MDEV-10138 Support for decimals up to 38 digits

Decimals with float, double and decimal now works the following way:

- DECIMAL_NOT_SPECIFIED is used when declaring DECIMALS without a firm number
  of decimals.  It's only used in asserts and my_decimal_int_part.
- FLOATING_POINT_DECIMALS (31) is used to mark that a FLOAT or DOUBLE
  was defined without decimals. This is regarded as a floating point value.
- Max decimals allowed for FLOAT and DOUBLE is FLOATING_POINT_DECIMALS-1
- Clients assumes that float and double with decimals >= NOT_FIXED_DEC are
  floating point values (no decimals)
- In the .frm decimals=FLOATING_POINT_DECIMALS are used to define
  floating point for float and double (31, like before)

To ensure compatibility with old clients we do:

- When storing float and double, we change NOT_FIXED_DEC to
  FLOATING_POINT_DECIMALS.
- When creating fields from .frm we change for float and double
  FLOATING_POINT_DEC to NOT_FIXED_DEC
- When sending definition for a float/decimal field without decimals
  to the client as part of a result set we convert NOT_FIXED_DEC to
  FLOATING_POINT_DECIMALS.
- variance() and std() has changed to limit the decimals to
  FLOATING_POINT_DECIMALS -1 to not get the double converted floating point.
  (This was to preserve compatiblity)
- FLOAT and DOUBLE still have 30 as max number of decimals.

Bugs fixed:

variance() printed more decimals than we support for double values.

New behaviour:
- Strings now have 38 decimals instead of 30 when converted to decimal
- CREATE ... SELECT with a decimal with > 30 decimals will create a column
  with a smaller range than before as we are trying to preserve the number of
  decimals.


Other changes
- We are now using the obsolete bit FIELDFLAG_LEFT_FULLSCREEN to specify
  decimals > 31
- NOT_FIXED_DEC is now declared in one place
- For clients, NOT_FIXED_DEC is always 31 (to ensure compatibility).
  On the server NOT_FIXED_DEC is DECIMAL_NOT_SPECIFIED (39)
- AUTO_SEC_PART_DIGITS is taken from DECIMAL_NOT_SPECIFIED
- DOUBLE conversion functions are now using DECIMAL_NOT_SPECIFIED instead of
  NOT_FIXED_DEC

include/m_string.h

@@ -23,6 +23,7 @@
 #define _m_string_h
 
 #include "my_global.h"                          /* HAVE_* */
+#include "my_decimal_limits.h"
 
 #ifndef __USE_GNU
 #define __USE_GNU				/* We want to use stpcpy */
@@ -138,14 +139,13 @@ size_t my_fcvt(double x, int precision, char *to, my_bool *error);
 size_t my_gcvt(double x, my_gcvt_arg_type type, int width, char *to,
                my_bool *error);
 
-#define NOT_FIXED_DEC 31
-
 /*
   The longest string my_fcvt can return is 311 + "precision" bytes.
-  Here we assume that we never cal my_fcvt() with precision >= NOT_FIXED_DEC
+  Here we assume that we never cal my_fcvt() with
+  precision >= DECIMAL_NOT_SPECIFIED
   (+ 1 byte for the terminating '\0').
 */
-#define FLOATING_POINT_BUFFER (311 + NOT_FIXED_DEC)
+#define FLOATING_POINT_BUFFER (311 + DECIMAL_NOT_SPECIFIED)
 
 /*
   We want to use the 'e' format in some cases even if we have enough space

include/my_decimal_limits.h

@@ -31,10 +31,16 @@
   digits * number of decimal digits in one our big digit - number of decimal
   digits in one our big digit decreased by 1 (because we always put decimal
   point on the border of our big digits))
+
+  With normal precession we can handle 65 digits. MariaDB can store in
+  the .frm up to 63 digits.  By default we use DECIMAL_NOT_SPECIFIED digits
+  when converting strings to decimal, so we don't want to set this too high.
+  To not use up all digits for the scale we limit the number of decimals to
+  38.
 */
 #define DECIMAL_MAX_PRECISION (DECIMAL_MAX_POSSIBLE_PRECISION - 8*2)
-#define DECIMAL_MAX_SCALE 30
-#define DECIMAL_NOT_SPECIFIED 31
+#define DECIMAL_MAX_SCALE 38
+#define DECIMAL_NOT_SPECIFIED 39
 
