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
+ gamma
+
+ gamma ( double precision )
+ double precision
+
+
+ Gamma function
+
+
+ gamma(0.5)
+ 1.772453850905516
+
+
+ gamma(6)
+ 120
+
+
+
+
+
+
gcd
gcd ( numeric_type, numeric_type )
@@ -1436,6 +1457,23 @@ SELECT NOT(ROW(table.*) IS NOT NULL) FRO
+
+
+
+ lgamma
+
+ lgamma ( double precision )
+ double precision
+
+
+ Natural logarithm of the absolute value of the gamma function
+
+
+ lgamma(1000)
+ 5905.220423209181
+
+
+
diff --git a/src/backend/utils/adt/float.c b/src/backend/utils/adt/float.c
new file mode 100644
index f709c21..4694ea2
--- a/src/backend/utils/adt/float.c
+++ b/src/backend/utils/adt/float.c
@@ -2787,6 +2787,97 @@ 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;
+
+ /*
+ * Per the POSIX spec, return NaN if the input is NaN, +/-infinity if the
+ * input is +/-0, NaN if the input is -infinity, and infinity if the input
+ * is infinity.
+ */
+ if (isnan(arg1))
+ PG_RETURN_FLOAT8(get_float8_nan());
+ if (arg1 == 0)
+ {
+ if (signbit(arg1))
+ PG_RETURN_FLOAT8(-get_float8_infinity());
+ else
+ PG_RETURN_FLOAT8(get_float8_infinity());
+ }
+ if (isinf(arg1))
+ {
+ if (arg1 < 0)
+ PG_RETURN_FLOAT8(get_float8_nan());
+ else
+ PG_RETURN_FLOAT8(get_float8_infinity());
+ }
+
+ /*
+ * Note that the POSIX/C99 gamma function is called "tgamma", not "gamma".
+ *
+ * For negative integer inputs, it may raise a domain error or a pole
+ * error, or return NaN or +/-infinity (the POSIX spec indicates that this
+ * may change in future implementations). Try to distinguish these cases
+ * from other overflow cases, and give a more specific error message.
+ */
+ errno = 0;
+ result = tgamma(arg1);
+ if (errno != 0 || isinf(result) || isnan(result))
+ {
+ if (arg1 < 0 && floor(arg1) == arg1)
+ ereport(ERROR,
+ errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+ errmsg("the gamma function is undefined for negative integer inputs"));
+ float_overflow_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;
+
+ /* Per the POSIX spec, return NaN if the input is NaN */
+ if (isnan(arg1))
+ PG_RETURN_FLOAT8(get_float8_nan());
+
+ errno = 0;
+ result = lgamma(arg1);
+
+ /*
+ * If an ERANGE error occurs, it means there is an overflow. This can
+ * happen if the input is 0, a negative integer, -infinity, or infinity.
+ * In each of those cases, the correct result is infinity. Otherwise, it
+ * is a genuine overflow error.
+ */
+ if (unlikely(errno == ERANGE))
+ {
+ if (isinf(arg1) || (arg1 <= 0 && floor(arg1) == arg1))
+ result = get_float8_infinity();
+ else
+ 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..a31624b
--- a/src/test/regress/expected/float8.out
+++ b/src/test/regress/expected/float8.out
@@ -830,6 +830,53 @@ 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 (float8 '-infinity'),
+ ('-0'), (0), (0.5), (1), (2), (3), (4), (5),
+ (float8 'infinity'), (float8 'nan')) AS t(x);
+ x | gamma | lgamma
+-----------+-----------------+------------------
+ -Infinity | NaN | Infinity
+ -0 | -Infinity | Infinity
+ 0 | Infinity | Infinity
+ 0.5 | 1.7724538509055 | 0.5723649429247
+ 1 | 1 | 0
+ 2 | 1 | 0
+ 3 | 2 | 0.69314718055995
+ 4 | 6 | 1.7917594692281
+ 5 | 24 | 3.1780538303479
+ Infinity | Infinity | Infinity
+ NaN | NaN | NaN
+(11 rows)
+
+-- invalid inputs for gamma()
+SELECT gamma(-1);
+ERROR: the gamma function is undefined for negative integer inputs
+SELECT gamma(1000000);
+ERROR: value out of range: overflow
+-- valid for lgamma()
+SELECT lgamma(-1);
+ lgamma
+----------
+ Infinity
+(1 row)
+
+SELECT lgamma(1000000);
+ lgamma
+-----------------
+ 12815504.569148
+(1 row)
+
+-- inavlid input for lgamma()
+SELECT lgamma(1e308);
+ERROR: value out of range: overflow
+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..de2656a
--- a/src/test/regress/sql/float8.sql
+++ b/src/test/regress/sql/float8.sql
@@ -245,6 +245,27 @@ 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 (float8 '-infinity'),
+ ('-0'), (0), (0.5), (1), (2), (3), (4), (5),
+ (float8 'infinity'), (float8 'nan')) AS t(x);
+-- invalid inputs for gamma()
+SELECT gamma(-1);
+SELECT gamma(1000000);
+-- valid for lgamma()
+SELECT lgamma(-1);
+SELECT lgamma(1000000);
+-- inavlid input for lgamma()
+SELECT lgamma(1e308);
+
+RESET extra_float_digits;
+
-- test for over- and underflow
INSERT INTO FLOAT8_TBL(f1) VALUES ('10e400');