Prevent internal overflows in date-vs-timestamp and related comparisons.

The date-vs-timestamp, date-vs-timestamptz, and timestamp-vs-timestamptz
comparators all worked by promoting the first type to the second and
then doing a simple same-type comparison.  This works fine, except
when the conversion result is out of range, in which case we throw an
entirely avoidable error.  The sources of such failures are
(a) type date can represent dates much farther in the future than
the timestamp types can;
(b) timezone rotation might cause a just-in-range timestamp value to
become a just-out-of-range timestamptz value.

Up to now we just ignored these corner-case issues, but now we have
an actual user complaint (bug #16657 from Huss EL-Sheikh), so let's
do something about it.

It turns out that commit 52ad1e659 already built all the necessary
infrastructure to support error-free comparisons, but neglected to
actually use it in the main-line code paths.  Fix that, do a little
bit of code style review, and remove the now-duplicate logic in
jsonpath_exec.c.

Back-patch to v13 where 52ad1e659 came in.  We could take this back
further by back-patching said infrastructure, but given the small
number of complaints so far, I don't feel a great need to.

Discussion: https://postgr.es/m/16657-cde2f876d8cc7971@postgresql.org

2 files changed, 5 insertions, 0 deletions

diff --git a/src/include/utils/date.h b/src/include/utils/date.h
index 4cdb1f97cc8..6fc491e6a6d 100644
--- a/src/include/utils/date.h
+++ b/src/include/utils/date.h
@@ -72,6 +72,9 @@ extern int32 anytime_typmod_check(bool istz, int32 typmod);
 extern double date2timestamp_no_overflow(DateADT dateVal);
 extern Timestamp date2timestamp_opt_overflow(DateADT dateVal, int *overflow);
 extern TimestampTz date2timestamptz_opt_overflow(DateADT dateVal, int *overflow);
+extern int32 date_cmp_timestamp_internal(DateADT dateVal, Timestamp dt2);
+extern int32 date_cmp_timestamptz_internal(DateADT dateVal, TimestampTz dt2);
+
 extern void EncodeSpecialDate(DateADT dt, char *str);
 extern DateADT GetSQLCurrentDate(void);
 extern TimeTzADT *GetSQLCurrentTime(int32 typmod);
diff --git a/src/include/utils/timestamp.h b/src/include/utils/timestamp.h
index 03a1de569f0..16c3fd8ec97 100644
--- a/src/include/utils/timestamp.h
+++ b/src/include/utils/timestamp.h
@@ -99,6 +99,8 @@ extern int	timestamp_cmp_internal(Timestamp dt1, Timestamp dt2);
 
 extern TimestampTz timestamp2timestamptz_opt_overflow(Timestamp timestamp,
 													  int *overflow);
+extern int32 timestamp_cmp_timestamptz_internal(Timestamp timestampVal,
+												TimestampTz dt2);
 
 extern int	isoweek2j(int year, int week);
 extern void isoweek2date(int woy, int *year, int *mon, int *mday);