Snapshot advancement for database systems

A non-transitory computer-readable medium having program instructions stored thereon that are capable of causing a computer system to perform operations comprising:

• receiving, by a query planner of a database, a query that defines a first database transaction that includes reading and updating a database value in the database;
• determining, by the query planner, that the query satisfies a set of criteria that allows a snapshot advancement from a first snapshot of the database to a second snapshot of the database;
• and
• based on the determining, providing, by the query planner and to an execution engine of the database, a snapshot advancement permission, wherein the snapshot advancement permission allows a relaxation of a requirement to perform the first database transaction using the first snapshot of the database such that:
• with the snapshot advancement permission, authorizes the execution engine is authorized to execute the query using the second snapshot in response to determining that a contention exists with a second database transaction over an instance of the database value associated with the first snapshot;
• and
• without the snapshot advancement permission, the execution engine indicates a failure of the first database transaction in response to determining that the contention exists.

A system, comprising:

• at least one processor;
• and
• memory having program instructions stored thereon that are executable by the at least one processor to implement a database system performing operations including:
• initiating, by an execution engine of a database, an execution of a query for a first database transaction using a first snapshot of the database, wherein the first database transaction includes a read of a database value and a modification of the database value;
• during the execution of the query, determining, by the execution engine, that an instance of the database value associated with the first snapshot is contended by a second database transaction;
• and
• in response to an authorization from a query planner of the database, continuing the execution of the query for the first database transaction using a second subsequent snapshot of the database and without restarting the execution of the query, wherein the authorization allows a relaxation of a requirement to perform the first database transaction using the first snapshot of the database such that, without the authorization, the execution engine indicates a failure of the first database transaction in response to determining that the instance of the database value associated with the first snapshot is contended by the second database transaction.