If the input to my job is the fileset [a, b, c, d], is the input to the sort strictly [map(a.0), map(a.1), map(b.0), map(b.1), map(c.0), map(c.1), map(d.0), map(d.1)]?

My motivation is having a series of files (which will of course be broken up into blocks) whose rows are [key, value]; where each of key and value are a simple string. I wish to concatenate these values together in the reducer per key in the order they are present in the input, despite there not being an explicit order-defining field.

Any advice much appreciated; this is proving to be a difficult query to Google for.

### Example

Input format

```
A First
A Another
A Third
B First
C First
C Another

```

Desired output

```
A First,Another,Third
B First
C First,Another

```

To reiterate, I'm uncertain if I can rely on getting First-Third in the correct order given files are being stored in separate blocks.