Package io.deephaven.engine.table.impl.util

Class FreezeBy

java.lang.Object
io.deephaven.engine.table.impl.util.FreezeBy
public class FreezeBy extends Object
FreezeBy records the first value for a given key in the output table and ignores subsequent changes. When keys are removed, the corresponding row is removed from the output table. When keys are added back on another cycle, the newly added value is frozen in the output. Only one row per key is allowed in the input. This is because the operation can not determine which is the correct row to freeze in cases where there are multiple rows per key. The freeze operation is not sensitive to RowSet changes (e.g., adds, removes, modifies, shifts); whether a row is updated is based solely on (1) a key did not exist in the input table at the start of the cycle and (2) it now exists in the input table. If the key did not exist, a frozen copy is taken. If the key did exist, then no modifications occur.

  • Method Details

    • freezeBy

      public static Table freezeBy(Table input)
      Freeze the input table.

      The input table may only have zero or one rows. The first added row will be frozen until the table becomes empty.

      Parameters:
      input - the table to freeze
      Returns:
      a frozen copy of the input table

    • freezeBy

      public static Table freezeBy(Table input, String... groupByColumns)
      Freeze the input table.

      When a key is added to the table, a copy is added to the output. When a key is removed, the row is removed from the output. The input may have only one row per key.

      Parameters:
      input - the table to freeze
      groupByColumns - the keys to freeze the table by
      Returns:
      a copy of the input table frozen by key

    • freezeBy

      public static Table freezeBy(Table input, Collection<String> groupByColumns)
      Freeze the input table.

      When a key is added to the table, a copy is added to the output. When a key is removed, the row is removed from the output. The input may have only one row per key.

      Parameters:
      input - the table to freeze
      groupByColumns - the keys to freeze the table by
      Returns:
      a copy of the input table frozen by key

    • freezeBy

      public static Table freezeBy(Table input, ColumnName... groupByColumns)
      Freeze the input table.

      When a key is added to the table, a copy is added to the output. When a key is removed, the row is removed from the output. The input may have only one row per key.

      Parameters:
      input - the table to freeze
      groupByColumns - the keys to freeze the table by
      Returns:
      a copy of the input table frozen by key