sharding-jdbc是基于mybatis做的
比如我们执行一个update,mybatis会进入SimpleExecutor
image
此时的stmt如下图
image
此时的statement为ShardingPreparedStatement,终于看到sharding的影子了
然后进入
shardingPreparedStatement的execute()方法
public booleanexecute()throwsSQLException {
try{
Collection preparedStatementUnits = route();
return newPreparedStatementExecutor(
getConnection().getShardingContext().getExecutorEngine(),routeResult.getSqlStatement().getType(), preparedStatementUnits, getParameters()).execute();
}finally{
clearBatch();
}
}
然后进入route
然后进入PreparedStatementRoutingEngine的route()方法
image
先第一个parse过程,看看一个sql被parse之后,parse出来什么东东来
sqlRouter有两个实现，我们主要看下面这个
ParsingSQLRouter
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然后进入SQLParser中的parse方法
以一个批量插入为例
下面是parse后的insertStatement
image
positionIndexMap里面的37指的是参数(values后面的参数)中的第37个
再看route过程
然后进入ParsingSQLRouter的route方法
public SQLRouteResult route(final String logicSQL, final List<Object> parameters, final SQLStatement sqlStatement) {
SQLRouteResult result = new SQLRouteResult(sqlStatement);
if (sqlStatement instanceof InsertStatement && null != ((InsertStatement) sqlStatement).getGeneratedKey()) {
processGeneratedKey(parameters, (InsertStatement) sqlStatement, result);
}
RoutingResult routingResult = route(parameters, sqlStatement);
SQLRewriteEngine rewriteEngine = new SQLRewriteEngine(shardingRule, logicSQL, sqlStatement);
boolean isSingleRouting = routingResult.isSingleRouting();
if (sqlStatement instanceof SelectStatement && null != ((SelectStatement) sqlStatement).getLimit()) {
processLimit(parameters, (SelectStatement) sqlStatement, isSingleRouting);
}
SQLBuilder sqlBuilder = rewriteEngine.rewrite(!isSingleRouting);
if (routingResult instanceof CartesianRoutingResult) {
for (CartesianDataSource cartesianDataSource : ((CartesianRoutingResult) routingResult).getRoutingDataSources()) {
for (CartesianTableReference cartesianTableReference : cartesianDataSource.getRoutingTableReferences()) {
result.getExecutionUnits().add(new SQLExecutionUnit(cartesianDataSource.getDataSource(), rewriteEngine.generateSQL(cartesianTableReference, sqlBuilder)));
}
}
} else {
for (TableUnit each : routingResult.getTableUnits().getTableUnits()) {
result.getExecutionUnits().add(new SQLExecutionUnit(each.getDataSourceName(), rewriteEngine.generateSQL(each, sqlBuilder)));
}
}
if (showSQL) {
SQLLogger.logSQL(logicSQL, sqlStatement, result.getExecutionUnits(), parameters);
}
return result;
}
RoutingResult routingResult = route(parameters, sqlStatement)的结果如下图
image
接着执行rewrite方法,进行sql重写
SQLBuilder sqlBuilder =rewriteEngine.rewrite(!isSingleRouting);
接着看
image
看里面在循环sqlToken,但是竟然没有处理MultiInsertValuesTokens!!!!坑爹啊
看最终route出来的结果
