From: Dean Rasheed <dean.a.rasheed@gmail.com>
To: pgsql-committers@lists.postgresql.org
Subject: pgsql: Fix division-by-zero error in to_char() with 'EEEE' format.
Date: Thu, 05 Aug 2021 08:40:56 +0000
Message-ID: <E1mBYvw-0003St-0L@gemulon.postgresql.org> (raw)
Fix division-by-zero error in to_char() with 'EEEE' format.
This fixes a long-standing bug when using to_char() to format a
numeric value in scientific notation -- if the value's exponent is
less than -NUMERIC_MAX_DISPLAY_SCALE-1 (-1001), it produced a
division-by-zero error.
The reason for this error was that get_str_from_var_sci() divides its
input by 10^exp, which it produced using power_var_int(). However, the
underflow test in power_var_int() causes it to return zero if the
result scale is too small. That's not a problem for power_var_int()'s
only other caller, power_var(), since that limits the rscale to 1000,
but in get_str_from_var_sci() the exponent can be much smaller,
requiring a much larger rscale. Fix by introducing a new function to
compute 10^exp directly, with no rscale limit. This also allows 10^exp
to be computed more efficiently, without any numeric multiplication,
division or rounding.
Discussion: https://postgr.es/m/CAEZATCWhojfH4whaqgUKBe8D5jNHB8ytzemL-PnRx+KCTyMXmg@mail.gmail.com
Branch
------
REL9_6_STABLE
Details
-------
https://git.postgresql.org/pg/commitdiff/ed3e1663c031e82def8c50ef31ee704777059459
Modified Files
--------------
src/backend/utils/adt/numeric.c | 66 ++++++++++++++++++++---------------
src/test/regress/expected/numeric.out | 33 ++++++++++++++++++
src/test/regress/sql/numeric.sql | 8 +++++
3 files changed, 78 insertions(+), 29 deletions(-)
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To: pgsql-committers@postgresql.org
Cc: dean.a.rasheed@gmail.com, pgsql-committers@lists.postgresql.org
Subject: Re: pgsql: Fix division-by-zero error in to_char() with 'EEEE' format.
In-Reply-To: <E1mBYvw-0003St-0L@gemulon.postgresql.org>
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