org.h2.expression
Class ConditionExists

java.lang.Object
  extended by org.h2.expression.Expression
      extended by org.h2.expression.Condition
          extended by org.h2.expression.ConditionExists

public class ConditionExists
extends Condition

An 'exists' condition as in WHERE EXISTS(SELECT ...)


Constructor Summary
ConditionExists(Query query)
           
 
Method Summary
 int getCost()
          Estimate the cost to process the expression.
 java.lang.String getSQL()
          Get the SQL statement of this expression.
 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.Condition
getDisplaySize, getPrecision, getScale, getType
 
Methods inherited from class org.h2.expression.Expression
addFilterConditions, createIndexConditions, getAlias, getBooleanValue, getColumnName, getNonAliasExpression, getNotIfPossible, getNullable, getSchemaName, getTableAlias, getTableName, isAutoIncrement, isConstant, isEverything, isValueSet, isWildcard, optimizeInJoin, toString
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Constructor Detail

ConditionExists

public ConditionExists(Query query)
Method Detail

getValue

public Value getValue(Session session)
               throws java.sql.SQLException
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
Throws:
java.sql.SQLException

optimize

public Expression optimize(Session session)
                    throws java.sql.SQLException
Description copied from class: Expression
Try to optimize the expression.

Specified by:
optimize in class Expression
Parameters:
session - the session
Returns:
the optimized expression
Throws:
java.sql.SQLException

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

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

mapColumns

public void mapColumns(ColumnResolver resolver,
                       int level)
                throws java.sql.SQLException
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
Throws:
java.sql.SQLException

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

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