Make activity search properly use GIN indexes

The original approach to search in GIN indexes is to use
`to_tsvector(text)` in the WHERE clause of the query. According to
postgres docs [pdoc], this method does not make use of the index,
while `to_tsvector(config, text)` does. This commit changed the
query to use the two-argument `to_tsvector()`.

[pdoc]: https://www.postgresql.org/docs/12/textsearch-tables.html

To obtain the search config in use, we make a query to the db first.
The `::regconfig::oid` hack is needed because Postgrex does not support
regconfig type directly [postgrexbug]. I use the conversion from and to
`oid` instead of `text` because I tested in the actual DB and querying
using the conversion via `text` is slow just as the one-argument
`to_tsvector()` variant.

[postgrexbug]: https://github.com/elixir-ecto/postgrex/issues/502

Backport of: https://git.pleroma.social/pleroma/pleroma/-/merge_requests/3519

Closes: https://git.pleroma.social/pleroma/pleroma/-/issues/2758

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 90e0ca82abfe3b3813595fd6de8c0e12e731a7a0..6609205652b34fb582cce16b1bdba582d105e881 100644 (file)
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -28,6 +28,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Mastodon API: Activity Search fallbacks on status fetching after a DB Timeout/Error
 - Mastodon API: Fix crash in Streamer related to reblogging
 - AdminAPI: List available frontends when `static/frontends` folder is missing
+- Make activity search properly use language-aware GIN indexes
 
 ## 2.4.0 - 2021-08-08
 

diff --git a/lib/pleroma/activity/search.ex b/lib/pleroma/activity/search.ex
index a5923519c3d7434534d848534093cd38144c99f1..09671f62103678237efcf4f38cc168fcf9609765 100644 (file)
--- a/lib/pleroma/activity/search.ex
+++ b/lib/pleroma/activity/search.ex
@@ -65,10 +65,17 @@ defmodule Pleroma.Activity.Search do
   end
 
   defp query_with(q, :gin, search_query, :plain) do
+    %{rows: [[tsc]]} =
+      Ecto.Adapters.SQL.query!(
+        Pleroma.Repo,
+        "select current_setting('default_text_search_config')::regconfig::oid;"
+      )
+
     from([a, o] in q,
       where:
         fragment(
-          "to_tsvector(?->>'content') @@ plainto_tsquery(?)",
+          "to_tsvector(?::oid::regconfig, ?->>'content') @@ plainto_tsquery(?)",
+          ^tsc,
           o.data,
           ^search_query
         )
@@ -76,10 +83,17 @@ defmodule Pleroma.Activity.Search do
   end
 
   defp query_with(q, :gin, search_query, :websearch) do
+    %{rows: [[tsc]]} =
+      Ecto.Adapters.SQL.query!(
+        Pleroma.Repo,
+        "select current_setting('default_text_search_config')::regconfig::oid;"
+      )
+
     from([a, o] in q,
       where:
         fragment(
-          "to_tsvector(?->>'content') @@ websearch_to_tsquery(?)",
+          "to_tsvector(?::oid::regconfig, ?->>'content') @@ websearch_to_tsquery(?)",
+          ^tsc,
           o.data,
           ^search_query
         )