postgres.git / summary / log / commit / refs
commit 54a0ec1bd6d5f46938b8da7bbcf7c3cb26b8638d
Author: Dean Rasheed <dean.a.rasheed@gmail.com>
Date: Sat Jul 10 11:50:05 2021 +0000
First released in: 15.0, 9.6.23, 10.18, 11.13, 12.8, 13.4, 14.0
Fix numeric_mul() overflow due to too many digits after decimal point.
This fixes an overflow error when using the numeric * operator if the
result has more than 16383 digits after the decimal point by rounding
the result. Overflow errors should only occur if the result has too
many digits *before* the decimal point.
Discussion: https://postgr.es/m/CAEZATCUmeFWCrq2dNzZpRj5+6LfN85jYiDoqm+ucSXhb9U2TbA@mail.gmail.com
src/backend/utils/adt/numeric.c | 10 +++++++++-
src/test/regress/expected/numeric.out | 6 ++++++
src/test/regress/sql/numeric.sql | 2 ++
3 files changed, 17 insertions(+), 1 deletion(-)
diff --git a/src/backend/utils/adt/numeric.c b/src/backend/utils/adt/numeric.c
index f51820c5186..3bc8ff0ebfe 100644
--- a/src/backend/utils/adt/numeric.c
+++ b/src/backend/utils/adt/numeric.c
@@ -202,6 +202,7 @@ struct NumericData
*/
#define NUMERIC_DSCALE_MASK 0x3FFF
+#define NUMERIC_DSCALE_MAX NUMERIC_DSCALE_MASK
#define NUMERIC_SIGN(n) \
(NUMERIC_IS_SHORT(n) ? \
@@ -2341,7 +2342,11 @@ numeric_mul(PG_FUNCTION_ARGS)
* Unlike add_var() and sub_var(), mul_var() will round its result. In the
* case of numeric_mul(), which is invoked for the * operator on numerics,
* we request exact representation for the product (rscale = sum(dscale of
- * arg1, dscale of arg2)).
+ * arg1, dscale of arg2)). If the exact result has more digits after the
+ * decimal point than can be stored in a numeric, we round it. Rounding
+ * after computing the exact result ensures that the final result is
+ * correctly rounded (rounding in mul_var() using a truncated product
+ * would not guarantee this).
*/
init_var_from_num(num1, &arg1);
init_var_from_num(num2, &arg2);
@@ -2349,6 +2354,9 @@ numeric_mul(PG_FUNCTION_ARGS)
init_var(&result);
mul_var(&arg1, &arg2, &result, arg1.dscale + arg2.dscale);
+ if (result.dscale > NUMERIC_DSCALE_MAX)
+ round_var(&result, NUMERIC_DSCALE_MAX);
+
res = make_result(&result);
free_var(&result);
diff --git a/src/test/regress/expected/numeric.out b/src/test/regress/expected/numeric.out
index b4c78a2b722..9291e6dc22d 100644
--- a/src/test/regress/expected/numeric.out
+++ b/src/test/regress/expected/numeric.out
@@ -1381,6 +1381,12 @@ select 4769999999999999999999999999999999999999999999999999999999999999999999999
47699999999999999999999999999999999999999999999999999999999999999999999999999999999999985230000000000000000000000000000000000000000000000000000000000000000000000000000000000001
(1 row)
+select (0.1 - 2e-16383) * (0.1 - 3e-16383) = 0.01 as rounds_to_point_zero_one;
+ rounds_to_point_zero_one
+--------------------------
+ t
+(1 row)
+
--
-- Test some corner cases for division
--
diff --git a/src/test/regress/sql/numeric.sql b/src/test/regress/sql/numeric.sql
index 7b3e818e928..da8bef3e764 100644
--- a/src/test/regress/sql/numeric.sql
+++ b/src/test/regress/sql/numeric.sql
@@ -841,6 +841,8 @@ select 4770999999999999999999999999999999999999999999999999999999999999999999999
select 4769999999999999999999999999999999999999999999999999999999999999999999999999999999999999 * 9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999;
+select (0.1 - 2e-16383) * (0.1 - 3e-16383) = 0.01 as rounds_to_point_zero_one;
+
--
-- Test some corner cases for division
--
[parent: 56533fce7345]