Add casts from int4 and int8 to numeric.

Joey Adams, per gripe from Ramanujam.  Review by myself and Tom Lane.

doc/src/sgml/datatype.sgml

@@ -886,15 +886,22 @@ ALTER SEQUENCE <replaceable class="parameter">tablename</replaceable>_<replaceab
    </para>
 
    <para>
-    Values of the <type>numeric</type> data type can be cast to
+    Values of the <type>numeric</type>, <type>int</type>, and
-    <type>money</type>.  Other numeric types can be converted to
+    <type>bigint</type> data types can be cast to <type>money</type>.
-    <type>money</type> by casting to <type>numeric</type> first, for example:
+    Conversion from the <type>real</type> and <type>double precision</type>
+    data types can be done by casting to <type>numeric</type> first, for
+    example:
 <programlisting>
-SELECT 1234::numeric::money;
+SELECT '12.34'::float8::numeric::money;
 </programlisting>
+    However, this is not recommended.  Floating point numbers should not be
+    used to handle money due to the potential for rounding errors.
+   </para>
+
+   <para>
     A <type>money</type> value can be cast to <type>numeric</type> without
     loss of precision. Conversion to other types could potentially lose
-    precision, and it must be done in two stages, for example:
+    precision, and must also be done in two stages:
 <programlisting>
 SELECT '52093.89'::money::numeric::float8;
 </programlisting>

src/backend/utils/adt/cash.c

@@ -26,6 +26,7 @@
 #include "libpq/pqformat.h"
 #include "utils/builtins.h"
 #include "utils/cash.h"
+#include "utils/int8.h"
 #include "utils/numeric.h"
 #include "utils/pg_locale.h"
 
@@ -92,7 +93,6 @@ num_word(Cash value)
 	return buf;
 }	/* num_word() */
 
-
 /* cash_in()
  * Convert a string to a cash data type.
  * Format is [$]###[,]###[.##]
@@ -938,3 +938,63 @@ numeric_cash(PG_FUNCTION_ARGS)
 
 	PG_RETURN_CASH(result);
 }
+
+/* int4_cash()
+ * Convert int4 (int) to cash
+ */
+Datum
+int4_cash(PG_FUNCTION_ARGS)
+{
+	int32	amount = PG_GETARG_INT32(0);
+	Cash	result;
+	int		fpoint;
+	int64   scale;
+	int		i;
+	struct lconv *lconvert = PGLC_localeconv();
+
+	/* see comments about frac_digits in cash_in() */
+	fpoint = lconvert->frac_digits;
+	if (fpoint < 0 || fpoint > 10)
+		fpoint = 2;
+
+	/* compute required scale factor */
+	scale = 1;
+	for (i = 0; i < fpoint; i++)
+		scale *= 10;
+
+	/* compute amount * scale, checking for overflow */
+	result = DatumGetInt64(DirectFunctionCall2(int8mul, Int64GetDatum(amount),
+						   Int64GetDatum(scale)));
+
+	PG_RETURN_CASH(result);
+}
+
+/* int8_cash()
+ * Convert int8 (bigint) to cash
+ */
+Datum
+int8_cash(PG_FUNCTION_ARGS)
+{
+	int64	amount = PG_GETARG_INT64(0);
+	Cash	result;
+	int		fpoint;
+	int64   scale;
+	int		i;
+	struct lconv *lconvert = PGLC_localeconv();
+
+	/* see comments about frac_digits in cash_in() */
+	fpoint = lconvert->frac_digits;
+	if (fpoint < 0 || fpoint > 10)
+		fpoint = 2;
+
+	/* compute required scale factor */
+	scale = 1;
+	for (i = 0; i < fpoint; i++)
+		scale *= 10;
+
+	/* compute amount * scale, checking for overflow */
+	result = DatumGetInt64(DirectFunctionCall2(int8mul, Int64GetDatum(amount),
+						   Int64GetDatum(scale)));
+
+	PG_RETURN_CASH(result);
+}

src/include/catalog/catversion.h

@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201103201
+#define CATALOG_VERSION_NO	201104051
 
 #endif

src/include/catalog/pg_cast.h

@@ -126,6 +126,8 @@ DATA(insert ( 1700	700 1745 i f ));
 DATA(insert ( 1700	701 1746 i f ));
 DATA(insert (  790 1700 3823 a f ));
 DATA(insert ( 1700	790 3824 a f ));
+DATA(insert ( 23	790 3811 a f ));
+DATA(insert ( 20	790 3812 a f ));
 
 /* Allow explicit coercions between int4 and bool */
 DATA(insert (	23	16	2557 e f ));

src/include/catalog/pg_proc.h

@@ -971,6 +971,10 @@ DATA(insert OID = 3823 (  numeric		   PGNSP PGUID 12 1 0 0 f f f t f s 1 0 1700
 DESCR("convert money to numeric");
 DATA(insert OID = 3824 (  money			   PGNSP PGUID 12 1 0 0 f f f t f s 1 0 790 "1700" _null_ _null_ _null_ _null_	numeric_cash _null_ _null_ _null_ ));
 DESCR("convert numeric to money");
+DATA(insert OID = 3811 (  money			   PGNSP PGUID 12 1 0 0 f f f t f s 1 0 790 "23" _null_ _null_ _null_ _null_	int4_cash _null_ _null_ _null_ ));
+DESCR("convert int4 to money");
+DATA(insert OID = 3812 (  money			   PGNSP PGUID 12 1 0 0 f f f t f s 1 0 790 "20" _null_ _null_ _null_ _null_	int8_cash _null_ _null_ _null_ ));
+DESCR("convert int8 to money");
 
 /* OIDS 900 - 999 */
 

src/include/utils/cash.h

@@ -67,4 +67,7 @@ extern Datum cash_words(PG_FUNCTION_ARGS);
 extern Datum cash_numeric(PG_FUNCTION_ARGS);
 extern Datum numeric_cash(PG_FUNCTION_ARGS);
 
+extern Datum int4_cash(PG_FUNCTION_ARGS);
+extern Datum int8_cash(PG_FUNCTION_ARGS);
+
 #endif   /* CASH_H */

src/test/regress/expected/money.out

@@ -185,3 +185,66 @@ SELECT * FROM money_data;
  $123.46
 (1 row)
 
+-- Cast int4/int8 to money
+SELECT 1234567890::money;
+       money       
+-------------------
+ $1,234,567,890.00
+(1 row)
+
+SELECT 12345678901234567::money;
+           money            
+----------------------------
+ $12,345,678,901,234,567.00
+(1 row)
+
+SELECT 123456789012345678::money;
+ERROR:  bigint out of range
+SELECT 9223372036854775807::money;
+ERROR:  bigint out of range
+SELECT (-12345)::money;
+    money    
+-------------
+ -$12,345.00
+(1 row)
+
+SELECT (-1234567890)::money;
+       money        
+--------------------
+ -$1,234,567,890.00
+(1 row)
+
+SELECT (-12345678901234567)::money;
+            money            
+-----------------------------
+ -$12,345,678,901,234,567.00
+(1 row)
+
+SELECT (-123456789012345678)::money;
+ERROR:  bigint out of range
+SELECT (-9223372036854775808)::money;
+ERROR:  bigint out of range
+SELECT 1234567890::int4::money;
+       money       
+-------------------
+ $1,234,567,890.00
+(1 row)
+
+SELECT 12345678901234567::int8::money;
+           money            
+----------------------------
+ $12,345,678,901,234,567.00
+(1 row)
+
+SELECT (-1234567890)::int4::money;
+       money        
+--------------------
+ -$1,234,567,890.00
+(1 row)
+
+SELECT (-12345678901234567)::int8::money;
+            money            
+-----------------------------
+ -$12,345,678,901,234,567.00
+(1 row)
+

src/test/regress/sql/money.sql

@@ -56,3 +56,18 @@ SELECT * FROM money_data;
 DELETE FROM money_data;
 INSERT INTO money_data VALUES ('$123.459');
 SELECT * FROM money_data;
+
+-- Cast int4/int8 to money
+SELECT 1234567890::money;
+SELECT 12345678901234567::money;
+SELECT 123456789012345678::money;
+SELECT 9223372036854775807::money;
+SELECT (-12345)::money;
+SELECT (-1234567890)::money;
+SELECT (-12345678901234567)::money;
+SELECT (-123456789012345678)::money;
+SELECT (-9223372036854775808)::money;
+SELECT 1234567890::int4::money;
+SELECT 12345678901234567::int8::money;
+SELECT (-1234567890)::int4::money;
+SELECT (-12345678901234567)::int8::money;