Package org.apache.derby.impl.store.access.btree.index

Class B2IFactory

  • All Implemented Interfaces:
    ModuleControl, ModuleSupportable, ConglomerateFactory, MethodFactory
    public class B2IFactory
extends java.lang.Object
implements ConglomerateFactory, ModuleControl
    The "B2I" (acronym for b-tree secondary index) factory manages b-tree conglomerates implemented on the raw store which are used as secondary indexes.

    Most of this code is generic to all conglomerates. This class might be more easily maintained as an abstract class in Raw/Conglomerate/Generic. The concrete ConglomerateFactories would simply have to supply the IMPLEMENTATIONID, FORMATUUIDSTRING, and implement createConglomerate and defaultProperties. Conglomerates which support more than one format would have to override supportsFormat, and conglomerates which support more than one implementation would have to override supportsImplementation.

    • Field Detail

      • IMPLEMENTATIONID

        private static final java.lang.String IMPLEMENTATIONID
        See Also:
        Constant Field Values

      • FORMATUUIDSTRING

        private static final java.lang.String FORMATUUIDSTRING
        See Also:
        Constant Field Values

      • formatUUID

        private UUID formatUUID

    • Constructor Detail

      • B2IFactory

        public B2IFactory()

    • Method Detail

      • getConglomerateFactoryId

        public int getConglomerateFactoryId()
        Return the conglomerate factory id.

        Return a number in the range of 0-15 which identifies this factory. Code which names conglomerates depends on this range currently, but could be easily changed to handle larger ranges. One hex digit seemed reasonable for the number of conglomerate types being currently considered (heap, btree, gist, gist btree, gist rtree, hash, others? ).

        Specified by:
        getConglomerateFactoryId in interface ConglomerateFactory
        Returns:
        an unique identifier used to the factory into the conglomid.
        See Also:
        ConglomerateFactory.getConglomerateFactoryId()

      • readConglomerate

        public Conglomerate readConglomerate​(TransactionManager xact_manager,
                                     ContainerKey container_key)
                              throws StandardException
        Return Conglomerate object for conglomerate with conglomid.

        Return the Conglomerate Object. This is implementation specific. Examples of what will be done is using the id to find the file where the conglomerate is located, and then executing implementation specific code to instantiate an object from reading a "special" row from a known location in the file. In the btree case the btree conglomerate is stored as a column in the control row on the root page.

        This operation is costly so it is likely an implementation using this will cache the conglomerate row in memory so that subsequent accesses need not perform this operation.

        The btree object returned by this routine may be installed in a cache so the object must not change.

        Specified by:
        readConglomerate in interface ConglomerateFactory
        Parameters:
        xact_manager - transaction to perform the create in.
        container_key - The unique id of the existing conglomerate.
        Returns:
        An instance of the conglomerate.
        Throws:
        StandardException - Standard exception policy.

      • insertUndoNotify

        public void insertUndoNotify​(AccessFactory access_factory,
                             Transaction xact,
                             PageKey page_key)
                      throws StandardException
        Interface to be called when an undo of an insert is processed.

        Implementer of this class provides interface to be called by the raw store when an undo of an insert is processed. Initial implementation will be by Access layer to queue space reclaiming events if necessary when a rows is logically "deleted" as part of undo of the original insert. This undo can happen a lot for many applications if they generate expected and handled duplicate key errors.

        Caller may decide to call or not based on deleted row count of the page, or if overflow rows/columns are present.

        Specified by:
        insertUndoNotify in interface ConglomerateFactory
        Parameters:
        access_factory - current access_factory of the aborted insert.
        xact - transaction that is being backed out.
        page_key - page key of the aborted insert.
        Throws:
        StandardException - Standard exception policy.

      • canSupport

        public boolean canSupport​(java.util.Properties startParams)
        Description copied from interface: ModuleSupportable
        See if this implementation can support any attributes that are listed in properties. This call may be made on a newly created instance before the boot() method has been called, or after the boot method has been called for a running module.

        The module can check for attributes in the properties to see if it can fulfill the required behaviour. E.g. the raw store may define an attribute called RawStore.Recoverable. If a temporary raw store is required the property RawStore.recoverable=false would be added to the properties before calling bootServiceModule. If a raw store cannot support this attribute its canSupport method would return null. Also see the Monitor class's prologue to see how the identifier is used in looking up properties.
        Actually a better way maybe to have properties of the form RawStore.Attributes.mandatory=recoverable,smallfootprint and RawStore.Attributes.requested=oltp,fast

        Specified by:
        canSupport in interface ModuleSupportable
        Returns:
        true if this instance can be used, false otherwise.

      • boot

        public void boot​(boolean create,
                 java.util.Properties startParams)
          throws StandardException
        Description copied from interface: ModuleControl
        Boot this module with the given properties. Creates a module instance that can be found using the findModule() methods of Monitor. The module can only be found using one of these findModule() methods once this method has returned.

        An implementation's boot method can throw StandardException. If it is thrown the module is not registered by the monitor and therefore cannot be found through a findModule(). In this case the module's stop() method is not called, thus throwing this exception must free up any resources.

        When create is true the contents of the properties object will be written to the service.properties of the persistent service. Thus any code that requires an entry in service.properties must explicitly place the value in this properties set using the put method.
        Typically the properties object contains one or more default properties sets, which are not written out to service.properties. These default sets are how callers modify the create process. In a JDBC connection database create the first set of defaults is a properties object that contains the attributes that were set on the jdbc:derby: URL. This attributes properties set has the second default properties set as its default. This set (which could be null) contains the properties that the user set on their DriverManager.getConnection() call, and are thus not owned by Derby code, and thus must not be modified by Derby code.

        When create is false the properties object contains all the properties set in the service.properties file plus a limited number of attributes from the JDBC URL attributes or connection properties set. This avoids properties set by the user compromising the boot process. An example of a property passed in from the JDBC world is the bootPassword for encrypted databases.

        Code should not hold onto the passed in properties reference after boot time as its contents may change underneath it. At least after the complete boot is completed, the links to all the default sets will be removed.

        Specified by:
        boot in interface ModuleControl
        Throws:
        StandardException - Module cannot be started.
        See Also:
        Monitor, ModuleFactory

      • stop

        public void stop()
        Description copied from interface: ModuleControl
        Stop the module. The module may be found via a findModule() method until some time after this method returns. Therefore the factory must be prepared to reject requests to it once it has been stopped. In addition other modules may cache a reference to the module and make requests of it after it has been stopped, these requests should be rejected as well.
        Specified by:
        stop in interface ModuleControl
        See Also:
        Monitor, ModuleFactory

      • getMonitor

        private static ModuleFactory getMonitor()
        Privileged Monitor lookup. Must be private so that user code can't call this entry point.