Camunda Database Schema Documentation

Camunda 7 Topics Discussion & Questions
1

Hi,
Is there a more comprehensive documentation available for the schema other than this? The document is good as a quick start on various tables but it is not really clear what some of the tables are used for.

2

I always thought those docs were pretty good :slight_smile: What kind of information seems to be missing? An example of a question you’re struggling to answer might also help us understand.

3

For example:

  1. What do the tables act_hi_dec_in and act_hi_dec_out store?
  2. The table act_hi_procinst has columns id_ and also proc_inst_id_. So what does the id_ signify?
  3. Which tables can tell me how to find the last_modified_date of a task?
4

That’s more clear, thank you.

That kind of documentation is a little bitter harder to write, I think, because there are an infinite number of vectors people, like you and like me, approach the documentation when we have issues. That’s where contributions from the community are super valuable. I would encourage anyone to contribute to the documentation when we identify gaps and can also clearly articulate the answers we were ultimately able to find.

That said, I don’t know of a source (other than the code) to augment what you already found in the docs and what you’d find sprinkled throughout. I can provide the following commentary on your additional questions however, sorry I couldn’t be of more help:

  1. ACT_HI_DECINST, ACT_HI_DEC_IN, and ACT_HI_DEC_OUT will contain the historical entries for the decision instances, decision input, and decision output (respectively).
  2. ID_ will be your process instance id and primary key. From what I’ve gathered PROC_INST_ID_ matches ID_, but I probably wouldn’t just assume that to always be true (to be safe). The real reason they both exist is unclear to me, but likely dates back a ways. I’d be curious if anyone can clarify that (might make for a good note in the docs too).
  3. I think this highly depends on what “last_modified_date of a task” means to you. Is this start/end of the activity? If so, START_TIME_ and END_TIME_ are available in ACT_HI_TASKINST. Does it mean add/delete/change of a task variable? That info might be available in ACT_HI_DETAIL depending on your history level. Does it mean a property on the task itself (e.g. priority, description)? That’s more complicated, but my follow up question would be why is that level of detail important?
2 Likes
5

@jgigliotti, I think these points answer most of my questions. For #3, yes I meant changes in task variables and noticed that ACT_HI_DETAIL has a column time_ to help me.

I will surely have a look at GitHub - camunda/camunda-docs-manual: Sources of the docs.camunda.org site and try to update / create more documentation as progress with my project.

Thank you