MDEV-12559 Split Item::temporal_precision() into virtual methods in Type_handler

- Adding a new virtual method Type_handler::Item_time_precision()
- Adding a new virtual method Type_handler::Item_datetime_precision()
- Removing Item::temporal_precision() and adding Item::time_precision()
  and Item::datetime_precision() instead.
- Moving Item_func_convert_tz::fix_length_and_dec() from item_timefunc.cc
  to item_timefunc.h. It's only two lines, and we're changing it anyway.
- Removing Item_temporal_typecast::fix_length_and_dec_generic(),
  moving this code to
  Type_handler::Item_{date|time|datetime}_typecast_fix_length_and_dec().
  This allows to get rid of one more field_type() call.
  Also, in the old reduction, Item_date_typecast::fix_length_and_dec()
  unnecessarily called args[0]->temporal_precision(). The new reduction
  does not call args[0]->datetime_precision(), as DATE does not
  have fractional digits.

sql/item.cc

@@ -555,27 +555,6 @@ uint Item::decimal_precision() const
 }
 
 
-uint Item::temporal_precision(enum_field_types type_arg)
-{
-  if (const_item() && result_type() == STRING_RESULT &&
-      !is_temporal_type(field_type()))
-  {
-    MYSQL_TIME ltime;
-    String buf, *tmp;
-    MYSQL_TIME_STATUS status;
-    DBUG_ASSERT(fixed);
-    if ((tmp= val_str(&buf)) &&
-        !(type_arg == MYSQL_TYPE_TIME ?
-         str_to_time(tmp->charset(), tmp->ptr(), tmp->length(),
-                     &ltime, TIME_TIME_ONLY, &status) :
-         str_to_datetime(tmp->charset(), tmp->ptr(), tmp->length(),
-                         &ltime, TIME_FUZZY_DATES, &status)))
-      return MY_MIN(status.precision, TIME_SECOND_PART_DIGITS);
-  }
-  return MY_MIN(decimals, TIME_SECOND_PART_DIGITS);
-}
-
-
 void Item::print_parenthesised(String *str, enum_query_type query_type,
                                enum precedence parent_prec)
 {

sql/item.h

@@ -1187,7 +1187,16 @@ class Item: public Value_source,
   /**
     TIME or DATETIME precision of the item: 0..6
   */
-  uint temporal_precision(enum_field_types type);
+  uint time_precision()
+  {
+    return const_item() ? type_handler()->Item_time_precision(this) :
+                          MY_MIN(decimals, TIME_SECOND_PART_DIGITS);
+  }
+  uint datetime_precision()
+  {
+    return const_item() ? type_handler()->Item_datetime_precision(this) :
+                          MY_MIN(decimals, TIME_SECOND_PART_DIGITS);
+  }
   /* 
     Returns true if this is constant (during query execution, i.e. its value
     will not change until next fix_fields) and its value is known.

sql/item_timefunc.cc

@@ -2009,13 +2009,6 @@ bool Item_func_from_unixtime::get_date(MYSQL_TIME *ltime,
 }
 
