5.2.6.10.3. 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 attributesprevQueries
andqueryKey
is provided,DataManager
executes the previous query and saves identifiers of retrieved entities in theSYS_QUERY_RESULT
table (corresponding tosys$QueryResult
entity), separating the sets of records by user sessions and the query session keyqueryKey
. -
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 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>