Fix GetCanonical and remove a page's cached canonicals when it is del…

…eted

app/crawler/crawler.go

@@ -215,7 +215,11 @@ func getText(node *html.Node) string {
 func Canonicalize(src string, db database.Database, url *url.URL) (*url.URL, error) {
 
 	// Check if we already have a canonical URL recorded
-	canonical, _ := db.GetCanonical(src, url.String())
+	canonical, err := db.GetCanonical(src, url.String())
+
+	if err != nil {
+		return nil, err
+	}
 
 	if canonical != nil {
 		return url.Parse(canonical.Canonical)

app/database/db.go

@@ -10,6 +10,8 @@ type Database interface {
 	HasDocument(source string, url string) (*bool, error)
 	// Fetch the document by URL (or the URL's canonical)
 	GetDocument(source string, url string) (*Page, error)
+	// Delete a document by its URL and remove all canonicals pointing to it
+	RemoveDocument(source string, url string) error
 
 	// Run a fulltext search with the given query
 	Search(sources []string, query string, page uint32, pageSize uint32) ([]Result, *uint32, error)

app/database/db_sqlite.go

@@ -32,6 +32,11 @@ func (db *SQLiteDatabase) AddDocument(source string, depth int32, referrer strin
 	return err
 }
 
+func (db *SQLiteDatabase) RemoveDocument(source string, url string) error {
+	_, err := db.conn.Exec("DELETE FROM pages WHERE source = ? AND url = ?;", source, url)
+	return err
+}
+
 func (db *SQLiteDatabase) HasDocument(source string, url string) (*bool, error) {
 	cursor := db.conn.QueryRow("SELECT 1 FROM pages WHERE source = ? AND (url = ? OR url IN (SELECT canonical FROM canonicals WHERE url = ?));", source, url, url)
 
@@ -320,12 +325,15 @@ func (db *SQLiteDatabase) QueuePagesOlderThan(source string, daysAgo int32) erro
 }
 
 func (db *SQLiteDatabase) GetCanonical(source string, url string) (*Canonical, error) {
-	cursor := db.conn.QueryRow("SELECT original, canonical, crawledAt FROM canonicals WHERE source = ? AND url = ?", source, url)
+	cursor := db.conn.QueryRow("SELECT url, canonical, crawledAt FROM canonicals WHERE source = ? AND url = ?", source, url)
 
 	canonical := &Canonical{}
 	err := cursor.Scan(&canonical.Original, &canonical.Canonical, &canonical.CrawledAt)
 
 	if err != nil {
+		if err == sql.ErrNoRows {
+			return nil, nil
+		}
 		return nil, err
 	}
 	return canonical, nil

app/database/db_sqlite_setup.sql

@@ -55,6 +55,11 @@ CREATE VIRTUAL TABLE IF NOT EXISTS pages_fts USING fts5(
     content=pages
 );
 
+-- When a page is deleted, delete its canonicals too
+CREATE TRIGGER IF NOT EXISTS delete_page_canonicals_on_page_delete AFTER DELETE ON pages BEGIN
+  DELETE FROM canonicals WHERE source = old.source AND canonical = old.url;
+END;
+
 -- Use triggers to automatically sync the FTS table with the content table
 -- https://sqlite.org/fts5.html#external_content_tables
 CREATE TRIGGER IF NOT EXISTS pages_auto_insert AFTER INSERT ON pages BEGIN

app/database/db_sqlite_test.go

@@ -178,6 +178,32 @@ func TestGetDocument(t *testing.T) {
 	}
 }
 
+func TestDeleteCanonicalsOnDeletePage(t *testing.T) {
+	db := createDB(t)
+
+	err := db.AddDocument("source1", 0, "", "https://example.com/", Finished, "Title", "Description", "Content", "")
+	if err != nil {
+		t.Fatalf("failed to add page: %v", err)
+	}
+	err = db.SetCanonical("source1", "https://www.example.com/", "https://example.com/")
+	if err != nil {
+		t.Fatalf("failed to set canonical: %v", err)
+	}
+	err = db.RemoveDocument("source1", "https://example.com/")
+	if err != nil {
+		t.Fatalf("failed to delete document: %v", err)
+	}
+
+	canonical, err := db.GetCanonical("source1", "https://www.example.com/")
+	if err != nil {
+		t.Fatalf("failed to get canonical: %v", err)
+	}
+
+	if canonical != nil {
+		t.Fatalf("canonical was not deleted: expected nil, got %+v", canonical)
+	}
+}
+
 func TestSearchQuery(t *testing.T) {
 	db := createDB(t)