Fix daterange canonicalization for +/- infinity.

The values 'infinity' and '-infinity' are a part of the DATE type
itself, so a bound of the date 'infinity' is not the same as an
unbounded/infinite range. However, it is still wrong to try to
canonicalize such values, because adding or subtracting one has no
effect. Fix by treating 'infinity' and '-infinity' the same as
unbounded ranges for the purposes of canonicalization (but not other
purposes).

Backpatch to all versions because it is inconsistent with the
documented behavior. Note that this could be an incompatibility for
applications relying on the behavior contrary to the documentation.

Author: Laurenz Albe
Reviewed-by: Thomas Munro
Discussion: https://postgr.es/m/77f24ea19ab802bc9bc60ddbb8977ee2d646aec1.camel%40cybertec.at
Backpatch-through: 9.4

2 files changed, 28 insertions, 0 deletions

diff --git a/src/test/regress/expected/rangetypes.out b/src/test/regress/expected/rangetypes.out
index accf1e0d9e2..60d875e898e 100644
--- a/src/test/regress/expected/rangetypes.out
+++ b/src/test/regress/expected/rangetypes.out
@@ -652,6 +652,30 @@ select daterange('2000-01-10'::date, '2000-01-11'::date, '(]');
  [01-11-2000,01-12-2000)
 (1 row)
 
+select daterange('-infinity'::date, '2000-01-01'::date, '()');
+       daterange        
+------------------------
+ (-infinity,01-01-2000)
+(1 row)
+
+select daterange('-infinity'::date, '2000-01-01'::date, '[)');
+       daterange        
+------------------------
+ [-infinity,01-01-2000)
+(1 row)
+
+select daterange('2000-01-01'::date, 'infinity'::date, '[)');
+       daterange       
+-----------------------
+ [01-01-2000,infinity)
+(1 row)
+
+select daterange('2000-01-01'::date, 'infinity'::date, '[]');
+       daterange       
+-----------------------
+ [01-01-2000,infinity]
+(1 row)
+
 -- test GiST index that's been built incrementally
 create table test_range_gist(ir int4range);
 create index test_range_gist_idx on test_range_gist using gist (ir);
diff --git a/src/test/regress/sql/rangetypes.sql b/src/test/regress/sql/rangetypes.sql
index 55638a85ee1..9fdb1953df5 100644
--- a/src/test/regress/sql/rangetypes.sql
+++ b/src/test/regress/sql/rangetypes.sql
@@ -165,6 +165,10 @@ select daterange('2000-01-10'::date, '2000-01-20'::date, '(]');
 select daterange('2000-01-10'::date, '2000-01-20'::date, '()');
 select daterange('2000-01-10'::date, '2000-01-11'::date, '()');
 select daterange('2000-01-10'::date, '2000-01-11'::date, '(]');
+select daterange('-infinity'::date, '2000-01-01'::date, '()');
+select daterange('-infinity'::date, '2000-01-01'::date, '[)');
+select daterange('2000-01-01'::date, 'infinity'::date, '[)');
+select daterange('2000-01-01'::date, 'infinity'::date, '[]');
 
 -- test GiST index that's been built incrementally
 create table test_range_gist(ir int4range);