Expression

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

Methods
static Expression[]	getExpressionColumns(Session session, ValueArray value) Extracts expression columns from ValueArray
static Expression[]	getExpressionColumns(Session session, ValueArray value) Extracts expression columns from ValueArray Parameters: session - the current session value - the value to extract columns from Returns: array of expression columns
static Expression[]	getExpressionColumns(Session session, ResultSet rs) Extracts expression columns from the given result set.
static Expression[]	getExpressionColumns(Session session, ResultSet rs) Extracts expression columns from the given result set. Parameters: session - the session rs - the result set Returns: an array of expression columns
void	addFilterConditions(TableFilter filter, boolean outerJoin) Add conditions to a table filter if they can be evaluated.
void	addFilterConditions(TableFilter filter, boolean outerJoin) Add conditions to a table filter if they can be evaluated. Parameters: filter - the table filter outerJoin - if the expression is part of an outer join
void	createIndexConditions(Session session, TableFilter filter) Create index conditions if possible and attach them to the table filter.
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
String	getAlias() Get the alias name of a column or SQL expression if it is not an aliased expression.
String	getAlias() Get the alias name of a column or SQL expression if it is not an aliased expression. Returns: the alias name
boolean	getBooleanValue(Session session) Get the value in form of a boolean expression.
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
String	getColumnName() Get the column name or alias name of this expression.
String	getColumnName() Get the column name or alias name of this expression. Returns: the column name
int	getCost() Estimate the cost to process the expression.
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
int	getDisplaySize() Get the display size of this expression.
int	getDisplaySize() Get the display size of this expression. Returns: the display size
Expression[]	getExpressionColumns(Session session) If this expression consists of column expressions it should return them.
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
Expression	getNonAliasExpression() Returns the main expression, skipping aliases.
Expression	getNonAliasExpression() Returns the main expression, skipping aliases. Returns: the expression
Expression	getNotIfPossible(Session session) If it is possible, return the negated expression.
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
int	getNullable() Check whether this expression is a column and can store NULL.
int	getNullable() Check whether this expression is a column and can store NULL. Returns: whether NULL is allowed
long	getPrecision() Get the precision of this expression.
long	getPrecision() Get the precision of this expression. Returns: the precision
String	getSQL() Get the SQL statement of this expression.
String	getSQL() Get the SQL statement of this expression. This may not always be the original SQL statement, specially after optimization. Returns: the SQL statement
int	getScale() Get the scale of this expression.
int	getScale() Get the scale of this expression. Returns: the scale
String	getSchemaName() Get the schema name, or null
String	getSchemaName() Get the schema name, or null Returns: the schema name
String	getTableAlias() Get the table alias name or null if this expression does not represent a column.
String	getTableAlias() Get the table alias name or null if this expression does not represent a column. Returns: the table alias name
String	getTableName() Get the table name, or null
String	getTableName() Get the table name, or null Returns: the table name
int	getType() Return the data type.
int	getType() Return the data type. The data type may not be known before the optimization phase. Returns: the type
Value	getValue(Session session) Return the resulting value for the current row.
Value	getValue(Session session) Return the resulting value for the current row. Parameters: session - the session Returns: the result
boolean	isAutoIncrement() Check if this is an auto-increment column.
boolean	isAutoIncrement() Check if this is an auto-increment column. Returns: true if it is an auto-increment column
boolean	isConstant() Check if this expression will always return the same value.
boolean	isConstant() Check if this expression will always return the same value. Returns: if the expression is constant
boolean	isEverything(ExpressionVisitor visitor) Check if this expression and all sub-expressions can fulfill a criteria.
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
boolean	isValueSet() Is the value of a parameter set.
boolean	isValueSet() Is the value of a parameter set. Returns: true if set
boolean	isWildcard() Only returns true if the expression is a wildcard.
boolean	isWildcard() Only returns true if the expression is a wildcard. Returns: if this expression is a wildcard
void	mapColumns(ColumnResolver resolver, int level) Map the columns of the resolver to expression columns.
void	mapColumns(ColumnResolver resolver, int level) Map the columns of the resolver to expression columns. Parameters: resolver - the column resolver level - the subquery nesting level
Expression	optimize(Session session) Try to optimize the expression.
Expression	optimize(Session session) Try to optimize the expression. Parameters: session - the session Returns: the optimized expression
void	setEvaluatable(TableFilter tableFilter, boolean value) Tell the expression columns whether the table filter can return values now.
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
String	toString() Convert this expression to a String.
String	toString() Convert this expression to a String. Returns: the string representation
void	updateAggregate(Session session) Update an aggregate value.
void	updateAggregate(Session session) 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