MDEV-15176 Storing DATETIME-alike VARCHAR data into TIME produces wrong results

When storing '0001-01-01 10:20:30x', execution went throw the last code
branch in Field_time::store_TIME_with_warning(), around the test
for (ltime->year || ltime->month). This then resulted into wrong results
because:

1. Field_time::store_TIME() does not check YYYYMM against zero.
  It assumes that ltime->days and ltime->hours are already properly set.
  So it mixed days to hours, even when YYYYMM was not zero.

2. Field_time_hires::store_TIME() does not check YYYYMM against zero.
  It assumes that ltime->year, ltime->month, ltime->days and ltime->hours
  are already properly set. So it always mixed days and even months(!) and years(!)
  to hours, using pack_time(). This gave even worse results comparing to #2.

3. Field_timef::store_TIME() did not check the entire YYYYMM for being zero.
  It only checked MM, but did not check YYYY. In case of a zero MM,
  it mixed days to hours, even if YYYY was not zero.
  The wrong code was in TIME_to_longlong_time_packed().

In the new reduction Field_time::store_TIME_with_warning() is responsible
to prepare the YYYYYMMDD part properly in all code branches
(with trailing garbage like 'x' and without trailing garbage).
It was reorganized into a more straightforward style.

Field_time:store_TIME(), Field_time_hires::store_TIME() and
TIME_to_longlong_time_packed() were fixed to do a DBUG_ASSERT
on non-zero ltime->year or ltime->month. The code testing ltime->month
was removed from TIME_to_longlong_time_packed(), as it's now
properly done on the caller level.

Truncation was moved from Field_timef::store_TIME() to
Field_time::store_TIME_with_warning().

So now all thee methods Field_time*::store_TIME() assume a properly
set input value:
- Only zero ltime->year and ltime->month are allowed.
- The value must be already properly truncated according to decimals()
  (this will help to add rounding soon, see MDEV-8894)

A "const" qualifier was added to the argument of Field_time*::store_TIME().

3 files changed, 35 insertions, 23 deletions

diff --git a/sql/compat56.cc b/sql/compat56.cc
index 704d1db9a98..be54a8760aa 100644
--- a/sql/compat56.cc
+++ b/sql/compat56.cc
@@ -45,8 +45,10 @@
 */
 longlong TIME_to_longlong_time_packed(const MYSQL_TIME *ltime)
 {
-  /* If month is 0, we mix day with hours: "1 00:10:10" -> "24:00:10" */
-  long hms= (((ltime->month ? 0 : ltime->day * 24) + ltime->hour) << 12) |
+  DBUG_ASSERT(ltime->year == 0);
+  DBUG_ASSERT(ltime->month == 0);
+  // Mix days with hours: "1 00:10:10" -> "24:00:10"
+  long hms= ((ltime->day * 24 + ltime->hour) << 12) |
             (ltime->minute << 6) | ltime->second;
   longlong tmp= MY_PACKED_TIME_MAKE(hms, ltime->second_part);
   return ltime->neg ? -tmp : tmp;
diff --git a/sql/field.cc b/sql/field.cc
index e954ac5b431..f6c48d7792b 100644
--- a/sql/field.cc
+++ b/sql/field.cc
@@ -5699,34 +5699,38 @@ int Field_time::store_TIME_with_warning(MYSQL_TIME *ltime,
                                         int was_cut,
                                         int have_smth_to_conv)
 {
-  Sql_condition::enum_warning_level trunc_level= Sql_condition::WARN_LEVEL_WARN;
-  int ret= 2;
   ASSERT_COLUMN_MARKED_FOR_WRITE_OR_COMPUTED;
 
