor)

Description copied from class: RexNode

Accepts a visitor, dispatching to the right overloaded visitXxx method.

Also see RexProgram.apply(RexVisitor, RexNode[], RexNode), which applies a visitor to several expressions simultaneously.

Specified by:

accept in class RexNode