 /**
   maximum length of string representation (number of maximum decimal

include/my_time.h

@@ -23,6 +23,7 @@
 #define _my_time_h_
 #include "my_global.h"
 #include "mysql_time.h"
+#include "my_decimal_limits.h"
 
 C_MODE_START
 
@@ -184,7 +185,7 @@ void set_zero_time(MYSQL_TIME *tm, enum enum_mysql_timestamp_type time_type);
   sent using binary protocol fit in this buffer.
 */
 #define MAX_DATE_STRING_REP_LENGTH 30
-#define AUTO_SEC_PART_DIGITS 31 /* same as NOT_FIXED_DEC */
+#define AUTO_SEC_PART_DIGITS DECIMAL_NOT_SPECIFIED
 
 int my_time_to_str(const MYSQL_TIME *l_time, char *to, uint digits);
 int my_date_to_str(const MYSQL_TIME *l_time, char *to);

include/mysql_com.h

@@ -21,6 +21,8 @@
 #ifndef _mysql_com_h
 #define _mysql_com_h
 
+#include "my_decimal_limits.h"
+
 #define HOSTNAME_LENGTH 60
 #define SYSTEM_CHARSET_MBMAXLEN 3
 #define NAME_CHAR_LEN	64              /* Field/table name length */
@@ -648,5 +650,18 @@ uchar *safe_net_store_length(uchar *pkg, size_t pkg_len, ulonglong length);
 #define MYSQL_STMT_HEADER       4
 #define MYSQL_LONG_DATA_HEADER  6
 
-#define NOT_FIXED_DEC           31
+/*
+  If a float or double field have more than this number of decimals,
+  it's regarded as floating point field without any specific number of
+  decimals
+*/
+
+#define FLOATING_POINT_DECIMALS 31
+
+/* Keep client compatible with earlier versions */
+#ifdef MYSQL_SERVER
+#define NOT_FIXED_DEC           DECIMAL_NOT_SPECIFIED
+#else
+#define NOT_FIXED_DEC           FLOATING_POINT_DECIMALS
+#endif
 #endif

libmysql/libmysql.c

@@ -3479,7 +3479,7 @@ static void fetch_float_with_conversion(MYSQL_BIND *param, MYSQL_FIELD *field,
     */
     char buff[FLOATING_POINT_BUFFER];
     size_t len;
-    if (field->decimals >= NOT_FIXED_DEC)
+    if (field->decimals >= FLOATING_POINT_DECIMALS)
       len= my_gcvt(value, type,
                    (int) MY_MIN(sizeof(buff)-1, param->buffer_length),
                    buff, NULL);

libmysqld/lib_sql.cc

@@ -1067,6 +1067,10 @@ bool Protocol::send_result_set_metadata(List<Item> *list, uint flags)
     client_field->type=   server_field.type;
     client_field->flags= (uint16) server_field.flags;
     client_field->decimals= server_field.decimals;
+    if (server_field.type == MYSQL_TYPE_FLOAT ||
+        server_field.type == MYSQL_TYPE_DOUBLE)
+      set_if_smaller(client_field->decimals, FLOATING_POINT_DECIMALS);
+
     client_field->db_length=		strlen(client_field->db);
     client_field->table_length=		strlen(client_field->table);
     client_field->name_length=		strlen(client_field->name);

