• Varun Gupta's avatar
    MDEV-17066: Bytes lost or Assertion `status_var.local_memory_used == 0 after... · 1e31d748
    Varun Gupta authored
    MDEV-17066: Bytes lost or Assertion `status_var.local_memory_used == 0 after DELETE with subquery with ROLLUP
    
    The issue here is when records are read from the temporary file
    (filesort result in this case) via a cache(rr_from_cache).
    The cache is initialized with init_rr_cache.
    For correlated subquery the cache allocation is happening at each execution
    of the subquery but the deallocation happens only once and that was
    when the query execution was done.
    
    So generally for subqueries we do two types of cleanup
    
    1) Full cleanup: we should free all resources of the query(like temp tables).
       This is done generally when the query execution is complete or the subquery
       re-execution is not needed (case with uncorrelated subquery)
    
    2) Partial cleanup: Minor cleanup that is required if
       the subquery needs recalculation. This is done for all the structures that
       need to be allocated for each execution (example SORT_INFO for filesort
       is allocated for each execution of the correlated subquery).
    
    The fix here would be free the cache used by rr_from_cache in the partial
    cleanup phase.
    1e31d748
sql_select.h 77 KB