Use floor() not rint() when reducing precision of fractional seconds in

timestamp_trunc, timestamptz_trunc, and interval_trunc().  This change
only affects the float-datetime case; the integer-datetime case already
behaved like truncation instead of rounding.  Per gripe from Mario Splivalo.

This is a pre-existing issue but I'm choosing not to backpatch, because
it's such a corner case and there have not been prior complaints.  The
issue is largely moot anyway given the trend towards integer datetimes.

diff --git a/src/backend/utils/adt/timestamp.c b/src/backend/utils/adt/timestamp.c
index a0bf47c2647063004a5b6465cdc5a570ee3ac09d..e00f729e6fcda08fd2633faefd1e856417f8f5f6 100644 (file)
--- a/src/backend/utils/adt/timestamp.c
+++ b/src/backend/utils/adt/timestamp.c
@@ -3338,13 +3338,13 @@ timestamp_trunc(PG_FUNCTION_ARGS)
 #ifdef HAVE_INT64_TIMESTAMP
                                fsec = (fsec / 1000) * 1000;
 #else
-                               fsec = rint(fsec * 1000) / 1000;
+                               fsec = floor(fsec * 1000) / 1000;
 #endif
                                break;
 
                        case DTK_MICROSEC:
 #ifndef HAVE_INT64_TIMESTAMP
-                               fsec = rint(fsec * 1000000) / 1000000;
+                               fsec = floor(fsec * 1000000) / 1000000;
 #endif
                                break;
 
@@ -3494,12 +3494,12 @@ timestamptz_trunc(PG_FUNCTION_ARGS)
 #ifdef HAVE_INT64_TIMESTAMP
                                fsec = (fsec / 1000) * 1000;
 #else
-                               fsec = rint(fsec * 1000) / 1000;
+                               fsec = floor(fsec * 1000) / 1000;
 #endif
                                break;
                        case DTK_MICROSEC:
 #ifndef HAVE_INT64_TIMESTAMP
-                               fsec = rint(fsec * 1000000) / 1000000;
+                               fsec = floor(fsec * 1000000) / 1000000;
 #endif
                                break;
 
@@ -3591,12 +3591,12 @@ interval_trunc(PG_FUNCTION_ARGS)
 #ifdef HAVE_INT64_TIMESTAMP
                                        fsec = (fsec / 1000) * 1000;
 #else
-                                       fsec = rint(fsec * 1000) / 1000;
+                                       fsec = floor(fsec * 1000) / 1000;
 #endif
                                        break;
                                case DTK_MICROSEC:
 #ifndef HAVE_INT64_TIMESTAMP
-                                       fsec = rint(fsec * 1000000) / 1000000;
+                                       fsec = floor(fsec * 1000000) / 1000000;
 #endif
                                        break;