Invalid input '.': expected an identifier character, whitespace, '|', a length specification, a property map or ']'

Hi @adam_cowley,
first of all, thanks for the answer.

I modified the query to be as follows:

    @Query(   "call apoc.periodic.iterate("
            + "\"UNWIND $items as item return item\" , "
            + "\"MERGE (s1:s{id:item.customId}) "
            + "WITH s1, item "
            + "MERGE (e1:e{id:item.customId}) "
            + "WITH s1, e1, item "
            + "CALL apoc.merge.relationship(s1, item.type, {id: item.customId, name: item.name}, {}, e1) YIELD relationship AS r RETURN *\", "
            + "{batchSize:5, parallel:true, iterateList:true,params:{items:$itemss}})")
    Result saveAll4(@Param("itemss") List<?> items);

But I'm experiencing the following error:

Unknown procedure output: `relationship` (line 1, column 258 (offset: 257))
"UNWIND $_batch AS _batch WITH _batch.item AS item  MERGE (s1:s{id:item.customId}) WITH s1, item MERGE (e1:e{id:item.customId}) WITH s1, e1, item CALL apoc.merge.relationship(s1, item.type, {id: item.customId, name: item.name}, {}, e1) YIELD relationship AS r RETURN *"

I ran the command CALL dbms.procedures() and verified that apoc.merge.relationship exists.

What else can it be?