From 06883d58ff29cf4fb8c32fd13ce9947796b9fb0f Mon Sep 17 00:00:00 2001 From: Dean Rasheed <dean.a.rasheed@gmail.com> Date: Sat, 10 Jul 2021 12:45:00 +0100 Subject: [PATCH] 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 eb78f0b9c2..d74001c311 100644 --- 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) ? \ @@ -2955,7 +2956,11 @@ 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); @@ -2963,6 +2968,9 @@ 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 30a5642b95..e0bc6d9116 100644 --- 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 db812c813a..2e7507639a 100644 --- 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 -- -- 2.24.1