Class FunctionTable

  • All Implemented Interfaces:
    RootTable, TableDataSource

    public class FunctionTable
    extends DefaultDataTable
    A table that has a number of columns and as many rows as the refering table. Tables of this type are used to construct aggregate and function columns based on an expression. They are joined with the result table in the last part of the query processing.

    For example, a query like 'select id, id * 2, 8 * 9 from Part' the columns 'id * 2' and '8 * 9' would be formed from this table.

    SYNCHRONIZATION ISSUE: Instances of this object are NOT thread safe. The reason it's not is because if 'getCellContents' is used concurrently it's possible for the same value to be added into the cache causing an error. It is not expected that this object will be shared between threads.

    • Field Detail

      • UNIQUE_KEY_SEQ

        private static int UNIQUE_KEY_SEQ
        The key used to make distinct unique ids for FunctionTables.

        NOTE: This is a thread-safe static mutable variable.

      • FUNCTION_TABLE_NAME

        private static final TableName FUNCTION_TABLE_NAME
        The table name given to all function tables.
      • unique_id

        private int unique_id
        A unique id given to this FunctionTable when it is created. No two FunctionTable objects may have the same number. This number is between 0 and 260 million.
      • fun_table_def

        private DataTableDef fun_table_def
        The DataTableDef object that describes the columns in this function table.
      • cross_ref_table

        private Table cross_ref_table
        The table that this function table cross references. This is not a parent table, but more like the table we will eventually be joined with.
      • exp_list

        private Expression[] exp_list
        The list of expressions that are evaluated to form each column.
      • exp_info

        private byte[] exp_info
        Some information about the expression list. If the value is 0 then the column is simple to solve and shouldn't be cached.
      • group_lookup

        private IntegerVector group_lookup
        The lookup mapping for row->group_index used for grouping.
      • group_links

        private IntegerVector group_links
        The group row links. Iterate through this to find all the rows in a group until bit 31 set.
      • whole_table_as_group

        private boolean whole_table_as_group
        Whether the whole table is a group.
      • whole_table_group

        private IntegerVector whole_table_group
        If the whole table is a group, this is the grouping rows. This is obtained via 'selectAll' of the reference table.
      • whole_table_group_size

        private int whole_table_group_size
        The total size of the whole table group size.
      • whole_table_is_simple_enum

        private boolean whole_table_is_simple_enum
        If the whole table is a simple enumeration (row index is 0 to getRowCount) then this is true.
      • context

        private QueryContext context
        The context of this function table.
    • Method Detail

      • calcValue

        private TObject calcValue​(int column,
                                  int row,
                                  DataCellCache cache)
        Return a TObject that represents the value of the 'column', 'row' of this table. If 'cache' is not null then the resultant value is added to the cache. If 'cache' is null, no caching happens.
      • setWholeTableAsGroup

        public void setWholeTableAsGroup()
        Sets the whole reference table as a single group.
      • createGroupMatrix

        public void createGroupMatrix​(Variable[] col_list)
        Creates a grouping matrix for the given tables. The grouping matrix is arranged so that each row of the referring table that is in the group is given a number that refers to the top group entry in the group list. The group list is a linked integer list that chains through each row item in the list.
      • getReferenceTable

        public Table getReferenceTable()
        Returns the Table this function is based on. We need to provide this method for aggregate functions.
      • rowGroup

        public int rowGroup​(int row_index)
        Returns the group of the row at the given index.
      • groupSize

        public int groupSize​(int group_number)
        The size of the group with the given number.
      • groupRows

        public IntegerVector groupRows​(int group_number)
        Returns an IntegerVector that represents the list of all rows in the group the index is at.
      • mergeWithReference

        public Table mergeWithReference​(Variable max_column)
        Returns a Table that is this function table merged with the cross reference table. The result table includes only one row from each group.

        The 'max_column' argument is optional (can be null). If it's set to a column in the reference table, then the row with the max value from the group is used as the group row. For example, 'Part.id' will return the row with the maximum part.id from each group.

      • topFromEachGroup

        IntegerVector topFromEachGroup()
        Returns a list of rows that represent one row from each distinct group in this table. This should be used to construct a virtual table of rows from each distinct group.
      • maxFromEachGroup

        IntegerVector maxFromEachGroup​(int col_num)
        Returns a list of rows that represent the maximum row of the given column from each distinct group in this table. This should be used to construct a virtual table of rows from each distinct group.
      • getCellContents

        public TObject getCellContents​(int column,
                                       int row)
        Returns an object that represents the information in the given cell in the table. This can be used to obtain information about the given table cells.
        Specified by:
        getCellContents in interface TableDataSource
        Specified by:
        getCellContents in class Table
      • addDataTableListener

        void addDataTableListener​(DataTableListener listener)
        Adds a DataTableListener to the DataTable objects at the root of this table tree hierarchy. If this table represents the join of a number of tables then the DataTableListener is added to all the DataTable objects at the root.

        A DataTableListener is notified of all modifications to the raw entries of the table. This listener can be used for detecting changes in VIEWs, for triggers or for caching of common queries.

        Specified by:
        addDataTableListener in class Table
      • removeDataTableListener

        void removeDataTableListener​(DataTableListener listener)
        Removes a DataTableListener from the DataTable objects at the root of this table tree hierarchy. If this table represents the join of a number of tables, then the DataTableListener is removed from all the DataTable objects at the root.
        Specified by:
        removeDataTableListener in class Table
      • lockRoot

        public void lockRoot​(int lock_key)
        Locks the root table(s) of this table so that it is impossible to overwrite the underlying rows that may appear in this table. This is used when cells in the table need to be accessed 'outside' the lock. So we may have late access to cells in the table. 'lock_key' is a given key that will also unlock the root table(s). NOTE: This is nothing to do with the 'LockingMechanism' object.
        Specified by:
        lockRoot in class Table
      • unlockRoot

        public void unlockRoot​(int lock_key)
        Unlocks the root tables so that the underlying rows may once again be used if they are not locked and have been removed. This should be called some time after the rows have been locked.
        Specified by:
        unlockRoot in class Table
      • hasRootsLocked

        public boolean hasRootsLocked()
        Returns true if the table has its row roots locked (via the lockRoot(int) method.
        Specified by:
        hasRootsLocked in class Table
      • resultTable

        public static Table resultTable​(DatabaseQueryContext context,
                                        Expression expression)
        Returns a FunctionTable that has a single Expression evaluated in it. The column name is 'result'.
      • resultTable

        public static Table resultTable​(DatabaseQueryContext context,
                                        TObject ob)
        Returns a FunctionTable that has a single TObject in it. The column title is 'result'.
      • resultTable

        public static Table resultTable​(DatabaseQueryContext context,
                                        java.lang.Object ob)
        Returns a FunctionTable that has a single Object in it. The column title is 'result'.
      • resultTable

        public static Table resultTable​(DatabaseQueryContext context,
                                        int result_val)
        Returns a FunctionTable that has an int value made into a BigDecimal. The column title is 'result'.