1. A computer-implemented method, comprising: receiving, with a processor of a computer, a hierarchical document to be processed by a pipeline of transformations; determining whether a next downstream transformation accesses content of each schema node in an associated input schema, wherein the associated input schema is a polymorphic schema that includes a wildcard schema node; in response to determining that the next downstream transformation is not accessing the content of each schema node in the associated input schema, collecting data items corresponding to each schema node that the next downstream transformation is not accessing into a single compressed event, wherein the collected data items of the single compressed event correspond to content of the wildcard schema node; passing the collected data items to the next downstream transformation as the single compressed event, wherein the downstream transformation does not access the content of the single compressed event; and transforming polymorphic schemas that use inheritance relationships between a parent schema node and corresponding child schema nodes to polymorphic schemas without inheritance relationships using wildcard schema nodes by: adding a wildcard schema node that provides a match for additional sub-elements and attributes of child schema nodes to the parent schema node; and removing the inheritance relationship.
2. The method of claim 1 , wherein a pipeline processor collects the data items and passes the collected data items to the next downstream transformation, wherein the pipeline processor is coupled to multiple, individual transformations.