Documentation of 'org.apache.derby.impl.store.access.btree.BTree' Java class
BTree
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org.apache.derby.impl.store.access.btree

Class BTree

  • All Implemented Interfaces:
    java.io.Externalizable, java.io.Serializable, java.lang.Comparable, Formatable, Storable, TypedFormat, Conglomerate, DataValueDescriptor, Orderable
    Direct Known Subclasses:
    B2I

    public abstract class BTree
extends GenericConglomerate
    A b-tree object corresponds to an instance of a b-tree conglomerate. It contains the static information about a conglomerate which is built at create conglomerate time.

    This generic implementation is expected to be extended by the concreate implementations.

    The fields are set when the conglomerate is created and never changed thereafter. When alter table is supported then it will change under the control of a table level lock.

    They have package scope because they're read by the scans and controllers.

    A table of all conglomerates in the system is maintained by the accessmanager. A cache of conglomerates is maintained in the accessmanager, and references to the read only objects are handed out. A copy of the Conglomerate object is kept in the control row of the root page, so that during logical undo this information can be read without needing to access the possibly corrupt table maintained by the access manager.

    See Also:
    Serialized Form

    • Field Detail

      • ROOTPAGEID

        public static final long ROOTPAGEID
        The page number of the root page is always at the fixed page number: ROOTPAGEID. This means that given an open container, during logical undo one can always find the root page and look up the conglomerate information.
        See Also:
        Constant Field Values

      • PROPERTY_MAX_ROWS_PER_PAGE_PARAMETER

        public static final java.lang.String PROPERTY_MAX_ROWS_PER_PAGE_PARAMETER
        Property name for the maximum number of rows to place in a btree page (leaf or branch). Equal to 'derby.access.btreeMaxRowPerPage'. Used by tests and debugging to exactly control split points, and to make it easier to test tall trees without needing lots of data.

      • PROPERTY_ALLOWDUPLICATES

        public static final java.lang.String PROPERTY_ALLOWDUPLICATES
        See Also:
        Constant Field Values

      • PROPERTY_NKEYFIELDS

        public static final java.lang.String PROPERTY_NKEYFIELDS
        See Also:
        Constant Field Values

      • PROPERTY_NUNIQUECOLUMNS

        public static final java.lang.String PROPERTY_NUNIQUECOLUMNS
        See Also:
        Constant Field Values

      • PROPERTY_PARENTLINKS

        public static final java.lang.String PROPERTY_PARENTLINKS
        See Also:
        Constant Field Values

      • PROPERTY_UNIQUE_WITH_DUPLICATE_NULLS

        public static final java.lang.String PROPERTY_UNIQUE_WITH_DUPLICATE_NULLS
        See Also:
        Constant Field Values

    • Constructor Detail

      • BTree

        public BTree()

    • Method Detail

      • lockTable

        public abstract ConglomerateController lockTable(TransactionManager xact_manager,
                                                 int open_mode,
                                                 int lock_level,
                                                 int isolation_level)
                                          throws StandardException
        Lock the base table.

        Assumes that segment of the base container is the same as the segment of the btree segment.

        RESOLVE - we really want to get the lock without opening the container. raw store will be providing this.

        Parameters:
        xact_manager - Transaction to associate the lock with.
        Throws:
        StandardException - Standard exception policy.

      • createTemplate

        public final DataValueDescriptor[] createTemplate(Transaction rawtran)
                                           throws StandardException
        Create a template for this conglomerate.

        Reads the format id's of each of the columns and manufactures object of the given type for each. It then uses these "empty" objects to create a template row.

        This method is public so that B2IUndo() can call it.

        Returns:
        The new template.
        Throws:
        StandardException - Standard exception policy.

      • isUnique

        public final boolean isUnique()
        Is this a "unique" index?

      • setUniqueWithDuplicateNulls

        public void setUniqueWithDuplicateNulls(boolean uniqueWithDuplicateNulls)
        Set if the index is unique only for non null keys
        Parameters:
        uniqueWithDuplicateNulls - true if the index will be unique only for non null keys

      • isUniqueWithDuplicateNulls

        public boolean isUniqueWithDuplicateNulls()
        Returns if the index type is uniqueWithDuplicateNulls.
        Returns:
        is index type is uniqueWithDuplicateNulls

      • addColumn

        public void addColumn(TransactionManager xact_manager,
                      int column_id,
                      Storable template_column,
                      int collation_id)
               throws StandardException
        Add a column to the conglomerate.

