Adaptive disk spill based on memory usage of shared storage

A non-transitory computer readable storage medium storing computer-executable instructions for a hybrid transactional/analytical processing (HTAP) database including an online transaction processing (OLTP) engine, an online analytical processing (OLAP) engine provided separately from the OLTP engine, and a shared storage including a mass storage device holding data of multiple tenants, wherein

• when executed by processing circuitry, the computer-executable instructions cause the processing circuitry to implement a query executor of the share storage configured to:
• provision a preventative memory usage threshold for the shared storage, the preventative memory usage threshold being lower than a system memory usage threshold;
• continuously monitor actual memory usage of the shared storage while the shared storage is responding to one or more queries from the OLTP engine or OLAP engine;
• and
• upon determining the actual memory usage of an operator evaluating the one or more of the queries from the OLTP engine or OLAP engine at the shared storage exceeds the preventative memory usage threshold but does not exceed the system memory usage threshold, spill one or more fragments of query memory corresponding to the one or more queries to the mass storage device, without terminating the one or more queries.