asyncio [asyncio] [bug]在使用AsyncConnection或AsyncSession作为上下文管理器释放对象时,特别是在__aexit__()上下文管理器退出时,将asyncio.shield()添加到连接和会话释放过程中。 当上下文管理器完成时,这似乎有助于使用其他并发库(如anyio、uvloop)时取消任务时正确释放连接池中的连接。 参考:#814
The %DateTimeIn meta-SQL variable expands to platform-specific SQL for a DateTime value in the Where clause of a SQL Select or Update statement, or when a DateTime value is passed in an Insert statement. 对于SQL Select或Update语句的Where子句中的DateTime值,或者当在Insert语句中传递DateTime值时,...
生成AST(抽象语法树),作用是SQL–>SqlNode*|*|*+--->SqlJoin(SqlNode)*|*|*SqlToRelConverter.convertQuery// 语义分析,生成逻辑计划,作用是SqlNode–>RelNode*|*|*+--->LogicalProject(RelNode)// Abstract Syntax Tree,未优化的
SQL queries do not have features to express business logic (for example a complex currency conversion). As a consequence, such business logic cannot be pushed down into the database (even if it is mainly based on standard aggregations like SUM(Sales), and so on). An SQL query can only r...
ReassignLambdaVariableID) :+ Batch("LocalRelation", fixedPoint, ConvertToLocalRelation, PropagateEmptyRelation, // PropagateEmptyRelation can change the nullability of an attribute from nullable to // non-nullable when an empty relation child of a Union is removed UpdateAttributeNullability) :+ // ...
RexNode: 行表达式(标量表达式),蕴含的是对一行数据的处理逻辑。每个行表达式都有数据的类型。这是因为在 Valdiation 的过程中,编译器会推导出表达式的结果类型。常见的行表达式包括字面量 RexLiteral, 变量 RexVariable,函数或操作符调用 RexCall 等。RexNode 通过 RexBuilder 进行构建。