Support for HashSet<T> properties?

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This thread is a wild ride. You’ve been warned.

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For my use case, a HashSet<long> property is preferable to List<long>, but it seems even though most other collections get mapped to array columns in Postgres without issue, HashSet<T> does not.

Is there any chance that it’ll be supported in the future? And, for now, is there any way I can tell Npg to treat it as a List<T>?

[roji]

@Atulin the timestamp errors are due to a big change that was introduced in 6.0.0-rc.1. In a nutshell, the provider now strictly maps UTC DateTimes to timestamp with time zone and Local/Unspecified DateTimes to timestamp without time zone; it also no longer allows you to mix these two types (e.g. by comparing them).

See the release notes for more details. In any case, this shouldn’t be related to your HashSet work above

[Atulin]

Aight, not as scary as I thought, it all boils down to

public class NpgHashsetConverter<T> : ValueConverter<HashSet<T>, List<T>>, INpgsqlArrayConverter
{
    public NpgHashsetConverter() : base(
        hs => new List<T>(hs), 
        ls => new HashSet<T>(ls)
        ) { }

    public ValueConverter ElementConverter => new ValueConverter<T, T>(x => x, x => x);
}

it would seem.

But now I’ve no clue how to even use this thing. I thought this is going to be fine

public class ChaptersRead
{
    // ...
    public HashSet<long> Chapters { get; init; }

    public class Configuration : IEntityTypeConfiguration<ChaptersRead>
    {
        public void Configure(EntityTypeBuilder<ChaptersRead> builder)
        {
            builder
                .Property(cr => cr.Chapters)
                .HasPostgresArrayConversion<long, HashSet<long>>(new NpgHashsetConverter<long>());
        }
    }
}

but it seems not, it wants me to use a long[] array somewhere there for some godforsaken reason