Class LeafControlRow

  • All Implemented Interfaces:
    TypedFormat, AuxObject

    public class LeafControlRow
    extends ControlRow
    Format IDACCESS_BTREE_LEAFCONTROLROW_V1_ID
    Purpose
    Btree pages all have a control row at the front of every page. To determine the type of row, read the first column which is a format id and it tells what kind of control row it is.
    Upgrade
    This format was made obsolete in the kimono release.
    Disk Layoutcolumn 1 - control row type : StorableFormatId column 2 - left sibling page number : SQLLongint column 3 - right sibling page number: SQLLongint column 4 - parent page number : SQLLongint column 5 - level number (0 is leaf) : SQLLongint column 6 - isRoot : SQLLongint column 7 - Conglomerate object : null unless it is root else a Conglomerate object, matching that of current table. Currently this field is only used by logical undo and the type of object is inferred by the logical undo code.
    • Constructor Detail

      • LeafControlRow

        public LeafControlRow()
        No arg constructor.

        Public no arg constructor is for the monitor to call for format id implemenation, it should not be called for any other reason.

      • LeafControlRow

        LeafControlRow​(OpenBTree btree,
                       Page page,
                       ControlRow parent,
                       boolean isRoot)
                throws StandardException
        Constructs a leaf-page control row, for a newly allocated leaf page.
        Parameters:
        btree - The open btree to allocate this page from.
        page - The newly allocated page where the control row will be inserted.
        parent - The parent of the leaf page. Set to null for root. RESOLVE (mikem) - set to null otherwise?
        isRoot - Is this page the root of the tree?
        Throws:
        StandardException - Standard exception policy.
    • Method Detail

      • allocate

        private static LeafControlRow allocate​(OpenBTree btree,
                                               ControlRow parent)
                                        throws StandardException
        Allocate a new leaf page to the conglomerate.
        Parameters:
        btree - The open conglomerate from which to get the leaf from
        parent - The parent page of the newly allocated page, null if allocating root page.
        Throws:
        StandardException - Standard exception policy.
      • get_left_nondeleted_rowcnt

        private float get_left_nondeleted_rowcnt​(int startslot)
                                          throws StandardException
        Return the number of non-deleted rows from slot 1 through "startslot"

        Return the number of non-deleted rows that exist on the page starting at slot one through "startslot".

        RESOLVE (mikem) - is the expense of this routine worth it, it is only used for costing. Could an estimate from the nonDeletedRecordCount() be used instead?

        Parameters:
        startslot - Count non deleted row up to and including this slot.
        Returns:
        The requested non_deleted_row_count.
        Throws:
        StandardException - Standard exception policy.
      • controlRowInit

        protected final void controlRowInit()
        Perform page specific initialization.

        Specified by:
        controlRowInit in class ControlRow
      • initEmptyBtree

        public static void initEmptyBtree​(OpenBTree open_btree)
                                   throws StandardException
        Initialize conglomerate with one page, to be a 1 page btree. Given a conglomerate which already has one page allocated to it, initialize the page to be a leaf-root page with no entries. Allocate the control row and store it on the page.
        Parameters:
        open_btree - The open btree to initialize (container is open).
        Throws:
        StandardException - Standard exception policy.
      • getNumberOfControlRowColumns

        protected final int getNumberOfControlRowColumns()
        Get the number of columns in the control row.

        Control rows all share the first columns as defined by this class and then add columns to the end of the control row. For instance a branch control row add a child page pointer field.

        Specified by:
        getNumberOfControlRowColumns in class ControlRow
        Returns:
        The total number of columns in the control row.
      • isLeftmostLeaf

        public boolean isLeftmostLeaf()
                               throws StandardException
        Is the current page the leftmost leaf of tree?

        Specified by:
        isLeftmostLeaf in class ControlRow
        Returns:
        true if the current page is the leftmost leaf of the tree, else return false.
        Throws:
        StandardException - Standard exception policy.
      • isRightmostLeaf

        public boolean isRightmostLeaf()
                                throws StandardException
        Is the current page the rightmost leaf of tree?

        Specified by:
        isRightmostLeaf in class ControlRow
        Returns:
        true if the current page is the rightmost leaf of the tree, else return false.
        Throws:
        StandardException - Standard exception policy.
      • search

        public ControlRow search​(SearchParameters sp)
                          throws StandardException
        Perform a search of this leaf page, ultimately returning the latched leaf page and row slot after which the given key belongs. The slot is returned in the result structure. If the key exists on the page, the result.exact will be true. Otherwise, result.exact will be false, and the row slot returned will be the one immediately preceding the position at which the key belongs.
        Specified by:
        search in class ControlRow
        Throws:
        StandardException - Standard exception policy.
      • searchLeft

        protected ControlRow searchLeft​(OpenBTree btree)
                                 throws StandardException
        Search and return the left most leaf page.

        Perform a recursive search, ultimately returning the leftmost leaf page which is the first leaf page in the leaf sibling chain. (This method might better be called getFirstLeafPage()).

