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Merge kpettersson@bk-internal.mysql.com:/home/bk/mysql-5.0-runtime

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into  adventure.(none):/home/thek/Development/cpp/mysql-5.0-runtime
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thek@adventure.(none) 2007-09-03 10:59:44 +02:00
commit 0184f50f27
1 changed files with 30 additions and 1 deletions
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31
sql/sql_cache.cc
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@ -1032,6 +1032,13 @@ 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");
/*
@ -1078,7 +1085,29 @@ 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"));