数据库中间件Mycat源码解析：Mycat的SQL解析和路由
Posted 闲庭细步
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mycat对sql的解析分为两部分，一个是普通sql，另一个是PreparedStatment。
下面以解析普通sql为例分析（另一种方式大同小异），sql从客户端发过来后server接收后会调用FrontendCommandHandler的handle方法，这个方法会调用FrontendConnection的query方法，接着query方法会调用ServerQueryHandler的query方法，接着调用ServerConnection的execute方法。如下图所示：
public void execute(String sql, int type) {
//连接状态检查
if (this.isClosed()) {
LOGGER.warn("ignore execute ,server connection is closed " + this);
return;
}
// 事务状态检查
if (txInterrupted) {
writeErrMessage(ErrorCode.ER_YES,
"Transaction error, need to rollback." + txInterrputMsg);
return;
}
// 检查当前使用的DB
String db = this.schema;
boolean isDefault = true;
if (db == null) {
db = SchemaUtil.detectDefaultDb(sql, type);
if (db == null) {
writeErrMessage(ErrorCode.ERR_BAD_LOGICDB, "No MyCAT Database selected");
return;
}
isDefault = false;
}
// 兼容phpAdmin's, 支持对mysql元数据的模拟返回
//// TODO: 2016/5/20 支持更多information_schema特性
if (ServerParse.SELECT == type
&& db.equalsIgnoreCase("information_schema") ) {
MysqlInformationSchemaHandler.handle(sql, this);
return;
}
if (ServerParse.SELECT == type
&& sql.contains("mysql")
&& sql.contains("proc")) {
SchemaUtil.SchemaInfo schemaInfo = SchemaUtil.parseSchema(sql);
if (schemaInfo != null
&& "mysql".equalsIgnoreCase(schemaInfo.schema)
&& "proc".equalsIgnoreCase(schemaInfo.table)) {
// 兼容MySQLWorkbench
MysqlProcHandler.handle(sql, this);
return;
}
}
SchemaConfig schema = MycatServer.getInstance().getConfig().getSchemas().get(db);
if (schema == null) {
writeErrMessage(ErrorCode.ERR_BAD_LOGICDB,
"Unknown MyCAT Database '" + db + "'");
return;
}
//fix navicat SELECT STATE AS `State`, ROUND(SUM(DURATION),7) AS `Duration`, CONCAT(ROUND(SUM(DURATION)/*100,3), '%') AS `Percentage` FROM INFORMATION_SCHEMA.PROFILING WHERE QUERY_ID= GROUP BY STATE ORDER BY SEQ
if(ServerParse.SELECT == type &&sql.contains(" INFORMATION_SCHEMA.PROFILING ")&&sql.contains("CONCAT(ROUND(SUM(DURATION)/*100,3)"))
{
InformationSchemaProfiling.response(this);
return;
}
/* 当已经设置默认schema时，可以通过在sql中指定其它schema的方式执行
* 相关sql，已经在mysql客户端中验证。
* 所以在此处增加关于sql中指定Schema方式的支持。
*/
if (isDefault && schema.isCheckSQLSchema() && isNormalSql(type)) {
SchemaUtil.SchemaInfo schemaInfo = SchemaUtil.parseSchema(sql);
if (schemaInfo != null && schemaInfo.schema != null && !schemaInfo.schema.equals(db)) {
SchemaConfig schemaConfig = MycatServer.getInstance().getConfig().getSchemas().get(schemaInfo.schema);
if (schemaConfig != null)
schema = schemaConfig;
}
}
routeEndExecuteSQL(sql, type, schema);
} 最后有个routeEndExecuteSQL方法，它会首先调用RouteService的route方法先进行路由，然后调用HintSQLHandler的route方法，这个方法里调用RouteStrategy的route方法，这里使用了一个策略模式，包含下面几种sql类型，不同类型使用不同策略。public final class ServerParse {
public static final int OTHER = -1;
public static final int BEGIN = 1;
public static final int COMMIT = 2;
public static final int DELETE = 3;
public static final int INSERT = 4;
public static final int REPLACE = 5;
public static final int ROLLBACK = 6;
public static final int SELECT = 7;
public static final int SET = 8;
public static final int SHOW = 9;
public static final int START = 10;
public static final int UPDATE = 11;
public static final int KILL = 12;
public static final int SAVEPOINT = 13;
public static final int USE = 14;
public static final int EXPLAIN = 15;
public static final int EXPLAIN2 = 151;
public static final int KILL_QUERY = 16;
public static final int HELP = 17;
