How to delete all attributes from the schema in solr?

At least in version 6.6 of the Schema API and up to the current version 7.5 of it, you can pass multiple commands in a single post (see 6.6 and 7.5 documenation, respectively). There are multiple accepted formats, but the most intuitive one (I think) is just passing an array for the action you want to perform:

curl -X POST -H 'Content-type: application/json' -d '{  "delete-field": [    {"name": "trans"},    {"name": "other_field"}  ]}' 'http://arteika:8983/solr/trans/schema'

So. How do we obtain the names of the fields we want to delete? That can be done by querying the Schema:

curl -X GET -H 'Content-type: application/json' 'http://arteika:8983/solr/trans/schema'

In particular, the copyFields, dynamicFields and fields keys in the schema object in the response.

I automated clearing all copy field rules, dynamic field rules and fields as follows. You can of course use any kind of script that is available to you. I used Python 3 (might work with Python 2, I did not test that).

import jsonimport requests# load schema informationapi = 'http://arteika:8983/solr/trans/schema'r = requests.get(api)# delete copy field rulesnames = [(o['source'], o['dest']) for o in r.json()['schema']['copyFields']]payload = {'delete-copy-field': [{'source': name[0], 'dest': name[1]} for name in names]}requests.post(api, data = json.dumps(payload),                   headers = {'Content-type': 'application/json'})# delete dynamic fieldsnames = [o['name'] for o in r.json()['schema']['dynamicFields']]payload = {'delete-dynamic-field': [{'name': name} for name in names]}requests.post(api, data = json.dumps(payload),                   headers = {'Content-type': 'application/json'})# delete fieldsnames = [o['name'] for o in r.json()['schema']['fields']]payload = {'delete-field': [{'name': name} for name in names]}requests.post(api, data = json.dumps(payload),                   headers = {'Content-type': 'application/json'})

Just a note: I received status 400 responses at first, with null error messages. Had a bit of a hard time figuring out how to fix those, so I'm sharing what worked for me. Changing the default of updateRequestProcessorChain in solrconfig.xml to false (default="${update.autoCreateFields:false}") and restarting the Solr service made those errors go away for me. The fields I was deleting were created automatically, that may have something to do with that.