org.h2.expression

Class Comparison

java.lang.Object

org.h2.expression.Expression

org.h2.expression.Comparison

public class Comparison
extends Expression

Example comparison expressions are ID=1, NAME=NAME, NAME IS NULL.

Field Summary

Fields

Modifier and Type	Field and Description
static int	BIGGER The comparison type meaning > as in ID>1.
static int	BIGGER_EQUAL The comparison type meaning >= as in ID>=1.
static int	EQUAL The comparison type meaning = as in ID=1.
static int	EQUAL_NULL_SAFE The comparison type meaning ID IS 1 (ID IS NOT DISTINCT FROM 1).
static int	FALSE This is a pseudo comparison type that is only used for index conditions.
static int	IN_LIST This is a pseudo comparison type that is only used for index conditions.
static int	IN_QUERY This is a pseudo comparison type that is only used for index conditions.
static int	IS_NOT_NULL The comparison type meaning IS NOT NULL as in NAME IS NOT NULL.
static int	IS_NULL The comparison type meaning IS NULL as in NAME IS NULL.
static int	NOT_EQUAL The comparison type meaning <> as in ID<>1.
static int	NOT_EQUAL_NULL_SAFE The comparison type meaning ID IS NOT 1 (ID IS DISTINCT FROM 1).
static int	NULL_SAFE This is a flag meaning the comparison is null safe (meaning never returns NULL even if one operand is NULL).
static int	SMALLER The comparison type meaning < as in ID<1.
static int	SMALLER_EQUAL The comparison type meaning <= as in ID<=1.
static int	SPATIAL_INTERSECTS This is a comparison type that is only used for spatial index conditions (operator "&&").

Constructor Summary

Constructors

Constructor and Description
Comparison(Session session, int compareType, Expression left, Expression right)

Method Summary

Methods

Modifier and Type	Method and Description
void	addFilterConditions(TableFilter filter, boolean outerJoin) Add conditions to a table filter if they can be evaluated.
void	createIndexConditions(Session session, TableFilter filter) Create index conditions if possible and attach them to the table filter.
int	getCost() Estimate the cost to process the expression.
int	getDisplaySize() Get the display size of this expression.
Expression	getExpression(boolean getLeft) Get the left or the right sub-expression of this condition.
Expression	getNotIfPossible(Session session) If it is possible, return the negated expression.
long	getPrecision() Get the precision of this expression.
int	getScale() Get the scale of this expression.
java.lang.String	getSQL() Get the SQL statement of this expression.
int	getType() Return the data type.
Value	getValue(Session session) Return the resulting value for the current row.
boolean	isEverything(ExpressionVisitor visitor) Check if this expression and all sub-expressions can fulfill a criteria.
void	mapColumns(ColumnResolver resolver, int level) Map the columns of the resolver to expression columns.
Expression	optimize(Session session) Try to optimize the expression.
void	setEvaluatable(TableFilter tableFilter, boolean b) Tell the expression columns whether the table filter can return values now.
void	updateAggregate(Session session) Update an aggregate value.

Methods inherited from class org.h2.expression.Expression

getAlias, getBooleanValue, getColumnName, getExpressionColumns, getExpressionColumns, getNonAliasExpression, getNullable, getSchemaName, getTableAlias, getTableName, isAutoIncrement, isConstant, isValueSet, isWildcard, toString

Methods inherited from class java.lang.Object

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

Field Detail

NULL_SAFE

public static final int NULL_SAFE

This is a flag meaning the comparison is null safe (meaning never returns NULL even if one operand is NULL). Only EQUAL and NOT_EQUAL are supported currently.

See Also:

Constant Field Values

EQUAL

public static final int EQUAL

The comparison type meaning = as in ID=1.

See Also:

Constant Field Values

EQUAL_NULL_SAFE

public static final int EQUAL_NULL_SAFE

The comparison type meaning ID IS 1 (ID IS NOT DISTINCT FROM 1).

See Also:

Constant Field Values

BIGGER_EQUAL

public static final int BIGGER_EQUAL

The comparison type meaning >= as in ID>=1.

See Also:

Constant Field Values

BIGGER

public static final int BIGGER

The comparison type meaning > as in ID>1.

See Also:

Constant Field Values

SMALLER_EQUAL

public static final int SMALLER_EQUAL

The comparison type meaning <= as in ID<=1.

See Also:

Constant Field Values

SMALLER

public static final int SMALLER

The comparison type meaning < as in ID<1.

See Also:

Constant Field Values

NOT_EQUAL

public static final int NOT_EQUAL

The comparison type meaning <> as in ID<>1.

See Also:

Constant Field Values

NOT_EQUAL_NULL_SAFE

public static final int NOT_EQUAL_NULL_SAFE

The comparison type meaning ID IS NOT 1 (ID IS DISTINCT FROM 1).

See Also:

Constant Field Values

IS_NULL

public static final int IS_NULL

The comparison type meaning IS NULL as in NAME IS NULL.

