Unordered array content on PATCH about base-repo

[chkalch]

I made more tests and it seems that ordering is always the same for same inputs, but differs for other strings, but ordering is not alphabetically.

I also found out that there is no difference in the output when inserting strings at a different position (other index in path), so either index in path is ignored completely or some sorting is applied afterwards.

[ThomasJejkal]

While this issue has impact in base-repo, it actually relates to kit-data-manager/service-base and src/main/java/edu/kit/datamanager/util/PatchUtil.java. However, also there only a third party library is used where it comes to the following line of code at the end: https://github.com/java-json-tools/json-patch/blob/55b27b96045baa4ef356b2b183304551f64a18e4/src/main/java/com/github/fge/jsonpatch/AddOperation.java#L130

As one can see, the index is properly evaluated and the new element should be added at the correct position, but there is a "but". Afterwards, the modified resource is written to the basebase and what you see as an "array" is actually represented as Set of strings, which has no index/primary key that can be utilized for sorting as it is the case for sets of complex objects. For strings, only uniqueness of entries, but no specific order is guaranteed from the database side. This indeed leads to unpredictable behaviour in terms of ordering, but I'm afraid it is working as intended. ;-)

[chkalch]

Indeed, it's also not possible to add the same value twice (never tried that before), which also points to a set rather than an array.

Of course I would prefer that the order is retained and arrays behave like arrays (there are no sets in JSON specification) and JSON-Patch works like it should according to specification, but this would probably be more work than just adding an additional order/index column to the database - but it would also make repo more versatile.

So at least it should be clearly communicated everywhere in the documentation where these "set-arrays" occur, I used this documentation to dive into this topic and would suggest that you add a prominent notice at the top of the page.

[ThomasJejkal]

Thanks for the pointer, I've added a note.