        Currently B2I does not support this operation. input template column.

        Parameters:
        xact_manager - Transaction to associate the lock with.
        column_id - The column number to add this column at.
        template_column - An instance of the column to be added to table.
        collation_id - Collation id of the added column.
        Throws:
        StandardException - Standard exception policy.

      • getId

        public final ContainerKey getId()
        Get the id of the container of the conglomerate.

        Will have to change when a conglomerate could have more than one container. The ContainerKey is a combination of the container id and segment id.

        Returns:
        The ContainerKey.

      • create

        public void create(Transaction rawtran,
                   int segmentId,
                   long input_containerid,
                   DataValueDescriptor[] template,
                   java.util.Properties properties,
                   int conglom_format_id,
                   int tmpFlag)
            throws StandardException
        Do the generic part of creating a b-tree conglomerate. This method is called from the concrete subclass (which may also read some properties).

        This method processes all properties which are generic to all BTree's. It creates the container for the btree.

        The following properties are generic to a b-tree conglomerate. :

        • "allowDuplicates" (boolean). If set to true the table will allow rows which are duplicate in key column's 0 through (nUniqueColumns - 1). Currently only supports "false". This property is optional, defaults to false.
        • "nKeyFields" (integer) Columns 0 through (nKeyFields - 1) will be included in key of the conglomerate. This implementation requires that "nKeyFields" must be the same as the number of fields in the conglomerate, including the rowLocationColumn. Other implementations may relax this restriction to allow non-key fields in the index. This property is required.
        • "nUniqueColumns" (integer) Columns 0 through "nUniqueColumns" will be used to check for uniqueness. So for a standard SQL non-unique index implementation set "nUniqueColumns" to the same value as "nKeyFields"; and for a unique index set "nUniqueColumns" to "nKeyFields" - 1 (ie. don't include the rowLocationColumn in the uniqueness check). This property is required.
        • "maintainParentLinks" (boolean) Whether the b-tree pages maintain the page number of their parent. Only used for consistency checking. It takes a certain amount more effort to maintain these links, but they're really handy for ensuring that the index is consistent. This property is optional, defaults to true.
        Throws:
        StandardException - Thrown by underlying raw store, or thrown by this routine on an invalid containerid.

      • getContainerid

        public long getContainerid()
        Description copied from interface: Conglomerate
        Get the containerid of conglomerate.

        Will have to change when a conglomerate could have more than one containerid.

        Returns:
        The containerid.

      • getDynamicCompiledConglomInfo

        public DynamicCompiledOpenConglomInfo getDynamicCompiledConglomInfo()
                                                             throws StandardException
        Return dynamic information about the conglomerate to be dynamically reused in repeated execution of a statement.

        The dynamic info is a set of variables to be used in a given ScanController or ConglomerateController. It can only be used in one controller at a time. It is up to the caller to insure the correct thread access to this info. The type of info in this is a scratch template for btree traversal, other scratch variables for qualifier evaluation, ...

        Returns:
        The dynamic information.
        Throws:
        StandardException - Standard exception policy.

      • isTemporary

        public boolean isTemporary()
        Is this conglomerate temporary?

        Returns:
        whether conglomerate is temporary or not.

      • isNull

        public boolean isNull()
        Return whether the value is null or not. The containerid being zero is what determines nullness; subclasses are not expected to override this method.
        Returns:
        true if the value is null and false otherwise.
        See Also:
        Storable.isNull()

      • restoreToNull

        public void restoreToNull()
        Restore the in-memory representation to the null value. The containerid being zero is what determines nullness; subclasses are not expected to override this method.
        See Also:
        Storable.restoreToNull()

      • readExternal

        public void readExternal(java.io.ObjectInput in)
                  throws java.io.IOException,
                         java.lang.ClassNotFoundException
        Restore the in-memory representation from the stream.
        Throws:
        java.lang.ClassNotFoundException - Thrown if the stored representation is serialized and a class named in the stream could not be found.
        java.io.IOException - thrown by readObject()
        See Also:
        Externalizable.readExternal(java.io.ObjectInput)

      • writeExternal

        public void writeExternal(java.io.ObjectOutput out)
                   throws java.io.IOException
        Store the stored representation of the column value in the stream. It might be easier to simply store the properties - which would certainly make upgrading easier.
        Throws:
        java.io.IOException - thrown by writeObject()

      • toString

        public java.lang.String toString()
        Public toString() Method:
        Overrides:
        toString in class java.lang.Object
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