Improve handling of date_trunc() units for infinite input values

Previously, if an infinite value was passed to date_trunc(), then the
same infinite value would always be returned regardless of the field
unit given by the caller.  This commit updates the function so that an
error is returned when an invalid unit is passed to date_trunc() with an
infinite value.

This matches the behavior of date_trunc() with a finite value and
date_part() with an infinite value, making the handling of interval,
timestamp and timestamptz more consistent across the board for these two
functions.

Some tests are added to cover all these new failure cases, with an
unsupported unit and infinite values for the three data types.  There
were no test cases in core that checked all these patterns up to now.

Author: Joseph Koshakow
Discussion: https://postgr.es/m/CAAvxfHc4084dGzEJR0_pBZkDuqbPGc5wn7gK_M0XR_kRiCdUJQ@mail.gmail.com

6 files changed, 29 insertions, 0 deletions

diff --git a/src/test/regress/expected/interval.out b/src/test/regress/expected/interval.out
index e5d919d0cf0..a16e3ccdb2e 100644
--- a/src/test/regress/expected/interval.out
+++ b/src/test/regress/expected/interval.out
@@ -2219,6 +2219,15 @@ SELECT i AS interval, date_trunc('hour', i)
  -infinity | -infinity
 (2 rows)
 
+SELECT i AS interval, date_trunc('week', i)
+    FROM INFINITE_INTERVAL_TBL
+    WHERE NOT isfinite(i);
+ERROR:  unit "week" not supported for type interval
+DETAIL:  Months usually have fractional weeks.
+SELECT i AS interval, date_trunc('ago', i)
+    FROM INFINITE_INTERVAL_TBL
+    WHERE NOT isfinite(i);
+ERROR:  unit "ago" not recognized for type interval
 SELECT i AS interval, justify_days(i), justify_hours(i), justify_interval(i)
     FROM INFINITE_INTERVAL_TBL
     WHERE NOT isfinite(i);
diff --git a/src/test/regress/expected/timestamp.out b/src/test/regress/expected/timestamp.out
index e287260051c..6aaa19c8f4e 100644
--- a/src/test/regress/expected/timestamp.out
+++ b/src/test/regress/expected/timestamp.out
@@ -591,6 +591,8 @@ SELECT date_trunc( 'week', timestamp '2004-02-29 15:44:17.71393' ) AS week_trunc
  Mon Feb 23 00:00:00 2004
 (1 row)
 
+SELECT date_trunc( 'ago', timestamp 'infinity' ) AS invalid_trunc;
+ERROR:  unit "ago" not recognized for type timestamp without time zone
 -- verify date_bin behaves the same as date_trunc for relevant intervals
 -- case 1: AD dates, origin < input
 SELECT
diff --git a/src/test/regress/expected/timestamptz.out b/src/test/regress/expected/timestamptz.out
index b437613ac82..a6dd45626ce 100644
--- a/src/test/regress/expected/timestamptz.out
+++ b/src/test/regress/expected/timestamptz.out
@@ -701,6 +701,8 @@ SELECT date_trunc( 'week', timestamp with time zone '2004-02-29 15:44:17.71393'
  Mon Feb 23 00:00:00 2004 PST
 (1 row)
 
+SELECT date_trunc( 'ago', timestamp with time zone 'infinity' ) AS invalid_trunc;
+ERROR:  unit "ago" not recognized for type timestamp with time zone
 SELECT date_trunc('day', timestamp with time zone '2001-02-16 20:38:40+00', 'Australia/Sydney') as sydney_trunc;  -- zone name
          sydney_trunc         
 ------------------------------
@@ -719,6 +721,8 @@ SELECT date_trunc('day', timestamp with time zone '2001-02-16 20:38:40+00', 'VET
  Thu Feb 15 20:00:00 2001 PST
 (1 row)
 
+SELECT date_trunc('ago', timestamp with time zone 'infinity', 'GMT') AS invalid_zone_trunc;
+ERROR:  unit "ago" not recognized for type timestamp with time zone
 -- verify date_bin behaves the same as date_trunc for relevant intervals
 SELECT
   str,
diff --git a/src/test/regress/sql/interval.sql b/src/test/regress/sql/interval.sql
index 55054ae65d1..43bc793925e 100644
--- a/src/test/regress/sql/interval.sql
+++ b/src/test/regress/sql/interval.sql
@@ -776,6 +776,14 @@ SELECT i AS interval, date_trunc('hour', i)
     FROM INFINITE_INTERVAL_TBL
     WHERE NOT isfinite(i);
 
+SELECT i AS interval, date_trunc('week', i)
+    FROM INFINITE_INTERVAL_TBL
+    WHERE NOT isfinite(i);
+
+SELECT i AS interval, date_trunc('ago', i)
+    FROM INFINITE_INTERVAL_TBL
+    WHERE NOT isfinite(i);
+
 SELECT i AS interval, justify_days(i), justify_hours(i), justify_interval(i)
     FROM INFINITE_INTERVAL_TBL
     WHERE NOT isfinite(i);
diff --git a/src/test/regress/sql/timestamp.sql b/src/test/regress/sql/timestamp.sql
index 748469576d8..55f80530ea0 100644
--- a/src/test/regress/sql/timestamp.sql
+++ b/src/test/regress/sql/timestamp.sql
@@ -176,6 +176,8 @@ SELECT d1 - timestamp without time zone '1997-01-02' AS diff
 
 SELECT date_trunc( 'week', timestamp '2004-02-29 15:44:17.71393' ) AS week_trunc;
 
+SELECT date_trunc( 'ago', timestamp 'infinity' ) AS invalid_trunc;
+
 -- verify date_bin behaves the same as date_trunc for relevant intervals
 
 -- case 1: AD dates, origin < input
diff --git a/src/test/regress/sql/timestamptz.sql b/src/test/regress/sql/timestamptz.sql
index 6b91e7eddc7..a92586c363e 100644
--- a/src/test/regress/sql/timestamptz.sql
+++ b/src/test/regress/sql/timestamptz.sql
@@ -200,10 +200,14 @@ SELECT d1 - timestamp with time zone '1997-01-02' AS diff
    FROM TIMESTAMPTZ_TBL WHERE d1 BETWEEN '1902-01-01' AND '2038-01-01';
 
 SELECT date_trunc( 'week', timestamp with time zone '2004-02-29 15:44:17.71393' ) AS week_trunc;
+SELECT date_trunc( 'ago', timestamp with time zone 'infinity' ) AS invalid_trunc;
 
 SELECT date_trunc('day', timestamp with time zone '2001-02-16 20:38:40+00', 'Australia/Sydney') as sydney_trunc;  -- zone name
 SELECT date_trunc('day', timestamp with time zone '2001-02-16 20:38:40+00', 'GMT') as gmt_trunc;  -- fixed-offset abbreviation
 SELECT date_trunc('day', timestamp with time zone '2001-02-16 20:38:40+00', 'VET') as vet_trunc;  -- variable-offset abbreviation
+SELECT date_trunc('ago', timestamp with time zone 'infinity', 'GMT') AS invalid_zone_trunc;
+
+
 
 -- verify date_bin behaves the same as date_trunc for relevant intervals
 SELECT