org.h2.expression

Class Expression

java.lang.Object

org.h2.expression.Expression

All Implemented Interfaces:

HasSQL, Typed

Direct Known Subclasses:

Alias, ArrayConstructorByQuery, BetweenPredicate, CompareLike, Comparison, ConditionAndOr, ConditionAndOrN, ConditionIn, ConditionInArray, ConditionInConstantSet, ConditionInQuery, ConditionLocalAndGlobal, ConditionNot, DataAnalysisOperation, ExistsPredicate, ExpressionColumn, ExpressionList, Function0_1, IsJsonPredicate, JavaFunction, Operation0, Operation1, Operation1_2, Operation2, OperationN, SimpleCase, SimplePredicate, Subquery, UniquePredicate, Wildcard

public abstract class Expression
extends java.lang.Object
implements HasSQL, Typed

An expression is a operation, a value, or a function in a query.

Field Summary

Fields

Modifier and Type	Field and Description
static int	AUTO_PARENTHESES Wrap expression in parentheses only if it can't be safely included into other expressions without them.
static int	MAP_IN_AGGREGATE State for expressions inside an aggregate for mapColumns(ColumnResolver, int, int).
static int	MAP_IN_WINDOW State for expressions inside a window function for mapColumns(ColumnResolver, int, int).
static int	MAP_INITIAL Initial state for mapColumns(ColumnResolver, int, int).
static int	WITH_PARENTHESES Wrap expression in parentheses unconditionally.
static int	WITHOUT_PARENTHESES Do not wrap expression in 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
Expression()

Method Summary

Modifier and Type	Method and Description
void	addFilterConditions(TableFilter filter) Add conditions to a table filter if they can be evaluated.
void	createIndexConditions(SessionLocal session, TableFilter filter) Create index conditions if possible and attach them to the table filter.
java.lang.String	getAlias(SessionLocal session, int columnIndex) Get the alias name of a column or SQL expression if it is not an aliased expression.
boolean	getBooleanValue(SessionLocal session) Get the value in form of a boolean expression.
java.lang.String	getColumnName(SessionLocal session, int columnIndex) Get the column name or alias name of this expression.
java.lang.String	getColumnNameForView(SessionLocal session, int columnIndex) Get the column name of this expression for a view.
abstract int	getCost() Estimate the cost to process the expression.
java.lang.StringBuilder	getEnclosedSQL(java.lang.StringBuilder builder, int sqlFlags) Get the SQL statement of this expression.
Expression	getNonAliasExpression() Returns the main expression, skipping aliases.
Expression	getNotIfPossible(SessionLocal session) If it is possible, return the negated expression.
int	getNullable() Check whether this expression is a column and can store NULL.
java.lang.String	getSchemaName() Get the schema name, or null
java.lang.String	getSQL(int sqlFlags) Get the SQL statement of this expression.
java.lang.String	getSQL(int sqlFlags, int parentheses) Get the SQL statement of this expression.
java.lang.StringBuilder	getSQL(java.lang.StringBuilder builder, int sqlFlags) Appends the SQL statement of this object to the specified builder.
java.lang.StringBuilder	getSQL(java.lang.StringBuilder builder, int sqlFlags, int parentheses) Get the SQL statement of this expression.
Expression	getSubexpression(int index) Returns subexpression with specified index.
int	getSubexpressionCount() Returns count of subexpressions.
java.lang.String	getTableAlias() Get the table alias name or null if this expression does not represent a column.
java.lang.String	getTableName() Get the table name, or null
abstract TypeInfo	getType() Returns the data type.
abstract java.lang.StringBuilder	getUnenclosedSQL(java.lang.StringBuilder builder, int sqlFlags) Get the SQL statement of this expression.
abstract 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	isConstant() Check if this expression will always return the same value.
abstract boolean	isEverything(ExpressionVisitor visitor) Check if this expression and all sub-expressions can fulfill a criteria.
boolean	isIdentity() Check if this is an identity column.
boolean	isNullConstant() Check if this expression will always return the NULL value.
boolean	isValueSet() Is the value of a parameter set.
boolean	isWhenConditionOperand() Returns whether this expression is a right side of condition in a when operand.
abstract 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.
abstract Expression	optimize(SessionLocal session) Try to optimize the expression.
Expression	optimizeCondition(SessionLocal session) Try to optimize or remove the condition.
abstract void	setEvaluatable(TableFilter tableFilter, boolean value) Tell the expression columns whether the table filter can return values now.
java.lang.String	toString() Convert this expression to a String.
abstract void	updateAggregate(SessionLocal session, int stage) Update an aggregate value.
static java.lang.StringBuilder	writeExpressions(java.lang.StringBuilder builder, Expression[] expressions, int sqlFlags) Get the SQL snippet for an array of expressions.
static java.lang.StringBuilder	writeExpressions(java.lang.StringBuilder builder, java.util.List<? extends Expression> expressions, int sqlFlags) Get the SQL snippet for a list of expressions.

