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Last updated: 4 Apr 2017

local-links-manager: Deleting a local transaction link

Occasionally we may need to urgently delete a link prevent it being shown as the result for its local authority on a local transaction page on GOV.UK (such as https://www.gov.uk/pay-council-tax/lambeth).

Links to local government are editable using Local Links Manager, however this does not yet provide an easy way to find and edit URLs in bulk.

Assuming you know the link you want to delete and the page it appears on, in a local-links-manager Rails console:

Construct a variable using the bad URL to use in a LIKE query in the following steps:
```
domain_pattern = '%horrible.domain.com%'
```

Find all affected links:

Link.where('url LIKE ?', domain_pattern).count

Find the LGSL codes and local authority slugs for each of these local interactions. This will help with finding the URLs to cache-bust after you've deleted them:

lgsl_codes = Link.where('url LIKE ?', domain_pattern).map{ |l| l.service.lgsl_code}.uniq

la_slugs = Link.where('url LIKE ?', domain_pattern).map{|l| l.local_authority.slug}.uniq

Delete all affected links. (If a link does not exist, there's a fallback process culminating in the local authority homepage):
```
Link.where('url LIKE ?', domain_pattern).delete_all
```
It's possible that the same domain has been used for a local authority homepage, so check them too:
```
LocalAuthority.where('homepage_url LIKE ?', domain_pattern).count
```
If there are any here, set the homepage_url to nil. (It's better if you can set it to a real URL, but we can do that through the UI as part of a clean up if necessary)
```
LocalAuthority.where('homepage_url LIKE ?', domain_pattern).update_all(homepage_url: nil)
```
Frontend should now no longer be serving the bad links, but the pages containing them may be cached. You'll need to get a Publisher Rails console to find the artefact-slugs for the local transactions which use the LGSL codes for the links you've deleted (substituting the values into the array in this query):
```
LocalTransactionEdition.where(state: "published").in(:lgsl_code => [ <LGSL codes> ] ).each do |lte|
  print "LGSL code: #{lte.lgsl_code}    Slug: #{lte.slug}\n"
end
```
Combine the artefact and local authority slugs to build the paths to cache-bust - they're in this form:
```
/<artefact-slug>/<local-authority-slug>
```
for example
```
/pay-council-tax/lambeth
```
Flush the caches for the affected URLs. (Wildcard purging would make this easier, by allowing us to purge all paths under a local transaction rather than having to do each local authority page individually.)
Now you're done.