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Asked: 2024-09-30T18:40:36+05:30

I am working with Slick 3.5.1 and encountering an issue when trying to parse LocalDateTime values. It seems that the parser is only recognizing three digits for nanoseconds but I need it to handle up to nine digits. Does anyone have suggestions on how to modify the parsing behavior to accommodate this requirement?

I’m diving into some work with Slick 3.5.1, and I’ve hit a bit of a wall with parsing LocalDateTime values. So here’s the deal: I noticed that when I’m trying to parse local date-time strings, the parser seems to be limiting the nanoseconds to just three digits. But my use case definitely requires it to handle up to nine digits.

It’s important for my application to work with high-resolution timestamps, especially as I’m dealing with data that comes from various sources where the precision can vary significantly. For example, a timestamp representing an event might look like this: `2023-10-14T15:59:47.123456789`, and I need Slick to recognize that full precision instead of just truncating it to the first three digits: `2023-10-14T15:59:47.123`.

I’ve banged my head against the wall trying to figure out if there’s a configuration or a custom parser I can implement to get around this limitation. I mean, do I need to dive into Slick’s internals or perhaps write some custom code to handle parsing? If that’s the route, how do I ensure that I can seamlessly integrate it back into the slick workflow without causing other issues?

Also, I’m open to suggestions on alternative approaches or even looking towards other libraries that might facilitate this if Slick continues to be a pain. Just trying to find the best way to manage these timestamps without losing any precision, and it would be great to hear from anyone who’s tackled something similar. If you’ve run into this, what solutions did you come up with? Any tips, workarounds, or resources you could point me to?

Thanks in advance for any help – I’ve been stuck on this for a bit too long, and any insight would be super helpful.

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    2 Answers

    1. To handle parsing of LocalDateTime values with full nanosecond precision in Slick 3.5.1, you’ll likely need to implement a custom type mapper. By default, Slick may truncate nanoseconds to three digits, so creating a bespoke parser that supports the full nine-digit format will be paramount. You can achieve this by defining a new MappedColumnType for LocalDateTime that uses java.time.format.DateTimeFormatter to correctly parse your timestamps. For example, create a method that specifies a formatter able to read the complete string representation including nanoseconds:

      
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import slick.jdbc.PostgresProfile.api._

implicit val localDateTimeColumnType = MappedColumnType.base[LocalDateTime, String](
  dt => dt.format(DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.nnnnnnnnn")),
  str => LocalDateTime.parse(str, DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.nnnnnnnnn"))
)

      With this custom mapping in place, integrate it into your Slick model by applying it to the respective fields in your table mappings. Ensure you test this thoroughly with various timestamp formats from your sources. If you find Slick’s native functionality still not meeting your needs after this adjustment, consider using libraries like doobie or quill which may offer more flexibility for handling high-resolution timestamps.

    2. It sounds like you’re running into a classic issue with Slick’s handling of timestamps! Since you’re working with LocalDateTime values that need to maintain their full precision, you’ve got a couple of routes you can explore.

      First off, you might want to look into creating a custom mapper for LocalDateTime. Slick allows you to define your own mappers, which could help you get around the default behavior that’s truncating your nanoseconds. Here’s a simple outline of how to do it:

      
import java.sql.{PreparedStatement, ResultSet}
import java.time.LocalDateTime
import slick.jdbc.JdbcType

implicit val localDateTimeMapper: JdbcType[LocalDateTime] =
  MappedColumnType.base[LocalDateTime, String](
    { ld => ld.toString },
    { str => LocalDateTime.parse(str) }
  )

      This code should allow you to parse the full string representation of LocalDateTime with precision up to nanoseconds. Just make sure that the incoming data is in the correct format, or you may need to adjust the parsing method to match your specific requirements.

      Another thing to check is your database setup. Sometimes the database itself can have constraints on the precision it allows for timestamps. Make sure that your database datatype supports nanoseconds, which is typically TIMESTAMP(9) or similar, depending on your SQL dialect.

      If you find that working with Slick still feels limiting, consider whether using another library like doobie or quill may better suit your needs. These alternatives might provide more flexibility with high-resolution timestamps.

      Above all, take your time and test different approaches to see what works best for your specific situation. Good luck navigating through this challenge, and I hope you find a solution that keeps your timestamps intact!