1. A method of presenting to a user a lineage diagram representing a query plan, the method comprising: receiving by a computer a query plan from a query engine during a query planning mode when a logical query is processed by the query engine to generate the query plan, the query plan containing transformations used to convert the logical query into one or more native queries that are applicable to databases storing data relevant to the native queries; generating, during the query planning mode, a lineage diagram representing the query plan using one or more query subjects and one or more symbolic links representing the transformations and conceptual data streams between the query subjects connected by the symbolic links, wherein at least a first query subject in the lineage diagram references a second query subject defined by a metadata model describing a plurality of layers of abstraction of the database storing data relevant to the native queries, and wherein at least one query subject in the lineage diagram references a database table present in one of the databases storing data relevant to the native queries; receiving user selection of a query subject presented in the lineage diagram; changing, in the lineage diagram, presentation of the selected query subject to show one or more corresponding query subjects that are represented by the selected query subject such that lineage of the selected query subject is interactively shown in the diagram using the corresponding query subjects in a same or different layer of the metadata model; allowing the user to select one of the symbolic links visual in a current view; and expanding or collapsing the selected symbolic link to show or hide one or more query subjects that are represented by the selected symbolic link based on the user's selection.