Apache Derby Database Engine and Embedded JDBC Driver 10.17.1.0 · org.apache.derby.catalog.IndexDescriptor

This interface describes an index. It is used in the column SYS.SYSCONGLOMERATES.DESCRIPTOR and describes everything about an index except the index name and the table on which the index is defined. That information is available in the columns NAME and TABLEID of the table SYS.SYSCONGLOMERATES.

Whereas non-deferrable constraints are backed by UNIQUE indexes, deferrable constraints are backed by non-unique indexes. The duplicate checking on inserts and updates for deferrable constraints are handled at the language level, not by the store level. The following table shows the correspondence between the constraint types and the index attributes used:

Non-deferrable PRIMARY KEY and UNIQUE NOT NULL on all constraint columns

                           \  Value  | Number of index columns | Check
  Attribute                 \        | in physical BTree key   | in
  --------------------------------------------------------------------
  unique                     | true  | N - 1 (row location     |
  isUniqueWithDuplicateNulls | false |        not part of key) | Store
  uniqueDeferrable           | false |                         | Btree
  hasDeferrableChecking      | false |                         | code

Non-deferrable UNIQUE, where at least one constraint column is nullable.

                           \  Value  | Number of index columns | Check
  Attribute                 \        | in physical BTree key   | in
  ------------------------------------------------------------ -------
  unique                     | false | N                       |
  isUniqueWithDuplicateNulls | true  |                         | Store
  uniqueDeferrable           | false |                         | Btree
  hasDeferrableChecking      | false |                         | code

Deferrable PRIMARY KEY and UNIQUE NOT NULL on all constraint columns

                           \  Value  | Number of index columns | Check
  Attribute                 \        | in physical BTree key   | in
  ------------------------------------------------------------ -------
  unique                     | false | N                       |
  isUniqueWithDuplicateNulls | false |                         | Lang.
  uniqueDeferrable           | true  |                         | code
  hasDeferrableChecking      | true  |                         |

Deferrable UNIQUE, where at least one constraint column is nullable.

                           \  Value  | Number of index columns | Check
  Attribute                 \        | in physical BTree key   | in
  ------------------------------------------------------------ -------
  unique                     | false | N                       |
  isUniqueWithDuplicateNulls | true  |                         | Lang.
  uniqueDeferrable           | false |                         | code
  hasDeferrableChecking      | true  |                         |

Method Summary

Modifier and Type	Method and Description
public int[]	Returns: an array of column positions in the base table baseColumnPositions() Returns an array of column positions in the base table.
public int	Returns: the position of the column in the key getKeyColumnPosition(int Position of column in heap row heapColumnPosition) Returns the postion of a column.
public boolean	Returns: true if the index is used to support a deferrable constraint hasDeferrableChecking() Returns true if the index is used to support a deferrable constraint.
public String	Returns: the type of the index indexType() Returns the type of the index.
public boolean[]	Returns: array of boolean telling asc/desc info for each index key isAscending() Returns array of boolean telling asc/desc info for each index key column for convenience of using together with baseColumnPositions method.
public boolean	Returns: true if the specified column is ascending in the index isAscending(Integer Key column number keyColumnPosition) Returns true if the specified column is ascending in the index (1-based).
public boolean	Returns: true if the specified column is descending in the index isDescending(Integer Key column number keyColumnPosition) Returns true if the specified column is descending in the index (1-based).
public boolean	Returns: true if the index is unique isUnique() Returns true if the index is unique.
public boolean	Returns: `true` if the index represents such a constraint isUniqueDeferrable() The index represents a PRIMARY KEY or a UNIQUE NOT NULL constraint which is deferrable.
public boolean	Returns: true if the index is duplicate keys only for null key parts isUniqueWithDuplicateNulls() Returns true if the index is duplicate keys only for null key parts.
public int	Returns: the number of ordered columns numberOfOrderedColumns() Returns the number of ordered columns.
public void	setBaseColumnPositions(int[] Positions of base columns baseColumnPositions) set the baseColumnPositions field of the index descriptor.
public void	setIsAscending(boolean[] Set the direction of each column in the key isAscending) set the isAscending field of the index descriptor.
public void	setNumberOfOrderedColumns(int Number of ordered columns numberOfOrderedColumns) set the numberOfOrderedColumns field of the index descriptor.

