4.2.6.10.2. Sequential Queries

DataManager can select data from the results of previous requests. This ability 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, the DataManager executes the previous query and saves identifiers of retrieved entities in 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 gets deleted from SYS_QUERY_RESULT table and refilled again.

The table SYS_QUERY_RESULT should be periodically cleaned of all unnecessary query results left by terminated user sessions. This is done by the deleteForInactiveSessions() method of the QueryResultsManagerAPI bean. In an application with enabled cuba.allowQueryFromSelected property this method should be called by scheduled tasks, for example: 

<task:scheduled-tasks scheduler="scheduler">
    <task:scheduled ref="cuba_QueryResultsManager" method="deleteForInactiveSessions" fixed-rate="600000"/>
</task:scheduled-tasks>

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