Adding public method to reset a prepared statement

Sources/SQLite/Core/Statement.swift

@@ -185,7 +185,11 @@ public final class Statement {
         try connection.sync { try connection.check(sqlite3_step(handle)) == SQLITE_ROW }
     }
 
-    fileprivate func reset(clearBindings shouldClear: Bool = true) {
+    public func reset() {
+        reset(clearBindings: true)
+    }
+
+    fileprivate func reset(clearBindings shouldClear: Bool) {
         sqlite3_reset(handle)
         if shouldClear { sqlite3_clear_bindings(handle) }
     }

Tests/SQLiteTests/StatementTests.swift

@@ -34,4 +34,61 @@ class StatementTests: SQLiteTestCase {
 
         XCTAssertEqual(names.map({ "\($0)@example.com" }), emails.sorted())
     }
+
+    /// Check that a statement reset will close the implicit transaction, allowing wal file to checkpoint
+    func test_reset_statement() throws {
+        // Remove old test db if any
+        let path = "\(NSTemporaryDirectory())/SQLite.swift Tests.sqlite3"
+        try? FileManager.default.removeItem(atPath: path)
+        try? FileManager.default.removeItem(atPath: path + "-shm")
+        try? FileManager.default.removeItem(atPath: path + "-wal")
+
+        // create new db on disk in wal mode
+        let db = try Connection(.uri(path))
+        let url = URL(fileURLWithPath: db.description)
+        XCTAssertEqual(url.lastPathComponent, "SQLite.swift Tests.sqlite3")
+        try db.run("PRAGMA journal_mode=WAL;")
+
+        // create users table
+        try db.execute("""
+            CREATE TABLE users (
+                id INTEGER PRIMARY KEY,
+                email TEXT NOT NULL UNIQUE,
+                age INTEGER,
+                salary REAL,
+                admin BOOLEAN NOT NULL DEFAULT 0 CHECK (admin IN (0, 1)),
+                manager_id INTEGER,
+                created_at DATETIME,
+                FOREIGN KEY(manager_id) REFERENCES users(id)
+            )
+            """
+        )
+
+        // insert single row
+        try db.run("INSERT INTO \"users\" (email, age, admin) values (?, ?, ?)",
+                   "[email protected]", 1.datatypeValue, false.datatypeValue)
+
+        // prepare a statement and read a single row. This will incremeent the cursor which
+        // prevents the implicit transaction from closing.
+        // https://www.sqlite.org/lang_transaction.html#implicit_versus_explicit_transactions
+        let statement = try db.prepare("SELECT email FROM users")
+        XCTAssert(try statement.step())
+        let blob = statement.row[0] as Blob
+        XCTAssertEqual("[email protected]", String(bytes: blob.bytes, encoding: .utf8)!)
+
+        // verify that the transaction is not closed, which prevents wal_checkpoints (both explicit and auto)
+        do {
+            try db.run("pragma wal_checkpoint(truncate)")
+            XCTFail("Database should be locked")
+        } catch {
+            // pass
+        }
+
+        // reset the prepared statement, allowing the implicit transaction to close
+        statement.reset()
+
+        // truncate succeeds
+        try db.run("pragma wal_checkpoint(truncate)")
+    }
+
 }