1. A method comprising: receiving a plurality of sketches by a computing device, wherein each sketch is associated with a node of a plurality of nodes of a graph; receiving an influence query for a subset of the plurality of nodes of a specified size having a maximum influence by the computing device, wherein the influence query is a query for an estimate of the subset of nodes of the plurality of nodes of the specified size with a maximum combined influence, wherein the influence of a node is a measure of how connected the node in the graph is to the other nodes of the graph; determining a first node of the plurality of nodes that when added to the subset of the plurality of nodes increases an influence of the subset of the plurality of nodes by a greatest amount using the sketch associated with the first node and the sketches associated with the nodes in the subset of the plurality of nodes by the computing device; adding the determined first node to the subset of the plurality of nodes by the computing device; determining that the subset of the plurality of nodes is of the specified size by the computing device; and in response to the determination, providing the subset of the plurality of nodes by the computing device.