From 01e0538e8b12591283835a2ff629428262684574 Mon Sep 17 00:00:00 2001 From: Tom Lane Date: Fri, 26 Jul 2019 11:59:00 -0400 Subject: [PATCH] Fix loss of fractional digits for large values in cash_numeric(). Money values exceeding about 18 digits (depending on lc_monetary) could be inaccurately converted to numeric, due to select_div_scale() deciding it didn't need to compute any fractional digits. Force its hand by setting the dscale of one division input to equal the number of fractional digits we need. In passing, rearrange the logic to not do useless work in locales where money values are considered integral. Per bug #15925 from Slawomir Chodnicki. Back-patch to all supported branches. Discussion: https://postgr.es/m/15925-da9953e2674bb5c8@postgresql.org --- src/backend/utils/adt/cash.c | 56 +++++++++++++++++++---------- src/test/regress/expected/money.out | 16 ++++++++- src/test/regress/sql/money.sql | 6 +++- 3 files changed, 57 insertions(+), 21 deletions(-) diff --git a/src/backend/utils/adt/cash.c b/src/backend/utils/adt/cash.c index c92e9d5046..6515fc8ec6 100644 --- a/src/backend/utils/adt/cash.c +++ b/src/backend/utils/adt/cash.c @@ -1032,13 +1032,8 @@ Datum cash_numeric(PG_FUNCTION_ARGS) { Cash money = PG_GETARG_CASH(0); - Numeric result; + Datum result; int fpoint; - int64 scale; - int i; - Datum amount; - Datum numeric_scale; - Datum quotient; struct lconv *lconvert = PGLC_localeconv(); /* see comments about frac_digits in cash_in() */ @@ -1046,22 +1041,45 @@ cash_numeric(PG_FUNCTION_ARGS) if (fpoint < 0 || fpoint > 10) fpoint = 2; - /* compute required scale factor */ - scale = 1; - for (i = 0; i < fpoint; i++) - scale *= 10; + /* convert the integral money value to numeric */ + result = DirectFunctionCall1(int8_numeric, Int64GetDatum(money)); - /* form the result as money / scale */ - amount = DirectFunctionCall1(int8_numeric, Int64GetDatum(money)); - numeric_scale = DirectFunctionCall1(int8_numeric, Int64GetDatum(scale)); - quotient = DirectFunctionCall2(numeric_div, amount, numeric_scale); + /* scale appropriately, if needed */ + if (fpoint > 0) + { + int64 scale; + int i; + Datum numeric_scale; + Datum quotient; - /* forcibly round to exactly the intended number of digits */ - result = DatumGetNumeric(DirectFunctionCall2(numeric_round, - quotient, - Int32GetDatum(fpoint))); + /* compute required scale factor */ + scale = 1; + for (i = 0; i < fpoint; i++) + scale *= 10; + numeric_scale = DirectFunctionCall1(int8_numeric, + Int64GetDatum(scale)); - PG_RETURN_NUMERIC(result); + /* + * Given integral inputs approaching INT64_MAX, select_div_scale() + * might choose a result scale of zero, causing loss of fractional + * digits in the quotient. We can ensure an exact result by setting + * the dscale of either input to be at least as large as the desired + * result scale. numeric_round() will do that for us. + */ + numeric_scale = DirectFunctionCall2(numeric_round, + numeric_scale, + Int32GetDatum(fpoint)); + + /* Now we can safely divide ... */ + quotient = DirectFunctionCall2(numeric_div, result, numeric_scale); + + /* ... and forcibly round to exactly the intended number of digits */ + result = DirectFunctionCall2(numeric_round, + quotient, + Int32GetDatum(fpoint)); + } + + PG_RETURN_DATUM(result); } /* numeric_cash() diff --git a/src/test/regress/expected/money.out b/src/test/regress/expected/money.out index ab86595fc0..fc71a72fed 100644 --- a/src/test/regress/expected/money.out +++ b/src/test/regress/expected/money.out @@ -1,6 +1,8 @@ -- -- MONEY -- +-- Note that we assume lc_monetary has been set to C. +-- CREATE TABLE money_data (m money); INSERT INTO money_data VALUES ('123'); SELECT * FROM money_data; @@ -476,7 +478,7 @@ SELECT (-12345678901234567)::numeric::money; -$12,345,678,901,234,567.00 (1 row) --- Cast from money +-- Cast from money to numeric SELECT '12345678901234567'::money::numeric; numeric ---------------------- @@ -489,3 +491,15 @@ SELECT '-12345678901234567'::money::numeric; -12345678901234567.00 (1 row) +SELECT '92233720368547758.07'::money::numeric; + numeric +---------------------- + 92233720368547758.07 +(1 row) + +SELECT '-92233720368547758.08'::money::numeric; + numeric +----------------------- + -92233720368547758.08 +(1 row) + diff --git a/src/test/regress/sql/money.sql b/src/test/regress/sql/money.sql index 37b9ecce1f..5e746286c9 100644 --- a/src/test/regress/sql/money.sql +++ b/src/test/regress/sql/money.sql @@ -1,6 +1,8 @@ -- -- MONEY -- +-- Note that we assume lc_monetary has been set to C. +-- CREATE TABLE money_data (m money); @@ -122,6 +124,8 @@ SELECT (-1234567890)::int4::money; SELECT (-12345678901234567)::int8::money; SELECT (-12345678901234567)::numeric::money; --- Cast from money +-- Cast from money to numeric SELECT '12345678901234567'::money::numeric; SELECT '-12345678901234567'::money::numeric; +SELECT '92233720368547758.07'::money::numeric; +SELECT '-92233720368547758.08'::money::numeric;