MDEV-20732 MDB now correctly estimates a length of the FORMAT() result for

doubles in scientific notation with a big integer part.

mysql-test/main/ctype_many.test

@@ -225,9 +225,11 @@ DROP TABLE t1;
 --echo # Bug#58371 Assertion failed: !s.uses_buffer_owned_by(this) with format string function
 --echo #
 
+--disable_ps_protocol
 SET NAMES latin1;
 DO CONVERT(CAST(SUBSTRING_INDEX(FORMAT(1,'1111'), FORMAT('','Zpq'),1) 
                 AS BINARY(0)) USING utf8);
+--enable_ps_protocol
 --echo #
 --echo # End of 5.1 tests
 --echo #

mysql-test/main/ctype_utf32.result

@@ -1588,7 +1588,7 @@ CREATE TABLE t1 AS SELECT format(123,2,'no_NO');
 SHOW CREATE TABLE t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
-  `format(123,2,'no_NO')` varchar(45) CHARACTER SET utf32 DEFAULT NULL
+  `format(123,2,'no_NO')` varchar(17) CHARACTER SET utf32 DEFAULT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 SELECT * FROM t1;
 format(123,2,'no_NO')

mysql-test/main/func_str.result

@@ -745,7 +745,7 @@ t1	CREATE TABLE `t1` (
   `conv(130,16,10)` varchar(64) DEFAULT NULL,
   `hex(130)` varchar(6) DEFAULT NULL,
   `char(130)` varbinary(4) DEFAULT NULL,
-  `format(130,10)` varchar(45) DEFAULT NULL,
+  `format(130,10)` varchar(25) DEFAULT NULL,
   `left(_latin2'a',1)` varchar(1) CHARACTER SET latin2 DEFAULT NULL,
   `right(_latin2'a',1)` varchar(1) CHARACTER SET latin2 DEFAULT NULL,
   `lcase(_latin2'a')` varchar(1) CHARACTER SET latin2 DEFAULT NULL,
@@ -2708,7 +2708,7 @@ create table t1(a float);
 insert into t1 values (1.33);
 select format(a, 2) from t1;
 Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
-def					format(a, 2)	253	57	4	Y	0	39	8
+def					format(a, 2)	253	4	4	Y	0	39	8
 format(a, 2)
 1.33
 drop table t1;
@@ -3042,7 +3042,7 @@ CREATE TABLE t1 AS SELECT format(123,2,'no_NO');
 SHOW CREATE TABLE t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
-  `format(123,2,'no_NO')` varchar(45) DEFAULT NULL
+  `format(123,2,'no_NO')` varchar(17) DEFAULT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 SELECT * FROM t1;
 format(123,2,'no_NO')

sql/item_strfunc.cc

@@ -2666,10 +2666,17 @@ const int FORMAT_MAX_DECIMALS= 30;
 
 bool Item_func_format::fix_length_and_dec()
 {
-  uint32 char_length= args[0]->max_char_length();
-  uint32 max_sep_count= (char_length / 3) + (decimals ? 1 : 0) + /*sign*/1;
+  uint32 char_length= args[0]->type_handler()->Item_decimal_notation_int_digits(args[0]);
+  uint dec= FORMAT_MAX_DECIMALS;
+  if (args[1]->const_item() && !args[1]->is_expensive())
+  {
+    Longlong_hybrid tmp= args[1]->to_longlong_hybrid();
+    if (!args[1]->null_value)
+      dec= tmp.to_uint(FORMAT_MAX_DECIMALS);
+  }
+  uint32 max_sep_count= (char_length / 3) + (dec ? 1 : 0) + /*sign*/1;
   collation.set(default_charset());
-  fix_char_length(char_length + max_sep_count + decimals);
+  fix_char_length(char_length + max_sep_count + dec);
   if (arg_count == 3)
     locale= args[2]->basic_const_item() ? args[2]->locale_from_val_str() : NULL;
   else

sql/sql_type.cc

@@ -3490,7 +3490,6 @@ uint32 Type_handler_temporal_result::max_display_length(const Item *item) const
   return item->max_length;
 }
 
-
 uint32 Type_handler_string_result::max_display_length(const Item *item) const
 {
   return item->max_length;
@@ -3515,6 +3514,50 @@ uint32 Type_handler_general_purpose_int::max_display_length(const Item *item)
   return type_limits_int_by_unsigned_flag(item->unsigned_flag)->char_length();
 }
 