 
-void Item_func_convert_tz::fix_length_and_dec()
-{
-  fix_attributes_datetime(args[0]->temporal_precision(MYSQL_TYPE_DATETIME));
-  maybe_null= true;
-}
-
-
 bool Item_func_convert_tz::get_date(MYSQL_TIME *ltime,
                                     ulonglong fuzzy_date __attribute__((unused)))
 {
@@ -2099,8 +2092,7 @@ void Item_date_add_interval::fix_length_and_dec()
   if (arg0_field_type == MYSQL_TYPE_DATETIME ||
       arg0_field_type == MYSQL_TYPE_TIMESTAMP)
   {
-    uint dec= MY_MAX(args[0]->temporal_precision(MYSQL_TYPE_DATETIME),
-                     interval_dec);
+    uint dec= MY_MAX(args[0]->datetime_precision(), interval_dec);
     set_handler(&type_handler_datetime);
     fix_attributes_datetime(dec);
   }
@@ -2119,7 +2111,7 @@ void Item_date_add_interval::fix_length_and_dec()
   }
   else if (arg0_field_type == MYSQL_TYPE_TIME)
   {
-    uint dec= MY_MAX(args[0]->temporal_precision(MYSQL_TYPE_TIME), interval_dec);
+    uint dec= MY_MAX(args[0]->time_precision(), interval_dec);
     if (int_type >= INTERVAL_DAY && int_type != INTERVAL_YEAR_MONTH)
     {
       set_handler(&type_handler_time2);
@@ -2133,8 +2125,7 @@ void Item_date_add_interval::fix_length_and_dec()
   }
   else
   {
-    uint dec= MY_MAX(args[0]->temporal_precision(MYSQL_TYPE_DATETIME),
-                     interval_dec);
+    uint dec= MY_MAX(args[0]->datetime_precision(), interval_dec);
     set_handler(&type_handler_string);
     collation.set(default_charset(), DERIVATION_COERCIBLE, MY_REPERTOIRE_ASCII);
     fix_char_length_temporal_not_fixed_dec(MAX_DATETIME_WIDTH, dec);
@@ -2669,15 +2660,13 @@ void Item_func_add_time::fix_length_and_dec()
       arg0_field_type == MYSQL_TYPE_TIMESTAMP ||
       is_date)
   {
-    uint dec= MY_MAX(args[0]->temporal_precision(MYSQL_TYPE_DATETIME),
-                     args[1]->temporal_precision(MYSQL_TYPE_TIME));
+    uint dec= MY_MAX(args[0]->datetime_precision(), args[1]->time_precision());
     set_handler(&type_handler_datetime2);
     fix_attributes_datetime(dec);
   }
   else if (arg0_field_type == MYSQL_TYPE_TIME)
   {
-    uint dec= MY_MAX(args[0]->temporal_precision(MYSQL_TYPE_TIME),
-                     args[1]->temporal_precision(MYSQL_TYPE_TIME));
+    uint dec= MY_MAX(args[0]->time_precision(), args[1]->time_precision());
     set_handler(&type_handler_time2);
     fix_attributes_time(dec);
   }

sql/item_timefunc.h

@@ -443,16 +443,13 @@ class Item_func_dayname :public Item_func_weekday
 
 class Item_func_seconds_hybrid: public Item_func_numhybrid
 {
-protected:
-  virtual enum_field_types arg0_expected_type() const = 0;
 public:
   Item_func_seconds_hybrid(THD *thd): Item_func_numhybrid(thd) {}
   Item_func_seconds_hybrid(THD *thd, Item *a): Item_func_numhybrid(thd, a) {}
-  void fix_length_and_dec()
+  void fix_length_and_dec_generic(uint dec)
   {
-    if (arg_count)
-      decimals= args[0]->temporal_precision(arg0_expected_type());
-    set_if_smaller(decimals, TIME_SECOND_PART_DIGITS);
+    DBUG_ASSERT(dec <= TIME_SECOND_PART_DIGITS);
+    decimals= dec;
     max_length=17 + (decimals ? decimals + 1 : 0);
     maybe_null= true;
     set_handler_by_result_type(decimals ? DECIMAL_RESULT : INT_RESULT);
@@ -466,8 +463,6 @@ class Item_func_seconds_hybrid: public Item_func_numhybrid
 class Item_func_unix_timestamp :public Item_func_seconds_hybrid
 {
   bool get_timestamp_value(my_time_t *seconds, ulong *second_part);
-protected:
-  enum_field_types arg0_expected_type() const { return MYSQL_TYPE_DATETIME; }
 public:
   Item_func_unix_timestamp(THD *thd): Item_func_seconds_hybrid(thd) {}
   Item_func_unix_timestamp(THD *thd, Item *a):
@@ -491,6 +486,10 @@ class Item_func_unix_timestamp :public Item_func_seconds_hybrid
       return FALSE;
     return mark_unsupported_function(func_name(), "()", arg, VCOL_TIME_FUNC);
   }
+  void fix_length_and_dec()
+  {
+    fix_length_and_dec_generic(arg_count ? args[0]->datetime_precision() : 0);
+  }
   longlong int_op();
   my_decimal *decimal_op(my_decimal* buf);
   Item *get_copy(THD *thd, MEM_ROOT *mem_root)
@@ -500,8 +499,6 @@ class Item_func_unix_timestamp :public Item_func_seconds_hybrid
 
