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

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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.
This commit is contained in:
Tom Lane
2008-04-04 18:45:36 +00:00
parent b6f0ad4b0e
commit a0fad9762a
7 changed files with 470 additions and 32 deletions
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3
src/include/utils/builtins.h
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@ -7,7 +7,7 @@
* Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
* Portions Copyright (c) 1994, Regents of the University of California
*
* $PostgreSQL: pgsql/src/include/utils/builtins.h,v 1.311 2008/04/04 16:57:21 momjian Exp $
* $PostgreSQL: pgsql/src/include/utils/builtins.h,v 1.312 2008/04/04 18:45:36 tgl Exp $
*
*-------------------------------------------------------------------------
*/
@ -845,6 +845,7 @@ extern Datum numeric_add(PG_FUNCTION_ARGS);
extern Datum numeric_sub(PG_FUNCTION_ARGS);
extern Datum numeric_mul(PG_FUNCTION_ARGS);
extern Datum numeric_div(PG_FUNCTION_ARGS);
extern Datum numeric_div_trunc(PG_FUNCTION_ARGS);
extern Datum numeric_mod(PG_FUNCTION_ARGS);
extern Datum numeric_inc(PG_FUNCTION_ARGS);
extern Datum numeric_smaller(PG_FUNCTION_ARGS);