test(engine): cover TransactionalHeapTest and tempFile

src/test/kotlin/kestrel/store/engine/TransactionalHeapTest.kt

@@ -0,0 +1,118 @@
+package kestrel.store.engine
+
+import kestrel.store.heap.HeapFileException
+import kestrel.store.page.BufferPool
+import kestrel.store.page.DiskManager
+import kestrel.store.txn.TransactionManager
+import java.io.File
+import java.nio.file.Files
+import kotlin.test.Test
+import kotlin.test.assertEquals
+import kotlin.test.assertFailsWith
+import kotlin.test.assertTrue
+
+class TransactionalHeapTest {
+    private fun tempFile(prefix: String): File = Files.createTempFile(prefix, ".db").toFile().also { it.deleteOnExit() }
+
+    private inner class Fixture {
+        val diskManager = DiskManager(tempFile("kestrel-txheap-data"))
+        val bufferPool = BufferPool(diskManager, 32)
+        val wal = kestrel.store.wal.WriteAheadLog(tempFile("kestrel-txheap-wal"))
+        val txnManager = TransactionManager(wal, diskManager)
+        val tracker = TouchedPageTracker()
+        val heap = TransactionalHeap.create(bufferPool, txnManager, tracker)
+
+        fun abort(txnId: Long) {
+            txnManager.abort(txnId)
+            for (pageId in tracker.forget(txnId)) bufferPool.invalidate(pageId)
+        }
+    }
+
+    @Test
+    fun aCommittedInsertIsVisibleToLaterTransactions() {
+        val fx = Fixture()
+        val writer = fx.txnManager.begin()
+        val rid = fx.heap.insert(writer, "durable row".toByteArray())
+        fx.txnManager.commit(writer)
+
+        val reader = fx.txnManager.begin()
+        assertEquals("durable row", String(fx.heap.get(reader, rid)))
+        assertEquals(listOf(rid), fx.heap.scan(reader).map { it.first })
+    }
+
+    @Test
+    fun anAbortedInsertDisappearsImmediatelyEvenThoughItsPageIsStillCached() {
+        val fx = Fixture()
+        val writer = fx.txnManager.begin()
+        val rid = fx.heap.insert(writer, "should vanish".toByteArray())
+        fx.abort(writer)
+
+        val reader = fx.txnManager.begin()
+        assertTrue(fx.heap.scan(reader).isEmpty(), "an aborted insert must not be visible, cache or no cache")
+        assertFailsWith<Exception> { fx.heap.get(reader, rid) }
+    }
+
+    @Test
+    fun updateThenAbortRestoresThePriorValue() {
+        val fx = Fixture()
+        val setup = fx.txnManager.begin()
+        val rid = fx.heap.insert(setup, "original".toByteArray())
+        fx.txnManager.commit(setup)
+
+        val writer = fx.txnManager.begin()
+        fx.heap.update(writer, rid, "changed".toByteArray())
+        fx.abort(writer)
+
+        val reader = fx.txnManager.begin()
+        assertEquals("original", String(fx.heap.get(reader, rid)))
+    }
+
+    @Test
+    fun deleteThenAbortRestoresTheRecord() {
+        val fx = Fixture()
+        val setup = fx.txnManager.begin()
+        val rid = fx.heap.insert(setup, "keep me".toByteArray())
+        fx.txnManager.commit(setup)
+
+        val writer = fx.txnManager.begin()
+        fx.heap.delete(writer, rid)
+        fx.abort(writer)
+
+        val reader = fx.txnManager.begin()
+        assertEquals("keep me", String(fx.heap.get(reader, rid)))
+    }
+
+    @Test
+    fun destroyFreesEveryPageSoALaterHeapReusesThemInsteadOfGrowingTheFile() {
+        val fx = Fixture()
+        val writer = fx.txnManager.begin()
+        for (i in 0 until 40) fx.heap.insert(writer, ByteArray(200) { i.toByte() })
+        fx.txnManager.commit(writer)
+        val peak = fx.diskManager.allocatedPageCount()
+
+        val destroyer = fx.txnManager.begin()
+        fx.heap.destroy(destroyer)
+        fx.txnManager.commit(destroyer)
+
+        val fresh = TransactionalHeap.create(fx.bufferPool, fx.txnManager, fx.tracker)
+        val filler = fx.txnManager.begin()
+        for (i in 0 until 40) fresh.insert(filler, ByteArray(200) { i.toByte() })
+        fx.txnManager.commit(filler)
+
+        assertTrue(
+            fx.diskManager.allocatedPageCount() <= peak,
+            "expected the destroyed heap's pages to be reused by the new heap instead of growing the file " +
+                "further (peak=$peak, now=${fx.diskManager.allocatedPageCount()})"
+        )
+    }
+
+    @Test
+    fun oversizedRecordFailsWithoutLoggingAnything() {
+        val fx = Fixture()
+        val txnId = fx.txnManager.begin()
+        assertFailsWith<HeapFileException> {
+            fx.heap.insert(txnId, ByteArray(kestrel.store.heap.HeapPage.MAX_RECORD_SIZE + 1))
+        }
+        fx.txnManager.commit(txnId)
+    }
+}