hyracks/hyracks-tests/hyracks-storage-am-lsm-common-test/src/test/java/org/apache/hyracks/storage/am/lsm/common/VirtualFreePageManagerTest.java

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 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
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 *   http://www.apache.org/licenses/LICENSE-2.0
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package org.apache.hyracks.storage.am.lsm.common;

import static org.junit.Assert.assertEquals;

import org.junit.Test;

import org.apache.hyracks.api.exceptions.HyracksDataException;
import org.apache.hyracks.storage.am.lsm.common.freepage.VirtualFreePageManager;

public class VirtualFreePageManagerTest {

    private final int NUM_PAGES = 100;

    private void testInMemoryFreePageManager(VirtualFreePageManager virtualFreePageManager) throws HyracksDataException {
        // The first two pages are reserved for the BTree's metadata page and
        // root page.
        // The "actual" capacity is therefore numPages - 2.
        int capacity = virtualFreePageManager.getCapacity();
        assertEquals(capacity, NUM_PAGES - 2);
        for (int i = 0; i < capacity; i++) {
            int pageId = virtualFreePageManager.getFreePage(null);
            // The free pages start from page 2;
            assertEquals(i + 2, pageId);
        }
        // Start asking for 100 pages above the capacity.
        // Asking for pages above the capacity should be very rare, but
        // nevertheless succeed.
        // We expect isFull() to return true.
        for (int i = 0; i < 100; i++) {
            int pageId = virtualFreePageManager.getFreePage(null);
            assertEquals(capacity + i + 2, pageId);
        }
    }

    @Test
    public void test01() throws HyracksDataException {
        VirtualFreePageManager virtualFreePageManager = new VirtualFreePageManager(NUM_PAGES);
        testInMemoryFreePageManager(virtualFreePageManager);
        // We expect exactly the same behavior after a reset().
        virtualFreePageManager.reset();
        testInMemoryFreePageManager(virtualFreePageManager);
    }
}