core.logic

Rel relation PersistentHashSet becomes LazySeq after issuing a retraction

Details

  • Type: Defect Defect
  • Status: Closed Closed
  • Priority: Minor Minor
  • Resolution: Completed
  • Affects Version/s: None
  • Fix Version/s: None
  • Component/s: None
  • Labels:
  • Patch:
    Code

Description

The first retraction of facts from a relation transforms the internal PersistentHashSet -set var+atom, which guarantees uniqueness, into a LazySeq which allows duplicate facts to be added. Once the first retraction occurs, a LazySeq persists for the rest of the life of the relation. Only the value of the primary -set var+atom is affected, not the -index var+atom values.

This issue is not an external correctness issue but does affect performance of subsequent duplicate fact additions which grow the size relation.

Preparation:

user=> (defrel foo x y)
#<user$eval4287$fn__4288 user$eval4287$fn__4288@1a9d489b>
user=> (facts foo [[:joe :man][:jane :woman][:sue :boy]])
nil
user=> foo_2-set
#<Atom@52aaf223: #{[:joe :man] [:jane :woman] [:sue :boy]}>
user=> (class @foo_2-set)
clojure.lang.PersistentHashSet
user=> (retraction foo :jane :woman)
nil

Without patch applied:

user=> foo_2-set
#<Atom@52aaf223: ([:joe :man] [:sue :boy])>
user=> (class @foo_2-set)
clojure.lang.LazySeq
user=> (facts foo [[:joe :man][:jane :woman][:sue :boy]])
nil
user=> foo_2-set
#<Atom@52aaf223: ([:sue :boy] [:jane :woman] [:joe :man] [:joe :man] [:sue :boy])>
user=> (class @foo_2-set)
clojure.lang.LazySeq

With patch applied:

user=> foo_2-set
#<Atom@31eb9b15: #{[:joe :man] [:sue :boy]}>
user=> (class @foo_2-set)
clojure.lang.PersistentHashSet
user=> (facts foo [[:joe :man][:jane :woman][:sue :boy]])
nil
user=> foo_2-set
#<Atom@31eb9b15: #{[:joe :man] [:jane :woman] [:sue :boy]}>
user=> (class @foo_2-set)
clojure.lang.PersistentHashSet

I've filed this as a Minor issue as it does not affect core.logic correctness and degraded performance can be avoided by not re-asserting duplicate facts.

I will also issue a GitHub pull request which can be used or ignored at your convenience.

Activity

Aaron Brooks made changes -
Field Original Value New Value
Attachment core.logic-rel-002.patch [ 11479 ]
David Nolen made changes -
Resolution Completed [ 1 ]
Status Open [ 1 ] Resolved [ 5 ]
David Nolen made changes -
Status Resolved [ 5 ] Closed [ 6 ]

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Dates

  • Created:
    Updated:
    Resolved: