Re-implement division for numeric values using the traditional "schoolbook"

algorithm.  This is a good deal slower than our old roundoff-error-prone
code for long inputs, so we keep the old code for use in the transcendental
functions, where everything is approximate anyway.  Also create a
user-accessible function div(numeric, numeric) to provide access to the
exact result of trunc(x/y) --- since the regular numeric / operator will
round off its result, simply computing that expression in SQL doesn't
reliably give the desired answer.  This fixes bug #3387 and various related
corner cases, and improves the usefulness of PG for high-precision integer
arithmetic.

1 files changed, 18 insertions, 0 deletions

diff --git a/src/test/regress/sql/numeric.sql b/src/test/regress/sql/numeric.sql
index dc1452f9ef0..9fd6bba31ee 100644
--- a/src/test/regress/sql/numeric.sql
+++ b/src/test/regress/sql/numeric.sql
@@ -805,3 +805,21 @@ INSERT INTO num_input_test(n1) VALUES ('');
 INSERT INTO num_input_test(n1) VALUES (' N aN ');
 
 SELECT * FROM num_input_test;
+
+--
+-- Test some corner cases for division
+--
+
+select 999999999999999999999::numeric/1000000000000000000000;
+select div(999999999999999999999::numeric,1000000000000000000000);
+select mod(999999999999999999999::numeric,1000000000000000000000);
+select div(-9999999999999999999999::numeric,1000000000000000000000);
+select mod(-9999999999999999999999::numeric,1000000000000000000000);
+select div(-9999999999999999999999::numeric,1000000000000000000000)*1000000000000000000000 + mod(-9999999999999999999999::numeric,1000000000000000000000);
+select mod (70.0,70) ;
+select div (70.0,70) ;
+select 70.0 / 70 ;
+select 12345678901234567890 % 123;
+select 12345678901234567890 / 123;
+select div(12345678901234567890, 123);
+select div(12345678901234567890, 123) * 123 + 12345678901234567890 % 123;