+/*************************************************************************/
+
+uint32 
+Type_handler_decimal_result::Item_decimal_notation_int_digits(const Item *item)
+                                                              const
+{
+  return item->decimal_int_part();
+}
+
+
+uint32 
+Type_handler_temporal_result::Item_decimal_notation_int_digits(const Item *item)
+                                                               const
+{
+  return item->decimal_int_part();
+}
+
+
+uint32 
+Type_handler_bit::Item_decimal_notation_int_digits(const Item *item)
+                                                              const
+{
+  return Bit_decimal_notation_int_digits(item);
+}
+
+
+uint32
+Type_handler_general_purpose_int::Item_decimal_notation_int_digits(
+                                                   const Item *item) const
+{
+  return type_limits_int_by_unsigned_flag(item->unsigned_flag)->precision();
+}
+
+/*************************************************************************/
+
+/*
+    Decimal to binary digits ratio converges to log2(10) thus using 3 as
+    a divisor.
+*/
+uint32
+Type_handler_bit::Bit_decimal_notation_int_digits(const Item *item)
+{
+  return item->max_length/3+1;
+}
 
 /*************************************************************************/
 

sql/sql_type.h

@@ -3488,6 +3488,7 @@ class Type_handler
                           SORT_FIELD_ATTR *attr) const= 0;
 
   virtual uint32 max_display_length(const Item *item) const= 0;
+  virtual uint32 Item_decimal_notation_int_digits(const Item *item) const { return 0; }
   virtual uint32 calc_pack_length(uint32 length) const= 0;
   virtual void Item_update_null_value(Item *item) const= 0;
   virtual bool Item_save_in_value(THD *thd, Item *item, st_value *value) const= 0;
@@ -4236,6 +4237,7 @@ class Type_handler_decimal_result: public Type_handler_numeric
                   const Type_std_attributes *item,
                   SORT_FIELD_ATTR *attr) const;
   uint32 max_display_length(const Item *item) const;
+  uint32 Item_decimal_notation_int_digits(const Item *item) const;
   Item *create_typecast_item(THD *thd, Item *item,
                              const Type_cast_attributes &attr) const;
   bool Item_const_eq(const Item_const *a, const Item_const *b,
@@ -4529,6 +4531,7 @@ class Type_handler_general_purpose_int: public Type_handler_int_result
   virtual const Type_limits_int *
     type_limits_int_by_unsigned_flag(bool unsigned_flag) const= 0;
   uint32 max_display_length(const Item *item) const;
+  uint32 Item_decimal_notation_int_digits(const Item *item) const;
   bool Vers_history_point_resolve_unit(THD *thd, Vers_history_point *p) const;
 };
 
@@ -4554,6 +4557,7 @@ class Type_handler_temporal_result: public Type_handler
                                  const Type_all_attributes *attr,
                                  const st_value *value) const;
   uint32 max_display_length(const Item *item) const;
+  uint32 Item_decimal_notation_int_digits(const Item *item) const;
   bool can_change_cond_ref_to_const(Item_bool_func2 *target,
                                    Item *target_expr, Item *target_value,
                                    Item_bool_func2 *source,
@@ -4638,6 +4642,11 @@ class Type_handler_string_result: public Type_handler
                                          const Schema_specification_st *schema)
                                          const;
   uint32 max_display_length(const Item *item) const;
+/* 
+    The next method returns 309 for long stringified doubles in scientific
+    notation, e.g. FORMAT('1e308', 2).
+*/ 
+  uint32 Item_decimal_notation_int_digits(const Item *item) const { return 309; }
   bool Item_const_eq(const Item_const *a, const Item_const *b,
                      bool binary_cmp) const;
   bool Item_eq_value(THD *thd, const Type_cmp_attributes *attr,
@@ -5024,6 +5033,7 @@ class Type_handler_year: public Type_handler_int_result
     return PROTOCOL_SEND_SHORT;
   }
   uint32 max_display_length(const Item *item) const;
+  uint32 Item_decimal_notation_int_digits(const Item *item) const { return 4; };
   uint32 calc_pack_length(uint32 length) const { return 1; }
   bool Item_send(Item *item, Protocol *protocol, st_value *buf) const
   {
@@ -5073,6 +5083,8 @@ class Type_handler_bit: public Type_handler_int_result
     return PROTOCOL_SEND_STRING;
   }
   uint32 max_display_length(const Item *item) const;
+  uint32 Item_decimal_notation_int_digits(const Item *item) const;
+  static uint32 Bit_decimal_notation_int_digits(const Item *item); 
   uint32 calc_pack_length(uint32 length) const { return length / 8; }
   bool Item_send(Item *item, Protocol *protocol, st_value *buf) const
   {
@@ -5175,6 +5187,7 @@ class Type_handler_double: public Type_handler_real_result
   }
   bool type_can_have_auto_increment_attribute() const { return true; }
   uint32 max_display_length(const Item *item) const { return 53; }
+  uint32 Item_decimal_notation_int_digits(const Item *item) const { return 309; }
   uint32 calc_pack_length(uint32 length) const { return sizeof(double); }
   Item *create_typecast_item(THD *thd, Item *item,
                              const Type_cast_attributes &attr) const;