C#•4mo ago

✅ Npgsql.PostgresException

public class CreatePostHandler(
    IHttpContextAccessor contextAccessor,
    DatabaseContext db,
    ISender mediator,
    IValidator<CreatePostCommand> validator)
    : RequestHandler(contextAccessor), IRequestHandler<CreatePostCommand, Result<Post>>
{
    private const string StorageContainer = "images";

    public async Task<Result<Post>> Handle(CreatePostCommand request, CancellationToken cancellationToken)
    {
        try
        {
            var validationResult = await ValidateInputAsync(request, cancellationToken);
            if (!validationResult.IsValid)
                return Result<Post>.Failure("Invalid input received.",
                    validationResult.ErrorMessages(), 400);

            var newBlobName = $"{Guid.NewGuid()}{request.File.GetExtensionType()}";
            var uploadResult = await UploadFileAsync(newBlobName, request.File, cancellationToken);

            if (!uploadResult.IsSuccessful)
                return uploadResult.ToResult(_ => new Post());

            var uri = uploadResult.Data;
            var nsfwResult = await ClassifyFileAsync(uri, cancellationToken);
            if (!nsfwResult.IsSuccessful)
            {
                await DeleteNewlyUploadedFileAsync(newBlobName, cancellationToken);
                return nsfwResult.ToResult<Post>(default!);
            }

            var post = new Post
            {
                Caption = request.Caption,
                Url = uri.ToString(),
                AuthorId = UserId
            };

            return await CreatePostAsync(post, cancellationToken);
        }
        catch (Exception e)
        {
            return Result<Post>.Failure("Something unexpected occurred.", [e.ToString()], 500);
        }
    }

    private async Task<ValidationResult> ValidateInputAsync(CreatePostCommand request,
        CancellationToken cancellationToken)
    {
        return await validator.ValidateAsync(request, cancellationToken);
    }

    private async Task DeleteNewlyUploadedFileAsync(string blobName, CancellationToken cancellationToken)
    {
        await mediator.Send(
            new DeleteFileFromStorageCommand(blobName, StorageContainer),
            cancellationToken);
    }

    private async Task<Result<Uri>> UploadFileAsync(string blobName, IFormFile file,
        CancellationToken cancellationToken)
    {
        return await mediator.Send(new UploadFileToStorageCommand
        {
            ContainerName = StorageContainer,
            BlobName = blobName,
            ContentType = file.ContentType,
            Stream = file.OpenReadStream()
        }, cancellationToken);
    }

    private async Task<Result> ClassifyFileAsync(Uri uri, CancellationToken cancellationToken)
    {
        return await mediator.Send(new ClassifyImageCommand(uri), cancellationToken);
    }

    private async Task<Result<Post>> CreatePostAsync(Post post, CancellationToken cancellationToken)
    {
        var hashtags = await mediator.Send(new ExtractHashtagsCommand(post.Caption), cancellationToken);
        foreach (var hashtag in hashtags)
            post.Hashtags.Add(hashtag);

        db.Posts.Add(post);
        await db.SaveChangesAsync(cancellationToken);
        return Result<Post>.Success(post);
    }
}

public class CreatePostHandler(
    IHttpContextAccessor contextAccessor,
    DatabaseContext db,
    ISender mediator,
    IValidator<CreatePostCommand> validator)
    : RequestHandler(contextAccessor), IRequestHandler<CreatePostCommand, Result<Post>>
{
    private const string StorageContainer = "images";

    public async Task<Result<Post>> Handle(CreatePostCommand request, CancellationToken cancellationToken)
    {
        try
        {
            var validationResult = await ValidateInputAsync(request, cancellationToken);
            if (!validationResult.IsValid)
                return Result<Post>.Failure("Invalid input received.",
                    validationResult.ErrorMessages(), 400);

            var newBlobName = $"{Guid.NewGuid()}{request.File.GetExtensionType()}";
            var uploadResult = await UploadFileAsync(newBlobName, request.File, cancellationToken);

            if (!uploadResult.IsSuccessful)
                return uploadResult.ToResult(_ => new Post());

            var uri = uploadResult.Data;
            var nsfwResult = await ClassifyFileAsync(uri, cancellationToken);
            if (!nsfwResult.IsSuccessful)
            {
                await DeleteNewlyUploadedFileAsync(newBlobName, cancellationToken);
                return nsfwResult.ToResult<Post>(default!);
            }

            var post = new Post
            {
                Caption = request.Caption,
                Url = uri.ToString(),
                AuthorId = UserId
            };

            return await CreatePostAsync(post, cancellationToken);
        }
        catch (Exception e)
        {
            return Result<Post>.Failure("Something unexpected occurred.", [e.ToString()], 500);
        }
    }

    private async Task<ValidationResult> ValidateInputAsync(CreatePostCommand request,
        CancellationToken cancellationToken)
    {
        return await validator.ValidateAsync(request, cancellationToken);
    }

    private async Task DeleteNewlyUploadedFileAsync(string blobName, CancellationToken cancellationToken)
    {
        await mediator.Send(
            new DeleteFileFromStorageCommand(blobName, StorageContainer),
            cancellationToken);
    }

