org.h2.expression.condition

Class Comparison

java.lang.Object

org.h2.expression.Expression

org.h2.expression.condition.Comparison

All Implemented Interfaces:

HasSQL, Typed

public final 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 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	NOT_EQUAL The comparison type meaning <> as in ID<>1.
static int	NOT_EQUAL_NULL_SAFE The comparison type meaning ID IS DISTINCT FROM 1.
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 "&&").

Fields inherited from class org.h2.expression.Expression

AUTO_PARENTHESES, MAP_IN_AGGREGATE, MAP_IN_WINDOW, MAP_INITIAL, WITH_PARENTHESES, WITHOUT_PARENTHESES

Fields inherited from interface org.h2.util.HasSQL

ADD_PLAN_INFORMATION, DEFAULT_SQL_FLAGS, NO_CASTS, QUOTE_ONLY_WHEN_REQUIRED, REPLACE_LOBS_FOR_TRACE, TRACE_SQL_FLAGS

Constructor Summary

Constructors

Constructor and Description
Comparison(int compareType, Expression left, Expression right, boolean whenOperand)

Method Summary

Modifier and Type	Method and Description
void	createIndexConditions(SessionLocal session, TableFilter filter) Create index conditions if possible and attach them to the table filter.
int	getCost() Estimate the cost to process the expression.
Expression	getNotIfPossible(SessionLocal session) If it is possible, return the negated expression.
Expression	getSubexpression(int index) Returns subexpression with specified index.
int	getSubexpressionCount() Returns count of subexpressions.
TypeInfo	getType() Returns the data type.
java.lang.StringBuilder	getUnenclosedSQL(java.lang.StringBuilder builder, int sqlFlags) Get the SQL statement of this expression.
Value	getValue(SessionLocal session) Return the resulting value for the current row.
java.lang.StringBuilder	getWhenSQL(java.lang.StringBuilder builder, int sqlFlags) Appends the SQL statement of this when operand to the specified builder.
boolean	getWhenValue(SessionLocal session, Value left) Return the resulting value of when operand for the current row.
boolean	isEverything(ExpressionVisitor visitor) Check if this expression and all sub-expressions can fulfill a criteria.
boolean	isWhenConditionOperand() Returns whether this expression is a right side of condition in a when operand.
void	mapColumns(ColumnResolver resolver, int level, int state) Map the columns of the resolver to expression columns.
boolean	needParentheses() Returns whether this expressions needs to be wrapped in parentheses when it is used as an argument of other expressions.
Expression	optimize(SessionLocal 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(SessionLocal session, int stage) Update an aggregate value.

Methods inherited from class org.h2.expression.Expression

addFilterConditions, getAlias, getBooleanValue, getColumnName, getColumnNameForView, getEnclosedSQL, getNonAliasExpression, getNullable, getSchemaName, getSQL, getSQL, getSQL, getSQL, getTableAlias, getTableName, isConstant, isIdentity, isNullConstant, isValueSet, optimizeCondition, toString, writeExpressions, writeExpressions

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.h2.util.HasSQL

getTraceSQL

Field Detail

EQUAL

public static final int EQUAL

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

SMALLER

public static final int SMALLER

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

BIGGER_EQUAL

public static final int BIGGER_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 NOT DISTINCT FROM 1.

See Also:

Constant Field Values

NOT_EQUAL_NULL_SAFE

public static final int NOT_EQUAL_NULL_SAFE

The comparison type meaning ID IS DISTINCT FROM 1.

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

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

Constructor Detail

Comparison

public Comparison(int compareType,
                  Expression left,
                  Expression right,
                  boolean whenOperand)

Method Detail

needParentheses

public boolean needParentheses()

Description copied from class: Expression

Returns whether this expressions needs to be wrapped in parentheses when it is used as an argument of other expressions.

Overrides:

needParentheses in class Expression

Returns:

true if it is

getUnenclosedSQL

public java.lang.StringBuilder getUnenclosedSQL(java.lang.StringBuilder builder,
                                                int sqlFlags)

Description copied from class: Expression

Get the SQL statement of this expression. This may not always be the original SQL statement, especially after optimization. Enclosing '(' and ')' are never appended.

Specified by:

getUnenclosedSQL in class Expression

Parameters:

builder - string builder

sqlFlags - formatting flags

Returns:

the specified string builder

getWhenSQL

public java.lang.StringBuilder getWhenSQL(java.lang.StringBuilder builder,
                                          int sqlFlags)

Description copied from class: Expression

Appends the SQL statement of this when operand to the specified builder.

Overrides:

getWhenSQL in class Expression

Parameters:

builder - string builder

sqlFlags - formatting flags

Returns:

the specified string builder

optimize

public Expression optimize(SessionLocal 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(SessionLocal 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

getWhenValue

public boolean getWhenValue(SessionLocal session,
                            Value left)

Description copied from class: Expression

Return the resulting value of when operand for the current row.

Overrides:

getWhenValue in class Expression

Parameters:

session - the session

left - value on the left side

Returns:

the result

isWhenConditionOperand

public boolean isWhenConditionOperand()

Description copied from class: Expression

Returns whether this expression is a right side of condition in a when operand.

Overrides:

isWhenConditionOperand in class Expression

Returns:

true if it is, false otherwise

getNotIfPossible

public Expression getNotIfPossible(SessionLocal 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(SessionLocal 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(SessionLocal session,
                            int stage)

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

stage - select stage

mapColumns

public void mapColumns(ColumnResolver resolver,
                       int level,
                       int state)

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

state - current state for nesting checks, initial value is Expression.MAP_INITIAL

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

getSubexpressionCount

public int getSubexpressionCount()

Description copied from class: Expression

Returns count of subexpressions.

Overrides:

getSubexpressionCount in class Expression

Returns:

count of subexpressions

getSubexpression

public Expression getSubexpression(int index)

Description copied from class: Expression

Returns subexpression with specified index.

Overrides:

getSubexpression in class Expression

Parameters:

index - 0-based index

Returns:

subexpression with specified index, may be null

getType

public TypeInfo getType()

Description copied from class: Expression

Returns the data type. The data type may be unknown before the optimization phase.

Specified by:

getType in interface Typed

Specified by:

getType in class Expression

Returns:

the data type