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布尔运算--java位图搜索实现

时间:2016-06-12 02:06:07      阅读:195      评论:0      收藏:0      [点我收藏+]

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前言

布尔运算是伟大的布尔发明的代数运算,只有简单的逻辑与或非,一开始人们没发现没啥用,后来对计算机的影响太大了,从基础设施到搜索引擎无处不在。


场景

身为码农,在日常工作中,我也遇到了涉及它的需求。场景是这样的,我们的后台服务有一个复杂的配置,涉及到对用户多个维度的匹配,因为变化不会很频繁,

  每次都查询数据库显然不划算,数据量也不是太多,不到万的级别,人配置的嘛。    这样很自然的,缓存到服务器的内存吧,但是总不能蛮力的一个个匹配吧,也太啰嗦,效率也会很低,而且逻辑判断会有点复杂,配置主要是四个维度:机型、渠道、国家、版本,每个维度都是一个数组,有的值是一个["ALL"],意思是全部匹配;

引言

于是想到了布尔运算,比较简单,每个值都对应一长串数字位,有多少条数据,每个维度的每个值就是最多多少位。

  如总共10000条配置,则“中国”对应的位向量最多10000位,对于“中国”这个值,第100位是1就表示第100条配置包含这个"中国"维度值。
  查询国家是“中国”的就是从map中取“中国”对应的位向量和"ALL"对应的位向量做 或 运算。Java自带了大整数的实现:BigInteger;可以给构造方法传递一个代表二进制位的byte数组,byte数组的长度显然是: (配置条数/8)+1,BigInteger内部还会做些处理,主要是去除左边连续的0;

马上开始

由于我们是用的MongoDB数据库,操作是用的spring-data对mongoDB的封装。有Criteria和Query的API,这也是spring一贯的风格。

 于是,实现了一个通用的位图查询,和Criteria的API相似,这样代码改动可以很小(把import spring的包换成自己的就差不多完事了),不啰嗦了,上代码:

  
   先上测试case(例子有点low,将就看吧):

import java.util.Arrays;
import java.util.List;
import java.util.concurrent.atomic.AtomicInteger;

import org.junit.Assert;
import org.junit.Test;

import bitmapSearch.BitmapSearcher;
import bitmapSearch.Criteria;

public class BitmapSearchTest {

	@Test
	public void testQuery() {
		List<Car> cars = Arrays.asList(new Car(), //
				new Car("大众").setToAreas("ALL"), //
				new Car("耗子车", 3).setToAreas("某山区"), //
				new Car("东方红", 6).setToAreas("中国"));
		BitmapSearcher searcher = new BitmapSearcher(cars, new BitmapSearcher.IndexCreator<Car, String>() {
			@Override
			public String[] indexKeys() {
				return new String[] { "id", "brand", "legs", "toAreas", "desc" };
			}

			@Override
			public Object[] fieldValue(Car bean, String indexKey) {
				if ("id".equals(indexKey)) {
					return new Object[] { bean.id };
				} else if ("brand".equals(indexKey)) {
					return new Object[] { bean.getBrand() };
				} else if ("legs".equals(indexKey)) {
					return new Object[] { bean.getLegs() };
				} else if ("toAreas".equals(indexKey)) {
					return bean.getToAreas();
				}else if ("desc".equals(indexKey)) {
					return new Object[] { bean.getDesc() };
				}
				return null;
			}
		});
		Car rs1 = searcher.findOne(
				Criteria.where("legs").is(6)//
						.andOperator(new Criteria().orOperator(//
								Criteria.where("id").is(4), //
								Criteria.where("desc").is("MadeInChina")))//
				, null);//
		Assert.assertTrue(rs1.brand.equals("东方红"));
		List<Car> rs2 = searcher.find(Criteria.where("toAreas").in("中国", "ALL"));
		Assert.assertTrue(rs2 != null && rs2.size() == 2);
	}

	private static class Car {
		final int id;
		static AtomicInteger ID_GEN = new AtomicInteger();
		String brand = "QQ";
		int legs = 4;
		String[] toAreas;
		String desc = "";

		public Car() {
			super();
			id = ID_GEN.incrementAndGet();
		}

		public Car(String brand) {
			this();
			this.brand = brand;
		}

		public Car(String brand, int legs) {
			this();
			this.brand = brand;
			this.legs = legs;
		}

