Commit 85d70078 authored by thek@adventure.(none)'s avatar thek@adventure.(none)
Browse files

Merge adventure.(none):/home/thek/Development/cpp/bug21074/my50-bug21074 

into  adventure.(none):/home/thek/Development/cpp/mysql-5.0-runtime
parents 7a1942d2 f5ecb35e

sql/sql_cache.cc

+30 −1
Original line number Diff line number Diff line
@@ -1023,6 +1023,13 @@ Query_cache::send_result_to_client(THD *thd, char *sql, uint query_length) 
  Query_cache_block_table *block_table, *block_table_end;

  ulong tot_length;

  Query_cache_query_flags flags;

  const uint spin_treshold= 50000;

  const double lock_time_treshold= 0.1; /* Time in seconds */

  uint spin_count= 0;

  int lock_status= 0;

  ulong new_time= 0;

  ulong stop_time= 0;



  DBUG_ENTER("Query_cache::send_result_to_client");



  /*
@@ -1069,7 +1076,29 @@ Query_cache::send_result_to_client(THD *thd, char *sql, uint query_length) 
    }

  }



  STRUCT_LOCK(&structure_guard_mutex);

  stop_time= my_clock()+(ulong)lock_time_treshold*CLOCKS_PER_SEC;

  while ((lock_status= pthread_mutex_trylock(&structure_guard_mutex)) == EBUSY

         && spin_count < spin_treshold

         && new_time < stop_time)

  {

    spin_count++;

    if (spin_count%5)

      new_time= my_clock();

    pthread_yield();

  }



  if (lock_status != 0)

  {

    /*

      Query cache is too busy doing something else.

      Fall back on ordinary statement execution. We also mark this

      query as unsafe to cache because otherwise this thread will

      still be halted when the result set is stored to the cache.

    */

    thd->lex->safe_to_cache_query= FALSE; 

    goto err;

  }



  if (query_cache_size == 0 || flush_in_progress)

  {

    DBUG_PRINT("qcache", ("query cache disabled"));