Add some UUID support functions

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

doc/src/sgml/func.sgml

@@ -14127,6 +14127,14 @@ CREATE TYPE rainbow AS ENUM ('red', 'orange', 'yellow', 'green', 'blue', 'purple
    <primary>gen_random_uuid</primary>
   </indexterm>
 
+  <indexterm>
+   <primary>uuid_extract_timestamp</primary>
+  </indexterm>
+
+  <indexterm>
+   <primary>uuid_extract_version</primary>
+  </indexterm>
+
   <para>
    <productname>PostgreSQL</productname> includes one function to generate a UUID:
 <synopsis>
@@ -14141,6 +14149,28 @@ CREATE TYPE rainbow AS ENUM ('red', 'orange', 'yellow', 'green', 'blue', 'purple
    implement other standard algorithms for generating UUIDs.
   </para>
 
+  <para>
+   There are also functions to extract data from UUIDs:
+<synopsis>
+<function>uuid_extract_timestamp</function> (uuid) <returnvalue>timestamp with time zone</returnvalue>
+</synopsis>
+   This function extracts a <type>timestamp with time zone</type> from UUID
+   version 1.  For other versions, this function returns null.  Note that the
+   extracted timestamp is not necessarily exactly equal to the time the UUID
+   was generated; this depends on the implementation that generated the UUID.
+  </para>
+
+  <para>
+<synopsis>
+<function>uuid_extract_version</function> (uuid) <returnvalue>smallint</returnvalue>
+</synopsis>
+   This function extracts the version from a UUID of the variant described by
+   <ulink url="https://tools.ietf.org/html/rfc4122">RFC 4122</ulink>.  For
+   other variants, this function returns null.  For example, for a UUID
+   generated by <function>gen_random_uuid</function>, this function will
+   return 4.
+  </para>
+
   <para>
    <productname>PostgreSQL</productname> also provides the usual comparison
    operators shown in <xref linkend="functions-comparison-op-table"/> for

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);
+}

src/include/catalog/catversion.h

@@ -57,6 +57,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	202403181
+#define CATALOG_VERSION_NO	202403191
 
 #endif

src/include/catalog/pg_proc.dat

@@ -9170,6 +9170,13 @@
 { oid => '3432', descr => 'generate random UUID',
   proname => 'gen_random_uuid', proleakproof => 't', provolatile => 'v',
   prorettype => 'uuid', proargtypes => '', prosrc => 'gen_random_uuid' },
+{ oid => '9897', descr => 'extract timestamp from UUID',
+  proname => 'uuid_extract_timestamp', proleakproof => 't',
+  prorettype => 'timestamptz', proargtypes => 'uuid',
+  prosrc => 'uuid_extract_timestamp' },
+{ oid => '9898', descr => 'extract version from RFC 4122 UUID',
+  proname => 'uuid_extract_version', proleakproof => 't', prorettype => 'int2',
+  proargtypes => 'uuid', prosrc => 'uuid_extract_version' },
 
 # pg_lsn
 { oid => '3229', descr => 'I/O',

src/test/regress/expected/opr_sanity.out

@@ -872,6 +872,8 @@ xid8ge(xid8,xid8)
 xid8eq(xid8,xid8)
 xid8ne(xid8,xid8)
 xid8cmp(xid8,xid8)
+uuid_extract_timestamp(uuid)
+uuid_extract_version(uuid)
 -- restore normal output mode
 \a\t
 -- List of functions used by libpq's fe-lobj.c

src/test/regress/expected/uuid.out

@@ -168,5 +168,44 @@ SELECT count(DISTINCT guid_field) FROM guid1;
      2
 (1 row)
 
+-- extract functions
+-- version
+SELECT uuid_extract_version('11111111-1111-5111-8111-111111111111');  -- 5
+ uuid_extract_version 
+----------------------
+                    5
+(1 row)
+
+SELECT uuid_extract_version(gen_random_uuid());  -- 4
+ uuid_extract_version 
+----------------------
+                    4
+(1 row)
+
+SELECT uuid_extract_version('11111111-1111-1111-1111-111111111111');  -- null
+ uuid_extract_version 
+----------------------
+                     
+(1 row)
+
+-- timestamp
+SELECT uuid_extract_timestamp('C232AB00-9414-11EC-B3C8-9F6BDECED846') = 'Tuesday, February 22, 2022 2:22:22.00 PM GMT+05:00';  -- RFC 4122bis test vector
+ ?column? 
+----------
+ t
+(1 row)
+
+SELECT uuid_extract_timestamp(gen_random_uuid());  -- null
+ uuid_extract_timestamp 
+------------------------
+ 
+(1 row)
+
+SELECT uuid_extract_timestamp('11111111-1111-1111-1111-111111111111');  -- null
+ uuid_extract_timestamp 
+------------------------
+ 
+(1 row)
+
 -- clean up
 DROP TABLE guid1, guid2 CASCADE;

src/test/regress/sql/uuid.sql

@@ -85,5 +85,19 @@ INSERT INTO guid1 (guid_field) VALUES (gen_random_uuid());
 INSERT INTO guid1 (guid_field) VALUES (gen_random_uuid());
 SELECT count(DISTINCT guid_field) FROM guid1;
 
+
+-- extract functions
+
+-- version
+SELECT uuid_extract_version('11111111-1111-5111-8111-111111111111');  -- 5
+SELECT uuid_extract_version(gen_random_uuid());  -- 4
+SELECT uuid_extract_version('11111111-1111-1111-1111-111111111111');  -- null
+
+-- timestamp
+SELECT uuid_extract_timestamp('C232AB00-9414-11EC-B3C8-9F6BDECED846') = 'Tuesday, February 22, 2022 2:22:22.00 PM GMT+05:00';  -- RFC 4122bis test vector
+SELECT uuid_extract_timestamp(gen_random_uuid());  -- null
+SELECT uuid_extract_timestamp('11111111-1111-1111-1111-111111111111');  -- null
+
+
 -- clean up
 DROP TABLE guid1, guid2 CASCADE;