Accept "+infinity" in date and timestamp[tz] input.

The float and numeric types accept this variant spelling of
"infinity", so it seems like the datetime types should too.

Vik Fearing, some cosmetic mods by me

Discussion: https://postgr.es/m/d0bef637-2dbd-0a5d-e539-48243b6f6c5e@postgresfriends.org

src/backend/utils/adt/datetime.c

@@ -105,6 +105,7 @@ const char *const days[] = {"Sunday", "Monday", "Tuesday", "Wednesday",
  */
 static const datetkn datetktbl[] = {
 	/* token, type, value */
+	{"+infinity", RESERV, DTK_LATE},	/* same as "infinity" */
 	{EARLY, RESERV, DTK_EARLY}, /* "-infinity" reserved for "early time" */
 	{DA_D, ADBC, AD},			/* "ad" for years > 0 */
 	{"allballs", RESERV, DTK_ZULU}, /* 00:00:00 */

src/test/regress/expected/date.out

@@ -1373,6 +1373,12 @@ select isfinite('infinity'::date), isfinite('-infinity'::date), isfinite('today'
  f        | f        | t
 (1 row)
 
+select 'infinity'::date = '+infinity'::date as t;
+ t 
+---
+ t
+(1 row)
+
 --
 -- oscillating fields from non-finite date:
 --

src/test/regress/expected/timestamp.out

@@ -76,6 +76,12 @@ TRUNCATE TIMESTAMP_TBL;
 INSERT INTO TIMESTAMP_TBL VALUES ('-infinity');
 INSERT INTO TIMESTAMP_TBL VALUES ('infinity');
 INSERT INTO TIMESTAMP_TBL VALUES ('epoch');
+SELECT timestamp 'infinity' = timestamp '+infinity' AS t;
+ t 
+---
+ t
+(1 row)
+
 -- Postgres v6.0 standard output format
 INSERT INTO TIMESTAMP_TBL VALUES ('Mon Feb 10 17:32:01 1997 PST');
 -- Variations on Postgres v6.1 standard output format

src/test/regress/expected/timestamptz.out

@@ -87,6 +87,12 @@ TRUNCATE TIMESTAMPTZ_TBL;
 INSERT INTO TIMESTAMPTZ_TBL VALUES ('-infinity');
 INSERT INTO TIMESTAMPTZ_TBL VALUES ('infinity');
 INSERT INTO TIMESTAMPTZ_TBL VALUES ('epoch');
+SELECT timestamptz 'infinity' = timestamptz '+infinity' AS t;
+ t 
+---
+ t
+(1 row)
+
 -- Postgres v6.0 standard output format
 INSERT INTO TIMESTAMPTZ_TBL VALUES ('Mon Feb 10 17:32:01 1997 PST');
 -- Variations on Postgres v6.1 standard output format

src/test/regress/sql/date.sql

@@ -329,6 +329,8 @@ select 'infinity'::date, '-infinity'::date;
 select 'infinity'::date > 'today'::date as t;
 select '-infinity'::date < 'today'::date as t;
 select isfinite('infinity'::date), isfinite('-infinity'::date), isfinite('today'::date);
+select 'infinity'::date = '+infinity'::date as t;
+
 --
 -- oscillating fields from non-finite date:
 --

src/test/regress/sql/timestamp.sql

@@ -49,6 +49,8 @@ INSERT INTO TIMESTAMP_TBL VALUES ('-infinity');
 INSERT INTO TIMESTAMP_TBL VALUES ('infinity');
 INSERT INTO TIMESTAMP_TBL VALUES ('epoch');
 
+SELECT timestamp 'infinity' = timestamp '+infinity' AS t;
+
 -- Postgres v6.0 standard output format
 INSERT INTO TIMESTAMP_TBL VALUES ('Mon Feb 10 17:32:01 1997 PST');
 

src/test/regress/sql/timestamptz.sql

@@ -50,6 +50,8 @@ INSERT INTO TIMESTAMPTZ_TBL VALUES ('-infinity');
 INSERT INTO TIMESTAMPTZ_TBL VALUES ('infinity');
 INSERT INTO TIMESTAMPTZ_TBL VALUES ('epoch');
 
+SELECT timestamptz 'infinity' = timestamptz '+infinity' AS t;
+
 -- Postgres v6.0 standard output format
 INSERT INTO TIMESTAMPTZ_TBL VALUES ('Mon Feb 10 17:32:01 1997 PST');