Flattening a relational database. A method includes accessing a first database table. A first entry value is identified in a first entry from the first database table. The first entry value represents a plurality of entry values of corresponding entries in a second database table. An array is created that includes one or more representations of the plurality of entry values. At least a portion of the first database table is converted to one or more hierarchical record documents, with columns of the first database table represented at a first hierarchical level and values in entries in the columns represented at a second hierarchical level below the first hierarchical level for a corresponding column. Converting the first database table to one or more hierarchical record documents includes substituting the array in a hierarchical record document for each entry in the plurality of entries having the first entry value.