Interface IndexDescriptor

  • All Known Implementing Classes:
    IndexDescriptorImpl, IndexRowGenerator

    public interface 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

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

      • isUnique

        boolean isUnique()
        Returns true if the index is unique.
      • isUniqueWithDuplicateNulls

        boolean isUniqueWithDuplicateNulls()
        Returns true if the index is duplicate keys only for null key parts. This is effective only if isUnique is false.
      • isUniqueDeferrable

        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:
        true if the index represents such a constraint
      • hasDeferrableChecking

        boolean hasDeferrableChecking()
        Returns true if the index is used to support a deferrable constraint.
      • baseColumnPositions

        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.
      • getKeyColumnPosition

        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.

      • numberOfOrderedColumns

        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.

      • indexType

        java.lang.String indexType()
        Returns the type of the index. For now, we only support B-Trees, so the value "BTREE" is returned.
      • isAscending

        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.
      • isAscending

        boolean isAscending​(java.lang.Integer keyColumnPosition)
        Returns true if the specified column is ascending in the index (1-based).
      • isDescending

        boolean isDescending​(java.lang.Integer keyColumnPosition)
        Returns true if the specified column is descending in the index (1-based). In the current release, only ascending columns are supported.
      • setBaseColumnPositions

        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.
      • setIsAscending

        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.
      • setNumberOfOrderedColumns

        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.