MM-47374: Revert full text search (#21233)

* Revert "MM-46871: Add remining search parameters to be escaped (#20963)"

This reverts commit 8797bfcde7.

* Revert "MM-46503: Escape incorrect pg user search query (#20863)"

This reverts commit 8fd1762c3b.

* Revert "MM-44576 autocomplete names including utf 8 chars (#20367)"

This reverts commit 8444c45959.

store/sqlstore/user_store.go

@@ -1509,34 +1509,17 @@ func generateSearchQuery(query sq.SelectBuilder, terms []string, fields []string
 	for _, term := range terms {
 		searchFields := []string{}
 		termArgs := []any{}
-		var dbSpecificTerm string
-
-		if isPostgreSQL {
-			// Refer to https://www.postgresql.org/docs/current/functions-textsearch.html for the list of operators.
-			for _, c := range []string{":", "(", ")", "<", "!", "|"} {
-				// Escaping the special chars in case of a Postgres search.
-				term = strings.ReplaceAll(term, c, "\\"+c)
-			}
-		}
-
 		for _, field := range fields {
 			if isPostgreSQL {
-				if strings.TrimLeft(term, "@") == "" {
-					// For wildcard search, we need to fall back to pattern matching.
-					searchFields = append(searchFields, fmt.Sprintf("%s ILIKE ? escape '*' ", field))
-					dbSpecificTerm = fmt.Sprintf("%s%%", strings.TrimLeft(term, "@"))
-				} else {
-					searchFields = append(searchFields, fmt.Sprintf("to_tsvector(lower(%[1]s)) @@ to_tsquery(concat(lower(?),':*'))", field))
-					dbSpecificTerm = strings.TrimLeft(term, "@")
-				}
+				searchFields = append(searchFields, fmt.Sprintf("lower(%s) LIKE lower(?) escape '*' ", field))
 			} else {
 				searchFields = append(searchFields, fmt.Sprintf("%s LIKE ? escape '*' ", field))
-				dbSpecificTerm = fmt.Sprintf("%s%%", strings.TrimLeft(term, "@"))
 			}
-			termArgs = append(termArgs, dbSpecificTerm)
+			termArgs = append(termArgs, fmt.Sprintf("%s%%", strings.TrimLeft(term, "@")))
 		}
 		query = query.Where(fmt.Sprintf("(%s)", strings.Join(searchFields, " OR ")), termArgs...)
 	}
+
 	return query
 }