v4-gamma-and-lgamma.patch

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
new file mode 100644
index 461fc3f..b2a3368
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -1399,6 +1399,27 @@ SELECT NOT(ROW(table.*) IS NOT NULL) FRO
       <row>
        <entry role="func_table_entry"><para role="func_signature">
         <indexterm>
+         <primary>gamma</primary>
+        </indexterm>
+        <function>gamma</function> ( <type>double precision</type> )
+        <returnvalue>double precision</returnvalue>
+       </para>
+       <para>
+        Gamma function
+       </para>
+       <para>
+        <literal>gamma(0.5)</literal>
+        <returnvalue>1.772453850905516</returnvalue>
+       </para>
+       <para>
+        <literal>gamma(6)</literal>
+        <returnvalue>120</returnvalue>
+       </para></entry>
+      </row>
+
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
          <primary>gcd</primary>
         </indexterm>
         <function>gcd</function> ( <replaceable>numeric_type</replaceable>, <replaceable>numeric_type</replaceable> )
@@ -1436,6 +1457,23 @@ SELECT NOT(ROW(table.*) IS NOT NULL) FRO
        </para></entry>
       </row>
 
+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>lgamma</primary>
+        </indexterm>
+        <function>lgamma</function> ( <type>double precision</type> )
+        <returnvalue>double precision</returnvalue>
+       </para>
+       <para>
+        Natural logarithm of the absolute value of the gamma function
+       </para>
+       <para>
+        <literal>lgamma(1000)</literal>
+        <returnvalue>5905.220423209181</returnvalue>
+       </para></entry>
+      </row>
+
       <row>
        <entry role="func_table_entry"><para role="func_signature">
         <indexterm>
diff --git a/src/backend/utils/adt/float.c b/src/backend/utils/adt/float.c
new file mode 100644
index f709c21..6e3252e
--- a/src/backend/utils/adt/float.c
+++ b/src/backend/utils/adt/float.c
@@ -2787,6 +2787,80 @@ derfc(PG_FUNCTION_ARGS)
 }
 
 
+/* ========== GAMMA FUNCTIONS ========== */
+
+
+/*
+ *		dgamma			- returns the gamma function of arg1
+ */
+Datum
+dgamma(PG_FUNCTION_ARGS)
+{
+	float8		arg1 = PG_GETARG_FLOAT8(0);
+	float8		result;
+
+	/* note: the POSIX/C99 gamma function is called "tgamma", not "gamma" */
+	errno = 0;
+	result = tgamma(arg1);
+
+	/*
+	 * If an ERANGE error occurs, it means there is an overflow. This may also
+	 * happen if the input is +/-0, which is not a genuine overflow, and the
+	 * result should be +/-infinity.
+	 *
+	 * On some platforms, tgamma() will not set errno but just return infinity
+	 * or zero to report overflow/underflow; therefore, test both cases (note
+	 * that, like the exponential function, the gamma function has no zeros).
+	 */
+	if (errno == ERANGE && arg1 != 0)
+	{
+		if (result != 0.0)
+			float_overflow_error();
+		else
+			float_underflow_error();
+	}
+	else if (isinf(result) && arg1 != 0 && !isinf(arg1))
+		float_overflow_error();
+	else if (result == 0.0)
+		float_underflow_error();
+
+	PG_RETURN_FLOAT8(result);
+}
+
+
+/*
+ *		dlgamma			- natural logarithm of absolute value of gamma of arg1
+ */
+Datum
+dlgamma(PG_FUNCTION_ARGS)
+{
+	float8		arg1 = PG_GETARG_FLOAT8(0);
+	float8		result;
+
+	/*
+	 * Note: lgamma may not be thread-safe because it may write to a global
+	 * variable signgam, which may not be thread-local. However, this doesn't
+	 * matter to us, since we don't use signgam.
+	 */
+	errno = 0;
+	result = lgamma(arg1);
+
+	/*
+	 * If an ERANGE error occurs, it means there is an overflow. This also
+	 * happens if the input is zero or a negative integer, which are not
+	 * genuine overflows, and the result should be infinity.
+	 *
+	 * On some platforms, lgamma() will not set errno but just return infinity
+	 * to report overflow, but it should never underflow.
+	 */
+	if ((errno == ERANGE || isinf(result)) && !isinf(arg1) &&
+		!(arg1 <= 0 && floor(arg1) == arg1))
+		float_overflow_error();
+
+	PG_RETURN_FLOAT8(result);
+}
+
+
 
 /*
  *		=========================
diff --git a/src/include/catalog/pg_proc.dat b/src/include/catalog/pg_proc.dat
new file mode 100644
index ff5436a..cee8398
--- a/src/include/catalog/pg_proc.dat
+++ b/src/include/catalog/pg_proc.dat
@@ -3490,6 +3490,13 @@
   proname => 'erfc', prorettype => 'float8', proargtypes => 'float8',
   prosrc => 'derfc' },
 
