1. A method of matching a content item in a data file to a search entity comprising: maintaining a plurality of entity-action pairs and bidding parameters specific to each entity-action pair of the plurality of entity-action pairs; receiving a first search query from a client device, the first search query including a query term indicative of a first search entity; identifying, from the plurality of entity-action pairs, a first entity-action pair comprising the first search entity and a first online action and a second entity-action pair comprising the first search entity and a second online action that is different from the first online action responsive to the query term indicative of the first search entity in the received first search query; identifying a second search entity not included in the first search query and identified using the first search entity and a knowledge graph of search entities; conducting a first content auction for the first entity-action pair based on bidding parameters specific to the first entity-action pair and a second content auction for the second entity-action pair based on bidding parameters specific to the second entity-action pair responsive to identifying the first entity-action pair and the second entity-action pair; determining a first set of third-party content items associated with the first entity-action pair for participating in the first content auction, each third-party content item of the first set of third-party content items including executable instructions for causing an application of the client device to automatically perform the first online action upon actuating that third-party content item by the client device; determining a second set of third-party content items associated with the first entity-action pair for participating in the second content auction, each third-party content item of the second set of third-party content items including executable instructions for causing the application of the client device to automatically perform the second online action upon actuating that third-party content item by the client device; selecting, responsive to the first content auction, a first content item of a first third-party content provider based on a first bidding parameter of the first third-party content provider specific to the first entity-action pair and selecting, responsive to the second content auction, a second content item of a second third-party content provider based on a second bidding parameter of the second third-party content provider-specific to the second entity-action pair, the first and second content items for presenting with search results corresponding to the first search query on the client device; and selecting, responsive to identifying the second search entity, a link associated with the second search entity for presenting with the search results corresponding to the first search query on the client device, wherein actuation of the link by the client device causes the first search query to be replaced with a second search query associated with the second search entity and new content items to be selected instead of the first and second content items.