org.h2.index
Class HashIndex

java.lang.Object
  extended by org.h2.engine.DbObjectBase
      extended by org.h2.schema.SchemaObjectBase
          extended by org.h2.index.BaseIndex
              extended by org.h2.index.HashIndex
All Implemented Interfaces:
DbObject, Index, SchemaObject
Direct Known Subclasses:
NonUniqueHashIndex

public class HashIndex
extends BaseIndex

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


Field Summary
protected  int indexColumn
          The index of the indexed column.
 
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, TABLE_OR_VIEW, TRIGGER, USER, USER_DATATYPE
 
Constructor Summary
HashIndex(RegularTable table, int id, java.lang.String indexName, IndexColumn[] columns, IndexType indexType)
           
 
Method Summary
 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)
          Estimate the cost to search for rows given the search mask.
 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, commit, compareRows, find, findNext, getColumnIndex, getColumns, getCreateSQL, getCreateSQLForCopy, getDropSQL, getIndexColumns, getIndexType, getPlanSQL, getRow, getTable, getType, initBaseIndex, isHidden, isRowIdIndex, 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, 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
 

Field Detail

indexColumn

protected final int indexColumn
The index of the indexed column.

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

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)
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 - the search mask
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