public static final int MYSQL_CMD_COMMENT = 18;
public static final int MYSQL_COMMENT = 19;
public static final int CALL = 20;
public static final int DESCRIBE = 21;
public static final int LOAD_DATA_INFILE_SQL = 99;
public static final int DDL = 100;使用不同的路由方法是在routeNormalSqlWithAST中决定的，
public RouteResultset routeNormalSqlWithAST(SchemaConfig schema,
String stmt, RouteResultset rrs, String charset,
LayerCachePool cachePool) throws SQLNonTransientException {
/**
* 只有mysql时只支持mysql语法
*/
SQLStatementParser parser = null;
if (schema.isNeedSupportMultiDBType()) {
parser = new MycatStatementParser(stmt);
} else {
parser = new MySqlStatementParser(stmt);
}
MycatSchemaStatVisitor visitor = null;
SQLStatement statement;
/**
* 解析出现问题统一抛SQL语法错误
*/
try {
statement = parser.parseStatement();
visitor = new MycatSchemaStatVisitor();
} catch (Exception t) {
LOGGER.error("DruidMycatRouteStrategyError", t);
throw new SQLSyntaxErrorException(t);
}
/**
* 检验unsupported statement
*/
checkUnSupportedStatement(statement);
DruidParser druidParser = DruidParserFactory.create(schema, statement, visitor);
druidParser.parser(schema, rrs, statement, stmt,cachePool,visitor);
/**
* DruidParser 解析过程中已完成了路由的直接返回
*/
if ( rrs.isFinishedRoute() ) {
return rrs;
}
/**
* 没有from的select语句或其他
*/
DruidShardingParseInfo ctx= druidParser.getCtx() ;
if((ctx.getTables() == null || ctx.getTables().size() == 0)&&(ctx.getTableAliasMap()==null||ctx.getTableAliasMap().isEmpty()))
{
return RouterUtil.routeToSingleNode(rrs, schema.getRandomDataNode(), druidParser.getCtx().getSql());
}
if(druidParser.getCtx().getRouteCalculateUnits().size() == 0) {
RouteCalculateUnit routeCalculateUnit = new RouteCalculateUnit();
druidParser.getCtx().addRouteCalculateUnit(routeCalculateUnit);
}
SortedSet<RouteResultsetNode> nodeSet = new TreeSet<RouteResultsetNode>();
for(RouteCalculateUnit unit: druidParser.getCtx().getRouteCalculateUnits()) {
RouteResultset rrsTmp = RouterUtil.tryRouteForTables(schema, druidParser.getCtx(), unit, rrs, isSelect(statement), cachePool);
if(rrsTmp != null) {
for(RouteResultsetNode node :rrsTmp.getNodes()) {
nodeSet.add(node);
}
}
}
RouteResultsetNode[] nodes = new RouteResultsetNode[nodeSet.size()];
int i = 0;
for (Iterator<RouteResultsetNode> iterator = nodeSet.iterator(); iterator.hasNext();) {
nodes[i] = iterator.next();
i++;
}
rrs.setNodes(nodes);
//分表
/**
* subTables="t_order$1-2,t_order3"
*目前分表 1.6 开始支持 幵丏 dataNode 在分表条件下只能配置一个，分表条件下不支持join。
*/
if(rrs.isDistTable()){
return this.routeDisTable(statement,rrs);
}
return rrs;
} 它使用druid做数据库连接池，支持分库分表，下面我们以多个表的分库分表路由策略为例子进行分析。
public static void findRouteWithcConditionsForTables(SchemaConfig schema, RouteResultset rrs,
Map<String, Map<String, Set<ColumnRoutePair>>> tablesAndConditions,
Map<String, Set<String>> tablesRouteMap, String sql, LayerCachePool cachePool, boolean isSelect)
throws SQLNonTransientException {
//为分库表找路由
for(Map.Entry<String, Map<String, Set<ColumnRoutePair>>> entry : tablesAndConditions.entrySet()) {
String tableName = entry.getKey().toUpperCase();
TableConfig tableConfig = schema.getTables().get(tableName);
if(tableConfig == null) {
String msg = "can't find table define in schema "
+ tableName + " schema:" + schema.getName();
LOGGER.warn(msg);
throw new SQLNonTransientException(msg);
}
if(tableConfig.getDistTables()!=null && tableConfig.getDistTables().size()>0){
routeToDistTableNode(tableName,schema,rrs,sql, tablesAndConditions, cachePool,isSelect);
