org.apache.derby.iapi.sql.compile
Interface OptimizableList

All Known Implementing Classes:

FromList

public interface OptimizableList

OptimizableList provides services for optimizing a list of Optimizables (tables) in a query.

Method Summary

Optimizable	getOptimizable(int n) Return the nth Optimizable in the list.
void	initAccessPaths(Optimizer optimizer) Init the access paths for these optimizables.
boolean	legalJoinOrder(int numTablesInQuery) Tell whether the join order is legal.
boolean	optimizeJoinOrder() Tell whether the join order should be optimized.
void	reOrder(int[] joinOrder) Set the join order for this list of optimizables.
void	setOptimizable(int n, Optimizable optimizable) Set the nth Optimizable to the specified Optimizable.
int	size() Return the number of Optimizables in the list.
boolean	useStatistics() user can specify that s/he doesn't want statistics to be considered when optimizing the query.
void	verifyProperties(DataDictionary dDictionary) Verify that the Properties list with optimizer overrides, if specified, is valid

Method Detail

size

int size()

Return the number of Optimizables in the list.

Returns:

integer The number of Optimizables in the list.

getOptimizable

Optimizable getOptimizable(int n)

Return the nth Optimizable in the list.

Parameters:

n - "index" (0 based) into the list.

Returns:

Optimizable The nth Optimizables in the list.

setOptimizable

void setOptimizable(int n,
                    Optimizable optimizable)

Set the nth Optimizable to the specified Optimizable.

Parameters:

n - "index" (0 based) into the list.

optimizable - New nth Optimizable.

verifyProperties

void verifyProperties(DataDictionary dDictionary)
                      throws StandardException

Verify that the Properties list with optimizer overrides, if specified, is valid

Parameters:

dDictionary - The DataDictionary to use.

Throws:

StandardException - Thrown on error

reOrder

void reOrder(int[] joinOrder)

Set the join order for this list of optimizables. The join order is represented as an array of integers - each entry in the array stands for the order of the corresponding element in the list. For example, a joinOrder of {2, 0, 1} means that the 3rd Optimizable in the list (element 2, since we are zero-based) is the first one in the join order, followed by the 1st element in the list, and finally by the 2nd element in the list. This method shuffles this OptimizableList to match the join order. Obviously, the size of the array must equal the number of elements in the array, and the values in the array must be between 0 and the number of elements in the array minus 1, and the values in the array must be unique.

useStatistics

boolean useStatistics()

user can specify that s/he doesn't want statistics to be considered when optimizing the query.

optimizeJoinOrder

boolean optimizeJoinOrder()

Tell whether the join order should be optimized.

legalJoinOrder

boolean legalJoinOrder(int numTablesInQuery)

Tell whether the join order is legal.

initAccessPaths

void initAccessPaths(Optimizer optimizer)

Init the access paths for these optimizables.

Parameters:

optimizer - The optimizer being used.