Class DiskHashtable

java.lang.Object
org.apache.derby.iapi.store.access.DiskHashtable
public class DiskHashtable extends Object
This class is used by BackingStoreHashtable when the BackingStoreHashtable must spill to disk. It implements the methods of a hash table: put, get, remove, elements, however it is not implemented as a hash table. In order to minimize the amount of unique code it is implemented using a Btree and a heap conglomerate. The Btree indexes the hash code of the row key. The actual key may be too long for our Btree implementation. Created: Fri Jan 28 13:58:03 2005
Version:
1.0

  • Field Details

    • rowConglomerateId

      private final long rowConglomerateId

    • rowConglomerate

      private ConglomerateController rowConglomerate

    • btreeConglomerateId

      private final long btreeConglomerateId

    • btreeConglomerate

      private ConglomerateController btreeConglomerate

    • btreeRow

      private final DataValueDescriptor[] btreeRow

    • key_column_numbers

      private final int[] key_column_numbers

    • remove_duplicates

      private final boolean remove_duplicates

    • tc

      private final TransactionController tc

    • row

      private final DataValueDescriptor[] row

    • scanKey

      private final DataValueDescriptor[] scanKey

    • size

      private int size

    • keepStatistics

      private boolean keepStatistics

    • keepAfterCommit

      private final boolean keepAfterCommit

  • Constructor Details

    • DiskHashtable

      public DiskHashtable(TransactionController tc, DataValueDescriptor[] template, int[] collation_ids, int[] key_column_numbers, boolean remove_duplicates, boolean keepAfterCommit) throws StandardException
      Creates a new DiskHashtable instance.
      Parameters:
      tc -
      template - An array of DataValueDescriptors that serves as a template for the rows.
      key_column_numbers - The indexes of the key columns (0 based)
      remove_duplicates - If true then rows with duplicate keys are removed.
      keepAfterCommit - If true then the hash table is kept after a commit
      Throws:
      StandardException

  • Method Details

    • close

      public void close() throws StandardException
      Throws:
      StandardException

    • put

      public boolean put(Object key, Object[] row) throws StandardException
      Put a new row in the overflow structure.
      Parameters:
      row - The row to be inserted.
      Returns:
      true if the row was added, false if it was not added (because it was a duplicate and we are eliminating duplicates).
      Throws:
      StandardException - standard error policy

    • get

      public Object get(Object key) throws StandardException
      Get a row from the overflow structure.
      Parameters:
      key - If the rows only have one key column then the key value. If there is more than one key column then a KeyHasher
      Returns:
      null if there is no corresponding row, the row (DataValueDescriptor[]) if there is exactly one row with the key, or a Vector of all the rows with the key if there is more than one.
      Throws:
      StandardException

    • getRemove

      private Object getRemove(Object key, boolean remove, boolean existenceOnly) throws StandardException
      Throws:
      StandardException

    • rowMatches

      private boolean rowMatches(DataValueDescriptor[] row, Object key)

    • remove

      public Object remove(Object key) throws StandardException
      remove all rows with a given key from the hash table.
      Parameters:
      key - The key of the rows to remove.
      Returns:
      The removed row(s).
      Throws:
      StandardException - Standard exception policy.

    • size

      public int size()
      Returns:
      The number of rows in the hash table

    • elements

      public Enumeration<Object> elements() throws StandardException
      Return an Enumeration that can be used to scan entire table.

      RESOLVE - is it worth it to support this routine?

      Returns:
      The Enumeration.
      Throws:
      StandardException - Standard exception policy.

    • getContextOrNull

      private static Context getContextOrNull(String contextID)
      Privileged lookup of a Context. Must be private so that user code can't call this entry point.