		public String getBrand() {
			return brand;
		}

		public void setBrand(String brand) {
			this.brand = brand;
		}

		public int getLegs() {
			return legs;
		}

		public void setLegs(int legs) {
			this.legs = legs;
		}

		public Car setToAreas(String... toAreas) {
			this.toAreas = toAreas;
			return this;
		}

		public String[] getToAreas() {
			return toAreas;
		}

		public String getDesc() {
			return desc;
		}

		public void setDesc(String desc) {
			this.desc = desc;
		}

	}
}



其中,抽象一个内部类IndexCreator,把构造索引以及如何获取索引字段值的工作抛给用户
</pre><p></p><p></p><pre name="code" class="html">/**
 * 
 */
package bitmapSearch;

import java.math.BigInteger;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * 通用位图搜索工具类
 * 
 * @author HouKangxi
 *
 */
public final class BitmapSearcher {
	/**
	 * 对象list,只读。
	 */
	@SuppressWarnings("rawtypes")
	private final List beansList;
	/**
	 * 供搜索用的索引: K: index, value:<fieldVal--bits>
	 */
	private Map<Object, Map<Object, BigInteger>> indexMap;
	/**
	 * 索引构造器
	 */
	@SuppressWarnings("rawtypes")
	private final IndexCreator indexCreator;

	/**
	 * 索引构造器
	 * 
	 *
	 *
	 * @param <T,<span style="font-family: Arial, Helvetica, sans-serif;">INDEX</span>>
	 */
	public static interface IndexCreator<T, INDEX> {
		/**
		 * 返回一组索引
		 * 
		 * @return
		 */
		INDEX[] indexKeys();

		/**
		 * 获取指定索引名对应的字段值
		 * 
		 * @param bean
		 *            - list中的对象
		 * @param indexKey
		 *            - 索引名
		 * @return
		 */
		Object[] fieldValue(T bean, INDEX indexKey);
	}

	/**
	 * 构造方法
	 * 
	 * @param objList
	 *            - 对象list
	 * @param ic
	 *            - 索引构造器
	 */
	public <T, INDEX> BitmapSearcher(List<T> objList, IndexCreator<T, INDEX> ic) {
		indexCreator = ic;
		if (objList != null && objList.size() > 0) {
			beansList = Collections.unmodifiableList(objList);
			createAllIndex();
		} else {
			beansList = Collections.emptyList();
		}
	}

	Map<Object, BigInteger> getBitmap(Object key) {
		return indexMap.get(key);
	}

	/**
	 * 查询一个结果
	 * 
	 * @param <T>
	 * 
	 * @param criteria
	 *            - 查询条件
	 * @param sorter
	 *            - 指定的排序器
	 * @return
	 */
	public <T> T findOne(Criteria criteria, Comparator<T> sorter) {
		List<T> list = find(criteria);
		if (list == null || list.isEmpty()) {
			return null;
		}
		if (sorter != null)
			Collections.sort(list, sorter);
		// 取出第一个
		return list.get(0);
	}

	/**
	 * 查询 list
	 * 
	 * @param <T>
	 * @param criteria
	 * @return
	 */
	@SuppressWarnings("unchecked")
	public <T> List<T> find(Criteria criteria) {
		if (beansList == null || beansList.isEmpty()) {
			return null;
		}
		BigInteger bInt = criteria.proc(this, null);
		if (bInt == null) {
			return null;
		}
		ArrayList<Integer> indexes = new ArrayList<Integer>();
		int idx;
		while ((idx = bInt.getLowestSetBit()) >= 0) {
			indexes.add(idx);
			// 将当前值与它减去1的值做&运算,正好下次可以得到最右边的 1
			bInt = bInt.and(bInt.subtract(BigInteger.ONE));
		}
		// 序号 indexes 天然是从小到大排列,且不会重复,因为每次都是找最右边的1
		if (indexes.isEmpty()) {
			return null;
		}
		@SuppressWarnings("rawtypes")
		ArrayList rslist = new ArrayList(indexes.size());
                for (int i : indexes) {
		     rslist.add(beansList.get(i));
		}
		return rslist;
	}

