problem with reading source code-pull out nondeterministic expresssions

[汪洋 <ti...@icloud.com>]

Hi fellas,
I am new to spark and I have a newbie question. I am currently reading the source code in spark sql catalyst analyzer. I not quite understand the partial function in PullOutNondeterministric. What does it mean by "pull out”? Why do we have to do the "pulling out”?
I would really appreciate it if somebody explain it to me. 
Thanks. 

Re: problem with reading source code-pull out nondeterministic expresssions

[汪洋 <ti...@icloud.com>]

I get it, thanks!

> 在 2015年12月31日，上午3:00，Michael Armbrust <mi...@databricks.com> 写道：
> 
> The goal here is to ensure that the non-deterministic value is evaluated only once, so the result won't change for a given row (i.e. when sorting).
> 
> On Tue, Dec 29, 2015 at 10:57 PM, 汪洋 <tiandiwoxin@icloud.com <ma...@icloud.com>> wrote:
> Hi fellas,
> I am new to spark and I have a newbie question. I am currently reading the source code in spark sql catalyst analyzer. I not quite understand the partial function in PullOutNondeterministric. What does it mean by "pull out”? Why do we have to do the "pulling out”?
> I would really appreciate it if somebody explain it to me. 
> Thanks. 
> 

Re: problem with reading source code-pull out nondeterministic expresssions

[Michael Armbrust <mi...@databricks.com>]

The goal here is to ensure that the non-deterministic value is evaluated
only once, so the result won't change for a given row (i.e. when sorting).

On Tue, Dec 29, 2015 at 10:57 PM, 汪洋 <ti...@icloud.com> wrote:

> Hi fellas,
> I am new to spark and I have a newbie question. I am currently reading the
> source code in spark sql catalyst analyzer. I not quite understand the
> partial function in PullOutNondeterministric. What does it mean by "pull
> out”? Why do we have to do the "pulling out”?
> I would really appreciate it if somebody explain it to me.
> Thanks.
>