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SQLITE3_AGGREGATE_CONTEXT(3)                          Library Functions Manual

     sqlite3_aggregate_context - Obtain Aggregate Function Context

     void *
     sqlite3_aggregate_context(sqlite3_context*, int nBytes);

     Implementations of aggregate SQL functions use this routine to allocate
     memory for storing their state.

     The first time the sqlite3_aggregate_context(C,N) routine is called for a
     particular aggregate function, SQLite allocates N of memory, zeroes out
     that memory, and returns a pointer to the new memory.  On second and
     subsequent calls to sqlite3_aggregate_context() for the same aggregate
     function instance, the same buffer is returned.
     Sqlite3_aggregate_context() is normally called once for each invocation
     of the xStep callback and then one last time when the xFinal callback is
     invoked.  When no rows match an aggregate query, the xStep() callback of
     the aggregate function implementation is never called and xFinal() is
     called exactly once.  In those cases, sqlite3_aggregate_context() might
     be called for the first time from within xFinal().

     The sqlite3_aggregate_context(C,N) routine returns a NULL pointer when
     first called if N is less than or equal to zero or if a memory allocate
     error occurs.

     The amount of space allocated by sqlite3_aggregate_context(C,N) is
     determined by the N parameter on first successful call.  Changing the
     value of N in subsequent call to sqlite3_aggregate_context() within the
     same aggregate function instance will not resize the memory allocation.
     Within the xFinal callback, it is customary to set N=0 in calls to
     sqlite3_aggregate_context(C,N) so that no pointless memory allocations

     SQLite automatically frees the memory allocated by
     sqlite3_aggregate_context() when the aggregate query concludes.

     The first parameter must be a copy of the  SQL function context that is
     the first parameter to the xStep or xFinal callback routine that
     implements the aggregate function.

     This routine must be called from the same thread in which the aggregate
     SQL function is running.


NetBSD 9.99                    December 19, 2018                   NetBSD 9.99