Search: sort results correctly when using postgres (#46466)

* Search: sort results correctly when using postgres

postgresql puts nulls first while both mysql and sqlite puts them last

* linting

pkg/services/sqlstore/migrator/dialect.go

@@ -27,6 +27,8 @@ type Dialect interface {
 	BooleanStr(bool) string
 	DateTimeFunc(string) string
 
+	OrderBy(order string) string
+
 	CreateIndexSQL(tableName string, index *Index) string
 	CreateTableSQL(table *Table) string
 	AddColumnSQL(tableName string, col *Column) string
@@ -308,3 +310,7 @@ func (b *BaseDialect) Lock(_ LockCfg) error {
 func (b *BaseDialect) Unlock(_ LockCfg) error {
 	return nil
 }
+
+func (b *BaseDialect) OrderBy(order string) string {
+	return order
+}

pkg/services/sqlstore/migrator/postgres_dialect.go

@@ -284,6 +284,19 @@ func (db *PostgresDialect) Lock(cfg LockCfg) error {
 	return nil
 }
 
+// OrderBy normalizes ordering so that nulls end up last in sorting, which they do by default in both sqlite and mysql but not postgres
+// order should be a string like `dashboard.id ASC`
+func (db *PostgresDialect) OrderBy(order string) string {
+	nullSort := "FIRST"
+	normalizedOrder := strings.ToUpper(strings.TrimSpace(order))
+
+	if strings.HasSuffix(normalizedOrder, " DESC") {
+		nullSort = "LAST"
+	}
+
+	return fmt.Sprintf("%s NULLS %s", order, nullSort)
+}
+
 func (db *PostgresDialect) Unlock(cfg LockCfg) error {
 	// trying to release a previously-acquired exclusive session level advisory lock.
 	// it will either return true if the lock is successfully released or

pkg/services/sqlstore/searchstore/builder.go

@@ -140,7 +140,12 @@ func (b *Builder) applyFilters() (ordering string) {
 		b.params = append(b.params, groupParams...)
 	}
 
-	orderBy := fmt.Sprintf(" ORDER BY %s", strings.Join(orders, ", "))
+	orderByCols := []string{}
+	for _, o := range orders {
+		orderByCols = append(orderByCols, b.Dialect.OrderBy(o))
+	}
+
+	orderBy := fmt.Sprintf(" ORDER BY %s", strings.Join(orderByCols, ", "))
 	b.sql.WriteString(orderBy)
 
 	order := strings.Join(orderJoins, "")