čt 12. 3. 2026 v 5:30 odesílatel Tom Lane <tgl@sss.pgh.pa.us> napsal:
Peter Eisentraut <peter@eisentraut.org> writes: > Maybe this could be written in such a way that it doesn't hardcode JSON > arrays specifically, but a type could have an iteration helper function > that would feed this feature?
+1. ISTM that this feature would make sense for subscriptable types, so one way to shoehorn it into the system without a lot of new overhead could be to extend struct SubscriptRoutines to offer optional support function(s) for iterating through all the elements of a subscriptable object.
attached patch do this - new interface has two methods: CreateForeachAIterator and iterate
+typedef struct _ForeachAIterator ForeachAIterator; + +/* + * ForeachAIiterator is used by PLpgSQL FOREACH IN ARRAY statement. + * Input value should not be null, and inside CreateForeachAIterator + * routine must be copied to current (statement) context. "iterate" + * routine is called under short life memory context, that is resetted + * after any call. + */ +struct _ForeachAIterator +{ + bool (*iterate) (ForeachAIterator *self, + Datum *value, + bool *isnull, + Oid *typid, + int32 *typmod); + /* Private fields might appear beyond this point... */ +}; + +typedef ForeachAIterator * (*CreateForeachAIterator) (Datum value, + Oid typid, + int32 typmod, + int slice, + Oid target_typid, + int32 target_typmod); + /* Struct returned by the SQL-visible subscript handler function */ typedef struct SubscriptRoutines { @@ -163,6 +189,9 @@ typedef struct SubscriptRoutines bool fetch_leakproof; /* is fetch SubscriptingRef leakproof? */ bool store_leakproof; /* is assignment SubscriptingRef * leakproof? */ + + /* returns iterator used by PL/pgSQL FOREACH statement */ + CreateForeachAIterator create_foreach_a_iterator; } SubscriptRoutines;
