Search: use multi-fields for Wildcard queries

[stsewd]

Wildcard queries are slow (on .org it returns 502, on .com since the db
is small it works just fine).

https://www.elastic.co/guide/en/elasticsearch/reference/current/query-dsl.html#query-dsl-allow-expensive-queries

These type of queries can be optimized by using the Wildcard field
https://www.elastic.co/guide/en/elasticsearch/reference/current/keyword.html#wildcard-field-type.

Currently that field isn't implemented in the ES dependencies,
but is just a subclass of the Keyword field (I'll see if I can send a PR
upstream).

As we still want to make use of the SimpleString queries,
I'm using the multi-fields feature.

This change is editing the index,
so we need to rebuild the index and re-index.

To test it locally:

• inv docker.manage 'search_index --rebuild'.
• inv docker.manage reindex_elasticsearch.
• Enable the DEFAULT_TO_FUZZY_SEARCH feature flag on a project.

I'm not sure how to write tests for this one,
and we can't test if this is really fast in production...
But testing it locally works and gives better results for both, sections and
domains!

This is based on #7582 since the wildcard field was added in ES 7.x.
As we are going to re-index when deploying 7.x, I think we can deploy this change together with that (otherwise we'll need to do the re-index again).

One example where you can see better results from domains (with the wildcard search there is a match in the title instead of matching the content)

[stsewd]

This isn't blocked anymore

[humitos]

I don't follow too much the ES code for this change, but if we are worried about the queries being slow, shouldn't we put this behind a feature flag and roll it out slowly?

[stsewd]

@humitos this feature is already in production under a feature flag, it's slow (doing a wildcard search on a no-wildcard field), that's why this PR, using a WildcardField should make it faster.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[ericholscher]

This looks like a good change, but I assume requires a reindex? I'm a little worried about this, but I guess we can always just roll back to the old index if this breaks during deploy?

[ericholscher]

💯

[stsewd]

@ericholscher just tested this locally, we don't need to re-index during deploy, we can do it later, or even just rebuilding a project would create the new fields to make use of them (some fields won't be highlighted till we re-index but is under a feature flag, so all good). I think we could just re-build some projects to test the change, and if it looks good we can re-index everything to test it more broadly with the feature flag.