Joining large database tables

A non-transitory computer product comprising a computer readable medium storing a plurality of instructions that, when executed by a computer, cause the computer to perform operations comprising:

• receiving, at a computer node, a query identifying a plurality of tables to be joined;
• identifying, by the computer node, one or more first entries in a first table that satisfy one or more criteria included in the query;
• creating, by the computer node, a first active flag structure that includes first flags,
• wherein at least one of the first flags indicates a true value and a flag of the first flags indicates a true value when a respective entry of the one or more first entries in the first table satisfies the one or more criteria, and
• wherein the flag of the first flags indicates a false value when the respective entry does not satisfy the one or more criteria included in the query;
• identifying, by the computer node, keys corresponding to one or more second entries in a second table based on the identified one or more first entries in the first table that are associated with a flag of the first flags indicating the true value;
• using the identified keys to generate a request corresponding to the one or more second entries in the second table, wherein the request includes a plurality of separate requests;
• determining, by the computer node, an identifier for each of the identified keys, the identifier specifying a memory location for a corresponding second entry;
• sending, by the computer node, the separate requests based on the identifiers;
• updating, by the computer node, at least one of the first flags of the first active flag structure that indicates a true value to indicate a false value based on a response to the request;
• identifying a first group of the first flags of the first active flag structure that indicate a true value;
• and
• retrieving data corresponding to the first group of the first flags for creating an output table.