See Also:

Constant Field Values

IS_NOT_NULL

public static final int IS_NOT_NULL

The comparison type meaning IS NOT NULL as in NAME IS NOT NULL.

See Also:

Constant Field Values

FALSE

public static final int FALSE

This is a pseudo comparison type that is only used for index conditions. It means the comparison will always yield FALSE. Example: 1=0.

See Also:

Constant Field Values

IN_LIST

public static final int IN_LIST

This is a pseudo comparison type that is only used for index conditions. It means equals any value of a list. Example: IN(1, 2, 3).

See Also:

Constant Field Values

IN_QUERY

public static final int IN_QUERY

This is a pseudo comparison type that is only used for index conditions. It means equals any value of a list. Example: IN(SELECT ...).

See Also:

Constant Field Values

SPATIAL_INTERSECTS

public static final int SPATIAL_INTERSECTS

This is a comparison type that is only used for spatial index conditions (operator "&&").

See Also:

Constant Field Values

Constructor Detail

Comparison

public Comparison(Session session,
          int compareType,
          Expression left,
          Expression right)

Method Detail

getSQL

public java.lang.String getSQL()

Description copied from class: Expression

Get the SQL statement of this expression. This may not always be the original SQL statement, specially after optimization.

Specified by:

getSQL in class Expression

Returns:

the SQL statement

optimize

public Expression optimize(Session session)

Description copied from class: Expression

Try to optimize the expression.

Specified by:

optimize in class Expression

Parameters:

session - the session

Returns:

the optimized expression

getValue

public Value getValue(Session session)

Description copied from class: Expression

Return the resulting value for the current row.

Specified by:

getValue in class Expression

Parameters:

session - the session

Returns:

the result

getNotIfPossible

public Expression getNotIfPossible(Session session)

Description copied from class: Expression

If it is possible, return the negated expression. This is used to optimize NOT expressions: NOT ID>10 can be converted to ID<=10. Returns null if negating is not possible.

Overrides:

getNotIfPossible in class Expression

Parameters:

session - the session

Returns:

the negated expression, or null

createIndexConditions

public void createIndexConditions(Session session,
                         TableFilter filter)

Description copied from class: Expression

Create index conditions if possible and attach them to the table filter.

Overrides:

createIndexConditions in class Expression

Parameters:

session - the session

filter - the table filter

setEvaluatable

public void setEvaluatable(TableFilter tableFilter,
                  boolean b)

Description copied from class: Expression

Tell the expression columns whether the table filter can return values now. This is used when optimizing the query.

Specified by:

setEvaluatable in class Expression

Parameters:

tableFilter - the table filter

b - true if the table filter can return value

updateAggregate

public void updateAggregate(Session session)

Description copied from class: Expression

Update an aggregate value. This method is called at statement execution time. It is usually called once for each row, but if the expression is used multiple times (for example in the column list, and as part of the HAVING expression) it is called multiple times - the row counter needs to be used to make sure the internal state is only updated once.

Specified by:

updateAggregate in class Expression

Parameters:

session - the session

addFilterConditions

public void addFilterConditions(TableFilter filter,
                       boolean outerJoin)

Description copied from class: Expression

Add conditions to a table filter if they can be evaluated.

Overrides:

addFilterConditions in class Expression

Parameters:

filter - the table filter

outerJoin - if the expression is part of an outer join

mapColumns

public void mapColumns(ColumnResolver resolver,
              int level)

Description copied from class: Expression

Map the columns of the resolver to expression columns.

Specified by:

mapColumns in class Expression

Parameters:

resolver - the column resolver

level - the subquery nesting level

isEverything

public boolean isEverything(ExpressionVisitor visitor)

Description copied from class: Expression

Check if this expression and all sub-expressions can fulfill a criteria. If any part returns false, the result is false.

Specified by:

isEverything in class Expression

Parameters:

visitor - the visitor

Returns:

if the criteria can be fulfilled

getCost

public int getCost()

Description copied from class: Expression

Estimate the cost to process the expression. Used when optimizing the query, to calculate the query plan with the lowest estimated cost.

Specified by:

getCost in class Expression

Returns:

the estimated cost

getExpression

public Expression getExpression(boolean getLeft)

Get the left or the right sub-expression of this condition.

Parameters:

getLeft - true to get the left sub-expression, false to get the right sub-expression.

Returns:

the sub-expression

getType

public int getType()

Description copied from class: Expression

Return the data type. The data type may not be known before the optimization phase.

Specified by:

getType in class Expression

Returns:

the type

getScale

public int getScale()

Description copied from class: Expression

Get the scale of this expression.

Specified by:

getScale in class Expression

Returns:

the scale

getPrecision

public long getPrecision()

Description copied from class: Expression

Get the precision of this expression.

Specified by:

getPrecision in class Expression

Returns:

the precision

getDisplaySize

public int getDisplaySize()

Description copied from class: Expression

Get the display size of this expression.

Specified by:

getDisplaySize in class Expression

Returns:

the display size