mysql-test/r/bug12427262.result

@@ -33,7 +33,7 @@ like "%show_table_lw_db%" AND FILE_NAME like "%.frm%" AND EVENT_NAME='wait/io/fi
 into @count_read_after;
 select @count_read_after-@count_read_before;
 @count_read_after-@count_read_before
-0.000000000000000000000000000000
+0.00000000000000000000000000000000000000
 show full tables;
 Tables_in_show_table_lw_db	Table_type
 t1	BASE TABLE
@@ -51,6 +51,6 @@ like "%show_table_lw_db%" AND FILE_NAME like "%.frm%" AND EVENT_NAME='wait/io/fi
 into @count_read_after;
 select @count_read_after-@count_read_before;
 @count_read_after-@count_read_before
-10.000000000000000000000000000000
+10.00000000000000000000000000000000000000
 drop table t1;
 drop database show_table_lw_db;

mysql-test/r/cast.result

@@ -390,9 +390,9 @@ ERROR 42000: Too big precision 66 specified for '1'. Maximum is 65.
 select cast(1 as decimal(66,6));
 ERROR 42000: Too big precision 66 specified for '1'. Maximum is 65.
 select cast(1 as decimal(64,63));
-ERROR 42000: Too big scale 63 specified for '1'. Maximum is 30.
+ERROR 42000: Too big scale 63 specified for '1'. Maximum is 38.
 select cast(1 as double(64,63));
-ERROR 42000: Too big scale 63 specified for '1'. Maximum is 30.
+ERROR 42000: Too big scale 63 specified for '1'. Maximum is 38.
 set names binary;
 select cast(_latin1'test' as char character set latin2);
 cast(_latin1'test' as char character set latin2)

mysql-test/r/ctype_binary.result

@@ -914,7 +914,7 @@ show create table t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
   `c1` varbinary(83) DEFAULT NULL,
-  `c2` decimal(65,30) DEFAULT NULL
+  `c2` decimal(65,38) DEFAULT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 drop table t1;
 select hex(concat(@@ft_max_word_len));
@@ -2621,7 +2621,7 @@ GROUP_CONCAT(CASE WHEN a THEN a ELSE '' END)
 1234567
 SELECT COALESCE(a,'') FROM t1 GROUP BY 1;
 Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
-def					COALESCE(a,'')	253	9	7	Y	128	31	63
+def					COALESCE(a,'')	253	9	7	Y	128	39	63
 COALESCE(a,'')
 1234567
 # All columns must be VARCHAR(9) with the same length:

mysql-test/r/ctype_cp1251.result

@@ -1323,7 +1323,7 @@ show create table t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
   `c1` varchar(83) CHARACTER SET cp1251 DEFAULT NULL,
-  `c2` decimal(65,30) DEFAULT NULL
+  `c2` decimal(65,38) DEFAULT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 drop table t1;
 select hex(concat(@@ft_max_word_len));
@@ -3030,7 +3030,7 @@ GROUP_CONCAT(CASE WHEN a THEN a ELSE '' END)
 1234567
 SELECT COALESCE(a,'') FROM t1 GROUP BY 1;
 Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
-def					COALESCE(a,'')	253	9	7	Y	0	31	51
+def					COALESCE(a,'')	253	9	7	Y	0	39	51
 COALESCE(a,'')
 1234567
 # All columns must be VARCHAR(9) with the same length:

mysql-test/r/ctype_latin1.result

@@ -1620,7 +1620,7 @@ show create table t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
   `c1` varchar(83) DEFAULT NULL,
-  `c2` decimal(65,30) DEFAULT NULL
+  `c2` decimal(65,38) DEFAULT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 drop table t1;
 select hex(concat(@@ft_max_word_len));
@@ -3327,7 +3327,7 @@ GROUP_CONCAT(CASE WHEN a THEN a ELSE '' END)
 1234567
 SELECT COALESCE(a,'') FROM t1 GROUP BY 1;
 Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
-def					COALESCE(a,'')	253	9	7	Y	0	31	8
+def					COALESCE(a,'')	253	9	7	Y	0	39	8
 COALESCE(a,'')
 1234567
 # All columns must be VARCHAR(9) with the same length:

