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Adding cost modifiers
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‎README.md‎

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@@ -88,3 +88,26 @@ $cache = new ApcCache();
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$schemaAnalyzer = new SchemaAnalyzer($conn->getSchemaManager(), $cache, "my_prefix");
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```
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## Changing the cost of the foreign keys to alter the shortest path
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If you are facing an ambiguity exception or if the shortest path simply does not suit you, you can alter the
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cost of the foreign keys.
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```php
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$schemaAnalyzer->setForeignKeyCost($tableName, $columnName, $cost);
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```
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The `$cost` can be any number. Remember that the default cost for a foreign key is **1**.
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SchemaAnalyzer comes with a set of default constants to help you work with costs:
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- `SchemaAnalyzer::WEIGHT_IMPORTANT` (0.75) for foreign keys that should be followed in priority
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- `SchemaAnalyzer::WEIGHT_IRRELEVANT` (2) for foreign keys that should be generally avoided
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- `SchemaAnalyzer::WEIGHT_IGNORE` (Infinity) for foreign keys that should never be used as part of the shortest path
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Another option is to add a cost modifier to a table. This will alter the cost of all foreign keys pointing to or
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originating from this table.
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```php
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$schemaAnalyzer->setTableCostModifier($tableName, $cost);
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```

‎src/SchemaAnalyzer.php‎

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@@ -24,6 +24,10 @@ class SchemaAnalyzer
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private static $WEIGHT_FK = 1;
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private static $WEIGHT_JOINTURE_TABLE = 1.5;
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const WEIGHT_IMPORTANT = 0.75;
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const WEIGHT_IRRELEVANT = 2;
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const WEIGHT_IGNORE = INF;
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/**
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* @var AbstractSchemaManager
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*/
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*/
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private $cachePrefix;
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/**
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* Nested arrays containing table => column => cost
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* @var float[][]
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*/
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private $alteredCosts = [];
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/**
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* Array containing table cost
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* @var float[]
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*/
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private $alteredTableCosts = [];
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/**
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* @param AbstractSchemaManager $schemaManager
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* @param Cache|null $cache The Doctrine cache service to use to cache results (optional)
@@ -239,7 +255,16 @@ private function buildSchemaGraph()
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foreach ($table->getForeignKeys() as $fk) {
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// Create an undirected edge, with weight = 1
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$edge = $graph->getVertex($table->getName())->createEdge($graph->getVertex($fk->getForeignTableName()));
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$edge->setWeight(self::$WEIGHT_FK);
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if (isset($this->alteredCosts[$fk->getLocalTable()->getName()][implode(',',$fk->getLocalColumns())])) {
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$cost = $this->alteredCosts[$fk->getLocalTable()->getName()][implode(',',$fk->getLocalColumns())];
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} else {
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$cost = self::$WEIGHT_FK;
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}
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if (isset($this->alteredTableCosts[$fk->getLocalTable()->getName()])) {
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$cost *= $this->alteredTableCosts[$fk->getLocalTable()->getName()];
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}
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$edge->setWeight($cost);
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$edge->getAttributeBag()->setAttribute('fk', $fk);
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}
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}
@@ -252,7 +277,11 @@ private function buildSchemaGraph()
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}
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$edge = $graph->getVertex($tables[0])->createEdge($graph->getVertex($tables[1]));
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$edge->setWeight(self::$WEIGHT_JOINTURE_TABLE);
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$cost = self::$WEIGHT_JOINTURE_TABLE;
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if (isset($this->alteredTableCosts[$junctionTable->getName()])) {
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$cost *= $this->alteredTableCosts[$junctionTable->getName()];
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}
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$edge->setWeight($cost);
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$edge->getAttributeBag()->setAttribute('junction', $junctionTable);
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}
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@@ -351,4 +380,45 @@ private function getTextualPath(array $path, Vertex $startVertex)
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return $textPath;
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}
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/**
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* Sets the cost of a foreign key.
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*
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* @param string $tableName
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* @param string $columnName
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* @param float $cost
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* @return $this
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*/
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public function setForeignKeyCost($tableName, $columnName, $cost) {
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$this->alteredCosts[$tableName][$columnName] = $cost;
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}
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/**
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* Sets the cost modifier of a table.
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*
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* @param string $tableName
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* @param float $cost
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* @return $this
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*/
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public function setTableCostModifier($tableName, $cost) {
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$this->alteredTableCosts[$tableName] = $cost;
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}
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/**
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* Sets the cost modifier of all tables at once.
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*
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* @param array<string, float> $tableCosts The key is the table name, the value is the cost modifier.
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*/
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public function setTableCostModifiers(array $tableCosts) {
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$this->alteredTableCosts = $tableCosts;
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}
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/**
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* Sets the cost of all foreign keys at once.
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*
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* @param array<string, array<string, float>> $fkCosts First key is the table name, second key is the column name, the value is the cost.
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*/
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public function setForeignKeyCosts(array $fkCosts) {
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$this->alteredCosts = $fkCosts;
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}
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}

