org.apache.derby.impl.store.access.conglomerate

Class GenericCostController

java.lang.Object

org.apache.derby.impl.store.access.conglomerate.GenericCostController

All Implemented Interfaces:

RowCountable, StoreCostController

Direct Known Subclasses:

HeapCostController

public abstract class GenericCostController
extends java.lang.Object
implements StoreCostController

A Generic class which implements the basic functionality needed for a cost controller.

Field Summary

Fields inherited from interface org.apache.derby.iapi.store.access.StoreCostController

BASE_CACHED_ROW_FETCH_COST, BASE_GROUPSCAN_ROW_COST, BASE_HASHSCAN_ROW_FETCH_COST, BASE_NONGROUPSCAN_ROW_FETCH_COST, BASE_ROW_PER_BYTECOST, BASE_UNCACHED_ROW_FETCH_COST, STORECOST_CLUSTERED, STORECOST_SCAN_NORMAL, STORECOST_SCAN_SET

Constructor Summary

Constructors

Constructor and Description
GenericCostController()

Method Summary

Modifier and Type	Method and Description
void	checkConsistency() Public Methods implementing ConglomerateController which just delegate to OpenConglomerate:
void	close()
void	debugConglomerate()
long	getEstimatedRowCount() Get the total estimated number of rows in the container.
double	getFetchFromFullKeyCost(FormatableBitSet validColumns, int access_type) Return the cost of exact key lookup.
java.util.Properties	getInternalTablePropertySet(java.util.Properties prop)
OpenConglomerate	getOpenConglom()
SpaceInfo	getSpaceInfo()
void	getTableProperties(java.util.Properties prop)
void	init(OpenConglomerate open_conglom) Public Methods of This class:
boolean	isKeyed()
boolean	isTableLocked() is the open btree table locked?
RowLocation	newRowLocationTemplate()
void	setEstimatedRowCount(long count) Set the total estimated number of rows in the container.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.apache.derby.iapi.store.access.StoreCostController

close, getFetchFromRowLocationCost, getScanCost, newRowLocationTemplate

Methods inherited from interface org.apache.derby.iapi.store.access.RowCountable

getEstimatedRowCount, setEstimatedRowCount

Constructor Detail

GenericCostController

public GenericCostController()

Method Detail

getFetchFromFullKeyCost

public double getFetchFromFullKeyCost(FormatableBitSet validColumns,
                                      int access_type)
                               throws StandardException

Return the cost of exact key lookup.

Return the estimated cost of calling ScanController.fetch() on the current conglomerate, with start and stop positions set such that an exact match is expected.

This call returns the cost of a fetchNext() performed on a scan which has been positioned with a start position which specifies exact match on all keys in the row.

Example:

In the case of a btree this call can be used to determine the cost of doing an exact probe into btree, giving all key columns. This cost can be used if the client knows it will be doing an exact key probe but does not have the key's at optimize time to use to make a call to getScanCost()

Specified by:

getFetchFromFullKeyCost in interface StoreCostController

Parameters:

validColumns - A description of which columns to return from row on the page into "templateRow." templateRow, and validColumns work together to describe the row to be returned by the fetch - see RowUtil for description of how these three parameters work together to describe a fetched "row".

access_type - Describe the type of access the query will be performing to the ScanController. STORECOST_CLUSTERED - The location of one scan is likely clustered "close" to the previous scan. For instance if the query plan were to used repeated "reopenScan()'s" to probe for the next key in an index, then this flag should be be specified. If this flag is not set then each scan will be costed independant of any other predicted scan access.

Returns:

The cost of the fetch.

Throws:

StandardException - Standard exception policy.

See Also:

RowUtil

init

public void init(OpenConglomerate open_conglom)
          throws StandardException

Public Methods of This class:

Throws:

StandardException

getOpenConglom

public OpenConglomerate getOpenConglom()

checkConsistency

public void checkConsistency()
                      throws StandardException

Public Methods implementing ConglomerateController which just delegate to OpenConglomerate:

Throws:

StandardException

debugConglomerate

public void debugConglomerate()
                       throws StandardException

Throws:

StandardException

getTableProperties

public void getTableProperties(java.util.Properties prop)
                        throws StandardException

Throws:

StandardException

getInternalTablePropertySet

public java.util.Properties getInternalTablePropertySet(java.util.Properties prop)
                                                 throws StandardException

Throws:

StandardException

getSpaceInfo

public SpaceInfo getSpaceInfo()
                       throws StandardException

Throws:

StandardException

close

public void close()
           throws StandardException

Throws:

StandardException

isKeyed

public boolean isKeyed()

newRowLocationTemplate

public RowLocation newRowLocationTemplate()
                                   throws StandardException

Throws:

StandardException

isTableLocked

public boolean isTableLocked()

is the open btree table locked?

getEstimatedRowCount

public long getEstimatedRowCount()
                          throws StandardException

Get the total estimated number of rows in the container.

The number is a rough estimate and may be grossly off. In general the server will cache the row count and then occasionally write the count unlogged to a backing store. If the system happens to shutdown before the store gets a chance to update the row count it may wander from reality.

This call is currently only supported on Heap conglomerates, it will throw an exception if called on btree conglomerates.

Returns:

The total estimated number of rows in the conglomerate.

Throws:

StandardException - Standard exception policy.

setEstimatedRowCount

public void setEstimatedRowCount(long count)
                          throws StandardException

Set the total estimated number of rows in the container.

Often, after a scan, the client of RawStore has a much better estimate of the number of rows in the container than what store has. For instance if we implement some sort of update statistics command, or just after a create index a complete scan will have been done of the table. In this case this interface allows the client to set the estimated row count for the container, and store will use that number for all future references.

This call is currently only supported on Heap conglomerates, it will throw an exception if called on btree conglomerates.

Parameters:

count - the estimated number of rows in the container.

Throws:

StandardException - Standard exception policy.