   if (!have_smth_to_conv)
   {
     bzero(ltime, sizeof(*ltime));
-    was_cut= MYSQL_TIME_WARN_TRUNCATED;
-    ret= 1;
+    store_TIME(ltime);
+    set_warnings(Sql_condition::WARN_LEVEL_WARN, str, MYSQL_TIME_WARN_TRUNCATED);
+    return 1;
   }
-  else if (!MYSQL_TIME_WARN_HAVE_WARNINGS(was_cut) &&
-           ((ltime->year || ltime->month) ||
-            MYSQL_TIME_WARN_HAVE_NOTES(was_cut)))
+  if (ltime->year != 0 || ltime->month != 0)
   {
-    if (ltime->year || ltime->month)
-      ltime->year= ltime->month= ltime->day= 0;
-    trunc_level= Sql_condition::WARN_LEVEL_NOTE;
-    was_cut|=  MYSQL_TIME_WARN_TRUNCATED;
-    ret= 3;
+    ltime->year= ltime->month= ltime->day= 0;
+    was_cut|= MYSQL_TIME_NOTE_TRUNCATED;
   }
-  set_warnings(trunc_level, str, was_cut, MYSQL_TIMESTAMP_TIME);
+  my_time_trunc(ltime, decimals());
   store_TIME(ltime);
-  return was_cut ? ret : 0;
+  if (!MYSQL_TIME_WARN_HAVE_WARNINGS(was_cut) &&
+      MYSQL_TIME_WARN_HAVE_NOTES(was_cut))
+  {
+    set_warnings(Sql_condition::WARN_LEVEL_NOTE, str,
+                 was_cut | MYSQL_TIME_WARN_TRUNCATED);
+    return 3;
+  }
+  set_warnings(Sql_condition::WARN_LEVEL_WARN, str, was_cut);
+  return was_cut ? 2 : 0;
 }
 
 
-void Field_time::store_TIME(MYSQL_TIME *ltime)
+void Field_time::store_TIME(const MYSQL_TIME *ltime)
 {
+  DBUG_ASSERT(ltime->year == 0);
+  DBUG_ASSERT(ltime->month == 0);
   long tmp= (ltime->day*24L+ltime->hour)*10000L +
             (ltime->minute*100+ltime->second);
   if (ltime->neg)
@@ -5960,8 +5964,10 @@ int Field_time_hires::reset()
 }
 
 
-void Field_time_hires::store_TIME(MYSQL_TIME *ltime)
+void Field_time_hires::store_TIME(const MYSQL_TIME *ltime)
 {
+  DBUG_ASSERT(ltime->year == 0);
+  DBUG_ASSERT(ltime->month == 0);
   ulonglong packed= sec_part_shift(pack_time(ltime), dec) + zero_point;
   store_bigendian(packed, ptr, Field_time_hires::pack_length());
 }
@@ -6143,9 +6149,8 @@ int Field_timef::reset()
   return 0;
 }
 
-void Field_timef::store_TIME(MYSQL_TIME *ltime)
+void Field_timef::store_TIME(const MYSQL_TIME *ltime)
 {
-  my_time_trunc(ltime, decimals());
   longlong tmp= TIME_to_longlong_time_packed(ltime);
   my_time_packed_to_binary(tmp, ptr, dec);
 }
diff --git a/sql/field.h b/sql/field.h
index f225b6269d3..281e95c31bb 100644
--- a/sql/field.h
+++ b/sql/field.h
@@ -2682,9 +2682,14 @@ class Field_time :public Field_temporal {
   */
   long curdays;
 protected:
-  virtual void store_TIME(MYSQL_TIME *ltime);
+  virtual void store_TIME(const MYSQL_TIME *ltime);
   int store_TIME_with_warning(MYSQL_TIME *ltime, const ErrConv *str,
                               int was_cut, int have_smth_to_conv);
+  void set_warnings(Sql_condition::enum_warning_level level,
+                    const ErrConv *str, int was_cut)
+  {
+    Field_temporal::set_warnings(level, str, was_cut, MYSQL_TIMESTAMP_TIME);
+  }
   bool check_zero_in_date_with_warn(ulonglong fuzzydate);
   static void do_field_time(Copy_field *copy);
 public:
@@ -2766,7 +2771,7 @@ public:
 */
 class Field_time_hires :public Field_time_with_dec {
   longlong zero_point;
-  void store_TIME(MYSQL_TIME *ltime);
+  void store_TIME(const MYSQL_TIME *);
 public:
   Field_time_hires(uchar *ptr_arg, uchar *null_ptr_arg, uchar null_bit_arg,
              enum utype unireg_check_arg, const LEX_CSTRING *field_name_arg,
@@ -2792,7 +2797,7 @@ public:
   TIME(0..6) - MySQL56 version
 */
 class Field_timef :public Field_time_with_dec {
-  void store_TIME(MYSQL_TIME *ltime);
+  void store_TIME(const MYSQL_TIME *);
   int do_save_field_metadata(uchar *metadata_ptr)
   {
     *metadata_ptr= (uchar) decimals();