Function bson_object_keys

pg_documentdb_core/src/io/bson_io.c:348–394

* bson_object_keys returns the set of keys for the object argument. * * The implementation is heavily based on jsonb_object_keys. * * This SRF operates in value-per-call mode. It processes the * object during the first call, and the keys are simply stashed * in an array, whose size is expanded as necessary. This is probably * safe enough for a list of keys of a single object, since they are

 * be so huge that it has major memory implications.
 */
Datum
bson_object_keys(PG_FUNCTION_ARGS)
{
	FuncCallContext *functionContext;
	BsonObjectKeysState *state;

	if (SRF_IS_FIRSTCALL())
	{
		MemoryContext oldcontext;
		pgbson *sourceBson = PG_GETARG_PGBSON(0);
		bson_iter_t sourceBsonIterator;

		PgbsonInitIterator(sourceBson, &sourceBsonIterator);

		functionContext = SRF_FIRSTCALL_INIT();
		oldcontext = MemoryContextSwitchTo(functionContext->multi_call_memory_ctx);

		state = palloc(sizeof(BsonObjectKeysState));

		state->resultSize = PgbsonCountKeys(sourceBson);
		state->resultCount = 0;
		state->sentCount = 0;
		state->result = palloc(state->resultSize * sizeof(Datum));

		while (bson_iter_next(&sourceBsonIterator))
		{
			const char *key = bson_iter_key(&sourceBsonIterator);

			state->result[state->resultCount++] = CStringGetTextDatum(key);
		}

		MemoryContextSwitchTo(oldcontext);
		functionContext->user_fctx = (void *) state;
	}

	functionContext = SRF_PERCALL_SETUP();
	state = (BsonObjectKeysState *) functionContext->user_fctx;

	if (state->sentCount < state->resultCount)
	{
		Datum next = state->result[state->sentCount++];

		SRF_RETURN_NEXT(functionContext, next);
	}

	SRF_RETURN_DONE(functionContext);
}


/*