The RDB$QUERY_OUTLINES system table contains query outline
    definitions that are used by the optimizer to retrieve known
    query outlines prior to optimization. The following table
    provides information on the columns of the RDB$QUERY_OUTLINES
    system table.

                                Data
    Column Name                 Type      Summary Description

    RDB$OUTLINE_NAME            char(31)  The query outline name.
    RDB$BLR_ID                  char 16   The BLR hashed identifier.
                                          This identifier is
                                          generated by the optimizer
                                          whenever a query outline is
                                          created.
    RDB$MODE                    integer   The query mode (MANDATORY
                                          or OPTIONAL).
    RDB$FLAGS                   integer   Flags.
    RDB$DESCRIPTION             list      A user-supplied description
                                of byte   of this outline.
                                varying
    RDB$OUTLINE_BLR             list      The compiled query outline.
                                of byte
                                varying
    RDB$SECURITY_CLASS          char(20)  Reserved for future use.
    RDB$CREATED                 date vms  Set when the outline is
                                          created.
    RDB$LAST_ALTERED            date vms  Reserved for future use.
    RDB$OUTLINE_CREATOR         char(31)  Creator of this outline.