• Ignite内存数据库与sql支持


    Ignite采用h2作为内存数据库,支持h2的一切sql语法。如果是本地缓存或者复制缓存,sql执行直接在本地h2数据库中执行,如果是分区缓存,ignite则会分解sql到多个h2数据库执行后再汇总。

    通过@QuerySqlField注解可以轻松的把对象属性映射到表字段,下述代码实现了缓存对象与h2表的映射关系:

    1、 class

    package com.coshaho.learn.ignite.sql;
    
    import org.apache.ignite.cache.query.annotations.QuerySqlField;
    
    public class Class 
    {
        @QuerySqlField(index = true)
        private int id;
        
        @QuerySqlField
        private String name;
        
        private int level;
    
        public Class(int id, String name)
        {
            this.id = id;
            this.name = name;
        }
        public int getId() {
            return id;
        }
    
        public void setId(int id) {
            this.id = id;
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
        public int getLevel() {
            return level;
        }
        public void setLevel(int level) {
            this.level = level;
        }
        @Override
        public String toString() {
            return "Class [id=" + id + ", name=" + name + ", level=" + level + "]";
        }
    }

    2、 Student

    package com.coshaho.learn.ignite.sql;
    
    import org.apache.ignite.cache.query.annotations.QuerySqlField;
    
    public class Student 
    {
        @QuerySqlField
        private int classId;
        
        @QuerySqlField
        private String name;
        
        @QuerySqlField
        private int age;
        
        public Student(int classId, String name, int age)
        {
            this.classId = classId;
            this.name = name;
            this.age = age;
        }
    
        public int getClassId() {
            return classId;
        }
    
        public void setClassId(int classId) {
            this.classId = classId;
        }
    
        public String getName() {
            return name;
        }
    
        public void setName(String name) {
            this.name = name;
        }
    
        public int getAge() {
            return age;
        }
    
        public void setAge(int age) {
            this.age = age;
        }
    
        @Override
        public String toString() {
            return "Student [classId=" + classId + ", name=" + name + ", age="
                    + age + "]";
        }
    }

    要把缓存对象存储到h2表中,还必须设置缓存的IndexedTypes,IndexedTypes必须成对出现,并且和缓存键值对类型相同。

    Ignite还支持不同缓存之间的关联查询,查询时把缓存名当做h2 schema就行,缓存关联查询时需要把缓存名设置为大写(应该是ignite bug)。

    测试代码如下:

    package com.coshaho.learn.ignite.sql;
    
    import java.util.List;
    
    import org.apache.ignite.Ignite;
    import org.apache.ignite.IgniteCache;
    import org.apache.ignite.Ignition;
    import org.apache.ignite.cache.CacheMode;
    import org.apache.ignite.cache.query.QueryCursor;
    import org.apache.ignite.cache.query.SqlFieldsQuery;
    import org.apache.ignite.configuration.CacheConfiguration;
    
    /**
     * 
     * IgniteDB.java Create on 2017年5月25日 下午11:00:35    
     *    
     * 类功能说明:   ignite内存数据库
     *
     * Copyright: Copyright(c) 2013 
     * Company: COSHAHO
     * @Version 1.0
     * @Author coshaho
     */
    public class IgniteDB 
    {
        public static void main(String[] args)
        {
            Ignite ignite = Ignition.start();
            CacheConfiguration<Integer, Class> classCfg = new CacheConfiguration<Integer, Class>();
            classCfg.setName("CLA");
            classCfg.setCacheMode(CacheMode.PARTITIONED);
            classCfg.setIndexedTypes(Integer.class, Class.class);
            IgniteCache<Integer, Class> classCache = ignite.getOrCreateCache(classCfg);
            classCache.put(1, new Class(1, "五年级一班"));
            classCache.put(2, new Class(2, "五年级二班"));
            
            CacheConfiguration<Integer, Student> stuCfg = new CacheConfiguration<Integer, Student>();
            stuCfg.setName("STU");
            stuCfg.setCacheMode(CacheMode.PARTITIONED);
            stuCfg.setIndexedTypes(Integer.class, Student.class);
            IgniteCache<Integer, Student> stuCache = ignite.getOrCreateCache(stuCfg);
            stuCache.put(1, new Student(1, "张三", 10));
            stuCache.put(2, new Student(1, "李四", 11));
            stuCache.put(3, new Student(2, "王五", 11));
            stuCache.put(4, new Student(2, "胜七", 10));
            
            SqlFieldsQuery sql = new SqlFieldsQuery(
                      "select concat(stu.classId, '----', stu.name) as stuinfo"
                      + " "
                      + "from Student as stu "
                      + "");
            
            QueryCursor<List<?>> cursor = stuCache.query(sql);
            for (List<?> row : cursor)
            {
                System.out.println("学生信息:" + row.get(0));
            }
            
            SqlFieldsQuery sql1 = new SqlFieldsQuery(
                      "select concat(cla.id, '----', cla.name) as clainfo"
                      + ", concat(stu.name, '----', stu.age) as stuinfo "
                      + "from Class as cla, STU.Student as stu "
                      + "where cla.id = stu.classId");
            
            QueryCursor<List<?>> cursor1 = classCache.query(sql1);
            for (List<?> row : cursor1)
            {
                System.out.println("班级信息:" + row.get(0) + ", 学生信息:" + row.get(1));
            }
        }
    }

    测试结果:

    [23:02:08] Ignite node started OK (id=6073a91e)
    [23:02:08] Topology snapshot [ver=1, servers=1, clients=0, CPUs=4, heap=0.88GB]
    学生信息:1----张三
    学生信息:1----李四
    学生信息:2----王五
    学生信息:2----胜七
    班级信息:1----五年级一班, 学生信息:张三----10
    班级信息:1----五年级一班, 学生信息:李四----11
    班级信息:2----五年级二班, 学生信息:王五----11
    班级信息:2----五年级二班, 学生信息:胜七----10

    可以看出来,ignite对sql的支持非常强大,对于需要频繁进行数据库操作的场景,ignite缓存相当有效。

     

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  • 原文地址:https://www.cnblogs.com/coshaho/p/6906450.html
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