Removing Used_tables_and_const_cache from "class udf_handler".

It was used only temporary, during udf_handler::fix_fields() time, and then copied to the owner Item_func_or_sum object. Changing the code to use the Used_tables_and_const_cache part of the owner Item_sum_or_func object directly.

Author: Alexander Barkov

sql/item.h

@@ -3617,10 +3617,6 @@ class Used_tables_and_const_cache
  used_tables_cache= 0;
  const_item_cache= true;
  }
- void used_tables_and_const_cache_copy(const Used_tables_and_const_cache *c)
- {
- *this= *c;
- }
  void used_tables_and_const_cache_join(const Item *item)
  {
  used_tables_cache|= item->used_tables();

sql/item_func.cc

@@ -3508,7 +3508,7 @@ udf_handler::fix_fields(THD *thd, Item_func_or_sum *func,
 
  /* Fix all arguments */
  func->maybe_null=0;
- used_tables_and_const_cache_init();
+ func->used_tables_and_const_cache_init();
 
  if ((f_args.arg_count=arg_count))
  {
@@ -3550,7 +3550,7 @@ udf_handler::fix_fields(THD *thd, Item_func_or_sum *func,
  func->with_sum_func= func->with_sum_func || item->with_sum_func;
  func->with_field= func->with_field || item->with_field;
  func->with_subselect|= item->with_subselect;
- used_tables_and_const_cache_join(item);
+ func->used_tables_and_const_cache_join(item);
  f_args.arg_type[i]=item->result_type();
  }
  //TODO: why all following memory is not allocated with 1 call of sql_alloc?
@@ -3572,7 +3572,7 @@ udf_handler::fix_fields(THD *thd, Item_func_or_sum *func,
  func->fix_length_and_dec();
  initid.max_length=func->max_length;
  initid.maybe_null=func->maybe_null;
- initid.const_item=const_item_cache;
+ initid.const_item=func->const_item_cache;
  initid.decimals=func->decimals;
  initid.ptr=0;
 
@@ -3637,13 +3637,12 @@ udf_handler::fix_fields(THD *thd, Item_func_or_sum *func,
  }
  func->max_length=MY_MIN(initid.max_length,MAX_BLOB_WIDTH);
  func->maybe_null=initid.maybe_null;
- const_item_cache=initid.const_item;
- /* 
- Keep used_tables_cache in sync with const_item_cache.
- See the comment in Item_udf_func::update_used tables.
- */ 
- if (!const_item_cache && !used_tables_cache)
- used_tables_cache= RAND_TABLE_BIT;
+ /*
+ The above call for init() can reset initid.const_item to "false",
+ e.g. when the UDF function wants to be non-deterministic.
+ See sequence_init() in udf_example.cc.
+ */
+ func->const_item_cache= initid.const_item;
  func->decimals=MY_MIN(initid.decimals,NOT_FIXED_DEC);
  }
  initialized=1;

sql/item_func.h

@@ -1364,6 +1364,15 @@ class Item_func_sleep :public Item_int_func
 
 class Item_udf_func :public Item_func
 {
+ /**
+ Mark "this" as non-deterministic if it uses no tables
+ and is not a constant at the same time.
+ */
+ void set_non_deterministic_if_needed()
+ {
+ if (!const_item_cache && !used_tables_cache)
+ used_tables_cache= RAND_TABLE_BIT;
+ }
 protected:
  udf_handler udf;
  bool is_expensive_processor(uchar *arg) { return TRUE; }
@@ -1379,7 +1388,7 @@ class Item_udf_func :public Item_func
  {
  DBUG_ASSERT(fixed == 0);
  bool res= udf.fix_fields(thd, this, arg_count, args);
- used_tables_and_const_cache_copy(&udf);
+ set_non_deterministic_if_needed();
  fixed= 1;
  return res;
  }
@@ -1430,8 +1439,7 @@ class Item_udf_func :public Item_func
  !(used_tables_cache & RAND_TABLE_BIT))
  {
  Item_func::update_used_tables();
- if (!const_item_cache && !used_tables_cache)
- used_tables_cache= RAND_TABLE_BIT;
+ set_non_deterministic_if_needed();
  }
  }
  void cleanup();

sql/item_sum.h

@@ -1209,9 +1209,27 @@ class Item_udf_sum : public Item_sum
  return TRUE;
 
  fixed= 1;
+ /*
+ We set const_item_cache to false in constructors.
+ It can be later changed to "true", in a Item_sum::make_const() call.
+ No make_const() calls should have happened so far.
+ */
+ DBUG_ASSERT(!const_item_cache);
  if (udf.fix_fields(thd, this, this->arg_count, this->args))
  return TRUE;
-
+ /**
+ The above call for udf.fix_fields() updates
+ the Used_tables_and_const_cache part of "this" as if it was a regular
+ non-aggregate UDF function and can change both const_item_cache and
+ used_tables_cache members.
+ - The used_tables_cache will be re-calculated in update_used_tables()
+ which is called from check_sum_func() below. So we don't care about
+ its current value.
+ - The const_item_cache must stay "false" until a Item_sum::make_const()
+ call happens, if ever. So we need to reset const_item_cache back to
+ "false" here.
+ */
+ const_item_cache= false;
  memcpy (orig_args, args, sizeof (Item *) * arg_count);
  return check_sum_func(thd, ref);
  }

sql/sql_udf.h

@@ -52,7 +52,7 @@ typedef struct st_udf_func
 
 class Item_result_field;
 
-class udf_handler :public Sql_alloc, public Used_tables_and_const_cache
+class udf_handler :public Sql_alloc
 {
  protected:
  udf_func *u_d;