Flexible in-memory column store placement

One or more non-transitory computer-readable media storing instructions, wherein the instructions include:

• instructions which, when executed by one or more hardware processors, cause storing, in a database that is accessible to a plurality of nodes, a unit-to-service mapping that maps a particular unit in the database to a particular database service, wherein the particular database service is a grouping of work executing in the database, wherein the particular unit includes one or more tables of the database;
• instructions which, when executed by one or more hardware processors, cause storing, in the database, a service-to-node mapping that maps the particular database service to one or more nodes, wherein the one or more nodes are less than all of the plurality of nodes;
• instructions which, when executed by one or more hardware processors, cause based on both the unit-to-service mapping and the service-to-node mapping, the one or more nodes treating the particular unit as in-memory enabled and nodes, of the plurality of nodes, other than the one or more nodes treating the particular unit as not in-memory enabled, wherein chunks of tables that belong to in-memory enabled units are eligible for being pre-loaded into volatile memory to speed up query processing;
• and
• wherein, each node of the one or more nodes treats the particular unit as in-memory enabled by loading at least a copy of a portion of the particular unit into local volatile memory in response to a load-triggering event;
• and
• instructions which, when executed by one or more hardware processors, cause as part of the loading at least the copy of the portion of the particular unit into the local volatile memory, converting the particular unit from a persistent-format to a mirror-format.