store/post: fix searching for phrases in postgres (#17042)

Co-authored-by: Mattermod <mattermod@users.noreply.github.com>

store/searchtest/post_layer.go

@@ -345,6 +345,11 @@ func testSearchExactPhraseInQuotes(t *testing.T, th *SearchTestHelper) {
 	require.NoError(t, err)
 	_, err = th.createPost(th.User.Id, th.ChannelBasic.Id, "channel test 123", "", model.POST_DEFAULT, 0, false)
 	require.NoError(t, err)
+	_, err = th.createPost(th.User.Id, th.ChannelBasic.Id, "channel something test 1 2 3", "", model.POST_DEFAULT, 0, false)
+	require.NoError(t, err)
+	_, err = th.createPost(th.User.Id, th.ChannelBasic.Id, "channel 1 2 3", "", model.POST_DEFAULT, 0, false)
+	require.NoError(t, err)
+
 	defer th.deleteUserPosts(th.User.Id)
 
 	params := &model.SearchParams{Terms: "\"channel test 1 2 3\""}

store/sqlstore/post_store.go

@@ -1490,6 +1490,8 @@ func (s *SqlPostStore) search(teamId string, userId string, params *model.Search
 
 		if params.OrTerms {
 			queryParams["Terms"] = "(" + strings.Join(strings.Fields(terms), " | ") + ")" + excludeClause
+		} else if strings.HasPrefix(terms, `"`) && strings.HasSuffix(terms, `"`) {
+			queryParams["Terms"] = "(" + strings.Join(strings.Fields(terms), " <-> ") + ")" + excludeClause
 		} else {
 			queryParams["Terms"] = "(" + strings.Join(strings.Fields(terms), " & ") + ")" + excludeClause
 		}