mysql-test/r/ctype_ucs.result

@@ -2523,7 +2523,7 @@ show create table t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
   `c1` varchar(83) CHARACTER SET ucs2 DEFAULT NULL,
-  `c2` decimal(65,30) DEFAULT NULL
+  `c2` decimal(65,38) DEFAULT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 drop table t1;
 select hex(concat(@@ft_max_word_len));
@@ -4230,7 +4230,7 @@ GROUP_CONCAT(CASE WHEN a THEN a ELSE '' END)
 1234567
 SELECT COALESCE(a,'') FROM t1 GROUP BY 1;
 Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
-def					COALESCE(a,'')	253	9	7	Y	0	31	8
+def					COALESCE(a,'')	253	9	7	Y	0	39	8
 COALESCE(a,'')
 1234567
 # All columns must be VARCHAR(9) with the same length:

mysql-test/r/ctype_utf32.result

@@ -1575,7 +1575,7 @@ 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(37) CHARACTER SET utf32 NOT NULL
+  `format(123,2,'no_NO')` varchar(45) CHARACTER SET utf32 NOT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 SELECT * FROM t1;
 format(123,2,'no_NO')

mysql-test/r/ctype_utf8.result

@@ -3365,7 +3365,7 @@ show create table t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
   `c1` varchar(83) CHARACTER SET utf8 DEFAULT NULL,
-  `c2` decimal(65,30) DEFAULT NULL
+  `c2` decimal(65,38) DEFAULT NULL
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 drop table t1;
 select hex(concat(@@ft_max_word_len));
@@ -5072,7 +5072,7 @@ GROUP_CONCAT(CASE WHEN a THEN a ELSE '' END)
 1234567
 SELECT COALESCE(a,'') FROM t1 GROUP BY 1;
 Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
-def					COALESCE(a,'')	253	27	7	Y	0	31	33
+def					COALESCE(a,'')	253	27	7	Y	0	39	33
 COALESCE(a,'')
 1234567
 # All columns must be VARCHAR(9) with the same length:

mysql-test/r/dyncol.result

@@ -1458,8 +1458,8 @@ Note	1105	Cast to signed converted positive out-of-range integer to it's negativ
 # MDEV-7505 - Too large scale in DECIMAL dynamic column getter crashes
 #             mysqld
 #
-SELECT COLUMN_GET(`x`, 'y' AS DECIMAL(5,34));
-ERROR 42000: Too big scale 34 specified for ''y''. Maximum is 30.
+SELECT COLUMN_GET(`x`, 'y' AS DECIMAL(5,50));
+ERROR 42000: Too big scale 50 specified for ''y''. Maximum is 38.
 #
 # test of symbolic names
 #

mysql-test/r/func_digest.result

@@ -1411,18 +1411,18 @@ LENGTH(SHA2( 'computed', 512 )) / 2 * 8   = 512
 SET NAMES binary;
 SELECT sha2('1',224);
 Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
-def					sha2('1',224)	253	56	56	Y	128	31	63
+def					sha2('1',224)	253	56	56	Y	128	39	63
 sha2('1',224)
 e25388fde8290dc286a6164fa2d97e551b53498dcbf7bc378eb1f178
 SET NAMES utf8;
 SELECT sha2('1',224);
 Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
-def					sha2('1',224)	253	168	56	Y	0	31	33
+def					sha2('1',224)	253	168	56	Y	0	39	33
 sha2('1',224)
 e25388fde8290dc286a6164fa2d97e551b53498dcbf7bc378eb1f178
 SET NAMES latin1;
 SELECT sha2('1',224);
 Catalog	Database	Table	Table_alias	Column	Column_alias	Type	Length	Max length	Is_null	Flags	Decimals	Charsetnr
-def					sha2('1',224)	253	56	56	Y	0	31	8
+def					sha2('1',224)	253	56	56	Y	0	39	8
 sha2('1',224)
 e25388fde8290dc286a6164fa2d97e551b53498dcbf7bc378eb1f178