    private async Task<Result<Uri>> UploadFileAsync(string blobName, IFormFile file,
        CancellationToken cancellationToken)
    {
        return await mediator.Send(new UploadFileToStorageCommand
        {
            ContainerName = StorageContainer,
            BlobName = blobName,
            ContentType = file.ContentType,
            Stream = file.OpenReadStream()
        }, cancellationToken);
    }

    private async Task<Result> ClassifyFileAsync(Uri uri, CancellationToken cancellationToken)
    {
        return await mediator.Send(new ClassifyImageCommand(uri), cancellationToken);
    }

    private async Task<Result<Post>> CreatePostAsync(Post post, CancellationToken cancellationToken)
    {
        var hashtags = await mediator.Send(new ExtractHashtagsCommand(post.Caption), cancellationToken);
        foreach (var hashtag in hashtags)
            post.Hashtags.Add(hashtag);

        db.Posts.Add(post);
        await db.SaveChangesAsync(cancellationToken);
        return Result<Post>.Success(post);
    }
}

Any reasons as to why I'm getting this error?

16 Replies

SwaggerLife•4mo ago

 Microsoft.EntityFrameworkCore.Update[10000]
      An exception occurred in the database while saving changes for context type 'Quotifyr.DatabaseContext'.
      Microsoft.EntityFrameworkCore.DbUpdateException: An error occurred while saving the entity changes. See the inner exception for details.
       ---> Npgsql.PostgresException (0x80004005): 23505: duplicate key value violates unique constraint "PK_Hashtags"

 Microsoft.EntityFrameworkCore.Update[10000]
      An exception occurred in the database while saving changes for context type 'Quotifyr.DatabaseContext'.
      Microsoft.EntityFrameworkCore.DbUpdateException: An error occurred while saving the entity changes. See the inner exception for details.
       ---> Npgsql.PostgresException (0x80004005): 23505: duplicate key value violates unique constraint "PK_Hashtags"

The hashtags are getting created. When applying the hashtags to the post. It's giving me this error.

tera•4mo ago

it says it right there

duplicate key value violates unique constraint "PK_Hashtags"

you're trying to create a hashtag with a primary key that already exists

SwaggerLife•4mo ago

I'm not trying to create the hashtags though. The relationship between Post and Hashtag is many to many. I just want to create an entry in the joining table? Or have I misunderstood something?

tera•4mo ago

post.Hashtags.Add(hashtag);
...
await db.SaveChangesAsync(cancellationToken);

post.Hashtags.Add(hashtag);
...
await db.SaveChangesAsync(cancellationToken);

it will create a hashtag if hashtag is an untracked entity

SwaggerLife•4mo ago

I see, is there a way I can tell it not to create?

tera•4mo ago

you'd need to fetch those hashtags right there from the same dbcontext where you want to add them to the posts

var hashtags = await mediator.Send(new ExtractHashtagsCommand(post.Caption), cancellationToken);

var hashtags = await mediator.Send(new ExtractHashtagsCommand(post.Caption), cancellationToken);

this is no bueno, returning entities from somewhere, and then adding them to a different dbcontext

SwaggerLife•4mo ago

The think is that I don't want to rewrite the same code multiple times. There has to be a better way. At least I now know what the issue is. Thanks mate.

tera•4mo ago

there is always a way 😄 but might take a bit of reorganizing/refactoring np

tera•4mo ago

BTW i would recommend https://learn.microsoft.com/en-us/ef/core/change-tracking/

tera•4mo ago

not everything is relatable/needed but good to know the on a base level

SwaggerLife•4mo ago

@tera

    private async Task<Result<Post>> CreatePostAsync(Post post, CancellationToken cancellationToken)
    {
        var hashtags = await mediator.Send(new ExtractHashtagsCommand(post.Caption), cancellationToken);
        foreach (var hashtag in hashtags)
        {
            db.Hashtags.Attach(hashtag);
            post.Hashtags.Add(hashtag);
        }

        db.Posts.Add(post);
        await db.SaveChangesAsync(cancellationToken);
        return Result<Post>.Success(post);
    }

    private async Task<Result<Post>> CreatePostAsync(Post post, CancellationToken cancellationToken)
    {
        var hashtags = await mediator.Send(new ExtractHashtagsCommand(post.Caption), cancellationToken);
        foreach (var hashtag in hashtags)
        {
            db.Hashtags.Attach(hashtag);
            post.Hashtags.Add(hashtag);
        }

        db.Posts.Add(post);
        await db.SaveChangesAsync(cancellationToken);
        return Result<Post>.Success(post);
    }

Let's see if attach solves anything. Remmended by AI :kekw: Yep it fixed it :A_pepelaugh:

tera•4mo ago

using .Attach is a whole another can of worms, you probably should not be using it generally cos it usually solves code smell thats caused by something else so better fix root cause

SwaggerLife•4mo ago

Damn, I was so happy before

using .Attach is a whole another can of worms, you probably should not be using it generally

using .Attach is a whole another can of worms, you probably should not be using it generally

Let me see if there is a better way.

tera•4mo ago

well the only way is to refactor the code to fetch those hashtags right there in that method/from the same dbcontext you add them to

SwaggerLife•4mo ago

Yeah I will try that. Thanks for your help mate. I really appreciate it.

tera•4mo ago

no worries

Gaming

Programming

✅ Npgsql.PostgresException