MyCat - 源代码篇（14）

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数据库路由中间件MyCat - 源代码篇（14）

5. 路由模块

真正取得RouteResultset的步骤：AbstractRouteStrategy的route方法:
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对应源代码：

public RouteResultset route(SystemConfig sysConfig, SchemaConfig schema, int sqlType, String origSQL,            String charset, ServerConnection sc, LayerCachePool cachePool) throws SQLNonTransientException {    /**     * 处理一些路由之前的逻辑     * 全局序列号，父子表插入     */    if ( beforeRouteProcess(schema, sqlType, origSQL, sc) )        return null;    /**     * SQL 语句拦截     */    String stmt = MycatServer.getInstance().getSqlInterceptor().interceptSQL(origSQL, sqlType);    if (origSQL != stmt && LOGGER.isDebugEnabled()) {        LOGGER.debug("sql intercepted to " + stmt + " from " + origSQL);    }    //对应schema标签checkSQLschema属性，把表示schema的字符去掉    if (schema.isCheckSQLSchema()) {        stmt = RouterUtil.removeSchema(stmt, schema.getName());    }    RouteResultset rrs = new RouteResultset(stmt, sqlType);    /**     * 优化debug loaddata输出cache的日志会极大降低性能     */    if (LOGGER.isDebugEnabled() && origSQL.startsWith(LoadData.loadDataHint)) {        rrs.setCacheAble(false);    }       /**        * rrs携带ServerConnection的autocommit状态用于在sql解析的时候遇到        * select ... for update的时候动态设定RouteResultsetNode的canRunInReadDB属性        */    if (sc != null ) {        rrs.setAutocommit(sc.isAutocommit());    }    /**     * DDL 语句的路由     */    if (ServerParse.DDL == sqlType) {        return RouterUtil.routeToDDLNode(rrs, sqlType, stmt, schema);    }    /**     * 检查是否有分片     */    if (schema.isNoSharding() && ServerParse.SHOW != sqlType) {        rrs = RouterUtil.routeToSingleNode(rrs, schema.getDataNode(), stmt);    } else {        RouteResultset returnedSet = routeSystemInfo(schema, sqlType, stmt, rrs);        if (returnedSet == null) {            rrs = routeNormalSqlWithAST(schema, stmt, rrs, charset, cachePool);        }    }    return rrs;}

5.3 路由之前的逻辑 - 判断子表插入以及全局序列号的生成：

AbstractRouteStrategy.java

/** * 路由之前必要的处理 * 主要是全局序列号插入，还有子表插入 */private boolean beforeRouteProcess(SchemaConfig schema, int sqlType, String origSQL, ServerConnection sc)        throws SQLNonTransientException {    return RouterUtil.processWithMycatSeq(schema, sqlType, origSQL, sc)            || (sqlType == ServerParse.INSERT && RouterUtil.processERChildTable(schema, origSQL, sc))            || (sqlType == ServerParse.INSERT && RouterUtil.processInsert(schema, sqlType, origSQL, sc));}

这里利用了Java的一个特性，||表达式，前半部分如果为真，则后半部分不会被执行。首先执行RouterUtil.processWithMycatSeq(schema, sqlType, origSQL, sc)，这个方法是判断是否是显示使用全局序列号的sql语句，比如像：insert into table1(id,name) values(next value for MYCATSEQ_GLOBAL,‘test’);
对于这样的语句处理是先将改写next value for MYCATSEQ_GLOBAL 为调用全局ID生成的ID，之后进入AST语句解析路由

如果不是，则执行(sqlType == ServerParse.INSERT && RouterUtil.processERChildTable(schema, origSQL, sc))，这个方法判断是否是子表插入：
部分代码：

String tableName = StringUtil.getTableName(origSQL).toUpperCase();final TableConfig tc = schema.getTables().get(tableName);//判断是否为子表，如果不是，只会返回falseif (null != tc && tc.isChildTable()) {final RouteResultset rrs = new RouteResultset(origSQL, ServerParse.INSERT);String joinKey = tc.getJoinKey();//因为是Insert语句，用MySqlInsertStatement进行parseMySqlInsertStatement insertStmt = (MySqlInsertStatement) (new MySqlStatementParser(origSQL)).parseInsert();......

