MDEV-20023 Implement Oracle TRUNC() function

The following Oracle formats are supported:
Truncate to day: DD, DDD,J
Truncate to month: MM,MON,MONTH,RM
Truncate to Year: SYEAR,SYYYY,Y,YEAR,YY,YYY,YYYY

TRUNC(date) is same as TRUNC(date, "MM")

Author: montywi

include/my_time.h

@@ -176,9 +176,18 @@ double TIME_to_double(const MYSQL_TIME *my_time);
 int check_time_range(struct st_mysql_time *my_time, uint dec, int *warning);
 my_bool check_datetime_range(const MYSQL_TIME *ltime);
 
+/*
+  Accurate only for the past couple of centuries.
+  Also works with 2 digit year 01-99 (1971-2069)
+  Year 0 is ignored as MariaDB uses year 0 as 'not specifed'. This
+  matches how things how leap year was calculated in calc_days_in_year().
+*/
+
+#define isleap(y) (((y) & 3) == 0 && (((y) % 100) != 0 || (((y) % 400) == 0 && y != 0)))
 
 long calc_daynr(uint year,uint month,uint day);
 uint calc_days_in_year(uint year);
+uint calc_days_in_month(uint year, uint month);
 uint year_2000_handling(uint year);
 
 void my_init_time(void);

