Json: add support for collection of primitive types inside JSON columns

[maumar]

No description provided.

[ajcvickers]

Note from triage: also consider other issues related to primitive collections--see label area-primitive-collections.

[roji]

Note: similar to this, we could allow weakly-typed mapping via Dictionary as well (see #29825).

[Soundman32]

I have a working prototype for this from a few years back for .EF5 - should I see if I can resurrect it for EF7 ?

[roji]

@Soundman32 this tracks support specifically inside the new EF 7 JSON columns feature, so I'm guessing any work on EF 5 would need serious adjustment in order to be relevant. But you can always take a look.

[Soundman32]

@roji My prototype was purely for the Cosmos driver, so it might not be quite as simple as I first thought, but I'll have a go :-)

[Eirenarch]

Is this why Dictionary<string, string> with items in it ends up in the database as { }?

[roji]

@Elrenarch that sounds like a bug - can you please open a separate issue with a minimal, runnable code sample?

[Eirenarch]

@Elrenarch that sounds like a bug - can you please open a separate issue with a minimal, runnable code sample?

Done - #30707

[roji]

SEE COMMENT BELOW FIRST

@maumar this was also done as part of #30738... We have some basic testing there specifically for when the primitive collection is inside an owned JSON entity (calling Count, indexing), though at least in principle it shouldn't matter whether the collection is inside or not (see conversation #30738 (comment)). If we do decide to add more coverage, better to add a JSON owned entity to PrimitiveCollectionsTestBase with some tests on that, and remove Column_collection_inside_json_owned_entity from NonSharedPrimitiveCollectionsQueryRelationalTestBase.

Am leaving this issue open for a bit - let me know what you think, the basic testing we already have may be enough.

[roji]

Ah no, there's a problem with the way things currently are: the primitive collection is integrated as a string inside the larger owned entity JSON document, instead of as an in-line JSON array. For example, looking at the [TestOwner] table created by the Column_collection_inside_json_owned_entity test, I see:

{"Strings":"[\u0022foo\u0022,\u0022bar\u0022]"}`

i.e. the document contains a string value, which itself encodes an array inside. Instead, it should be:

{"Strings":["foo","bar"]}

So we still have a bit of work here.

[roji]

I think what needs to happen is something like the following:

• The (owned) JSON serialization/deserialization code needs to recognize primitive properties as such (via metadata which we're currently lacking, or possibly by checking whether the type mapping has ElementTypeMapping)
• When serialization encounters such a property, it needs to do more or less the same thing we'll do in the newly-introduced CollectionToJsonStringConverter: iterate over the elements, and call into the future type mapping API to serialize them (#30677)

This is all better handled after we do the move to the lower-level Utf8JsonReader/Writer APIs (#30604), and after the type mapping APIs are introduced (#30677)

[alrz]

There is numerous issues on json collection/dictionary support to a point that it's not clear what is exactly supported or not and at what verison.

Is there any docs / samples that detail this? Thanks.