4 files changed, 48 insertions, 5 deletions
diff --git a/src/include/datatype/timestamp.h b/src/include/datatype/timestamp.h
index 5fa38d20d84..d155f1b03b0 100644
--- a/src/include/datatype/timestamp.h
+++ b/src/include/datatype/timestamp.h
@@ -40,6 +40,10 @@ typedef int64 TimestampTz;
 typedef int64 TimeOffset;
 typedef int32 fsec_t;			/* fractional seconds (in microseconds) */
 
+
+/*
+ * Storage format for type interval.
+ */
 typedef struct
 {
 	TimeOffset	time;			/* all time units other than days, months and
@@ -48,6 +52,41 @@ typedef struct
 	int32		month;			/* months and years, after time for alignment */
 } Interval;
 
+/*
+ * Data structure representing a broken-down interval.
+ *
+ * For historical reasons, this is modeled on struct pg_tm for timestamps.
+ * Unlike the situation for timestamps, there's no magic interpretation
+ * needed for months or years: they're just zero or not.  Note that fields
+ * can be negative; however, because of the divisions done while converting
+ * from struct Interval, only tm_mday could be INT_MIN.  This is important
+ * because we may need to negate the values in some code paths.
+ */
+struct pg_itm
+{
+	int			tm_usec;
+	int			tm_sec;
+	int			tm_min;
+	int64		tm_hour;		/* needs to be wide */
+	int			tm_mday;
+	int			tm_mon;
+	int			tm_year;
+};
+
+/*
+ * Data structure for decoding intervals.  We could just use struct pg_itm,
+ * but then the requirement for tm_usec to be 64 bits would propagate to
+ * places where it's not really needed.  Also, omitting the fields that
+ * aren't used during decoding seems like a good error-prevention measure.
+ */
+struct pg_itm_in
+{
+	int64		tm_usec;		/* needs to be wide */
+	int			tm_mday;
+	int			tm_mon;
+	int			tm_year;
+};
+
 
 /* Limits on the "precision" option (typmod) for these data types */
 #define MAX_TIMESTAMP_PRECISION 6
diff --git a/src/include/pgtime.h b/src/include/pgtime.h
index 2977b13aabb..441d7847c12 100644
--- a/src/include/pgtime.h
+++ b/src/include/pgtime.h
@@ -23,6 +23,8 @@
 typedef int64 pg_time_t;
 
 /*
+ * Data structure representing a broken-down timestamp.
+ *
  * CAUTION: the IANA timezone library (src/timezone/) follows the POSIX
  * convention that tm_mon counts from 0 and tm_year is relative to 1900.
  * However, Postgres' datetime functions generally treat tm_mon as counting
@@ -44,6 +46,7 @@ struct pg_tm
 	const char *tm_zone;
 };
 
+/* These structs are opaque outside the timezone library */
 typedef struct pg_tz pg_tz;
 typedef struct pg_tzenum pg_tzenum;
 
diff --git a/src/include/utils/datetime.h b/src/include/utils/datetime.h
index 0d158f3e4bb..0801858d601 100644
--- a/src/include/utils/datetime.h
+++ b/src/include/utils/datetime.h
@@ -300,9 +300,9 @@ extern int	DecodeTimeOnly(char **field, int *ftype,
 						   int nf, int *dtype,
 						   struct pg_tm *tm, fsec_t *fsec, int *tzp);
 extern int	DecodeInterval(char **field, int *ftype, int nf, int range,
-						   int *dtype, struct pg_tm *tm, fsec_t *fsec);
+						   int *dtype, struct pg_itm_in *itm_in);
 extern int	DecodeISO8601Interval(char *str,
-								  int *dtype, struct pg_tm *tm, fsec_t *fsec);
+								  int *dtype, struct pg_itm_in *itm_in);
 
 extern void DateTimeParseError(int dterr, const char *str,
 							   const char *datatype) pg_attribute_noreturn();
@@ -315,7 +315,7 @@ extern int	DetermineTimeZoneAbbrevOffsetTS(TimestampTz ts, const char *abbr,
 extern void EncodeDateOnly(struct pg_tm *tm, int style, char *str);
 extern void EncodeTimeOnly(struct pg_tm *tm, fsec_t fsec, bool print_tz, int tz, int style, char *str);
 extern void EncodeDateTime(struct pg_tm *tm, fsec_t fsec, bool print_tz, int tz, const char *tzn, int style, char *str);
-extern void EncodeInterval(struct pg_tm *tm, fsec_t fsec, int style, char *str);
+extern void EncodeInterval(struct pg_itm *itm, int style, char *str);
 extern void EncodeSpecialTimestamp(Timestamp dt, char *str);
 
 extern int	ValidateDate(int fmask, bool isjulian, bool is2digits, bool bc,
diff --git a/src/include/utils/timestamp.h b/src/include/utils/timestamp.h
index c1a74f8e2b0..d33421d3809 100644
--- a/src/include/utils/timestamp.h
+++ b/src/include/utils/timestamp.h
@@ -88,8 +88,9 @@ extern int	timestamp2tm(Timestamp dt, int *tzp, struct pg_tm *tm,
 						 fsec_t *fsec, const char **tzn, pg_tz *attimezone);
 extern void dt2time(Timestamp dt, int *hour, int *min, int *sec, fsec_t *fsec);
 
-extern int	interval2tm(Interval span, struct pg_tm *tm, fsec_t *fsec);
-extern int	tm2interval(struct pg_tm *tm, fsec_t fsec, Interval *span);
+extern void interval2itm(Interval span, struct pg_itm *itm);
+extern int	itm2interval(struct pg_itm *itm, Interval *span);
+extern int	itmin2interval(struct pg_itm_in *itm_in, Interval *span);
 
 extern Timestamp SetEpochTimestamp(void);
 extern void GetEpochTime(struct pg_tm *tm);