Interface BuiltInMetadata.ColumnUniqueness

  • All Superinterfaces:
    All Known Subinterfaces:
    Enclosing class:

    public static interface BuiltInMetadata.ColumnUniqueness
    extends Metadata
    Metadata about whether a set of columns uniquely identifies a row.
    • Method Detail

      • areColumnsUnique

        java.lang.Boolean areColumnsUnique​(ImmutableBitSet columns,
                                           boolean ignoreNulls)
        Determines whether a specified set of columns from a specified relational expression are unique.

        For example, if the relational expression is a TableScan to T(A, B, C, D) whose key is (A, B), then:

        • areColumnsUnique([0, 1]) yields true,
        • areColumnsUnique([0]) yields false,
        • areColumnsUnique([0, 2]) yields false.

        Nulls can be ignored if the relational expression has filtered out null values.

        columns - column mask representing the subset of columns for which uniqueness will be determined
        ignoreNulls - if true, ignore null values when determining column uniqueness
        whether the columns are unique, or null if not enough information is available to make that determination