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

MAP_INITIAL

public static final int MAP_INITIAL

Initial state for mapColumns(ColumnResolver, int, int).

See Also:

Constant Field Values

MAP_IN_WINDOW

public static final int MAP_IN_WINDOW

State for expressions inside a window function for mapColumns(ColumnResolver, int, int).

See Also:

Constant Field Values

MAP_IN_AGGREGATE

public static final int MAP_IN_AGGREGATE

State for expressions inside an aggregate for mapColumns(ColumnResolver, int, int).

See Also:

Constant Field Values

AUTO_PARENTHESES

public static final int AUTO_PARENTHESES

Wrap expression in parentheses only if it can't be safely included into other expressions without them.

See Also:

Constant Field Values

WITH_PARENTHESES

public static final int WITH_PARENTHESES

Wrap expression in parentheses unconditionally.

See Also:

Constant Field Values

WITHOUT_PARENTHESES

public static final int WITHOUT_PARENTHESES

Do not wrap expression in parentheses.

See Also:

Constant Field Values

Constructor Detail

Expression

public Expression()

Method Detail

writeExpressions

public static java.lang.StringBuilder writeExpressions(java.lang.StringBuilder builder,
                                                       java.util.List<? extends Expression> expressions,
                                                       int sqlFlags)

Get the SQL snippet for a list of expressions.

Parameters:

builder - the builder to append the SQL to

expressions - the list of expressions

sqlFlags - formatting flags

Returns:

the specified string builder

writeExpressions

public static java.lang.StringBuilder writeExpressions(java.lang.StringBuilder builder,
                                                       Expression[] expressions,
                                                       int sqlFlags)

Get the SQL snippet for an array of expressions.

Parameters:

builder - the builder to append the SQL to

expressions - the list of expressions

sqlFlags - formatting flags

Returns:

the specified string builder

getValue

public abstract Value getValue(SessionLocal session)

Return the resulting value for the current row.

Parameters:

session - the session

Returns:

the result

getType

public abstract TypeInfo getType()

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

Specified by:

getType in interface Typed

Returns:

the data type

mapColumns

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

Map the columns of the resolver to expression columns.

Parameters:

resolver - the column resolver

level - the subquery nesting level

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

optimize

public abstract Expression optimize(SessionLocal session)

Try to optimize the expression.

Parameters:

session - the session

Returns:

the optimized expression

optimizeCondition

public final Expression optimizeCondition(SessionLocal session)

Try to optimize or remove the condition.

Parameters:

session - the session

Returns:

the optimized condition, or null

setEvaluatable

public abstract void setEvaluatable(TableFilter tableFilter,
                                    boolean value)

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

Parameters:

tableFilter - the table filter

value - true if the table filter can return value

getSQL

public final java.lang.String getSQL(int sqlFlags)

Description copied from interface: HasSQL

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

Specified by:

getSQL in interface HasSQL

Parameters:

sqlFlags - formatting flags

Returns:

the SQL statement

getSQL

public final java.lang.StringBuilder getSQL(java.lang.StringBuilder builder,
                                            int sqlFlags)

Description copied from interface: HasSQL

Appends the SQL statement of this object to the specified builder.

Specified by:

getSQL in interface HasSQL

Parameters:

builder - string builder

sqlFlags - formatting flags

Returns:

the specified string builder

getSQL

public final java.lang.String getSQL(int sqlFlags,
                                     int parentheses)

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

Parameters:

sqlFlags - formatting flags

parentheses - parentheses mode

Returns:

the SQL statement

getSQL

public final java.lang.StringBuilder getSQL(java.lang.StringBuilder builder,
                                            int sqlFlags,
                                            int parentheses)

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

Parameters:

builder - string builder

sqlFlags - formatting flags

parentheses - parentheses mode

Returns:

the specified string builder

needParentheses

public boolean needParentheses()

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

Returns:

true if it is

getEnclosedSQL

public final java.lang.StringBuilder getEnclosedSQL(java.lang.StringBuilder builder,
                                                    int sqlFlags)

Get the SQL statement of this expression. This may not always be the original SQL statement, especially after optimization. Enclosing '(' and ')' are always appended.

