org.h2.index

Class HashIndex

java.lang.Object

org.h2.engine.DbObjectBase

org.h2.schema.SchemaObjectBase

org.h2.index.BaseIndex

org.h2.index.HashIndex

All Implemented Interfaces:

DbObject, Index, SchemaObject

public class HashIndex
extends BaseIndex

An unique index based on an in-memory hash map.

Field Summary

Fields inherited from class org.h2.index.BaseIndex

columnIds, columns, indexColumns, indexType, isMultiVersion, table

Fields inherited from class org.h2.engine.DbObjectBase

comment, database, trace

Fields inherited from interface org.h2.engine.DbObject

AGGREGATE, COMMENT, CONSTANT, CONSTRAINT, FUNCTION_ALIAS, INDEX, RIGHT, ROLE, SCHEMA, SEQUENCE, SETTING, SYNONYM, TABLE_OR_VIEW, TRIGGER, USER, USER_DATATYPE

Constructor Summary

Constructors

Constructor and Description
HashIndex(RegularTable table, int id, java.lang.String indexName, IndexColumn[] columns, IndexType indexType)

Method Summary

Modifier and Type	Method and Description
void	add(Session session, Row row) Add a row to the index.
boolean	canGetFirstOrLast() Check if the index can directly look up the lowest or highest value of a column.
boolean	canScan() Can this index iterate over all rows?
void	checkRename() Check if this object can be renamed.
void	close(Session session) Close this index.
Cursor	find(Session session, SearchRow first, SearchRow last) Find a row or a list of rows and create a cursor to iterate over the result.
Cursor	findFirstOrLast(Session session, boolean first) Find the first (or last) value of this index.
double	getCost(Session session, int[] masks, TableFilter[] filters, int filter, SortOrder sortOrder, java.util.HashSet<Column> allColumnsSet) Estimate the cost to search for rows given the search mask.
long	getDiskSpaceUsed() Get the used disk space for this index.
long	getRowCount(Session session) Get the row count of this table, for the given session.
long	getRowCountApproximation() Get the approximated row count for this table.
boolean	needRebuild() Check if the index needs to be rebuilt.
void	remove(Session session) Remove the index.
void	remove(Session session, Row row) Remove a row from the index.
void	truncate(Session session) Remove all rows from the index.

Methods inherited from class org.h2.index.BaseIndex

canFindNext, checkIndexColumnTypes, commit, compareRows, createLookupBatch, find, findNext, getColumnIndex, getColumns, getCostRangeIndex, getCreateSQL, getCreateSQLForCopy, getDropSQL, getDuplicateKeyException, getIndexColumns, getIndexType, getPlanSQL, getRow, getTable, getType, initBaseIndex, isFindUsingFullTableScan, isFirstColumn, isHidden, isRowIdIndex, mayHaveNullDuplicates, removeChildrenAndResources, setSortedInsertMode

Methods inherited from class org.h2.schema.SchemaObjectBase

getSchema, getSQL, initSchemaObjectBase

Methods inherited from class org.h2.engine.DbObjectBase

getChildren, getComment, getDatabase, getId, getModificationId, getName, initDbObjectBase, invalidate, isTemporary, isValid, rename, setComment, setModified, setObjectName, setTemporary, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.h2.schema.SchemaObject

getSchema

Methods inherited from interface org.h2.engine.DbObject

getChildren, getComment, getDatabase, getId, getName, getSQL, isTemporary, rename, setComment, setTemporary

Constructor Detail

HashIndex

public HashIndex(RegularTable table,
                 int id,
                 java.lang.String indexName,
                 IndexColumn[] columns,
                 IndexType indexType)

Method Detail

truncate

public void truncate(Session session)

Description copied from interface: Index

Remove all rows from the index.

Parameters:

session - the session

add

public void add(Session session,
                Row row)

Description copied from interface: Index

Add a row to the index.

Parameters:

session - the session to use

row - the row to add

remove

public void remove(Session session,
                   Row row)

Description copied from interface: Index

Remove a row from the index.

Parameters:

session - the session

row - the row

find

public Cursor find(Session session,
                   SearchRow first,
                   SearchRow last)

Description copied from interface: Index

Find a row or a list of rows and create a cursor to iterate over the result.

Parameters:

session - the session

first - the first row, or null for no limit

last - the last row, or null for no limit

Returns:

the cursor to iterate over the results

getRowCount

public long getRowCount(Session session)

Description copied from interface: Index

Get the row count of this table, for the given session.

Parameters:

session - the session

Returns:

the row count

getRowCountApproximation

public long getRowCountApproximation()

Description copied from interface: Index

Get the approximated row count for this table.

Returns:

the approximated row count

getDiskSpaceUsed

public long getDiskSpaceUsed()

Description copied from interface: Index

Get the used disk space for this index.

Returns:

the estimated number of bytes

close

public void close(Session session)

Description copied from interface: Index

Close this index.

Parameters:

session - the session used to write data

remove

public void remove(Session session)

Description copied from interface: Index

Remove the index.

Parameters:

session - the session

getCost

public double getCost(Session session,
                      int[] masks,
                      TableFilter[] filters,
                      int filter,
                      SortOrder sortOrder,
                      java.util.HashSet<Column> allColumnsSet)

Description copied from interface: Index

Estimate the cost to search for rows given the search mask. There is one element per column in the search mask. For possible search masks, see IndexCondition.

Parameters:

session - the session

masks - per-column comparison bit masks, null means 'always false', see constants in IndexCondition

filters - all joined table filters

filter - the current table filter index

sortOrder - the sort order

allColumnsSet - the set of all columns

Returns:

the estimated cost

checkRename

public void checkRename()

Description copied from class: DbObjectBase

Check if this object can be renamed. System objects may not be renamed.

Specified by:

checkRename in interface DbObject

Specified by:

checkRename in class DbObjectBase

needRebuild

public boolean needRebuild()

Description copied from interface: Index

Check if the index needs to be rebuilt. This method is called after opening an index.

Returns:

true if a rebuild is required.

canGetFirstOrLast

public boolean canGetFirstOrLast()

Description copied from interface: Index

Check if the index can directly look up the lowest or highest value of a column.

Returns:

true if it can

findFirstOrLast

public Cursor findFirstOrLast(Session session,
                              boolean first)

Description copied from interface: Index

Find the first (or last) value of this index. The cursor returned is positioned on the correct row, or on null if no row has been found.

Parameters:

session - the session

first - true if the first (lowest for ascending indexes) or last value should be returned

Returns:

a cursor (never null)

canScan

public boolean canScan()

Description copied from interface: Index

Can this index iterate over all rows?

Specified by:

canScan in interface Index

Overrides:

canScan in class BaseIndex

Returns:

true if it can