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Bug#33143: Incorrect ORDER BY for ROUND()/TRUNCATE() result

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The ROUND(X, D) function would change the Item::decimals field during
execution to achieve the effect of a dynamic number of decimal digits.
This caused a series of bugs:
Bug #30617:Round() function not working under some circumstances in InnoDB
Bug #33402:ROUND with decimal and non-constant cannot round to 0 decimal places
Bug #30889:filesort and order by with float/numeric crashes server
Fixed by never changing the number of shown digits for DECIMAL when
used with a nonconstant number of decimal digits.


mysql-test/r/type_decimal.result:
  Bug#33143: Test result
mysql-test/t/type_decimal.test:
  Bug#33143: Test case
sql/item_func.cc:
  Bug#33143: 
  - Moved the DECIMAL_MAX_SCALE limitation to fix_length_and_dec.
  - Removed resetting of Item::decimals field.
  - set the frac field of the output value to current scale.
strings/decimal.c:
  Bug#33143: It is necessary to set all digits in the buffer following the 
  rounded one to zero, as they may now be displayed.
This commit is contained in:
unknown
2008-01-14 16:16:36 +01:00
parent 62a7e160bc
commit f9440588f5
4 changed files with 125 additions and 9 deletions
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16
strings/decimal.c
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@ -1595,9 +1595,21 @@ decimal_round(decimal_t *from, decimal_t *to, int scale,
x+=10;
*buf1=powers10[pos]*(x-y);
}
if (frac0 < 0)
/*
In case we're rounding e.g. 1.5e9 to 2.0e9, the decimal_digit_t's inside
the buffer are as follows.
Before <1, 5e8>
After <2, 5e8>
Hence we need to set the 2nd field to 0.
The same holds if we round 1.5e-9 to 2e-9.
*/
if (frac0 < frac1)
{
dec1 *end=to->buf+intg0, *buf=buf1+1;
dec1 *buf= to->buf + ((scale == 0 && intg0 == 0) ? 1 : intg0 + frac0);
dec1 *end= to->buf + len;
while (buf < end)
*buf++=0;
}