org.h2.expression
Class ExpressionColumn

java.lang.Object
  extended by org.h2.expression.Expression
      extended by org.h2.expression.ExpressionColumn

public class ExpressionColumn
extends Expression

A expression that represents a column of a table or view.


Constructor Summary
ExpressionColumn(Database database, Column column)
           
ExpressionColumn(Database database, java.lang.String schemaName, java.lang.String tableAlias, java.lang.String columnName)
           
 
Method Summary
 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.
 Column getColumn()
           
 java.lang.String getColumnName()
          Get the column name or alias name of this expression.
 int getCost()
          Estimate the cost to process the expression.
 int getDisplaySize()
          Get the display size of this expression.
 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 getOriginalColumnName()
           
 java.lang.String getOriginalTableAliasName()
           
 long getPrecision()
          Get the precision of this expression.
 int getScale()
          Get the scale of this expression.
 java.lang.String getSchemaName()
          Get the schema name, or null
 java.lang.String getSQL()
          Get the SQL statement of this expression.
 TableFilter getTableFilter()
           
 java.lang.String getTableName()
          Get the table name, or null
 int getType()
          Return the data type.
 Value getValue(Session session)
          Return the resulting value for the current row.
 boolean isAutoIncrement()
          Check if this is an auto-increment column.
 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
addFilterConditions, getBooleanValue, getExpressionColumns, getExpressionColumns, getExpressionColumns, getNonAliasExpression, getTableAlias, isConstant, isEverything, isValueSet, isWildcard, toString
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Constructor Detail

ExpressionColumn

public ExpressionColumn(Database database,
                        Column column)

ExpressionColumn

public ExpressionColumn(Database database,
                        java.lang.String schemaName,
                        java.lang.String tableAlias,
                        java.lang.String columnName)
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

getTableFilter

public TableFilter getTableFilter()

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

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

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

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

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

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

getColumn

public Column getColumn()

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

getOriginalColumnName

public java.lang.String getOriginalColumnName()

getOriginalTableAliasName

public java.lang.String getOriginalTableAliasName()

getColumnName

public java.lang.String getColumnName()
Description copied from class: Expression
Get the column name or alias name of this expression.

Overrides:
getColumnName in class Expression
Returns:
the column name

getSchemaName

public java.lang.String getSchemaName()
Description copied from class: Expression
Get the schema name, or null

Overrides:
getSchemaName in class Expression
Returns:
the schema name

getTableName

public java.lang.String getTableName()
Description copied from class: Expression
Get the table name, or null

Overrides:
getTableName in class Expression
Returns:
the table name

getAlias

public java.lang.String getAlias()
Description copied from class: Expression
Get the alias name of a column or SQL expression if it is not an aliased expression.

Overrides:
getAlias in class Expression
Returns:
the alias name

isAutoIncrement

public boolean isAutoIncrement()
Description copied from class: Expression
Check if this is an auto-increment column.

Overrides:
isAutoIncrement in class Expression
Returns:
true if it is an auto-increment column

getNullable

public int getNullable()
Description copied from class: Expression
Check whether this expression is a column and can store NULL.

Overrides:
getNullable in class Expression
Returns:
whether NULL is allowed

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

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

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