Module com.darkcollective.relix.cost
Package com.darkcollective.relix.cost

Class RelationProperties

java.lang.Object
com.darkcollective.relix.cost.RelationProperties
public final class RelationProperties extends Object
Logical properties of a relation, derived bottom-up over a RelNode tree and consumed by the optimizer and planner.

This first increment carries distinctness — whether the relation is guaranteed free of duplicate rows — backed by a key model:

  • wholeRowDistinct() — the entire row is unique (the relation is a set), without enumerating the columns. Produced by operators whose output is a set regardless of input (δ, ∪, ∩, −, ∆, ÷, transitive closure).
  • keys() — explicit candidate keys, each a set of column names on which rows are unique (an empty key set means "at most one row"). Produced where the unique columns are known structurally (a grouping aggregation's keys, a group-wise ∀'s keys).

A relation is duplicate-free iff its whole row is distinct or it has any candidate key — the question DIST-001 (redundant δ elimination) asks.

The carrier also records boundedness. The distinctness factories default it to Boundedness.BOUNDED (every relation in the language is finite today); the boundedness-aware PropertyDeriver.derive(com.darkcollective.relix.ast.RelNode, BoundednessSource) overlays the derived value via withBoundedness(com.darkcollective.relix.cost.Boundedness). A physical ordering descriptor is the remaining Phase-C extension. Column names are compared case-insensitively (stored lowercased), matching Schema.

Instances are immutable value objects.

  • Method Summary

    Modifier and Type
    Method
    Description
    Boundedness
    boundedness()
    The relation's boundedness — whether it is provably finite.
    boolean
    equals(Object o)
     
    int
    hashCode()
     
    boolean
    isDuplicateFree()
    Whether the relation is guaranteed to contain no duplicate rows — it is whole-row distinct or has at least one candidate key.
    static RelationProperties
    key(Collection<String> columns)
    Properties of a relation unique on exactly the given key columns (an empty collection denotes a relation of at most one row).
    Set<Set<String>>
    keys()
    The known candidate keys — each an immutable set of lowercased column names on which rows are unique.
    static RelationProperties
    none()
    Properties of a relation about which nothing is known — not duplicate-free, no candidate keys.
    String
    toString()
     
    static RelationProperties
    wholeRow()
    Properties of a relation whose entire row is guaranteed unique (a set), without enumerating its columns — e.g.
    boolean
    wholeRowDistinct()
    Whether the entire row is known to be unique without an enumerated key.
    RelationProperties
    withBoundedness(Boundedness newBoundedness)
    Returns a copy of these properties with the boundedness replaced — used by the boundedness-aware derivation to overlay the structurally-derived distinctness with a source-derived boundedness.

    Methods inherited from class java.lang.Object

    clone, finalize, getClass, notify, notifyAll, wait, wait, wait

  • Method Details

    • none

      public static RelationProperties none()
      Properties of a relation about which nothing is known — not duplicate-free, no candidate keys. The conservative default for leaves and operators that may introduce duplicates.
      Returns:
      the empty properties; never null

    • wholeRow

      public static RelationProperties wholeRow()
      Properties of a relation whose entire row is guaranteed unique (a set), without enumerating its columns — e.g. the output of δ or a set operation.
      Returns:
      whole-row-distinct properties; never null

    • key

      public static RelationProperties key(Collection<String> columns)
      Properties of a relation unique on exactly the given key columns (an empty collection denotes a relation of at most one row).
      Parameters:
      columns - the key columns; must not be null (may be empty)
      Returns:
      properties carrying that single candidate key; never null

    • withBoundedness

      public RelationProperties withBoundedness(Boundedness newBoundedness)
      Returns a copy of these properties with the boundedness replaced — used by the boundedness-aware derivation to overlay the structurally-derived distinctness with a source-derived boundedness.
      Parameters:
      newBoundedness - the boundedness to set; must not be null
      Returns:
      a copy carrying newBoundedness; never null

    • isDuplicateFree

      public boolean isDuplicateFree()
      Whether the relation is guaranteed to contain no duplicate rows — it is whole-row distinct or has at least one candidate key.
      Returns:
      true if the relation is provably duplicate-free

    • wholeRowDistinct

      public boolean wholeRowDistinct()
      Whether the entire row is known to be unique without an enumerated key.
      Returns:
      true if the relation is whole-row distinct

    • keys

      public Set<Set<String>> keys()
      The known candidate keys — each an immutable set of lowercased column names on which rows are unique.

      Staged, not dead. Today the keys are read only through isDuplicateFree(), whose sole caller asks the yes/no question DIST-001 needs; which columns form the key is derived on every derivation and never inspected. That is deliberate rather than accidental: the rules that would consume the column sets — candidate-key survival through π, key propagation through a join, and the set-op idempotence laws — are filed and unshipped, and deriving the keys is what makes writing them a rule rather than a rule plus a new derivation. Dropping the detail to a boolean now would have to be undone by the first of them.

      The key model that is load-bearing today is the separate RelationStatistics.keys() — read by StatisticsDistinctnessSource (a keyed base relation is duplicate-free) and by Planner.indexBacked (a merge key that prefixes a candidate key is index-backed). The two are not interchangeable: those are declared keys of a base table, these are keys derived through the operator tree.

      Returns:
      an immutable set of candidate keys; never null, possibly empty

    • boundedness

      public Boundedness boundedness()
      The relation's boundedness — whether it is provably finite.
      Returns:
      the boundedness; never null

    • equals

      public boolean equals(Object o)
      Overrides:
      equals in class Object

    • hashCode

      public int hashCode()
      Overrides:
      hashCode in class Object

    • toString

      public String toString()
      Overrides:
      toString in class Object