Expression

java.lang.Object
- org.h2.expression.Expression

Direct Known Subclasses:

Alias, BinaryOperation, CompareLike, Comparison, ConcatenationOperation, ConditionAndOr, ConditionIn, ConditionInConstantSet, ConditionInParameter, ConditionInQuery, ConditionLocalAndGlobal, ConditionNot, DataAnalysisOperation, ExistsPredicate, ExpressionColumn, ExpressionList, Format, Function, IntervalOperation, IsJsonPredicate, JavaFunction, Parameter, Rownum, SequenceValue, SimplePredicate, Subquery, TimeZoneOperation, UnaryOperation, UniquePredicate, ValueExpression, Variable, Wildcard
```
public abstract class Expression
extends java.lang.Object
```
An expression is a operation, a value, or a function in a query.

Field Summary

Fields
Modifier and Type	Field and Description
`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)`.

Constructor Summary

Constructors
Constructor and Description

Expression()

Constructors
Constructor and Description
`Expression()`

Method Summary

Methods
Modifier and Type	Method and Description
`void`	`addFilterConditions(TableFilter filter)` 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.
`java.lang.String`	`getAlias()` Get the alias name of a column or SQL expression if it is not an aliased expression.
`boolean`	`getBooleanValue(Session session)` Get the value in form of a boolean expression.
`java.lang.String`	`getColumnName()` Get the column name or alias name of this expression.
`abstract int`	`getCost()` Estimate the cost to process the expression.
`Expression[]`	`getExpressionColumns(Session session)` If this expression consists of column expressions it should return them.
`static Expression[]`	`getExpressionColumns(Session session, ResultInterface result)` Extracts expression columns from the given result set.
`protected static Expression[]`	`getExpressionColumns(Session session, ValueCollectionBase value)` Extracts expression columns from ValueArray
`Expression`	`getNonAliasExpression()` Returns the main expression, skipping aliases.
`Expression`	`getNotIfPossible(Session 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(boolean alwaysQuote)` Get the SQL statement of this expression.
`abstract java.lang.StringBuilder`	`getSQL(java.lang.StringBuilder builder, boolean alwaysQuote)` Appends the SQL statement of this expression to the specified builder.
`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.
`java.lang.StringBuilder`	`getUnenclosedSQL(java.lang.StringBuilder builder, boolean alwaysQuote)` Appends the SQL statement of this expression to the specified builder.
`abstract Value`	`getValue(Session session)` Return the resulting value for the current row.
`boolean`	`isAutoIncrement()` Check if this is an auto-increment column.
`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`	`isNullConstant()` Check if this expression will always return the NULL value.
`boolean`	`isValueSet()` Is the value of a parameter set.
`abstract void`	`mapColumns(ColumnResolver resolver, int level, int state)` Map the columns of the resolver to expression columns.
`abstract Expression`	`optimize(Session session)` Try to optimize the expression.
`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(Session session, int stage)` Update an aggregate value.
`static void`	`writeExpressions(java.lang.StringBuilder builder, Expression[] expressions, boolean alwaysQuote)` Get the SQL snippet for an array of expressions.
`static void`	`writeExpressions(java.lang.StringBuilder builder, java.util.List<? extends Expression> expressions, boolean alwaysQuote)` 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

- 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
- Constructor Detail
  - Expression
```
public Expression()
```
- Method Detail
  - writeExpressions
```
public static void writeExpressions(java.lang.StringBuilder builder,
                    java.util.List<? extends Expression> expressions,
                    boolean alwaysQuote)
```
    Get the SQL snippet for a list of expressions.
    
    Parameters:
    builder - the builder to append the SQL to
    expressions - the list of expressions
    alwaysQuote - quote all identifiers
  - writeExpressions
```
public static void writeExpressions(java.lang.StringBuilder builder,
                    Expression[] expressions,
                    boolean alwaysQuote)
```
    Get the SQL snippet for an array of expressions.
    
    Parameters:
    builder - the builder to append the SQL to
    expressions - the list of expressions
    alwaysQuote - quote all identifiers
  - getValue
```
public abstract Value getValue(Session 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 not be known before the optimization phase.
    
    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(Session session)
```
    Try to optimize the expression.
    
    Parameters:
    session - the session
    
    Returns:
    the optimized expression
  - 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 java.lang.String getSQL(boolean alwaysQuote)
```
    Get the SQL statement of this expression. This may not always be the original SQL statement, specially after optimization.
    
    Parameters:
    alwaysQuote - quote all identifiers
    
    Returns:
    the SQL statement
  - getSQL
```
public abstract java.lang.StringBuilder getSQL(java.lang.StringBuilder builder,
                             boolean alwaysQuote)
```
    Appends the SQL statement of this expression to the specified builder. This may not always be the original SQL statement, specially after optimization.
    
    Parameters:
    builder - string builder
    alwaysQuote - quote all identifiers
    
    Returns:
    the specified string builder
  - getUnenclosedSQL
```
public java.lang.StringBuilder getUnenclosedSQL(java.lang.StringBuilder builder,
                                       boolean alwaysQuote)
```
    Appends the SQL statement of this expression to the specified builder. This may not always be the original SQL statement, specially after optimization. Enclosing '(' and ')' are removed.
    
    Parameters:
    builder - string builder
    alwaysQuote - quote all identifiers
    
    Returns:
    the specified string builder
  - updateAggregate
```
public abstract void updateAggregate(Session 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(Session 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
  - isAutoIncrement
```
public boolean isAutoIncrement()
```
    Check if this is an auto-increment column.
    
    Returns:
    true if it is an auto-increment column
  - getBooleanValue
```
public boolean getBooleanValue(Session 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(Session 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()
```
    Get the column name or alias name of this expression.
    
    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()
```
    Get the alias name of a column or SQL expression if it is not an aliased expression.
    
    Returns:
    the alias name
  - 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
  - getExpressionColumns
```
public Expression[] getExpressionColumns(Session session)
```
    If this expression consists of column expressions it should return them.
    
    Parameters:
    session - the session
    
    Returns:
    array of expression columns if applicable, null otherwise
  - getExpressionColumns
```
protected static Expression[] getExpressionColumns(Session session,
                                ValueCollectionBase value)
```
    Extracts expression columns from ValueArray
    
    Parameters:
    session - the current session
    value - the value to extract columns from
    
    Returns:
    array of expression columns
  - getExpressionColumns
```
public static Expression[] getExpressionColumns(Session session,
                                ResultInterface result)
```
    Extracts expression columns from the given result set.
    
    Parameters:
    session - the session
    result - the result
    
    Returns:
    an array of expression columns
  - 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

Class Expression

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

MAP_INITIAL

MAP_IN_WINDOW

MAP_IN_AGGREGATE

Constructor Detail

Expression

Method Detail

writeExpressions

writeExpressions

getValue

getType

mapColumns

optimize

setEvaluatable

getSQL

getSQL

getUnenclosedSQL

updateAggregate

isEverything

getCost

getNotIfPossible

isConstant

isNullConstant

isValueSet

isAutoIncrement

getBooleanValue

createIndexConditions

getColumnName

getSchemaName

getTableName

getNullable

getTableAlias

getAlias

getNonAliasExpression

addFilterConditions

toString

getExpressionColumns

getExpressionColumns

getExpressionColumns

getSubexpressionCount

getSubexpression