+{ oid => '8702', descr => 'gamma function',
+  proname => 'gamma', prorettype => 'float8', proargtypes => 'float8',
+  prosrc => 'dgamma' },
+{ oid => '8703', descr => 'natural logarithm of absolute value of gamma function',
+  proname => 'lgamma', prorettype => 'float8', proargtypes => 'float8',
+  prosrc => 'dlgamma' },
+
 { oid => '1618',
   proname => 'interval_mul', prorettype => 'interval',
   proargtypes => 'interval float8', prosrc => 'interval_mul' },
diff --git a/src/test/regress/expected/float8.out b/src/test/regress/expected/float8.out
new file mode 100644
index 344d6b7..5c91ef1
--- a/src/test/regress/expected/float8.out
+++ b/src/test/regress/expected/float8.out
@@ -830,6 +830,128 @@ FROM (VALUES (float8 '-infinity'),
 (22 rows)
 
 RESET extra_float_digits;
+-- gamma functions
+-- we run these with extra_float_digits = -1, to get consistently rounded
+-- results on all platforms.
+SET extra_float_digits = -1;
+SELECT x,
+       gamma(x),
+       lgamma(x)
+FROM (VALUES (0.5), (1), (2), (3), (4), (5)) AS t(x);
+  x  |      gamma      |      lgamma      
+-----+-----------------+------------------
+ 0.5 | 1.7724538509055 |  0.5723649429247
+   1 |               1 |                0
+   2 |               1 |                0
+   3 |               2 | 0.69314718055995
+   4 |               6 |  1.7917594692281
+   5 |              24 |  3.1780538303479
+(6 rows)
+
+-- test special cases for gamma functions
+SELECT gamma(float8 '-infinity');
+ gamma 
+-------
+   NaN
+(1 row)
+
+SELECT lgamma(float8 '-infinity');
+  lgamma  
+----------
+ Infinity
+(1 row)
+
+SELECT gamma(float8 '-1000000.5');
+ERROR:  value out of range: underflow
+SELECT lgamma(float8 '-1000000.5');
+      lgamma      
+------------------
+ -12815524.147684
+(1 row)
+
+SELECT gamma(float8 '-1000000');
+ gamma 
+-------
+   NaN
+(1 row)
+
+SELECT lgamma(float8 '-1000000');
+  lgamma  
+----------
+ Infinity
+(1 row)
+
+SELECT gamma(float8 '-1');
+ gamma 
+-------
+   NaN
+(1 row)
+
+SELECT lgamma(float8 '-1');
+  lgamma  
+----------
+ Infinity
+(1 row)
+
+SELECT gamma(float8 '-0');
+   gamma   
+-----------
+ -Infinity
+(1 row)
+
+SELECT lgamma(float8 '-0');
+  lgamma  
+----------
+ Infinity
+(1 row)
+
+SELECT gamma(float8 '0');
+  gamma   
+----------
+ Infinity
+(1 row)
+
+SELECT lgamma(float8 '0');
+  lgamma  
+----------
+ Infinity
+(1 row)
+
+SELECT gamma(float8 '1000000');
+ERROR:  value out of range: overflow
+SELECT lgamma(float8 '1000000');
+     lgamma      
+-----------------
+ 12815504.569148
+(1 row)
+
+SELECT lgamma(float8 '1e308');
+ERROR:  value out of range: overflow
+SELECT gamma(float8 'infinity');
+  gamma   
+----------
+ Infinity
+(1 row)
+
+SELECT lgamma(float8 'infinity');
+  lgamma  
+----------
+ Infinity
+(1 row)
+
+SELECT gamma(float8 'nan');
+ gamma 
+-------
+   NaN
+(1 row)
+
+SELECT lgamma(float8 'nan');
+ lgamma 
+--------
+    NaN
+(1 row)
+
+RESET extra_float_digits;
 -- test for over- and underflow
 INSERT INTO FLOAT8_TBL(f1) VALUES ('10e400');
 ERROR:  "10e400" is out of range for type double precision
diff --git a/src/test/regress/sql/float8.sql b/src/test/regress/sql/float8.sql
new file mode 100644
index 98e9926..36fd7b8
--- a/src/test/regress/sql/float8.sql
+++ b/src/test/regress/sql/float8.sql
@@ -245,6 +245,36 @@ FROM (VALUES (float8 '-infinity'),
 
 RESET extra_float_digits;
 
+-- gamma functions
+-- we run these with extra_float_digits = -1, to get consistently rounded
+-- results on all platforms.
+SET extra_float_digits = -1;
+SELECT x,
+       gamma(x),
+       lgamma(x)
+FROM (VALUES (0.5), (1), (2), (3), (4), (5)) AS t(x);
+-- test special cases for gamma functions
+SELECT gamma(float8 '-infinity');
+SELECT lgamma(float8 '-infinity');
+SELECT gamma(float8 '-1000000.5');
+SELECT lgamma(float8 '-1000000.5');
+SELECT gamma(float8 '-1000000');
+SELECT lgamma(float8 '-1000000');
+SELECT gamma(float8 '-1');
+SELECT lgamma(float8 '-1');
+SELECT gamma(float8 '-0');
+SELECT lgamma(float8 '-0');
+SELECT gamma(float8 '0');
+SELECT lgamma(float8 '0');
+SELECT gamma(float8 '1000000');
+SELECT lgamma(float8 '1000000');
+SELECT lgamma(float8 '1e308');
+SELECT gamma(float8 'infinity');
+SELECT lgamma(float8 'infinity');
+SELECT gamma(float8 'nan');
+SELECT lgamma(float8 'nan');
+RESET extra_float_digits;
+
 -- test for over- and underflow
 INSERT INTO FLOAT8_TBL(f1) VALUES ('10e400');