unionexec

type UnionExec ¶

type UnionExec struct {
	exec.BaseExecutor
	Concurrency int
	// contains filtered or unexported fields
}

UnionExec pulls all it's children's result and returns to its parent directly. A "resultPuller" is started for every child to pull result from that child and push it to the "resultPool", the used "Chunk" is obtained from the corresponding "resourcePool". All resultPullers are running concurrently.

                          +----------------+
+---> resourcePool 1 ---> | resultPuller 1 |-----+
|                         +----------------+     |
|                                                |
|                         +----------------+     v
+---> resourcePool 2 ---> | resultPuller 2 |-----> resultPool ---+
|                         +----------------+     ^               |
|                               ......           |               |
|                         +----------------+     |               |
+---> resourcePool n ---> | resultPuller n |-----+               |
|                         +----------------+                     |
|                                                                |
|                          +-------------+                       |
|--------------------------| main thread | <---------------------+
                           +-------------+

func (e *UnionExec) Close() error

func (e *UnionExec) Next(ctx context.Context, req *chunk.Chunk) error

func (e *UnionExec) Open(context.Context) error