Parameters:

builder - string builder

sqlFlags - formatting flags

Returns:

the specified string builder

getUnenclosedSQL

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

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

Parameters:

builder - string builder

sqlFlags - formatting flags

Returns:

the specified string builder

updateAggregate

public abstract void updateAggregate(SessionLocal session,
                                     int stage)

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.

Parameters:

session - the session

stage - select stage

isEverything

public abstract boolean isEverything(ExpressionVisitor visitor)

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

Parameters:

visitor - the visitor

Returns:

if the criteria can be fulfilled

getCost

public abstract int getCost()

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

Returns:

the estimated cost

getNotIfPossible

public Expression getNotIfPossible(SessionLocal session)

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.

Parameters:

session - the session

Returns:

the negated expression, or null

isConstant

public boolean isConstant()

Check if this expression will always return the same value.

Returns:

if the expression is constant

isNullConstant

public boolean isNullConstant()

Check if this expression will always return the NULL value.

Returns:

if the expression is constant NULL value

isValueSet

public boolean isValueSet()

Is the value of a parameter set.

Returns:

true if set

isIdentity

public boolean isIdentity()

Check if this is an identity column.

Returns:

true if it is an identity column

getBooleanValue

public boolean getBooleanValue(SessionLocal session)

Get the value in form of a boolean expression. Returns true or false. In this database, everything can be a condition.

Parameters:

session - the session

Returns:

the result

createIndexConditions

public void createIndexConditions(SessionLocal session,
                                  TableFilter filter)

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

Parameters:

session - the session

filter - the table filter

getColumnName

public java.lang.String getColumnName(SessionLocal session,
                                      int columnIndex)

Get the column name or alias name of this expression.

Parameters:

session - the session

columnIndex - 0-based column index

Returns:

the column name

getSchemaName

public java.lang.String getSchemaName()

Get the schema name, or null

Returns:

the schema name

getTableName

public java.lang.String getTableName()

Get the table name, or null

Returns:

the table name

getNullable

public int getNullable()

Check whether this expression is a column and can store NULL.

Returns:

whether NULL is allowed

getTableAlias

public java.lang.String getTableAlias()

Get the table alias name or null if this expression does not represent a column.

Returns:

the table alias name

getAlias

public java.lang.String getAlias(SessionLocal session,
                                 int columnIndex)

Get the alias name of a column or SQL expression if it is not an aliased expression.

Parameters:

session - the session

columnIndex - 0-based column index

Returns:

the alias name

getColumnNameForView

public java.lang.String getColumnNameForView(SessionLocal session,
                                             int columnIndex)

Get the column name of this expression for a view.

Parameters:

session - the session

columnIndex - 0-based column index

Returns:

the column name for a view

getNonAliasExpression

public Expression getNonAliasExpression()

Returns the main expression, skipping aliases.

Returns:

the expression

addFilterConditions

public void addFilterConditions(TableFilter filter)

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

Parameters:

filter - the table filter

toString

public java.lang.String toString()

Convert this expression to a String.

Overrides:

toString in class java.lang.Object

Returns:

the string representation

getSubexpressionCount

public int getSubexpressionCount()

Returns count of subexpressions.

Returns:

count of subexpressions

getSubexpression

public Expression getSubexpression(int index)

Returns subexpression with specified index.

Parameters:

index - 0-based index

Returns:

subexpression with specified index, may be null

Throws:

java.lang.IndexOutOfBoundsException - if specified index is not valid

getWhenValue

public boolean getWhenValue(SessionLocal session,
                            Value left)

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

Parameters:

session - the session

left - value on the left side

Returns:

the result

getWhenSQL

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

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

Parameters:

builder - string builder

sqlFlags - formatting flags

Returns:

the specified string builder

isWhenConditionOperand

public boolean isWhenConditionOperand()

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

Returns:

true if it is, false otherwise