From e511d878f3bbc205cd260a79740e646eea3c1cd3 Mon Sep 17 00:00:00 2001
From: Tom Lane <tgl@sss.pgh.pa.us>
Date: Tue, 29 Mar 2016 17:09:21 -0400
Subject: Allow to_timestamp(float8) to convert float infinity to timestamp
 infinity.

With the original SQL-function implementation, such cases failed because
we don't support infinite intervals.  Converting the function to C lets
us bypass the interval representation, which should be a bit faster as
well as more flexible.

Vitaly Burovoy, reviewed by Anastasia Lubennikova
---
 src/backend/utils/adt/timestamp.c | 58 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 58 insertions(+)

(limited to 'src/backend/utils/adt/timestamp.c')

diff --git a/src/backend/utils/adt/timestamp.c b/src/backend/utils/adt/timestamp.c
index c9e5270a9eb..b9c26b68544 100644
--- a/src/backend/utils/adt/timestamp.c
+++ b/src/backend/utils/adt/timestamp.c
@@ -737,6 +737,64 @@ make_timestamptz_at_timezone(PG_FUNCTION_ARGS)
 	PG_RETURN_TIMESTAMPTZ(result);
 }
 
+/*
+ * to_timestamp(double precision)
+ * Convert UNIX epoch to timestamptz.
+ */
+Datum
+float8_timestamptz(PG_FUNCTION_ARGS)
+{
+	float8		seconds = PG_GETARG_FLOAT8(0);
+	TimestampTz result;
+
+	/* Deal with NaN and infinite inputs ... */
+	if (isnan(seconds))
+		ereport(ERROR,
+				(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
+				 errmsg("timestamp cannot be NaN")));
+
+	if (isinf(seconds))
+	{
+		if (seconds < 0)
+			TIMESTAMP_NOBEGIN(result);
+		else
+			TIMESTAMP_NOEND(result);
+	}
+	else
+	{
+		/* Out of range? */
+		if (seconds <
+			(float8) SECS_PER_DAY * (DATETIME_MIN_JULIAN - UNIX_EPOCH_JDATE))
+			ereport(ERROR,
+					(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
+					 errmsg("timestamp out of range: \"%g\"", seconds)));
+
+		if (seconds >=
+			(float8) SECS_PER_DAY * (TIMESTAMP_END_JULIAN - UNIX_EPOCH_JDATE))
+			ereport(ERROR,
+					(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
+					 errmsg("timestamp out of range: \"%g\"", seconds)));
+
+		/* Convert UNIX epoch to Postgres epoch */
+		seconds -= ((POSTGRES_EPOCH_JDATE - UNIX_EPOCH_JDATE) * SECS_PER_DAY);
+
+#ifdef HAVE_INT64_TIMESTAMP
+		result = seconds * USECS_PER_SEC;
+#else
+		result = seconds;
+#endif
+
+		/* Recheck in case roundoff produces something just out of range */
+		if (!IS_VALID_TIMESTAMP(result))
+			ereport(ERROR,
+					(errcode(ERRCODE_DATETIME_VALUE_OUT_OF_RANGE),
+					 errmsg("timestamp out of range: \"%g\"",
+							PG_GETARG_FLOAT8(0))));
+	}
+
+	PG_RETURN_TIMESTAMP(result);
+}
+
 /* timestamptz_out()
  * Convert a timestamp to external form.
  */
-- 
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