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Commit4a586bd

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Add regression test for various power expressions with a zero base, and
adjust source code to be more modular.
1 parent6b4e9d1 commit4a586bd

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3 files changed

+25
-16
lines changed

3 files changed

+25
-16
lines changed

‎src/backend/utils/adt/numeric.c‎

Lines changed: 17 additions & 16 deletions
Original file line numberDiff line numberDiff line change
@@ -14,7 +14,7 @@
1414
* Copyright (c) 1998-2008, PostgreSQL Global Development Group
1515
*
1616
* IDENTIFICATION
17-
* $PostgreSQL: pgsql/src/backend/utils/adt/numeric.c,v 1.111 2008/05/0819:25:38 momjian Exp $
17+
* $PostgreSQL: pgsql/src/backend/utils/adt/numeric.c,v 1.112 2008/05/0822:17:54 momjian Exp $
1818
*
1919
*-------------------------------------------------------------------------
2020
*/
@@ -5170,21 +5170,6 @@ power_var(NumericVar *base, NumericVar *exp, NumericVar *result)
51705170
intlocal_rscale;
51715171
doubleval;
51725172

5173-
/*
5174-
*This avoids log(0) for cases of 0 raised to a non-integer.
5175-
*Also, while 0 ^ 0 can be either 1 or indeterminate (error), we
5176-
*treat it as one because most programming languages do this.
5177-
*http://en.wikipedia.org/wiki/Exponentiation#Zero_to_the_zero_power
5178-
*/
5179-
if (cmp_var(base,&const_zero)==0)
5180-
{
5181-
if (cmp_var(exp,&const_zero)==0)
5182-
set_var_from_var(&const_one,result);
5183-
else
5184-
set_var_from_var(&const_zero,result);
5185-
return;
5186-
}
5187-
51885173
/* If exp can be represented as an integer, use power_var_int */
51895174
if (exp->ndigits==0||exp->ndigits <=exp->weight+1)
51905175
{
@@ -5217,6 +5202,17 @@ power_var(NumericVar *base, NumericVar *exp, NumericVar *result)
52175202
free_var(&x);
52185203
}
52195204

5205+
/*
5206+
*This avoids log(0) for cases of 0 raised to a non-integer.
5207+
*0 ^ 0 handled by power_var_int().
5208+
*/
5209+
if (cmp_var(base,&const_zero)==0)
5210+
{
5211+
set_var_from_var(&const_zero,result);
5212+
result->dscale=NUMERIC_MIN_SIG_DIGITS;/* no need to round */
5213+
return;
5214+
}
5215+
52205216
init_var(&ln_base);
52215217
init_var(&ln_num);
52225218

@@ -5284,6 +5280,11 @@ power_var_int(NumericVar *base, int exp, NumericVar *result, int rscale)
52845280
switch (exp)
52855281
{
52865282
case0:
5283+
/*
5284+
*While 0 ^ 0 can be either 1 or indeterminate (error), we
5285+
*treat it as 1 because most programming languages do this.
5286+
*http://en.wikipedia.org/wiki/Exponentiation#Zero_to_the_zero_power
5287+
*/
52875288
set_var_from_var(&const_one,result);
52885289
result->dscale=rscale;/* no need to round */
52895290
return;

‎src/test/regress/expected/float8.out‎

Lines changed: 6 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -349,6 +349,12 @@ SELECT '' AS bad, f.f1 * '1e200' from FLOAT8_TBL f;
349349
ERROR: value out of range: overflow
350350
SELECT '' AS bad, f.f1 ^ '1e200' from FLOAT8_TBL f;
351351
ERROR: value out of range: overflow
352+
SELECT 0 ^ 0 + 0 ^ 1 + 0 ^ 0.0 + 0 ^ 0.5;
353+
?column?
354+
----------
355+
2
356+
(1 row)
357+
352358
SELECT '' AS bad, ln(f.f1) from FLOAT8_TBL f where f.f1 = '0.0' ;
353359
ERROR: cannot take logarithm of zero
354360
SELECT '' AS bad, ln(f.f1) from FLOAT8_TBL f where f.f1 < '0.0' ;

‎src/test/regress/sql/float8.sql‎

Lines changed: 2 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -129,6 +129,8 @@ SELECT '' AS bad, f.f1 * '1e200' from FLOAT8_TBL f;
129129

130130
SELECT''AS bad,f.f1 ^'1e200'from FLOAT8_TBL f;
131131

132+
SELECT0 ^0+0 ^1+0 ^0.0+0 ^0.5;
133+
132134
SELECT''AS bad, ln(f.f1)from FLOAT8_TBL fwheref.f1='0.0' ;
133135

134136
SELECT''AS bad, ln(f.f1)from FLOAT8_TBL fwheref.f1<'0.0' ;

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