3.2.6.2.5. Sequential Queries

DataManager can select data from the results of previous requests. This capability is used by the generic filter for sequential application of filters.

The mechanism works as follows:

  • If a LoadContext with defined attributes prevQueries and queryKey is provided, DataManager executes the previous query and saves identifiers of retrieved entities in the SYS_QUERY_RESULT table (corresponding to sys$QueryResult entity), separating the sets of records by user sessions and the query session key queryKey.

  • The current query is modified to be combined with the results of the previous one, so that the resulting data complies with the conditions of both queries combined by AND.

  • The process may be further repeated. In this case the gradually reduced set of previous results is deleted from the SYS_QUERY_RESULT table and refilled again.

The SYS_QUERY_RESULT table is periodically cleaned of old query results left by terminated user sessions. This is done by the deleteForInactiveSessions() method of the QueryResultsManagerAPI bean which is invoked by a Spring scheduler defined in cuba-spring.xml. By default, it is done once in 10 minutes, but you can set a desired interval in milliseconds using the cuba.deleteOldQueryResultsInterval application property of the core module.