这里注意，所有类型的SQL语句都有druid对应的SQLparser，比如说这里的插入语句就用MySqlInsertStatement解析。druidparser在这节先不讲，会在 AST语义解析路由中详细讲述。

这里写图片描述
接上面代码：

//判断条件完整性，取得解析后语句列中的joinkey列的index    int joinKeyIndex = getJoinKeyIndex(insertStmt.getColumns(), joinKey);    if (joinKeyIndex == -1) {        String inf = "joinKey not provided :" + tc.getJoinKey() + "," + insertStmt;        LOGGER.warn(inf);        throw new SQLNonTransientException(inf);    }    //子表不支持批量插入    if (isMultiInsert(insertStmt)) {        String msg = "ChildTable multi insert not provided";        LOGGER.warn(msg);        throw new SQLNonTransientException(msg);    }    //取得joinkey的值    String joinKeyVal = insertStmt.getValues().getValues().get(joinKeyIndex).toString();    String sql = insertStmt.toString();    // try to route by ER parent partion key    //如果是二级子表（父表不再有父表）,并且分片字段正好是joinkey字段，调用routeByERParentKey    RouteResultset theRrs = RouterUtil.routeByERParentKey(sc, schema, ServerParse.INSERT, sql, rrs, tc, joinKeyVal);    if (theRrs != null) {        boolean processedInsert=false;        //判断是否需要全局序列号              if ( sc!=null && tc.isAutoIncrement()) {                  String primaryKey = tc.getPrimaryKey();                  processedInsert=processInsert(sc,schema,ServerParse.INSERT,sql,tc.getName(),primaryKey);              }              if(processedInsert==false){                rrs.setFinishedRoute(true);                  sc.getSession2().execute(rrs, ServerParse.INSERT);              }        return true;    }    // route by sql query root parent's datanode    //如果不是二级子表或者分片字段不是joinKey字段结果为空，则启动异步线程去后台分片查询出datanode    //只要查询出上一级表的parentkey字段的对应值在哪个分片即可    final String findRootTBSql = tc.getLocateRTableKeySql().toLowerCase() + joinKeyVal;    if (LOGGER.isDebugEnabled()) {        LOGGER.debug("find root parent's node sql " + findRootTBSql);    }    ListenableFuture<String> listenableFuture = MycatServer.getInstance().            getListeningExecutorService().submit(new Callable<String>() {        @Override        public String call() throws Exception {            FetchStoreNodeOfChildTableHandler fetchHandler = new FetchStoreNodeOfChildTableHandler();            return fetchHandler.execute(schema.getName(), findRootTBSql, tc.getRootParent().getDataNodes());        }    });    Futures.addCallback(listenableFuture, new FutureCallback<String>() {        @Override        public void onSuccess(String result) {            //结果为空，证明上一级表中不存在那条记录，失败            if (Strings.isNullOrEmpty(result)) {                StringBuilder s = new StringBuilder();                LOGGER.warn(s.append(sc.getSession2()).append(origSQL).toString() +                        " err:" + "can't find (root) parent sharding node for sql:" + origSQL);                sc.writeErrMessage(ErrorCode.ER_PARSE_ERROR, "can't find (root) parent sharding node for sql:" + origSQL);                return;            }            if (LOGGER.isDebugEnabled()) {                LOGGER.debug("found partion node for child table to insert " + result + " sql :" + origSQL);            }            //找到分片，进行插入（和其他的一样，需要判断是否需要全局自增ID）            boolean processedInsert=false;                  if ( sc!=null && tc.isAutoIncrement()) {                      try {                          String primaryKey = tc.getPrimaryKey();                    processedInsert=processInsert(sc,schema,ServerParse.INSERT,origSQL,tc.getName(),primaryKey);                } catch (SQLNonTransientException e) {                    LOGGER.warn("sequence processInsert error,",e);                    sc.writeErrMessage(ErrorCode.ER_PARSE_ERROR , "sequence processInsert error," + e.getMessage());                }                  }                  if(processedInsert==false){                    RouteResultset executeRrs = RouterUtil.routeToSingleNode(rrs, result, origSQL);                    sc.getSession2().execute(executeRrs, ServerParse.INSERT);                  }        }        @Override        public void onFailure(Throwable t) {            StringBuilder s = new StringBuilder();            LOGGER.warn(s.append(sc.getSession2()).append(origSQL).toString() +                    " err:" + t.getMessage());            sc.writeErrMessage(ErrorCode.ER_PARSE_ERROR, t.getMessage() + " " + s.toString());        }    }, MycatServer.getInstance().            getListeningExecutorService());    return true;}return false;

如果返回false，则继续执行(sqlType == ServerParse.INSERT && RouterUtil.processInsert(schema, sqlType, origSQL, sc))
这个是处理一般的SQL插入语句，将其中的自增主键字段的值改写成内置的全局ID生成器生成的id。
RouterUtil.java:

public static boolean processInsert(SchemaConfig schema, int sqlType,                                        String origSQL, ServerConnection sc) throws SQLNonTransientException {    String tableName = StringUtil.getTableName(origSQL).toUpperCase();    TableConfig tableConfig = schema.getTables().get(tableName);    boolean processedInsert=false;    //判断是有自增字段    if (null != tableConfig && tableConfig.isAutoIncrement()) {        String primaryKey = tableConfig.getPrimaryKey();        processedInsert=processInsert(sc,schema,sqlType,origSQL,tableName,primaryKey);    }    return processedInsert;}

