use a different query to fetch materialized view structure

pkg/statements/sql.go

@@ -92,6 +92,23 @@ WHERE
 
 	// ---------------------------------------------------------------------------
 
+	PG_MATERIALIZED_VIEW_SCHEMA = `
+SELECT 
+  attname as column_name, 
+  atttypid::regtype AS data_type,
+  (case when attnotnull IS TRUE then 'NO' else 'YES' end) as is_nullable,
+  null as character_maximum_length,
+  null as character_set_catalog,
+  null as column_default
+FROM
+  pg_attribute
+WHERE
+  attrelid = $1::regclass AND
+  attnum > 0 AND
+  NOT attisdropped`
+
+	// ---------------------------------------------------------------------------
+
 	PG_ACTIVITY = `
 SELECT
   datname,