Method Detail

baseColumnPositions	back to summary
public int[] baseColumnPositions() Returns an array of column positions in the base table. Each index column corresponds to a column position in the base table, except the column representing the location of the row in the base table. The returned array holds the column positions in the base table, so, if entry 2 is the number 4, the second column in the index is the fourth column in the table. Returns:int[] an array of column positions in the base table

baseColumnPositions

back to summary

public int[] baseColumnPositions()

Returns an array of column positions in the base table. Each index column corresponds to a column position in the base table, except the column representing the location of the row in the base table. The returned array holds the column positions in the base table, so, if entry 2 is the number 4, the second column in the index is the fourth column in the table.

Returns:int[]: an array of column positions in the base table

getKeyColumnPosition	back to summary
public int getKeyColumnPosition(int heapColumnPosition) Returns the postion of a column. Returns the position of a column within the key (1-based). 0 means that the column is not in the key. Same as the above method, but it uses int instead of Integer. Parameters heapColumnPosition:int Position of column in heap row Returns:int the position of the column in the key

getKeyColumnPosition

back to summary

public int getKeyColumnPosition(int heapColumnPosition)

Returns the postion of a column.

Returns the position of a column within the key (1-based). 0 means that the column is not in the key. Same as the above method, but it uses int instead of Integer.

Parameters

heapColumnPosition:int: Position of column in heap row

Returns:int

the position of the column in the key

hasDeferrableChecking	back to summary
public boolean hasDeferrableChecking() Returns true if the index is used to support a deferrable constraint. Returns:boolean true if the index is used to support a deferrable constraint

hasDeferrableChecking

back to summary

public boolean hasDeferrableChecking()

Returns true if the index is used to support a deferrable constraint.

Returns:boolean: true if the index is used to support a deferrable constraint

indexType	back to summary
public String indexType() Returns the type of the index. For now, we only support B-Trees, so the value "BTREE" is returned. Returns:String the type of the index

indexType

back to summary

public String indexType()

Returns the type of the index. For now, we only support B-Trees, so the value "BTREE" is returned.

Returns:String: the type of the index

isAscending	back to summary
public boolean[] isAscending() Returns array of boolean telling asc/desc info for each index key column for convenience of using together with baseColumnPositions method. Both methods return an array with subscript starting from 0. Returns:boolean[] array of boolean telling asc/desc info for each index key

isAscending

back to summary

public boolean[] isAscending()

Returns array of boolean telling asc/desc info for each index key column for convenience of using together with baseColumnPositions method. Both methods return an array with subscript starting from 0.

Returns:boolean[]: array of boolean telling asc/desc info for each index key

isAscending	back to summary
public boolean isAscending(Integer keyColumnPosition) Returns true if the specified column is ascending in the index (1-based). Parameters keyColumnPosition:Integer Key column number Returns:boolean true if the specified column is ascending in the index

isAscending

back to summary

public boolean isAscending(Integer keyColumnPosition)

Returns true if the specified column is ascending in the index (1-based).

Parameters

keyColumnPosition:Integer: Key column number

Returns:boolean

true if the specified column is ascending in the index

isDescending	back to summary
public boolean isDescending(Integer keyColumnPosition) Returns true if the specified column is descending in the index (1-based). In the current release, only ascending columns are supported. Parameters keyColumnPosition:Integer Key column number Returns:boolean true if the specified column is descending in the index

isDescending

back to summary

public boolean isDescending(Integer keyColumnPosition)

Returns true if the specified column is descending in the index (1-based). In the current release, only ascending columns are supported.