	private void createAllIndex() {
		Map<Object, Map<Object, byte[]>> t_Index = new HashMap<Object, Map<Object, byte[]>>();
		Object[] keyNames = indexCreator.indexKeys();
		for (int i = 0; i < keyNames.length; i++) {
			t_Index.put(keyNames[i], new HashMap<Object, byte[]>());
		}
		int i = 0;
		final int SUM = beansList.size();
		for (Object o : beansList) {
			createIndex(o, t_Index, SUM, i, keyNames);
			i++;
		}
		indexMap = new HashMap<Object, Map<Object, BigInteger>>(t_Index.size());
		bytes2BigInteger(t_Index, indexMap);
	}

	private void createIndex(Object o, Map<Object, Map<Object, byte[]>> t_Index, final int SUM, final int index,
			Object[] indexes) {
		if (o == null) {
			return;
		}
		final int bytesLen = (SUM >> 3) + 1;
		final int byteIndex = bytesLen - 1 - (index >> 3);
		final int value = 1 << (index % 8);

		for (int i = 0; i < indexes.length; i++) {
			Object key = indexes[i];
			@SuppressWarnings("unchecked")
			Object fieldValues[] = indexCreator.fieldValue(o, key);
			if (fieldValues == null) {
				continue;
			}
			Map<Object, byte[]> bIntMap = t_Index.get(key);
			for (Object fieldValue : fieldValues) {
				if (fieldValue != null) {
					byte[] bInt = bIntMap.get(fieldValue);
					if (bInt == null) {
						bIntMap.put(fieldValue, bInt = new byte[bytesLen]);
					}
					bInt[byteIndex] |= value;
				}
			}
		}
	}

	@SuppressWarnings("unchecked")
	private void bytes2BigInteger(Map<Object, Map<Object, byte[]>> t_Index,
			Map<Object, Map<Object, BigInteger>> bigInts) {
		for (Map.Entry<Object, Map<Object, byte[]>> entry : t_Index.entrySet()) {
			Object key = entry.getKey();
			Map<Object, byte[]> value = entry.getValue();
			if (value == null || value.isEmpty()) {
				continue;
			}
			@SuppressWarnings("rawtypes")
			Map ov = value;
			for (Map.Entry<Object, byte[]> v : value.entrySet()) {
				ov.put(v.getKey(), new BigInteger(v.getValue()));
			}
			bigInts.put(key, ov);
		}
	}

}


下面是Criteria的一些实现类:

/**
 * 
 */
package bitmapSearch;


import java.math.BigInteger;
import java.util.LinkedList;
import java.util.List;


/**
 * 通用查询约束
 * 
 * @author houkangxi
 *
 */
public class Criteria {
	protected Object key;


	protected List<Criteria> chain;
	private Criteria prev = this;


	public Criteria() {
		chain = new LinkedList<Criteria>();
	}


	public Criteria(Object key) {
		this();
		this.key = key;
	}


	Criteria(int noInitChain) {
	}


	public static Criteria where(Object key) {
		return new Criteria(key);
	}


	private Criteria addToChain(Criteria c) {
		prev = c;
		chain.add(c);
		return this;
	}


	public Criteria is(Object val) {
		prev.addToChain(new CriteriaOpIs(prev.key, val));
		return this;
	}


	public Criteria ne(Object val) {
		prev.addToChain(new CriteriaOpNot(prev.key, val));
		return this;
	}


	public Criteria in(Object... val) {
		prev.addToChain(new CriteriaOpIn(prev.key, val));
		return this;
	}


	public Criteria and(String key) {
		return addToChain(new CriteriaOpAnd(key));
	}


	public Criteria or(String key) {
		return addToChain(new CriteriaOpOr(key));
	}


	public Criteria andOperator(Criteria... o) {
		return addToChain(new CriteriaOpAnd(o));
	}


	public Criteria orOperator(Criteria... o) {
		return addToChain(new CriteriaOpOr(o));
	}


	BigInteger proc(BitmapSearcher sea, BigInteger prev) {
		if (chain == null) {
			return null;
		}
		BigInteger rs = prev;
		for (Criteria c : chain) {
			rs = c.proc(sea, rs);
		}
		return rs;
	}


	@Override
	public String toString() {
		return getClass().getSimpleName() + "@key=" + key;
	}
}

