New SQLite function to decode struct JSON

helper/db.php

@@ -29,6 +29,9 @@ protected function init()
         // register our JSON function with variable parameters
         $this->sqlite->getPdo()->sqliteCreateFunction('STRUCT_JSON', [$this, 'STRUCT_JSON'], -1);
 
+        // register our JSON decode function with variable parameters
+        $this->sqlite->getPdo()->sqliteCreateFunction('STRUCT_LOOKUP', [$this, 'STRUCT_LOOKUP'], -1);
+
         // this function is meant to be overwritten by plugins
         $this->sqlite->getPdo()->sqliteCreateFunction('IS_PUBLISHER', [$this, 'IS_PUBLISHER'], -1);
     }
@@ -83,6 +86,25 @@ public function STRUCT_JSON(...$args) // phpcs:ignore PSR1.Methods.CamelCapsMeth
         return json_encode($args, JSON_THROW_ON_ERROR);
     }
 
+    /**
+     * Decodes a struct JSON structure and returns the requested value
+     *
+     * @param ...$args
+     * @return mixed|null
+     */
+    public function STRUCT_LOOKUP(...$args) // phpcs:ignore PSR1.Methods.CamelCapsMethodName.NotCamelCaps
+    {
+        $json = $args[0];
+        $field = $args[1];
+
+        try {
+            $vals = json_decode($json, true, 512, JSON_THROW_ON_ERROR);
+        } catch (\JsonException $exception) {
+            return null;
+        }
+        return $vals[$field];
+    }
+
     /**
      * This dummy implementation can be overwritten by a plugin
      *

types/Lookup.php

@@ -245,7 +245,8 @@ public function select(QueryBuilder $QB, $tablealias, $colname, $alias)
             $tablealias,
             $schema,
             $rightalias,
-            "$tablealias.$colname = STRUCT_JSON($rightalias.pid, CAST($rightalias.rid AS DECIMAL)) " .
+            "STRUCT_LOOKUP($tablealias.$colname, 0) = $rightalias.pid " .
+            "AND STRUCT_LOOKUP($tablealias.$colname, 1) = $rightalias.rid " .
             "AND $rightalias.latest = 1"
         );
         $column->getType()->select($QB, $rightalias, $field, $alias);