Implement modulo operator for MONEY/SMALLMONEY types

Description
-----------
Due to the missing modulo operator for MONEY/SMALLMONEY types, it will choose
the other Postgres internal alternatives like int4mod and numeric_mod, which will
involve additional implicit CASTing between MONEY/SMALLMONEY types and other types.
These CASTings could cause loss of precision and wrong results. What's more, the result
of calculation won't be MONEY/SMALLMONEY types any more.

Fix
---
Implement the modulo function and operator for MONEY/SMALLMONEY types. The reason why we don't
need to implement the functions between MONEY/SMALLMONEY types and interger types is that it
will choose the MONEY-MONEY/SMALLMONEY-SMALLMONEY functions to calculate. And the result type is
expected.

Task: BABEL-5480
Signed-off-by: Bo Li <[email protected]>

contrib/babelfishpg_common/sql/money/fixeddecimal--1.1.0_base_parallel.sql

@@ -466,6 +466,20 @@ ALTER OPERATOR FAMILY fixeddecimal_ops USING hash ADD
 CREATE DOMAIN sys.MONEY as sys.FIXEDDECIMAL CHECK (VALUE >= -922337203685477.5808 AND VALUE <= 922337203685477.5807);
 CREATE DOMAIN sys.SMALLMONEY as sys.FIXEDDECIMAL CHECK (VALUE >= -214748.3648 AND VALUE <= 214748.3647);
 
+-- Define modulo operator directly on MONEY type.
+-- Otherwise the operator between Integer and SMALLMONEY will tend to choose the fixeddecimal version,
+-- which will return the result in MONEY type.
+CREATE FUNCTION sys.fixeddecimalmod(sys.MONEY, sys.MONEY)
+RETURNS sys.MONEY
+AS 'babelfishpg_money', 'fixeddecimalmod'
+LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
+
+CREATE OPERATOR sys.% (
+    LEFTARG    = sys.MONEY,
+    RIGHTARG   = sys.MONEY,
+    PROCEDURE  = fixeddecimalmod
+);
+
 --
 -- Cross type operators with int8
 --
@@ -1645,6 +1659,11 @@ RETURNS sys.SMALLMONEY
 AS 'babelfishpg_money', 'fixeddecimaldiv'
 LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
 
+CREATE FUNCTION sys.fixeddecimalmod(sys.SMALLMONEY, sys.SMALLMONEY)
+RETURNS sys.SMALLMONEY
+AS 'babelfishpg_money', 'fixeddecimalmod'
+LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
+
 CREATE OPERATOR sys.+ (
     LEFTARG    = sys.SMALLMONEY,
     RIGHTARG   = sys.SMALLMONEY,
@@ -1676,6 +1695,12 @@ CREATE OPERATOR sys./ (
     PROCEDURE  = fixeddecimaldiv
 );
 
+CREATE OPERATOR sys.% (
+    LEFTARG    = sys.SMALLMONEY,
+    RIGHTARG   = sys.SMALLMONEY,
+    PROCEDURE  = fixeddecimalmod
+);
+
 CREATE FUNCTION sys.fixeddecimalint8pl(sys.SMALLMONEY, INT8)
 RETURNS sys.SMALLMONEY
 AS 'babelfishpg_money', 'fixeddecimalint8pl'

contrib/babelfishpg_common/sql/upgrades/babelfish_common_helper--5.0.0--5.1.0.sql

@@ -13,6 +13,31 @@ SELECT set_config('search_path', 'sys, '||current_setting('search_path'), false)
  * So make sure that any SQL statement (DDL/DML) being added here can be executed multiple times without affecting
  * final behaviour.
  */
+CREATE OR REPLACE FUNCTION sys.fixeddecimalmod(sys.MONEY, sys.MONEY)
+RETURNS sys.MONEY
+AS 'babelfishpg_money', 'fixeddecimalmod'
+LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
+
+DROP OPERATOR IF EXISTS sys.% (sys.MONEY, sys.MONEY);
+
+CREATE OPERATOR sys.% (
+    LEFTARG    = sys.MONEY,
+    RIGHTARG   = sys.MONEY,
+    PROCEDURE  = fixeddecimalmod
+);
+
+CREATE OR REPLACE FUNCTION sys.fixeddecimalmod(sys.SMALLMONEY, sys.SMALLMONEY)
+RETURNS sys.SMALLMONEY
+AS 'babelfishpg_money', 'fixeddecimalmod'
+LANGUAGE C IMMUTABLE STRICT PARALLEL SAFE;
+
+DROP OPERATOR IF EXISTS sys.% (sys.SMALLMONEY, sys.SMALLMONEY);
+
+CREATE OPERATOR sys.% (
+    LEFTARG    = sys.SMALLMONEY,
+    RIGHTARG   = sys.SMALLMONEY,
+    PROCEDURE  = fixeddecimalmod
+);
 
 -- Reset search_path to not affect any subsequent scripts
 SELECT set_config('search_path', trim(leading 'sys, ' from current_setting('search_path')), false);

contrib/babelfishpg_money/fixeddecimal.c

@@ -161,6 +161,7 @@ PG_FUNCTION_INFO_V1(fixeddecimalpl);
 PG_FUNCTION_INFO_V1(fixeddecimalmi);
 PG_FUNCTION_INFO_V1(fixeddecimalmul);
 PG_FUNCTION_INFO_V1(fixeddecimaldiv);
+PG_FUNCTION_INFO_V1(fixeddecimalmod);
 PG_FUNCTION_INFO_V1(fixeddecimalabs);
 PG_FUNCTION_INFO_V1(fixeddecimallarger);
 PG_FUNCTION_INFO_V1(fixeddecimalsmaller);
@@ -1750,6 +1751,32 @@ fixeddecimaldiv(PG_FUNCTION_ARGS)
 	PG_RETURN_INT64((int64) result);
 }
 
+Datum
+fixeddecimalmod(PG_FUNCTION_ARGS)
+{
+	int64		dividend = PG_GETARG_INT64(0);
+	int64		divisor = PG_GETARG_INT64(1);
+
+	if (divisor == 0)
+	{
+		ereport(ERROR,
+				(errcode(ERRCODE_DIVISION_BY_ZERO),
+				 errmsg("division by zero")));
+		/* ensure compiler realizes we mustn't reach the division (gcc bug) */
+		PG_RETURN_NULL();
+	}
+
+	/*
+»    * Some machines throw a floating-point exception for INT_MIN % -1, which
+»    * is a bit silly since the correct answer is perfectly well-defined,
+»    * namely zero. Refer to function int4mod in Postgres.
+»    */
+	if (divisor == -1)
+		PG_RETURN_INT64(0);
+
+	PG_RETURN_INT64(dividend % divisor);
+}
+
 /* fixeddecimalabs()
  * Absolute value
  */