/**
 * 
 */
package bitmapSearch;

import java.math.BigInteger;
import java.util.Arrays;

/**
 * @author houkangxi
 *
 */
abstract class CriteriaChain extends Criteria {

	CriteriaChain(String key) {
		super(key);
	}

	CriteriaChain(Criteria[] list) {
		super(0);
		this.chain = Arrays.asList(list);
	}

	protected abstract BigInteger op(BigInteger o1, BigInteger o2);

	@Override
	protected final BigInteger proc(BitmapSearcher sea, BigInteger prev) {
		if (chain == null || chain.isEmpty()) {
			return null;
		}
		BigInteger h = chain.get(0).proc(sea, null);
		for (int i = 1; i < chain.size() && h != null; i++) {
			h = op(h, chain.get(i).proc(sea, h));
		}
		if (prev == null) {
			return h;
		} else if (h != null) {
			return op(prev, h);
		}
		return null;
	}

}

/**
 * 
 */
package bitmapSearch;

import java.math.BigInteger;

/**
 * And (且)查询
 * @author houkangxi
 *
 */
class CriteriaOpAnd extends CriteriaChain {

	CriteriaOpAnd(String key) {
		super(key);
	}

	CriteriaOpAnd(Criteria[] list) {
		super(list);
	}

	@Override
	protected BigInteger op(BigInteger o1, BigInteger o2) {
		if (o2 == null || o1 == null) {
			return null;
		}
		return o1.and(o2);
	}
}
/**
 * 
 */
package bitmapSearch;

import java.math.BigInteger;
import java.util.Map;

/**
 * IN 查询
 * @author houkangxi
 *
 */
class CriteriaOpIn extends Criteria {
	Object[] colls;

	CriteriaOpIn(Object key, Object[] colls) {
		super(key);
		this.colls = colls;
	}

	@Override
	protected BigInteger proc(BitmapSearcher sea, BigInteger prev) {
		Map<Object, BigInteger> bitmap = sea.getBitmap(key);
		if (bitmap == null || colls == null) {
			return null;
		}
		BigInteger bit = null;
		for (int i = 0; i < colls.length; i++) {
			Object val = colls[i];
			BigInteger I = bitmap.get(val);
			if (I != null) {
				bit = bit == null ? I : bit.or(I);
			}
		}
		return bit;
	}
}
/**
 * 
 */
package bitmapSearch;

import java.math.BigInteger;
import java.util.Map;

/**
 * Is查询
 * 
 * @author houkangxi
 *
 */
class CriteriaOpIs extends Criteria {
	private Object ov;

	CriteriaOpIs(Object k, Object ov) {
		super(k);
		this.ov = ov;
	}

	@Override
	protected BigInteger proc(BitmapSearcher sea, BigInteger prev) {
		Map<Object, BigInteger> bimap = sea.getBitmap(key);
		if (bimap == null) {
			return null;
		}
		return bimap.get(ov);
	}
}
/**
 * 
 */
package bitmapSearch;

import java.math.BigInteger;
import java.util.Map;

/**
 * NOT (非)查询
 * @author houkangxi
 *
 */
class CriteriaOpNot extends Criteria {
	private Object ov;

	CriteriaOpNot(Object k, Object ov) {
		super(k);
		this.ov = ov;
	}

	@Override
	protected BigInteger proc(BitmapSearcher sea, BigInteger prev) {
		Map<Object, BigInteger> bimap = sea.getBitmap(key);
		if (bimap == null) {
			return null;
		}
		BigInteger b = bimap.get(ov);
		if (b == null) {
			return null;
		}
		return b.not();
	}
}
/**
 * 
 */
package bitmapSearch;

import java.math.BigInteger;

/**
 * Or (或)查询
 * @author houkangxi
 *
 */
class CriteriaOpOr extends CriteriaChain {

	CriteriaOpOr(String k) {
		super(k);
	}

	CriteriaOpOr(Criteria[] list) {
		super(list);
	}

	@Override
	protected BigInteger op(BigInteger o1, BigInteger o2) {
		if (o2 == null) {
			return o1;
		}
		if (o1 == null) {
			return o2;
		}
		return o1.or(o2);
	}
}

布尔运算--java位图搜索实现

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原文地址:http://blog.csdn.net/hkxxx/article/details/51637342

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