Avoid unexpected conversion overflow in planner for distant date values.

The "date" type supports a wider range of dates than int64 timestamps do.
However, there is pre-int64-timestamp code in the planner that assumes that
all date values can be converted to timestamp with impunity.  Fortunately,
what we really need out of the conversion is always a double (float8)
value; so even when the date is out of timestamp's range it's possible to
produce a sane answer.  All we need is a code path that doesn't try to
force the result into int64.  Per trouble report from David Rericha.

Back-patch to all supported versions.  Although this is surely a corner
case, there's not much point in advertising a date range wider than
timestamp's if we will choke on such values in unexpected places.

1 files changed, 2 insertions, 0 deletions

diff --git a/src/include/utils/date.h b/src/include/utils/date.h
index 874b6017e53..14d64ad067e 100644
--- a/src/include/utils/date.h
+++ b/src/include/utils/date.h
@@ -91,6 +91,8 @@ typedef struct
 
 
 /* date.c */
+extern double date2timestamp_no_overflow(DateADT dateVal);
+
 extern Datum date_in(PG_FUNCTION_ARGS);
 extern Datum date_out(PG_FUNCTION_ARGS);
 extern Datum date_recv(PG_FUNCTION_ARGS);