ExpressionVisitor

The visitor pattern is used to iterate through all expressions of a query to optimize a statement.

Methods
static HashSet	allColumnsForTableFilters(TableFilter[] filters) Get the set of columns of all tables.
static HashSet	allColumnsForTableFilters(TableFilter[] filters) Get the set of columns of all tables. Parameters: filters - the filters Returns: the set of columns
static ExpressionVisitor	getColumnsVisitor(HashSet columns) Create a new visitor to get all referenced columns.
static ExpressionVisitor	getColumnsVisitor(HashSet columns) Create a new visitor to get all referenced columns. Parameters: columns - the columns map Returns: the new visitor
static ExpressionVisitor	getDependenciesVisitor(HashSet dependencies) Create a new visitor object to collect dependencies.
static ExpressionVisitor	getDependenciesVisitor(HashSet dependencies) Create a new visitor object to collect dependencies. Parameters: dependencies - the dependencies set Returns: the new visitor
static ExpressionVisitor	getMaxModificationIdVisitor()
static ExpressionVisitor	getMaxModificationIdVisitor()
static ExpressionVisitor	getNotFromResolverVisitor(ColumnResolver resolver) Create a new visitor to check if no expression depends on the given resolver.
static ExpressionVisitor	getNotFromResolverVisitor(ColumnResolver resolver) Create a new visitor to check if no expression depends on the given resolver. Parameters: resolver - the resolver Returns: the new visitor
static ExpressionVisitor	getOptimizableVisitor(Table table) Create a new visitor to check if all aggregates are for the given table.
static ExpressionVisitor	getOptimizableVisitor(Table table) Create a new visitor to check if all aggregates are for the given table. Parameters: table - the table Returns: the new visitor
void	addColumn(Column column) Add a new column to the set of columns.
void	addColumn(Column column) Add a new column to the set of columns. This is used for GET_COLUMNS visitors. Parameters: column - the additional column.
void	addDataModificationId(long value) Update the field maxDataModificationId if this value is higher than the current value.
void	addDataModificationId(long value) Update the field maxDataModificationId if this value is higher than the current value. This is used for SET_MAX_DATA_MODIFICATION_ID visitors. Parameters: value - the data modification id
void	addDependency(DbObject obj) Add a new dependency to the set of dependencies.
void	addDependency(DbObject obj) Add a new dependency to the set of dependencies. This is used for GET_DEPENDENCIES visitors. Parameters: obj - the additional dependency.
HashSet	getDependencies() Get the dependency set.
HashSet	getDependencies() Get the dependency set. This is used for GET_DEPENDENCIES visitors. Returns: the set
long	getMaxDataModificationId() Get the last data modification.
long	getMaxDataModificationId() Get the last data modification. This is used for SET_MAX_DATA_MODIFICATION_ID visitors. Returns: the maximum modification id
int	getQueryLevel()
int	getQueryLevel()
ColumnResolver	getResolver() Get the column resolver.
ColumnResolver	getResolver() Get the column resolver. This is used for NOT_FROM_RESOLVER visitors. Returns: the column resolver
Table	getTable() Get the table.
Table	getTable() Get the table. This is used for OPTIMIZABLE_MIN_MAX_COUNT_ALL visitors. Returns: the table
int	getType() Get the visitor type.
int	getType() Get the visitor type. Returns: the type
ExpressionVisitor	incrementQueryLevel(int offset) Increment or decrement the query level.
ExpressionVisitor	incrementQueryLevel(int offset) Increment or decrement the query level. Parameters: offset - 1 to increment, -1 to decrement Returns: a clone of this expression visitor, with the changed query level

Fields
static int	DETERMINISTIC = 2
static ExpressionVisitor	DETERMINISTIC_VISITOR
static int	EVALUATABLE = 3
static ExpressionVisitor	EVALUATABLE_VISITOR
static int	GET_COLUMNS = 9
static int	GET_DEPENDENCIES = 7
static int	INDEPENDENT = 0
static ExpressionVisitor	INDEPENDENT_VISITOR
static int	NOT_FROM_RESOLVER = 6
static int	OPTIMIZABLE_MIN_MAX_COUNT_ALL = 1
static int	QUERY_COMPARABLE = 8
static ExpressionVisitor	QUERY_COMPARABLE_VISITOR
static int	READONLY = 5
static ExpressionVisitor	READONLY_VISITOR
static int	SET_MAX_DATA_MODIFICATION_ID = 4

INDEPENDENT = 0

Is the value independent on unset parameters or on columns of a higher level query, or sequence values (that means can it be evaluated right now)?

OPTIMIZABLE_MIN_MAX_COUNT_ALL = 1

Are all aggregates MIN(column), MAX(column), or COUNT(*) for the given table (getTable)?

DETERMINISTIC = 2

Does the expression return the same results for the same parameters?

EVALUATABLE = 3

Can the expression be evaluated, that means are all columns set to 'evaluatable'?

SET_MAX_DATA_MODIFICATION_ID = 4

Request to set the latest modification id (addDataModificationId).

READONLY = 5

Does the expression have no side effects (change the data)?

NOT_FROM_RESOLVER = 6

Does an expression have no relation to the given table filter (getResolver)?

GET_DEPENDENCIES = 7

Request to get the set of dependencies (addDependency).

QUERY_COMPARABLE = 8

Can the expression be added to a condition of an outer query. Example: ROWNUM() can't be added as a condition to the inner query of select id from (select t.*, rownum as r from test t) where r between 2 and 3; Also a sequence expression must not be used.

GET_COLUMNS = 9

Get all referenced columns.

DETERMINISTIC_VISITOR

The visitor singleton for the type DETERMINISTIC.

EVALUATABLE_VISITOR

The visitor singleton for the type EVALUATABLE.

INDEPENDENT_VISITOR

The visitor singleton for the type INDEPENDENT.

QUERY_COMPARABLE_VISITOR

The visitor singleton for the type QUERY_COMPARABLE.

READONLY_VISITOR

The visitor singleton for the type EVALUATABLE.