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Fix numeric_mul() overflow due to too many digits after decimal point.

author Dean Rasheed <dean.a.rasheed@gmail.com>

2021年7月10日 11:42:59 +0000 (12:42 +0100)

committer Dean Rasheed <dean.a.rasheed@gmail.com>

2021年7月10日 11:42:59 +0000 (12:42 +0100)

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 patch | blob | blame | history

src/test/regress/expected/numeric.out patch | blob | blame | history

src/test/regress/sql/numeric.sql patch | blob | blame | history

diff --git a/src/backend/utils/adt/numeric.c b/src/backend/utils/adt/numeric.c

index bc71326fc8af59bbeb2a4e774d9b173439958f16..2a0f68f98b2af6f2af2bdaa39f763ff5ad5845f9 100644 (file)

--- a/src/backend/utils/adt/numeric.c

+++ b/src/backend/utils/adt/numeric.c

@@ -233,6 +233,7 @@ struct NumericData

#define NUMERIC_DSCALE_MASK 0x3FFF

+#define NUMERIC_DSCALE_MAX NUMERIC_DSCALE_MASK

#define NUMERIC_SIGN(n) \

(NUMERIC_IS_SHORT(n) ? \

@@ -2958,7 +2959,11 @@ numeric_mul_opt_error(Numeric num1, Numeric num2, bool *have_error)

* 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);

@@ -2966,6 +2971,9 @@ numeric_mul_opt_error(Numeric num1, Numeric num2, bool *have_error)

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_opt_error(&result, have_error);

free_var(&result);

diff --git a/src/test/regress/expected/numeric.out b/src/test/regress/expected/numeric.out

index 4ad485130bda0965b17d29f656af069665edd378..385e963a75f13cf0e8d9e9f1dede6ab62cf2bcf1 100644 (file)

--- a/src/test/regress/expected/numeric.out

+++ b/src/test/regress/expected/numeric.out

@@ -2145,6 +2145,12 @@ select 4769999999999999999999999999999999999999999999999999999999999999999999999

47699999999999999999999999999999999999999999999999999999999999999999999999999999999999985230000000000000000000000000000000000000000000000000000000000000000000000000000000000001

(1 row)

+select trim_scale((0.1 - 2e-16383) * (0.1 - 3e-16383));

+ trim_scale

+------------

+ 0.01

+(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 3784c5253d7ca30a6b2b8dc01965dbc81f84fe9d..7e17c28d51e39156cc01c2464b166bee4fc7ffd3 100644 (file)

--- a/src/test/regress/sql/numeric.sql

+++ b/src/test/regress/sql/numeric.sql

@@ -1044,6 +1044,8 @@ select 4770999999999999999999999999999999999999999999999999999999999999999999999

select 4769999999999999999999999999999999999999999999999999999999999999999999999999999999999999 * 9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999;

+select trim_scale((0.1 - 2e-16383) * (0.1 - 3e-16383));

-- Test some corner cases for division

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