        Specified by:
        searchLeft in class ControlRow
        Parameters:
        btree - The open btree to associate latches/locks with.
        Returns:
        The leftmost leaf page.
        Throws:
        StandardException - Standard exception policy.
      • searchRight

        protected ControlRow searchRight​(OpenBTree btree)
                                  throws StandardException
        Search and return the right most leaf page.

        Perform a recursive search, ultimately returning the rightmost leaf page which is the last leaf page in the leaf sibling chain. (This method might better be called getLastLeafPage()).

        Specified by:
        searchRight in class ControlRow
        Parameters:
        btree - The open btree to associate latches/locks with.
        Returns:
        The rightmost leaf page.
        Throws:
        StandardException - Standard exception policy.
      • shrinkFor

        protected boolean shrinkFor​(OpenBTree btree,
                                    DataValueDescriptor[] key)
                             throws StandardException
        Perform a recursive shrink operation for the key. If this method returns true, the caller should remove the corresponding entry for the page. This routine is not guaranteed to successfully shrink anything. The page lead to by the key might turn out not to be empty by the time shrink gets there, and shrinks will give up if there is a deadlock.

        The receiver page must be latched on entry and is returned unlatched.

        Specified by:
        shrinkFor in class ControlRow
        Throws:
        StandardException - Standard exception policy.
      • splitFor

        protected long splitFor​(OpenBTree open_btree,
                                DataValueDescriptor[] template,
                                BranchControlRow parent_page,
                                DataValueDescriptor[] splitrow,
                                int flag)
                         throws StandardException
        Perform a top down split pass making room for the the key in "row".

        Perform a split such that a subsequent call to insert given the argument index row will likely find room for it. Since latches are released the client must code for the case where another user has grabbed the space made available by the split pass and be ready to do another split.

        On entry, the parent is either null or latched, and the current page is latched. On exit, all pages will have been unlatched. If the parent is null, then this page is a root leaf page.

        Specified by:
        splitFor in class ControlRow
        Parameters:
        open_btree - The open btree to associate latches with.
        template - A scratch area to use while searching for split pass.
        parent_page - The parent page of the current page in the split pass. starts at null for root.
        splitrow - The key to make room for during the split pass.
        flag - A flag used to direct where point of split should be chosen.
        Returns:
        page number of the newly allocated leaf page created by split.
        Throws:
        StandardException - Standard exception policy.
      • growRoot

        private static void growRoot​(OpenBTree open_btree,
                                     DataValueDescriptor[] template,
                                     LeafControlRow leafroot)
                              throws StandardException
        Grow a new root page from a leaf page. Slightly tricky because we want to retain page 0 as the root.

        On entry, the current leaf root page is expected to be latched. On exit, all latches will have been released.

        The caller cannot not assume success. If we have to release latches this routine just returns and assumes the caller will retry the grow root if necessary.

        Throws:
        StandardException
      • getLeftChild

        protected ControlRow getLeftChild​(OpenBTree btree)
                                   throws StandardException
        Return the left child pointer for the page.

        Leaf pages don't have children, so they override this and return null.

        Specified by:
        getLeftChild in class ControlRow
        Parameters:
        btree - The open btree to associate latches/locks with.
        Returns:
        The page which is the leftmost child of this page.
        Throws:
        StandardException - Standard exception policy.
      • getRightChild

        protected ControlRow getRightChild​(OpenBTree btree)
                                    throws StandardException
        Return the right child pointer for the page.

        Leaf pages don't have children, so they override this and return null.

        Specified by:
        getRightChild in class ControlRow
        Parameters:
        btree - The open btree to associate latches/locks with.
        Returns:
        The page which is the rightmost child of this page.
        Throws:
        StandardException - Standard exception policy.
      • checkConsistency

        public int checkConsistency​(OpenBTree btree,
                                    ControlRow parent,
                                    boolean check_other_pages)
                             throws StandardException
        Perform consistency checks on a leaf page. Check consistency of the page and its children, returning the number of pages seen, and throwing errors if inconsistencies are found. The checks specific to a leaf page are:
      • Page is at level 0.
      • Version is a valid leaf page version.
      • Control row has right number of columns for leaf.
      • This method also performs the consistency checks that are common to both leaf and branch pages.
        Specified by:
        checkConsistency in class ControlRow
        Parameters:
        btree - The open btree to associate latches/locks with.
        parent - The parent page of this page, "null" if this page is root or if not maintaining parent links.
        check_other_pages - Should the consistency check go to other pages (this option breaks the latch protocol).
        Returns:
        The identifier to be used to open the conglomerate later.
        Throws:
        StandardException - Standard exception policy.
        See Also:
        ControlRow.checkGeneric(org.apache.derby.impl.store.access.btree.OpenBTree, org.apache.derby.impl.store.access.btree.ControlRow, boolean)
      • getTypeFormatId

        public int getTypeFormatId()
        Return my format identifier.
        Returns:
        The identifier. (A UUID stuffed in an array of 16 bytes).
        See Also:
        TypedFormat.getTypeFormatId()