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MDEV-23118 FORMAT(d1,dec) where dec=0/38 and d1 is DECIMAL(38,38) gives incorrect results

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FORMAT() can print more integer digits (than the argument has)
if rounding happens:

  FORMAT(9.9,0) -> '10'

The old code did not take this into account.

Fix:

1. One extra digit is needed in case of rounding

- If args[1] is a not-NULL constant, then reserve space for one extra integer
  digit if the requested number of decimals is less than args[0]->decimals.

- Otherwise, reserve space for one extra integer digit if
  args[0]->decimals is not 0, because rounding can potentially happen
  (depending on the exact data in arguments).

2. One extra digit is also needed if the argument has no integer digits,
   e.g. in a data type like DECIMAL(38,38).

The conditions 1 and 2 are ORed.

3. Fixing FORMAT_MAX_DECIMALS from 30 to 38. This was forgotten in 10.2.1
   (when the limit for the number of fractional digits in DECIMAL was extended).
This commit is contained in:
Alexander Barkov
2020-08-05 08:56:12 +04:00
parent 14a5f73cda
commit 0041dacc1b
5 changed files with 82 additions and 8 deletions
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8
mysql-test/main/func_math.result
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@ -2295,7 +2295,7 @@ FORMAT(-1e308,2)
SHOW CREATE TABLE t1;
Table Create Table
t1 CREATE TABLE `t1` (
`FORMAT(-1e308,2)` varchar(416) DEFAULT NULL
`FORMAT(-1e308,2)` varchar(417) DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1
DROP TABLE t1;
CREATE OR REPLACE TABLE t1 AS SELECT FORMAT('-1e308',2);
@ -2305,7 +2305,7 @@ FORMAT('-1e308',2)
SHOW CREATE TABLE t1;
Table Create Table
t1 CREATE TABLE `t1` (
`FORMAT('-1e308',2)` varchar(416) DEFAULT NULL
`FORMAT('-1e308',2)` varchar(417) DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1
DROP TABLE t1;
CREATE OR REPLACE TABLE t1 AS SELECT FORMAT(DATE'20191231',0),FORMAT(TIME'99:05:00',0),FORMAT(TIMESTAMP'2019-12-31 23:59:59.123456',0);
@ -2317,7 +2317,7 @@ Table Create Table
t1 CREATE TABLE `t1` (
`FORMAT(DATE'20191231',0)` varchar(11) DEFAULT NULL,
`FORMAT(TIME'99:05:00',0)` varchar(10) DEFAULT NULL,
`FORMAT(TIMESTAMP'2019-12-31 23:59:59.123456',0)` varchar(19) DEFAULT NULL
`FORMAT(TIMESTAMP'2019-12-31 23:59:59.123456',0)` varchar(21) DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1
DROP TABLE t1;
CREATE OR REPLACE TABLE t1 (y YEAR);
@ -3549,7 +3549,7 @@ FORMAT(f,0)
SHOW CREATE TABLE t2;
Table Create Table
t2 CREATE TABLE `t2` (
`FORMAT(f,0)` varchar(53) DEFAULT NULL
`FORMAT(f,0)` varchar(54) DEFAULT NULL
) ENGINE=MyISAM DEFAULT CHARSET=latin1
DROP TABLE t1,t2;
#