mysql-test/suite/compat/oracle/r/func_trunc.result

@@ -0,0 +1,122 @@
+# Test for function trunc()
+#
+# Simple test
+#
+select trunc("2025-07-27 12:01:02.123");
+trunc("2025-07-27 12:01:02.123")
+2025-07-27
+select trunc("2025-07-27 12:01:02.123","YY");
+trunc("2025-07-27 12:01:02.123","YY")
+2025-01-01
+select trunc("2025-07-27 12:01:02.123","MM");
+trunc("2025-07-27 12:01:02.123","MM")
+2025-07-01
+select trunc("2025-07-27 12:01:02.123","DD");
+trunc("2025-07-27 12:01:02.123","DD")
+2025-07-27
+select trunc("hello");
+trunc("hello")
+NULL
+Warnings:
+Warning	1292	Incorrect datetime value: 'hello'
+select trunc(1);
+trunc(1)
+NULL
+Warnings:
+Warning	1292	Incorrect datetime value: '1'
+# Ensure that trunc table name and column can still be used
+create table trunc (trunc int);
+insert into trunc (trunc) values (1);
+select trunc from trunc;
+trunc
+1
+drop table trunc;
+#
+# Test all format variations
+#
+CREATE TABLE t1(c2 datetime, c3 date, c4 timestamp);
+INSERT INTO t1 VALUES ('2021-11-12 00:23:12', '2021-11-12', '2021-11-12 00:23:12');
+INSERT INTO t1 VALUES ('0000-09-02 00:00:00', '0000-09-02', '1980-09-02 00:00:00');
+INSERT INTO t1 VALUES ('9999-09-02', '9999-09-02', '1980-09-02');
+create table t2 (format varchar(5)) engine=aria;
+insert into t2 values ("DD"),("DDD"),("J"),("MM"),("MON"),("MONTH"),("RM"),("SYEAR"),("SYYYY"),("Y"),("YEAR"),("YY"),("YYY"),("YYYY"), ("ZZZ");
+SELECT format,trunc(c2,format),trunc(c3,format),trunc(c4,format) from t2 straight_join t1;
+format	trunc(c2,format)	trunc(c3,format)	trunc(c4,format)
+DD	2021-11-12	2021-11-12	2021-11-12
+DDD	2021-11-12	2021-11-12	2021-11-12
+J	2021-11-12	2021-11-12	2021-11-12
+MM	2021-11-01	2021-11-01	2021-11-01
+MON	2021-11-01	2021-11-01	2021-11-01
+MONTH	2021-11-01	2021-11-01	2021-11-01
+RM	2021-11-01	2021-11-01	2021-11-01
+SYEAR	2021-01-01	2021-01-01	2021-01-01
+SYYYY	2021-01-01	2021-01-01	2021-01-01
+Y	2021-01-01	2021-01-01	2021-01-01
+YEAR	2021-01-01	2021-01-01	2021-01-01
+YY	2021-01-01	2021-01-01	2021-01-01
+YYY	2021-01-01	2021-01-01	2021-01-01
+YYYY	2021-01-01	2021-01-01	2021-01-01
+ZZZ	NULL	NULL	NULL
+DD	0000-09-02	0000-09-02	1980-09-02
+DDD	0000-09-02	0000-09-02	1980-09-02
+J	0000-09-02	0000-09-02	1980-09-02
+MM	0000-09-01	0000-09-01	1980-09-01
+MON	0000-09-01	0000-09-01	1980-09-01
+MONTH	0000-09-01	0000-09-01	1980-09-01
+RM	0000-09-01	0000-09-01	1980-09-01
+SYEAR	0000-01-01	0000-01-01	1980-01-01
+SYYYY	0000-01-01	0000-01-01	1980-01-01
+Y	0000-01-01	0000-01-01	1980-01-01
+YEAR	0000-01-01	0000-01-01	1980-01-01
+YY	0000-01-01	0000-01-01	1980-01-01
+YYY	0000-01-01	0000-01-01	1980-01-01
+YYYY	0000-01-01	0000-01-01	1980-01-01
+ZZZ	NULL	NULL	NULL
+DD	9999-09-02	9999-09-02	1980-09-02
+DDD	9999-09-02	9999-09-02	1980-09-02
+J	9999-09-02	9999-09-02	1980-09-02
+MM	9999-09-01	9999-09-01	1980-09-01
+MON	9999-09-01	9999-09-01	1980-09-01
+MONTH	9999-09-01	9999-09-01	1980-09-01
+RM	9999-09-01	9999-09-01	1980-09-01
+SYEAR	9999-01-01	9999-01-01	1980-01-01
+SYYYY	9999-01-01	9999-01-01	1980-01-01
+Y	9999-01-01	9999-01-01	1980-01-01
+YEAR	9999-01-01	9999-01-01	1980-01-01
+YY	9999-01-01	9999-01-01	1980-01-01
+YYY	9999-01-01	9999-01-01	1980-01-01
+YYYY	9999-01-01	9999-01-01	1980-01-01
+ZZZ	NULL	NULL	NULL
+Warnings:
+Warning	1292	Incorrect TRUNC value: 'ZZZ'
+Warning	1292	Incorrect TRUNC value: 'ZZZ'
+Warning	1292	Incorrect TRUNC value: 'ZZZ'
+Warning	1292	Incorrect TRUNC value: 'ZZZ'
+Warning	1292	Incorrect TRUNC value: 'ZZZ'
+Warning	1292	Incorrect TRUNC value: 'ZZZ'
+Warning	1292	Incorrect TRUNC value: 'ZZZ'
+Warning	1292	Incorrect TRUNC value: 'ZZZ'
+Warning	1292	Incorrect TRUNC value: 'ZZZ'
+#
+# Test wrong usage
+#
+select trunc('2021-11-12 00:23:12',"");
+trunc('2021-11-12 00:23:12',"")
+NULL
+Warnings:
+Warning	1292	Incorrect TRUNC value: ''
+select trunc("","DD");
+trunc("","DD")
+NULL
+Warnings:
+Warning	1292	Incorrect datetime value: ''
+select trunc();
+ERROR 42000: Incorrect parameter count in the call to native function 'trunc'
+select trunc(1);
+trunc(1)
+NULL
+Warnings:
+Warning	1292	Incorrect datetime value: '1'
+select trunc(1,2,3);
+ERROR 42000: Incorrect parameter count in the call to native function 'trunc'
+drop table t1,t2;

