[MM-5046] Fix emails search for Postgres DB (#21590)

* Support emails search in Postgres

* Add @ exception for postgres

* update comment

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

store/sqlstore/file_info_store.go

@@ -606,8 +606,7 @@ func (fs SqlFileInfoStore) Search(paramsList []*model.SearchParams, userId, team
 		terms := params.Terms
 		excludedTerms := params.ExcludedTerms
 
-		// these chars have special meaning and can be treated as spaces
-		for _, c := range specialSearchChar {
+		for _, c := range fs.specialSearchChars() {
 			terms = strings.Replace(terms, c, " ", -1)
 			excludedTerms = strings.Replace(excludedTerms, c, " ", -1)
 		}

store/sqlstore/post_store.go

@@ -1788,18 +1788,6 @@ func (s *SqlPostStore) getParentsPostsPostgreSQL(channelId string, offset int, l
 	return posts, nil
 }
 
-var specialSearchChar = []string{
-	"<",
-	">",
-	"+",
-	"-",
-	"(",
-	")",
-	"~",
-	"@",
-	":",
-}
-
 // GetNthRecentPostTime returns the CreateAt time of the nth most recent post.
 func (s *SqlPostStore) GetNthRecentPostTime(n int64) (int64, error) {
 	if n <= 0 {
@@ -1989,8 +1977,7 @@ func (s *SqlPostStore) search(teamId string, userId string, params *model.Search
 		}
 	}
 
-	// these chars have special meaning and can be treated as spaces
-	for _, c := range specialSearchChar {
+	for _, c := range s.specialSearchChars() {
 		terms = strings.Replace(terms, c, " ", -1)
 		excludedTerms = strings.Replace(excludedTerms, c, " ", -1)
 	}

store/sqlstore/store.go

@@ -335,6 +335,28 @@ func (ss *SqlStore) DriverName() string {
 	return *ss.settings.DriverName
 }
 
+// specialSearchChars have special meaning and can be treated as spaces
+func (ss *SqlStore) specialSearchChars() []string {
+	chars := []string{
+		"<",
+		">",
+		"+",
+		"-",
+		"(",
+		")",
+		"~",
+		":",
+	}
+
+	// Postgres can handle "@" without any errors
+	// Also helps postgres in enabling search for EmailAddresses
+	if ss.DriverName() != model.DatabaseDriverPostgres {
+		chars = append(chars, "@")
+	}
+
+	return chars
+}
+
 // computeBinaryParam returns whether the data source uses binary_parameters
 // when using Postgres
 func (ss *SqlStore) computeBinaryParam() (bool, error) {