Fix #2190: Magicset bug

src/ast/transform/MagicSet.cpp

@@ -160,13 +160,6 @@ std::set<QualifiedName> MagicSetTransformer::getWeaklyIgnoredRelations(const Tra
         });
     }
 
-    // - Any eqrel relation
-    for (auto* rel : program.getRelations()) {
-        if (rel->getRepresentation() == RelationRepresentation::EQREL) {
-            weaklyIgnoredRelations.insert(rel->getQualifiedName());
-        }
-    }
-
     // - Any relation with functional dependencies
     for (auto* rel : program.getRelations()) {
         if (!rel->getFunctionalDependencies().empty()) {

src/main.cpp

@@ -523,7 +523,8 @@ int main(int argc, char** argv) {
                     mk<ast::transform::RemoveRedundantRelationsTransformer>());
 
     // Magic-Set pipeline
-    auto magicPipeline = mk<ast::transform::PipelineTransformer>(mk<ast::transform::MagicSetTransformer>(),
+    auto magicPipeline = mk<ast::transform::PipelineTransformer>(
+            mk<ast::transform::ExpandEqrelsTransformer>(), mk<ast::transform::MagicSetTransformer>(),
             mk<ast::transform::ResolveAliasesTransformer>(),
             mk<ast::transform::RemoveRelationCopiesTransformer>(),
             mk<ast::transform::RemoveEmptyRelationsTransformer>(),

tests/semantic/CMakeLists.txt

@@ -60,6 +60,7 @@ positive_test(duplicates)
 positive_test(eqrel_tests)
 positive_test(eqrel_tests2)
 positive_test(eqrel_tests3)
+positive_test(eqrel_tests4)
 positive_test(equivalent)
 negative_test(execution_plan)
 positive_test(extended_subtypes)

tests/semantic/eqrel_tests4/a__.csv

@@ -0,0 +1,3 @@
+0
+1
+2

tests/semantic/eqrel_tests4/b__.csv

@@ -0,0 +1,3 @@
+0
+1
+2

tests/semantic/eqrel_tests4/eqrel_tests4.dl

@@ -0,0 +1,29 @@
+// Souffle - A Datalog Compiler
+// Copyright (c) 2022, The Souffle Developers. All rights reserved
+// Licensed under the Universal Permissive License v 1.0 as shown at:
+// - https://opensource.org/licenses/UPL
+// - <souffle root>/licenses/SOUFFLE-UPL.txt
+
+// Magic set transformations requires an explicit representation of
+// eqrel relations so that they can be properly specialized. See
+// issue #2190.
+//
+
+.pragma "magic-transform" "*"
+
+.decl notEqrel(x:number,y:number)
+.decl isEqrel(x:number, y:number) eqrel
+.decl a__(a:number)
+.decl b__(a:number)
+
+notEqrel(x, y) :- isEqrel(x, y).
+isEqrel(x, y) :- notEqrel(x, y).
+isEqrel(0,1).
+notEqrel(1,2).
+
+.output a__
+.output b__ // Output node
+
+a__(a) :- notEqrel(a, a).
+b__(c) :- !a__(b), a__(c), a__(b).
+b__(a) :- a__(a).