Search: Add optional rum indexing / searching.

1 files changed, 15 insertions, 0 deletions

diff --git a/docs/config.md b/docs/config.md
index 43ea24d80..99cee25cd 100644
--- a/docs/config.md
+++ b/docs/config.md
@@ -537,3 +537,18 @@ Configure OAuth 2 provider capabilities:
 * `shortcode_globs`: Location of custom emoji files. `*` can be used as a wildcard. Example `["/emoji/custom/**/*.png"]`
 * `groups`: Emojis are ordered in groups (tags). This is an array of key-value pairs where the key is the groupname and the value the location or array of locations. `*` can be used as a wildcard. Example `[Custom: ["/emoji/*.png", "/emoji/custom/*.png"]]`
 * `default_manifest`: Location of the JSON-manifest. This manifest contains information about the emoji-packs you can download. Currently only one manifest can be added (no arrays).
+
+## Database options
+
+### RUM indexing for full text search
+* `rum_enabled`: If RUM indexes should be used. Defaults to `false`.
+
+RUM indexes are an alternative indexing scheme that is not included in PostgreSQL by default. While they may eventually be mainlined, for now they have to be installed as a PostgreSQL extension from https://github.com/postgrespro/rum.
+
+Their advantage over the standard GIN indexes is that they allow efficient ordering of search results by timestamp, which makes search queries a lot faster on larger servers, by one or two orders of magnitude. They take up around 3 times as much space as GIN indexes.
+
+To enable them, both the `rum_enabled` flag has to be set and the following special migration has to be run:
+
+`mix ecto.migrate --migrations-path priv/repo/optional_migrations/rum_indexing/`
+
+This will probably take a long time.