From 794f10f6b920670cb9750b043a2b2587059d5051 Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <peter@eisentraut.org>
Date: Tue, 19 Mar 2024 09:30:24 +0100
Subject: Add some UUID support functions
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Add uuid_extract_timestamp() and uuid_extract_version().

Author: Andrey Borodin
Reviewed-by: Sergey Prokhorenko, Kirk Wolak, Przemysław Sztoch
Reviewed-by: Nikolay Samokhvalov, Jelte Fennema-Nio, Aleksander Alekseev
Reviewed-by: Peter Eisentraut, Chris Travers, Lukas Fittl
Discussion: https://postgr.es/m/CAAhFRxitJv%3DyoGnXUgeLB_O%2BM7J2BJAmb5jqAT9gZ3bij3uLDA%40mail.gmail.com
---
 src/backend/utils/adt/uuid.c | 64 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 64 insertions(+)

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

diff --git a/src/backend/utils/adt/uuid.c b/src/backend/utils/adt/uuid.c
index e9c1ec61537..45eb1b2fea9 100644
--- a/src/backend/utils/adt/uuid.c
+++ b/src/backend/utils/adt/uuid.c
@@ -20,6 +20,7 @@
 #include "utils/fmgrprotos.h"
 #include "utils/guc.h"
 #include "utils/sortsupport.h"
+#include "utils/timestamp.h"
 #include "utils/uuid.h"
 
 /* sortsupport for uuid */
@@ -425,3 +426,66 @@ gen_random_uuid(PG_FUNCTION_ARGS)
 
 	PG_RETURN_UUID_P(uuid);
 }
+
+#define UUIDV1_EPOCH_JDATE  2299161 /* == date2j(1582,10,15) */
+
+/*
+ * Extract timestamp from UUID.
+ *
+ * Returns null if not RFC 4122 variant or not a version that has a timestamp.
+ */
+Datum
+uuid_extract_timestamp(PG_FUNCTION_ARGS)
+{
+	pg_uuid_t  *uuid = PG_GETARG_UUID_P(0);
+	int			version;
+	uint64		tms;
+	TimestampTz ts;
+
+	/* check if RFC 4122 variant */
+	if ((uuid->data[8] & 0xc0) != 0x80)
+		PG_RETURN_NULL();
+
+	version = uuid->data[6] >> 4;
+
+	if (version == 1)
+	{
+		tms = ((uint64) uuid->data[0] << 24)
+			+ ((uint64) uuid->data[1] << 16)
+			+ ((uint64) uuid->data[2] << 8)
+			+ ((uint64) uuid->data[3])
+			+ ((uint64) uuid->data[4] << 40)
+			+ ((uint64) uuid->data[5] << 32)
+			+ (((uint64) uuid->data[6] & 0xf) << 56)
+			+ ((uint64) uuid->data[7] << 48);
+
+		/* convert 100-ns intervals to us, then adjust */
+		ts = (TimestampTz) (tms / 10) -
+			((uint64) POSTGRES_EPOCH_JDATE - UUIDV1_EPOCH_JDATE) * SECS_PER_DAY * USECS_PER_SEC;
+
+		PG_RETURN_TIMESTAMPTZ(ts);
+	}
+
+	/* not a timestamp-containing UUID version */
+	PG_RETURN_NULL();
+}
+
+/*
+ * Extract UUID version.
+ *
+ * Returns null if not RFC 4122 variant.
+ */
+Datum
+uuid_extract_version(PG_FUNCTION_ARGS)
+{
+	pg_uuid_t  *uuid = PG_GETARG_UUID_P(0);
+	uint16		version;
+
+	/* check if RFC 4122 variant */
+	if ((uuid->data[8] & 0xc0) != 0x80)
+		PG_RETURN_NULL();
+
+	version = uuid->data[6] >> 4;
+
+	PG_RETURN_UINT16(version);
+}
-- 
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