‎tests/SchemaAnalyzerTest.php‎

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@@ -333,5 +333,83 @@ public function testAmbiguityExceptionWithNoJointure() {
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$this->assertTrue($exceptionTriggered);
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}
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public function testAmbiguityExceptionWithNoJointureAndModifiedWeight() {
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$schema = $this->getBaseSchema();
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$right = $schema->getTable("right");
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$right->addColumn("role_id", "integer", array("unsigned" => true));
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$right->addForeignKeyConstraint($schema->getTable('role'), array("role_id"), array("id"), array("onUpdate" => "CASCADE"));
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$right->addColumn("role_id2", "integer", array("unsigned" => true));
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$right->addForeignKeyConstraint($schema->getTable('role'), array("role_id2"), array("id"), array("onUpdate" => "CASCADE"));
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$schemaAnalyzer = new SchemaAnalyzer(new StubSchemaManager($schema));
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$schemaAnalyzer->setForeignKeyCost('right', 'role_id', SchemaAnalyzer::WEIGHT_IMPORTANT);
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$fks = $schemaAnalyzer->getShortestPath("role", "right");
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$this->assertCount(1, $fks);
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$this->assertEquals("right", $fks[0]->getLocalTable()->getName());
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$this->assertEquals("role", $fks[0]->getForeignTableName());
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}
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public function testAmbiguityExceptionWithJointureAndModifiedWeight() {
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$schema = $this->getBaseSchema();
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$role_right = $schema->createTable("role_right");
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$role_right->addColumn("role_id", "integer", array("unsigned" => true));
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$role_right->addColumn("right_id", "integer", array("unsigned" => true));
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$role_right->addForeignKeyConstraint($schema->getTable('role'), array("role_id"), array("id"), array("onUpdate" => "CASCADE"));
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$role_right->addForeignKeyConstraint($schema->getTable('right'), array("right_id"), array("id"), array("onUpdate" => "CASCADE"));
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$role_right->setPrimaryKey(["role_id", "right_id"]);
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$role_right2 = $schema->createTable("role_right2");
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$role_right2->addColumn("role_id", "integer", array("unsigned" => true));
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$role_right2->addColumn("right_id", "integer", array("unsigned" => true));
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$role_right2->addForeignKeyConstraint($schema->getTable('role'), array("role_id"), array("id"), array("onUpdate" => "CASCADE"));
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$role_right2->addForeignKeyConstraint($schema->getTable('right'), array("right_id"), array("id"), array("onUpdate" => "CASCADE"));
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$role_right2->setPrimaryKey(["role_id", "right_id"]);
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$schemaAnalyzer = new SchemaAnalyzer(new StubSchemaManager($schema));
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$schemaAnalyzer->setTableCostModifier("role_right2", SchemaAnalyzer::WEIGHT_IRRELEVANT);
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$fks = $schemaAnalyzer->getShortestPath("role", "right");
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$this->assertCount(2, $fks);
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$this->assertEquals("role_right", $fks[0]->getLocalTable()->getName());
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$this->assertEquals("role", $fks[0]->getForeignTableName());
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$this->assertEquals("role_right", $fks[1]->getLocalTable()->getName());
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$this->assertEquals("right", $fks[1]->getForeignTableName());
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}
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public function testAmbiguityExceptionWithJointureAndModifiedWeight2() {
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$schema = $this->getBaseSchema();
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$role_right = $schema->createTable("role_right");
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$role_right->addColumn("role_id", "integer", array("unsigned" => true));
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$role_right->addColumn("right_id", "integer", array("unsigned" => true));
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$role_right->addForeignKeyConstraint($schema->getTable('role'), array("role_id"), array("id"), array("onUpdate" => "CASCADE"));
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$role_right->addForeignKeyConstraint($schema->getTable('right'), array("right_id"), array("id"), array("onUpdate" => "CASCADE"));
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$role_right->setPrimaryKey(["role_id", "right_id"]);
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$role_right2 = $schema->createTable("role_right2");
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$role_right2->addColumn("role_id", "integer", array("unsigned" => true));
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$role_right2->addColumn("right_id", "integer", array("unsigned" => true));
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$role_right2->addForeignKeyConstraint($schema->getTable('role'), array("role_id"), array("id"), array("onUpdate" => "CASCADE"));
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$role_right2->addForeignKeyConstraint($schema->getTable('right'), array("right_id"), array("id"), array("onUpdate" => "CASCADE"));
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$role_right2->setPrimaryKey(["role_id", "right_id"]);
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$schemaAnalyzer = new SchemaAnalyzer(new StubSchemaManager($schema));
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$schemaAnalyzer->setTableCostModifiers(["role_right2" => SchemaAnalyzer::WEIGHT_IRRELEVANT]);
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$schemaAnalyzer->setForeignKeyCosts([]);
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$fks = $schemaAnalyzer->getShortestPath("role", "right");
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$this->assertCount(2, $fks);
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$this->assertEquals("role_right", $fks[0]->getLocalTable()->getName());
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$this->assertEquals("role", $fks[0]->getForeignTableName());
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$this->assertEquals("role_right", $fks[1]->getLocalTable()->getName());
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$this->assertEquals("right", $fks[1]->getForeignTableName());
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}
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}
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