}
//全局表或者不分库的表略过（全局表后面再计算）
if(tableConfig.isGlobalTable() || schema.getTables().get(tableName).getDataNodes().size() == 1) {
continue;
} else {//非全局表：分库表、childTable、其他
Map<String, Set<ColumnRoutePair>> columnsMap = entry.getValue();
String joinKey = tableConfig.getJoinKey();
String partionCol = tableConfig.getPartitionColumn();
String primaryKey = tableConfig.getPrimaryKey();
boolean isFoundPartitionValue = partionCol != null && entry.getValue().get(partionCol) != null;
boolean isLoadData=false;
if (LOGGER.isDebugEnabled()
&& sql.startsWith(LoadData.loadDataHint)||rrs.isLoadData()) {
//由于load data一次会计算很多路由数据，如果输出此日志会极大降低load data的性能
isLoadData=true;
}
if(entry.getValue().get(primaryKey) != null && entry.getValue().size() == 1&&!isLoadData)
{//主键查找
// try by primary key if found in cache
Set<ColumnRoutePair> primaryKeyPairs = entry.getValue().get(primaryKey);
if (primaryKeyPairs != null) {
if (LOGGER.isDebugEnabled()) {
LOGGER.debug("try to find cache by primary key ");
}
String tableKey = schema.getName() + '_' + tableName;
boolean allFound = true;
for (ColumnRoutePair pair : primaryKeyPairs) {//可能id in(1,2,3)多主键
String cacheKey = pair.colValue;
String dataNode = (String) cachePool.get(tableKey, cacheKey);
if (dataNode == null) {
allFound = false;
continue;
} else {
if(tablesRouteMap.get(tableName) == null) {
tablesRouteMap.put(tableName, new HashSet<String>());
}
tablesRouteMap.get(tableName).add(dataNode);
continue;
}
}
if (!allFound) {
// need cache primary key ->datanode relation
if (isSelect && tableConfig.getPrimaryKey() != null) {
rrs.setPrimaryKey(tableKey + '.' + tableConfig.getPrimaryKey());
}
} else {//主键缓存中找到了就执行循环的下一轮
continue;
}
}
}
if (isFoundPartitionValue) {//分库表
Set<ColumnRoutePair> partitionValue = columnsMap.get(partionCol);
if(partitionValue == null || partitionValue.size() == 0) {
if(tablesRouteMap.get(tableName) == null) {
tablesRouteMap.put(tableName, new HashSet<String>());
}
tablesRouteMap.get(tableName).addAll(tableConfig.getDataNodes());
} else {
for(ColumnRoutePair pair : partitionValue) {
if(pair.colValue != null) {
Integer nodeIndex = tableConfig.getRule().getRuleAlgorithm().calculate(pair.colValue);
if(nodeIndex == null) {
String msg = "can't find any valid datanode :" + tableConfig.getName()
+ " -> " + tableConfig.getPartitionColumn() + " -> " + pair.colValue;
LOGGER.warn(msg);
throw new SQLNonTransientException(msg);
}
ArrayList<String> dataNodes = tableConfig.getDataNodes();
String node;
if (nodeIndex >=0 && nodeIndex < dataNodes.size()) {
node = dataNodes.get(nodeIndex);
} else {
node = null;
String msg = "Can't find a valid data node for specified node index :"
+ tableConfig.getName() + " -> " + tableConfig.getPartitionColumn()
+ " -> " + pair.colValue + " -> " + "Index : " + nodeIndex;
LOGGER.warn(msg);
throw new SQLNonTransientException(msg);
}
if(node != null) {
if(tablesRouteMap.get(tableName) == null) {
tablesRouteMap.put(tableName, new HashSet<String>());
}
tablesRouteMap.get(tableName).add(node);
}
}
if(pair.rangeValue != null) {
Integer[] nodeIndexs = tableConfig.getRule().getRuleAlgorithm()
.calculateRange(pair.rangeValue.beginValue.toString(), pair.rangeValue.endValue.toString());
ArrayList<String> dataNodes = tableConfig.getDataNodes();
String node;
for(Integer idx : nodeIndexs) {
if (idx >= 0 && idx < dataNodes.size()) {
node = dataNodes.get(idx);
} else {
String msg = "Can't find valid data node(s) for some of specified node indexes :"
