Sort options

[ray.wurlod]

They are not the same. Stable sort can apply even when you are not using either of the "Don't sort" options. Stable sort preserves existing order of rows when the sort keys match. This needs more memory than not doing a stable sort.

[gagan8877]

They are not the same. Stable sort can apply even when you are not using either of the "Don't sort" options. Stable sort preserves existing order of rows when the sort keys match. This needs more memory than not doing a stable sort.

Thanks Ray.
So as I understand, Don't Sort means - leave the dataset alone, don't do anything (but that contradicts the secondary key sorting scenario - Don't sort by primary key, it is already sorted, sort only by secondary key, if any) and Stable sort means sort the dataset and preserve the order of duplicate keys?

- correct?

[ray.wurlod]

Not correct. Stable sort means preserve the ARRIVAL ORDER OF ROWS - nothing to do with keys at all.

[gagan8877]

Not correct. Stable sort means preserve the ARRIVAL ORDER OF ROWS - nothing to do with keys at all.

My bad - I meant duplicate Key Values.

1. So lets say I have a dataset which is not sorted in the upstream stage and I set Stable Sort in the downstream stage - will be it sorted and the stage will try to preserve the order of similar key values? Y/N

2. A dataset which is sorted in the upstream stage and I set Stable Sort in the downstream stage - will be it try to resort it and the stage will try to preserve the order of similar key values (and thats why it is expensive) or will it not even try?

3. Don't Sort means - leave the dataset alone, don't even try to sort. If the upstream stage has the same primary and secondary keys, then leave it alone - dont sort at all, dont even try. if the upstream stage had only Primary Key and no Secondary keys, then sort the secondary keys - Primary Keys are already sorted? Y/N - please explain if No.

Thanks

[ray.wurlod]

1. No, setting stable sort alone will not cause the data to be sorted. However, this option does not become available unless you choose to sort the data (and specify sort key(s)) - it is THIS that gets the data sorted (whether a stable sort or not).

2. See answer to 1.

3. You specify this property for each sort key. If you specify don't sort for all sort keys, then the output order of rows is exactly the input order of rows (and you've wasted some resources).

[gagan8877]

1. No, setting stable sort alone will not cause the data to be sorted. However, this option does not become available unless you choose to sort the data (and specify sort key(s)) - it is THIS that gets the data sorted (whether a stable sort or not).

2. See answer to 1.

3. You specify this property for each sort key. If you specify don't sort for all sort keys, then the output order of rows is exactly the input order of rows (and you've wasted some resources).

Thanks Ray. This explanation was great - its much clearer now.