 class Item_func_time_to_sec :public Item_func_seconds_hybrid
 {
-protected:
-  enum_field_types arg0_expected_type() const { return MYSQL_TYPE_TIME; }
 public:
   Item_func_time_to_sec(THD *thd, Item *item):
     Item_func_seconds_hybrid(thd, item) {}
@@ -512,6 +509,10 @@ class Item_func_time_to_sec :public Item_func_seconds_hybrid
   {
     return !has_time_args();
   }
+  void fix_length_and_dec()
+  {
+    fix_length_and_dec_generic(args[0]->time_precision());
+  }
   longlong int_op();
   my_decimal *decimal_op(my_decimal* buf);
   Item *get_copy(THD *thd, MEM_ROOT *mem_root)
@@ -864,7 +865,11 @@ class Item_func_convert_tz :public Item_datetimefunc
   Item_func_convert_tz(THD *thd, Item *a, Item *b, Item *c):
     Item_datetimefunc(thd, a, b, c), from_tz_cached(0), to_tz_cached(0) {}
   const char *func_name() const { return "convert_tz"; }
-  void fix_length_and_dec();
+  void fix_length_and_dec()
+  {
+    fix_attributes_datetime(args[0]->datetime_precision());
+    maybe_null= true;
+  }
   bool get_date(MYSQL_TIME *res, ulonglong fuzzy_date);
   void cleanup();
   Item *get_copy(THD *thd, MEM_ROOT *mem_root)
@@ -1059,13 +1064,6 @@ class Item_temporal_typecast: public Item_temporal_func
   Item_temporal_typecast(THD *thd, Item *a): Item_temporal_func(thd, a) {}
   virtual const char *cast_type() const = 0;
   void print(String *str, enum_query_type query_type);
-  void fix_length_and_dec_generic(uint int_part_len)
-  {
-    if (decimals == NOT_FIXED_DEC)
-      decimals= args[0]->temporal_precision(field_type());
-    fix_attributes_temporal(int_part_len, decimals);
-    maybe_null= true;
-  }
 };
 
 class Item_date_typecast :public Item_temporal_typecast
@@ -1157,8 +1155,7 @@ class Item_func_timediff :public Item_timefunc
   const char *func_name() const { return "timediff"; }
   void fix_length_and_dec()
   {
-    uint dec= MY_MAX(args[0]->temporal_precision(MYSQL_TYPE_TIME),
-                     args[1]->temporal_precision(MYSQL_TYPE_TIME));
+    uint dec= MY_MAX(args[0]->time_precision(), args[1]->time_precision());
     fix_attributes_time(dec);
     maybe_null= true;
   }

sql/sql_type.cc

@@ -17,6 +17,7 @@
 #include "sql_type.h"
 #include "sql_const.h"
 #include "sql_class.h"
+#include "sql_time.h"
 #include "item.h"
 #include "log.h"
 
@@ -2689,7 +2690,11 @@ bool Type_handler_numeric::
 bool Type_handler::
        Item_time_typecast_fix_length_and_dec(Item_time_typecast *item) const
 {
-  item->fix_length_and_dec_generic(MIN_TIME_WIDTH);
+  uint dec= item->decimals == NOT_FIXED_DEC ?
+            item->arguments()[0]->time_precision() :
+            item->decimals;
+  item->fix_attributes_temporal(MIN_TIME_WIDTH, dec);
+  item->maybe_null= true;
   return false;
 }
 
