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Merge magare.gmz:/home/kgeorge/mysql/work/B30355-5.0-opt

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into  magare.gmz:/home/kgeorge/mysql/work/B30355-5.1-opt
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gkodinov/kgeorge@magare.gmz 2007-11-27 17:19:51 +02:00
commit 0f3db011d5
6 changed files with 112 additions and 6 deletions
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50
sql/item_func.h
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@ -1022,6 +1022,56 @@ public:
fixed= 1;
return res;
}
void update_used_tables()
{
/*
TODO: Make a member in UDF_INIT and return if a UDF is deterministic or
not.
Currently UDF_INIT has a member (const_item) that is an in/out
parameter to the init() call.
The code in udf_handler::fix_fields also duplicates the arguments
handling code in Item_func::fix_fields().
The lack of information if a UDF is deterministic makes writing
a correct update_used_tables() for UDFs impossible.
One solution to this would be :
- Add a is_deterministic member of UDF_INIT
- (optionally) deprecate the const_item member of UDF_INIT
- Take away the duplicate code from udf_handler::fix_fields() and
make Item_udf_func call Item_func::fix_fields() to process its
arguments as for any other function.
- Store the deterministic flag returned by <udf>_init into the
udf_handler.
- Don't implement Item_udf_func::fix_fields, implement
Item_udf_func::fix_length_and_dec() instead (similar to non-UDF
functions).
- Override Item_func::update_used_tables to call
Item_func::update_used_tables() and add a RAND_TABLE_BIT to the
result of Item_func::update_used_tables() if the UDF is
non-deterministic.
- (optionally) rename RAND_TABLE_BIT to NONDETERMINISTIC_BIT to
better describe its usage.
The above would require a change of the UDF API.
Until that change is done here's how the current code works:
We call Item_func::update_used_tables() only when we know that
the function depends on real non-const tables and is deterministic.
This can be done only because we know that the optimizer will
call update_used_tables() only when there's possibly a new const
table. So update_used_tables() can only make a Item_func more
constant than it is currently.
That's why we don't need to do anything if a function is guaranteed
to return non-constant (it's non-deterministic) or is already a
const.
*/
if ((used_tables_cache & ~PSEUDO_TABLE_BITS) &&
!(used_tables_cache & RAND_TABLE_BIT))
{
Item_func::update_used_tables();
if (!const_item_cache && !used_tables_cache)
used_tables_cache= RAND_TABLE_BIT;
}
}
void cleanup();
Item_result result_type () const { return udf.result_type(); }
table_map not_null_tables() const { return 0; }