调用processInsert(sc,schema,sqlType,origSQL,tableName,primaryKey)：

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public static boolean processInsert(ServerConnection sc,SchemaConfig schema,            int sqlType,String origSQL,String tableName,String primaryKey) throws SQLNonTransientException {    int firstLeftBracketIndex = origSQL.indexOf("(");    int firstRightBracketIndex = origSQL.indexOf(")");    String upperSql = origSQL.toUpperCase();    int valuesIndex = upperSql.indexOf("VALUES");    int selectIndex = upperSql.indexOf("SELECT");    int fromIndex = upperSql.indexOf("FROM");    //屏蔽insert into table1 select * from table2语句    if(firstLeftBracketIndex < 0) {        String msg = "invalid sql:" + origSQL;        LOGGER.warn(msg);        throw new SQLNonTransientException(msg);    }    //屏蔽批量插入    if(selectIndex > 0 &&fromIndex>0&&selectIndex>firstRightBracketIndex&&valuesIndex<0) {        String msg = "multi insert not provided" ;        LOGGER.warn(msg);        throw new SQLNonTransientException(msg);    }    //插入语句必须提供列结构，因为MyCat默认对于表结构无感知    if(valuesIndex + "VALUES".length() <= firstLeftBracketIndex) {        throw new SQLSyntaxErrorException("insert must provide ColumnList");    }    //如果主键不在插入语句的fields中，则需要进一步处理    boolean processedInsert=!isPKInFields(origSQL,primaryKey,firstLeftBracketIndex,firstRightBracketIndex);    if(processedInsert){        processInsert(sc,schema,sqlType,origSQL,tableName,primaryKey,firstLeftBracketIndex+1,origSQL.indexOf('(',firstRightBracketIndex)+1);    }    return processedInsert;}

对于主键不在插入语句的fields中的SQL，需要改写。比如hotnews主键为id，插入语句为：

insert into hotnews(title) values('aaa');

需要改写成：

insert into hotnews(id, title) values(next value for MYCATSEQ_hotnews,'aaa');

这个在下面这个函数实现：

private static void processInsert(ServerConnection sc, SchemaConfig schema, int sqlType, String origSQL,            String tableName, String primaryKey, int afterFirstLeftBracketIndex, int afterLastLeftBracketIndex) {    int primaryKeyLength = primaryKey.length();    int insertSegOffset = afterFirstLeftBracketIndex;    String mycatSeqPrefix = "next value for MYCATSEQ_";    int mycatSeqPrefixLength = mycatSeqPrefix.length();    int tableNameLength = tableName.length();    char[] newSQLBuf = new char[origSQL.length() + primaryKeyLength + mycatSeqPrefixLength + tableNameLength + 2];    origSQL.getChars(0, afterFirstLeftBracketIndex, newSQLBuf, 0);    primaryKey.getChars(0, primaryKeyLength, newSQLBuf, insertSegOffset);    insertSegOffset += primaryKeyLength;    newSQLBuf[insertSegOffset] = ',';    insertSegOffset++;    origSQL.getChars(afterFirstLeftBracketIndex, afterLastLeftBracketIndex, newSQLBuf, insertSegOffset);    insertSegOffset += afterLastLeftBracketIndex - afterFirstLeftBracketIndex;    mycatSeqPrefix.getChars(0, mycatSeqPrefixLength, newSQLBuf, insertSegOffset);    insertSegOffset += mycatSeqPrefixLength;    tableName.getChars(0, tableNameLength, newSQLBuf, insertSegOffset);    insertSegOffset += tableNameLength;    newSQLBuf[insertSegOffset] = ',';    insertSegOffset++;    origSQL.getChars(afterLastLeftBracketIndex, origSQL.length(), newSQLBuf, insertSegOffset);    processSQL(sc, schema, new String(newSQLBuf), sqlType);}

最后的processSQL(sc, schema, new String(newSQLBuf), sqlType);是将语句放入执行队列：
这里MyCat考虑NIO线程吞吐量以及全局ID生成线程安全的问题，使用如下流程执行需要全局ID的SQL insert语句。
processSQL(sc, schema, new String(newSQLBuf), sqlType)：

SessionSQLPair sessionSQLPair = new SessionSQLPair(sc.getSession2(), schema, sql, sqlType);MycatServer.getInstance().getSequnceProcessor().addNewSql(sessionSQLPair);

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