mysql-test/suite/compat/oracle/t/func_trunc.test

@@ -0,0 +1,48 @@
+--echo # Test for function trunc()
+
+--echo #
+--echo # Simple test
+--echo #
+
+select trunc("2025-07-27 12:01:02.123");
+select trunc("2025-07-27 12:01:02.123","YY");
+select trunc("2025-07-27 12:01:02.123","MM");
+select trunc("2025-07-27 12:01:02.123","DD");
+
+select trunc("hello");
+select trunc(1);
+
+--echo # Ensure that trunc table name and column can still be used
+
+create table trunc (trunc int);
+insert into trunc (trunc) values (1);
+select trunc from trunc;
+drop table trunc;
+
+--echo #
+--echo # Test all format variations
+--echo #
+
+CREATE TABLE t1(c2 datetime, c3 date, c4 timestamp);
+INSERT INTO t1 VALUES ('2021-11-12 00:23:12', '2021-11-12', '2021-11-12 00:23:12');
+INSERT INTO t1 VALUES ('0000-09-02 00:00:00', '0000-09-02', '1980-09-02 00:00:00');
+INSERT INTO t1 VALUES ('9999-09-02', '9999-09-02', '1980-09-02');
+
+create table t2 (format varchar(5)) engine=aria;
+insert into t2 values ("DD"),("DDD"),("J"),("MM"),("MON"),("MONTH"),("RM"),("SYEAR"),("SYYYY"),("Y"),("YEAR"),("YY"),("YYY"),("YYYY"), ("ZZZ");
+
+SELECT format,trunc(c2,format),trunc(c3,format),trunc(c4,format) from t2 straight_join t1;
+
+--echo #
+--echo # Test wrong usage
+--echo #
+
+select trunc('2021-11-12 00:23:12',"");
+select trunc("","DD");
+--error ER_WRONG_PARAMCOUNT_TO_NATIVE_FCT
+select trunc();
+select trunc(1);
+--error ER_WRONG_PARAMCOUNT_TO_NATIVE_FCT
+select trunc(1,2,3);
+
+drop table t1,t2;

sql-common/my_time.c

@@ -50,14 +50,22 @@ uchar days_in_month[]= {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31, 0};
 static long my_time_zone=0;
 
 
-/* Calc days in one year. works with 0 <= year <= 99 */
+/* Calc days in one year */
 
 uint calc_days_in_year(uint year)
 {
-  return ((year & 3) == 0 && (year%100 || (year%400 == 0 && year)) ?
-          366 : 365);
+  return isleap(year) ? 366 : 365;
 }
 
+/* Calc days in a month */
+
+uint calc_days_in_month(uint year, uint month)
+{
+  uint days= days_in_month[month-1];
+  if (month == 2 && isleap(year))
+    days= 29;
+  return days;
+}
 
 #ifdef DBUG_ASSERT_EXISTS
 

sql/item_create.cc

@@ -2590,6 +2590,41 @@ class Create_func_to_seconds : public Create_func_arg1
 };
 
 
+class Create_func_trunc : public Create_native_func
+{
+public:
+  Item *create_native(THD *thd, const LEX_CSTRING *name,
+                              List<Item> *item_list) override
+  {
+    Item *a[2];
+    uint arg_count= item_list == nullptr ? 0 : item_list->elements;
+
+    for (uint i=0; i < MY_MIN(array_elements(a), arg_count); i++)
+      a[i]= item_list->pop();
+    switch (arg_count)
+    {
+    case 1:
+      {
+        a[1]= new (thd->mem_root) Item_string_sys(thd, "DD",  2);
+        if (unlikely(a[1] == nullptr))
+          return nullptr;
+      }
+      /*fall through*/
+    case 2:
+      return new (thd->mem_root) Item_func_trunc(thd, a[0], a[1]);
+    }
+    my_error(ER_WRONG_PARAMCOUNT_TO_NATIVE_FCT, MYF(0), name->str);
+    return NULL;
+  }
+
+  static Create_func_trunc s_singleton;
+
+protected:
+  Create_func_trunc() = default;
+  ~Create_func_trunc() override = default;
+};
+
+
 class Create_func_ucase : public Create_func_arg1
 {
 public:
@@ -5986,6 +6021,9 @@ Create_func_to_seconds::create_1_arg(THD *thd, Item *arg1)
 }
 
 
+Create_func_trunc Create_func_trunc::s_singleton;
+
+
 Create_func_ucase Create_func_ucase::s_singleton;
 
 Item*
@@ -6555,6 +6593,7 @@ const Native_func_registry func_array[] =
   { { STRING_WITH_LEN("TO_CHAR") }, BUILDER(Create_func_to_char)},
   { { STRING_WITH_LEN("TO_DAYS") }, BUILDER(Create_func_to_days)},
   { { STRING_WITH_LEN("TO_SECONDS") }, BUILDER(Create_func_to_seconds)},
+  { { STRING_WITH_LEN("TRUNC") }, BUILDER(Create_func_trunc)},
   { { STRING_WITH_LEN("UCASE") }, BUILDER(Create_func_ucase)},
   { { STRING_WITH_LEN("UNCOMPRESS") }, BUILDER(Create_func_uncompress)},
   { { STRING_WITH_LEN("UNCOMPRESSED_LENGTH") }, BUILDER(Create_func_uncompressed_length)},