+ tableConfig.getName() + " -> " + tableConfig.getPartitionColumn();
LOGGER.warn(msg);
throw new SQLNonTransientException(msg);
}
if(node != null) {
if(tablesRouteMap.get(tableName) == null) {
tablesRouteMap.put(tableName, new HashSet<String>());
}
tablesRouteMap.get(tableName).add(node);
}
}
}
}
}
} else if(joinKey != null && columnsMap.get(joinKey) != null && columnsMap.get(joinKey).size() != 0) {//childTable (如果是select 语句的父子表join)之前要找到root table,将childTable移除,只留下root table
Set<ColumnRoutePair> joinKeyValue = columnsMap.get(joinKey);
Set<String> dataNodeSet = ruleByJoinValueCalculate(rrs, tableConfig, joinKeyValue);
if (dataNodeSet.isEmpty()) {
throw new SQLNonTransientException(
"parent key can't find any valid datanode ");
}
if (LOGGER.isDebugEnabled()) {
LOGGER.debug("found partion nodes (using parent partion rule directly) for child table to update "
+ Arrays.toString(dataNodeSet.toArray()) + " sql :" + sql);
}
if (dataNodeSet.size() > 1) {
routeToMultiNode(rrs.isCacheAble(), rrs, dataNodeSet, sql);
rrs.setFinishedRoute(true);
return;
} else {
rrs.setCacheAble(true);
routeToSingleNode(rrs, dataNodeSet.iterator().next(), sql);
return;
}
} else {
//没找到拆分字段，该表的所有节点都路由
if(tablesRouteMap.get(tableName) == null) {
tablesRouteMap.put(tableName, new HashSet<String>());
}
tablesRouteMap.get(tableName).addAll(tableConfig.getDataNodes());
}
}
}
} mycat会先找主键（支持多主键），根据主键去找不同的node节点，然后在不同的node分别执行sql，这样它就获取了sql的路由表，所谓的路由表就是查找表存在于哪些节点中。这个如果是在依据主键分库分表（同时存在多种分片类型如下图所示）的情况下主要通过分析sql中的存在的表名和主键的键值在schema配置中通过算法（RuleAlgorithm）查找的（如果没有主键范围就路由到所有节点），找到节点后，才具体去执行sql。
PartitionByDate PartitionByFileMap PartitionByHashMod PartitionByHotDate PartitionByJumpConsistentHash PartitionByLong PartitionByMod PartitionByMonth PartitionByMurmurHash PartitionByPattern PartitionByPrefixPattern PartitionByRangeDateHash PartitionByRangeMod PartitionByString PartitionDirectBySubString
在上面提到的routeEndExecuteSQL方法中找到路由节点后它会调用NonBlockingSession的execute方法，它分为单节点模式和多节点模式，下面以多节点模式为例，在这种情况下它会调用MultiNodeQueryHandler的execute方法。
public void execute() throws Exception {
final ReentrantLock lock = this.lock;
lock.lock();
try {
this.reset(rrs.getNodes().length);
this.fieldsReturned = false;
this.affectedRows = 0L;
this.insertId = 0L;
} finally {
lock.unlock();
}
MycatConfig conf = MycatServer.getInstance().getConfig();
startTime = System.currentTimeMillis();
LOGGER.debug("rrs.getRunOnSlave()-" + rrs.getRunOnSlave());
for (final RouteResultsetNode node : rrs.getNodes()) {
BackendConnection conn = session.getTarget(node);
if (session.tryExistsCon(conn, node)) {
LOGGER.debug("node.getRunOnSlave()-" + node.getRunOnSlave());
node.setRunOnSlave(rrs.getRunOnSlave()); // 实现 master/slave注解
LOGGER.debug("node.getRunOnSlave()-" + node.getRunOnSlave());
_execute(conn, node);
} else {
// create new connection
LOGGER.debug("node.getRunOnSlave()1-" + node.getRunOnSlave());
node.setRunOnSlave(rrs.getRunOnSlave()); // 实现 master/slave注解
LOGGER.debug("node.getRunOnSlave()2-" + node.getRunOnSlave());
PhysicalDBNode dn = conf.getDataNodes().get(node.getName());
dn.getConnection(dn.getDatabase(), autocommit, node, this, node);
// 注意该方法不仅仅是获取连接，获取新连接成功之后，会通过层层回调，最后回调到本类 的connectionAcquired
// 这是通过 上面方法的 this 参数的层层传递完成的。
// connectionAcquired 进行执行操作:
// session.bindConnection(node, conn);
// _execute(conn, node);
}
}
}到此优化后的sql被发给路由结果中的各个节点执行。
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