Parameters

keyColumnPosition:Integer: Key column number

Returns:boolean

true if the specified column is descending in the index

isUnique	back to summary
public boolean isUnique() Returns true if the index is unique. Returns:boolean true if the index is unique

isUnique

back to summary

public boolean isUnique()

Returns true if the index is unique.

Returns:boolean: true if the index is unique

isUniqueDeferrable back to summary

isUniqueDeferrable	back to summary
public boolean isUniqueDeferrable() The index represents a PRIMARY KEY or a UNIQUE NOT NULL constraint which is deferrable. `true` implies `isUnique() == false` and `isUniqueWithDuplicateNulls() == false` and `hasDeferrableChecking() == true`. Returns:boolean `true` if the index represents such a constraint

public boolean isUniqueDeferrable()

The index represents a PRIMARY KEY or a UNIQUE NOT NULL constraint which is deferrable. true implies isUnique() == false and isUniqueWithDuplicateNulls() == false and hasDeferrableChecking() == true.

Returns:boolean: true if the index represents such a constraint

isUniqueWithDuplicateNulls	back to summary
public boolean isUniqueWithDuplicateNulls() Returns true if the index is duplicate keys only for null key parts. This is effective only if isUnique is false. Returns:boolean true if the index is duplicate keys only for null key parts

isUniqueWithDuplicateNulls

back to summary

public boolean isUniqueWithDuplicateNulls()

Returns true if the index is duplicate keys only for null key parts. This is effective only if isUnique is false.

Returns:boolean: true if the index is duplicate keys only for null key parts

numberOfOrderedColumns	back to summary
public int numberOfOrderedColumns() Returns the number of ordered columns. In the future, it will be possible to store non-ordered columns in an index. These will be useful for covered queries. The ordered columns will be at the beginning of the index row, and they will be followed by the non-ordered columns. For now, all columns in an index must be ordered. Returns:int the number of ordered columns

numberOfOrderedColumns

back to summary

public int numberOfOrderedColumns()

Returns the number of ordered columns.

In the future, it will be possible to store non-ordered columns in an index. These will be useful for covered queries. The ordered columns will be at the beginning of the index row, and they will be followed by the non-ordered columns. For now, all columns in an index must be ordered.

Returns:int: the number of ordered columns

setBaseColumnPositions	back to summary
public void setBaseColumnPositions(int[] baseColumnPositions) set the baseColumnPositions field of the index descriptor. This is for updating the field in operations such as "alter table drop column" where baseColumnPositions is changed. Parameters baseColumnPositions:int[] Positions of base columns

setBaseColumnPositions

back to summary

public void setBaseColumnPositions(int[] baseColumnPositions)

set the baseColumnPositions field of the index descriptor. This is for updating the field in operations such as "alter table drop column" where baseColumnPositions is changed.

Parameters

baseColumnPositions:int[]: Positions of base columns

setIsAscending	back to summary
public void setIsAscending(boolean[] isAscending) set the isAscending field of the index descriptor. This is for updating the field in operations such as "alter table drop column" where isAscending is changed. Parameters isAscending:boolean[] Set the direction of each column in the key

setIsAscending

back to summary

public void setIsAscending(boolean[] isAscending)

set the isAscending field of the index descriptor. This is for updating the field in operations such as "alter table drop column" where isAscending is changed.

Parameters

isAscending:boolean[]: Set the direction of each column in the key

setNumberOfOrderedColumns	back to summary
public void setNumberOfOrderedColumns(int numberOfOrderedColumns) set the numberOfOrderedColumns field of the index descriptor. This is for updating the field in operations such as "alter table drop column" where numberOfOrderedColumns is changed. Parameters numberOfOrderedColumns:int Number of ordered columns

setNumberOfOrderedColumns

back to summary

public void setNumberOfOrderedColumns(int numberOfOrderedColumns)

set the numberOfOrderedColumns field of the index descriptor. This is for updating the field in operations such as "alter table drop column" where numberOfOrderedColumns is changed.

Parameters

numberOfOrderedColumns:int: Number of ordered columns

public Interface IndexDescriptor

Method Summary

Method Detail