data in native distributed NoSQL. But its incom‐ patibility with SQL and imperfection in ecosystem block it from defeating the relational database in the competition, so the relational database still holds committing and rolling back in other machines after the service is down. • MySQL, in the transaction block, the SQL execution is abnormal, and run Commit, and data re‐ mains consistent. • After XA transactions compute node in a ShardingSphere cluster exceeds its load, the circuit breaker function is used to block the traffic to the compute node, to ensure that the whole cluster continues to provide stable services

data in native distributed NoSQL. But its incom‐ patibility with SQL and imperfection in ecosystem block it from defeating the relational database in the competition, so the relational database still holds commit. XA Transaction Supported • Support Savepoint; • PostgreSQL/OpenGauss, in the transaction block, the SQL execution is abnormal，then run Com- mit，transactions are automatically rollback; • Support committing and rolling back in other machines after the service is down; • MySQL,in the transaction block, the SQL execution is abnormal, and run Commit, and data re‐ mains consistent. BASE Transaction

data in native distributed NoSQL. But its incom‐ patibility with SQL and imperfection in ecosystem block it from defeating the relational database in the competition, so the relational database still holds committing and rolling back in other machines after the service is down. • MySQL, in the transaction block, the SQL execution is abnormal, and run Commit, and data re‐ mains consistent. • After XA transactions compute node in a ShardingSphere cluster exceeds its load, the circuit breaker function is used to block the traffic to the compute node, to ensure that the whole cluster continues to provide stable services

data in native distributed NoSQL. But its incom‐ patibility with SQL and imperfection in ecosystem block it from defeating the relational database in the competition, so the relational database still holds commit. XA Transaction Supported • Support Savepoint; • PostgreSQL/OpenGauss, in the transaction block, the SQL execution is abnormal，then run Com- mit，transactions are automatically rollback; • Support committing and rolling back in other machines after the service is down; • MySQL,in the transaction block, the SQL execution is abnormal, and run Commit, and data re‐ mains consistent. BASE Transaction

data in native distributed NoSQL. But its incom‐ patibility with SQL and imperfection in ecosystem block it from defeating the relational database in the competition, so the relational database still holds database can commit. XA Supported • Support Savepoint; • PostgreSQL/OpenGauss, in the transaction block, the SQL execution is abnormal，then run Com- mit，transactions are automatically rollback; • Support committing and rolling back in other machines after the service is down; • MySQL,in the transaction block, the SQL execution is abnormal, and run Commit, and data re‐ mains consistent. XA Transaction managed

data in native distributed NoSQL. But its incom‐ patibility with SQL and imperfection in ecosystem block it from defeating the relational database in the competition, so the relational database still holds and rolling back in other machines after the service is down. • Savepoint. • In the transaction block, the SQL execution is abnormal, and run Commit, and data remains con‐ sistent. XA Transaction managed parseTreeCache (?) CacheOption Parse syntax tree local cache configuration sqlStatementCache (?) CacheOption sql statement local cache configuration Cache option Configuration Class：org.apache.shardingsphere

Auto-generated catch block e.printStackTrace(); } } if(preparedStatement!=null){ try { preparedStatement.close(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); if(connection!=null){ try { connection.close(); } catch (SQLException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } } 上边使用 jdbc 的原始方法（未经封装）实现了查询数据库表记录的操作。 1.1.2 jdbc 编程步骤： 1、 加载数据库驱动 name="cacheEnabled" value="true"/> 描述 允许值 默认值 cacheEnabled 对在此配置文件下的所有 cache 进行 全局性开/关设置。 true false true 要在你的 Mapper 映射文件中添加一行： <cache /> ，表示此 mapper 开启二级缓存。 6.3.3 实现序列化 二级缓存需要查询结果映射的 pojo 对象实现 java.io

ShardingSphere-JDBC 113 Apache ShardingSphere document 参数解释 类名称：org.apache.shardingsphere.sharding.api.config.cache.ShardingCacheConfiguration 可配置属性： 名称 数据类型 说明 • 默认值 * allowe dMaxSqlLength int 允许缓存的 SQL 长度 限制 cach e.ShardingCacheOptionsConfiguration 路由缓存 • 类名称：org.apache.shardingsphere.sharding.api.config.cache.ShardingCacheOptionsConfiguration 可配置属性： 名称 数据类型 说明 默认值 softValues boolean 是否软引用缓存值 • initialCapacity beans.util.Cache$Kind$2 was unintentionally initialized at build time. To see why com.sun.beans.util.Cache$Kind$2 got initialized use --trace-class- initialization=com.sun.beans.util.Cache$Kind$2 com

'SQL_PARSER' 'RULE' 返回值说明 列 说明 sql_comment_parse_enabled SQL 注释解析启用状态 parse_tree_cache 语法树缓存 sql_statement_cache SQL 语句缓存 9.2. ShardingSphere-Proxy 278 Apache ShardingSphere document 示例 • 查询解析引擎规则配置 -------- -------------------------------+ | sql_comment_parse_enabled | parse_tree_cache | sql_ statement_cache | +---------------------------+-----------------------------------------+------------ ShardingSphere document parseTreeCacheDefinition ::= 'PARSE_TREE_CACHE' '(' cacheOption ')' sqlStatementCacheDefinition ::= 'SQL_STATEMENT_CACHE' '(' cacheOption ')' sqlCommentParseEnabled ::= boolean cacheOption

'SQL_PARSER' 'RULE' 返回值说明 列 说明 sql_comment_parse_enabled SQL 注释解析启用状态 parse_tree_cache 语法树缓存 sql_statement_cache SQL 语句缓存 9.2. ShardingSphere-Proxy 272 Apache ShardingSphere document 示例 • 查询解析引擎规则配置 -------- -------------------------------+ | sql_comment_parse_enabled | parse_tree_cache | sql_ statement_cache | +---------------------------+-----------------------------------------+------------ ShardingSphere document parseTreeCacheDefinition ::= 'PARSE_TREE_CACHE' '(' cacheOption ')' sqlStatementCacheDefinition ::= 'SQL_STATEMENT_CACHE' '(' cacheOption ')' sqlCommentParseEnabled ::= boolean cacheOption