@@ -2697,7 +2702,8 @@ bool Type_handler::
 bool Type_handler::
        Item_date_typecast_fix_length_and_dec(Item_date_typecast *item) const
 {
-  item->fix_length_and_dec_generic(MAX_DATE_WIDTH);
+  item->fix_attributes_temporal(MAX_DATE_WIDTH, 0);
+  item->maybe_null= true;
   return false;
 }
 
@@ -2706,9 +2712,12 @@ bool Type_handler::
        Item_datetime_typecast_fix_length_and_dec(Item_datetime_typecast *item)
                                                  const
 {
-  item->fix_length_and_dec_generic(MAX_DATETIME_WIDTH);
+  uint dec= item->decimals == NOT_FIXED_DEC ?
+            item->arguments()[0]->datetime_precision() :
+            item->decimals;
+  item->fix_attributes_temporal(MAX_DATETIME_WIDTH, dec);
+  item->maybe_null= true;
   return false;
-
 }
 
 
@@ -3023,3 +3032,35 @@ bool Type_handler_string_result::
 }
 
 /***************************************************************************/
+
+uint Type_handler::Item_time_precision(Item *item) const
+{
+  return MY_MIN(item->decimals, TIME_SECOND_PART_DIGITS);
+}
+
+
+uint Type_handler::Item_datetime_precision(Item *item) const
+{
+  return MY_MIN(item->decimals, TIME_SECOND_PART_DIGITS);
+}
+
+
+uint Type_handler_string_result::Item_temporal_precision(Item *item,
+                                                         bool is_time) const
+{
+  MYSQL_TIME ltime;
+  StringBuffer<64> buf;
+  String *tmp;
+  MYSQL_TIME_STATUS status;
+  DBUG_ASSERT(item->fixed);
+  if ((tmp= item->val_str(&buf)) &&
+      !(is_time ?
+        str_to_time(tmp->charset(), tmp->ptr(), tmp->length(),
+                    &ltime, TIME_TIME_ONLY, &status) :
+        str_to_datetime(tmp->charset(), tmp->ptr(), tmp->length(),
+                        &ltime, TIME_FUZZY_DATES, &status)))
+    return MY_MIN(status.precision, TIME_SECOND_PART_DIGITS);
+  return MY_MIN(item->decimals, TIME_SECOND_PART_DIGITS);
+}
+
+/***************************************************************************/

sql/sql_type.h

@@ -389,6 +389,8 @@ class Type_handler
   {
     return true;
   }
+  virtual uint Item_time_precision(Item *item) const;
+  virtual uint Item_datetime_precision(Item *item) const;
   /**
     Makes a temporary table Field to handle numeric aggregate functions,
     e.g. SUM(DISTINCT expr), AVG(DISTINCT expr), etc.
@@ -1040,6 +1042,7 @@ class Type_handler_temporal_result: public Type_handler
 
 class Type_handler_string_result: public Type_handler
 {
+  uint Item_temporal_precision(Item *item, bool is_time) const;
 public:
   Item_result result_type() const { return STRING_RESULT; }
   Item_result cmp_type() const { return STRING_RESULT; }
@@ -1055,6 +1058,14 @@ class Type_handler_string_result: public Type_handler
                   const Type_std_attributes *item,
                   SORT_FIELD_ATTR *attr) const;
   uint32 max_display_length(const Item *item) const;
+  uint Item_time_precision(Item *item) const
+  {
+    return Item_temporal_precision(item, true);
+  }
+  uint Item_datetime_precision(Item *item) const
+  {
+    return Item_temporal_precision(item, false);
+  }
   int Item_save_in_field(Item *item, Field *field, bool no_conversions) const;
   String *print_item_value(THD *thd, Item *item, String *str) const
   {