MDEV-12506 Split Item_func_min_max::fix_length_and_dec() into methods in Type_handler + MDEV-12497 + MDEV-12504

This patch does the following:

1. Adds a new method Type_handler_hybrid_field_type::aggregate_for_min_max()

   - For non-traditional data types it uses
     type_handler_data->m_type_aggregator_for_result.find_handler()
     This allows pluggable data types to define in the future their
     own behavior of the result data type detection for LEAST/GREATEST.
     Also, this disallows expressions of the GEOMETRY data type
     (and its variants such as POINT) to be mixed in with
     numeric and temporal data types in LEAST/GREATEST.

   - For traditional data types it reproduces the old behavior of
     the result data type detection (but not attributes, see below).

2. Adds a new virtual method Type_handler::Item_func_min_max_fix_attributes()
   and reuses as much as possible the code that calculates data type attributes
   for CASE-alike functions (e.g. CASE..THEN, COALESCE, IF).

   As the old code responsible for attributes calculation in the old
   implementation of Item_func_min_max::fix_length_and_dec()
   was not fully correct, this automatically fixes the following bugs:

   - MDEV-12497 Wrong data type for LEAST(latin1_expr, utf8_expr)
     The old fix_length_and_dec() calculated max_length before
     character set aggregation. Now max_length is calculated after, in
     Item_func::count_string_length() called from
     Item_func::aggregate_attributes_string() called from
     Type_handler_string_result::Item_hybrid_func_fix_attributes() called from
     Type_handler::Item_func_min_max_fix_attributes() called from
     Item_func_min_max::fix_length_and_dec().

   - MDEV-12504 Wrong data type for LEAST(date_expr,time_expr)
     The old fix_length_and_dec() simply used the maximum of max_length
     among all arguments to set its own max_length and did not take
     into account that a mixture of DATE and TIME becomes DATETIME.
     Now this is correctly handled by:
     Type_handler_datetime_common::Item_hybrid_func_fix_attributes() called from
     Type_handler::Item_func_min_max_fix_attributes() called from
     Item_func_min_max::fix_length_and_dec().

3. Removes the old implementation of Item_func_min_max::fix_length_and_dec()
   and replaces it to calls of the new methods.

4. Cleanup: moves the code related to unsigned_flag processing
   from Type_handler_hybrid_field_type::aggregate_for_result()
   to   Type_handler_int_result::Item_hybrid_func_fix_attributes().
   This is done:
   - to avoid code duplication in
     Type_handler_hybrid_field_type::aggregate_for_min_max()
   - to get rid of one more call for field_type(), which is unfriendly
     to the conceipt of pluggable data types.

1 files changed, 190 insertions, 1 deletions

diff --git a/mysql-test/r/gis.result b/mysql-test/r/gis.result
index 6a7b7e7b8bf..77150ee3142 100644
--- a/mysql-test/r/gis.result
+++ b/mysql-test/r/gis.result
@@ -2792,7 +2792,7 @@ t2	CREATE TABLE `t2` (
 CREATE TABLE t2 AS SELECT a FROM t1 UNION SELECT b FROM t1
 ERROR: 
 Illegal parameter data types set and geometry for operation 'UNION'
-# This does not preserve geometry type (MDEV-9405)
+# This does not preserve geometry type (MDEV-12560)
 CREATE TABLE t1 AS SELECT COALESCE(NULL, Point(1,1));
 SHOW CREATE TABLE t1;
 Table	Create Table
@@ -3711,6 +3711,195 @@ CASE a WHEN POINT(1,1) THEN "a" WHEN POINT(1,2) THEN "b" END
 DROP PROCEDURE p1;
 DROP PROCEDURE p2;
 #
+# MDEV-12506 Split Item_func_min_max::fix_length_and_dec() into methods in Type_handler
+#
+CREATE PROCEDURE p2(query TEXT)
+BEGIN
+DECLARE errcount INT DEFAULT 0;
+DECLARE CONTINUE HANDLER FOR SQLEXCEPTION
+BEGIN
+SET errcount = errcount+1;
+#SHOW WARNINGS;
+GET DIAGNOSTICS CONDITION 1 @p= MESSAGE_TEXT;
+SELECT @p AS `ERROR: `;
+END;
+SELECT query AS ``;
+EXECUTE IMMEDIATE query;
+IF errcount = 0
+THEN
+SHOW CREATE TABLE t2;
+DROP TABLE t2;
+END IF;
+END;
+$$
+CREATE PROCEDURE p1(query TEXT)
+BEGIN
+SELECT query AS `-------------------------------------`;
+EXECUTE IMMEDIATE query;
+CALL p2('CREATE TABLE t2 AS SELECT LEAST(a,b) FROM t1');
+DROP TABLE t1;
+END;
+$$
+-------------------------------------
+CREATE TABLE t1 (a CHAR(10), b Point)
+
+CREATE TABLE t2 AS SELECT LEAST(a,b) FROM t1
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `LEAST(a,b)` longblob DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+-------------------------------------
+CREATE TABLE t1 (a VARCHAR(10), b Point)
+
+CREATE TABLE t2 AS SELECT LEAST(a,b) FROM t1
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `LEAST(a,b)` longblob DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+-------------------------------------
+CREATE TABLE t1 (a TINYTEXT, b Point)
+
+CREATE TABLE t2 AS SELECT LEAST(a,b) FROM t1
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `LEAST(a,b)` longblob DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+-------------------------------------
+CREATE TABLE t1 (a TEXT, b Point)
+
+CREATE TABLE t2 AS SELECT LEAST(a,b) FROM t1
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `LEAST(a,b)` longblob DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+-------------------------------------
+CREATE TABLE t1 (a MEDIUMTEXT, b Point)
+
+CREATE TABLE t2 AS SELECT LEAST(a,b) FROM t1
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `LEAST(a,b)` longblob DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+-------------------------------------
+CREATE TABLE t1 (a LONGTEXT, b Point)
+
+CREATE TABLE t2 AS SELECT LEAST(a,b) FROM t1
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `LEAST(a,b)` longblob DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+-------------------------------------
+CREATE TABLE t1 (a TINYINT, b Point)
+
+CREATE TABLE t2 AS SELECT LEAST(a,b) FROM t1
+ERROR: 
+Illegal parameter data types tinyint and geometry for operation 'least'
+-------------------------------------
+CREATE TABLE t1 (a SMALLINT, b Point)
+
+CREATE TABLE t2 AS SELECT LEAST(a,b) FROM t1
+ERROR: 
+Illegal parameter data types smallint and geometry for operation 'least'
+-------------------------------------
+CREATE TABLE t1 (a MEDIUMINT, b Point)
+
+CREATE TABLE t2 AS SELECT LEAST(a,b) FROM t1
+ERROR: 
+Illegal parameter data types mediumint and geometry for operation 'least'
+-------------------------------------
+CREATE TABLE t1 (a INT, b Point)
+
+CREATE TABLE t2 AS SELECT LEAST(a,b) FROM t1
+ERROR: 
+Illegal parameter data types int and geometry for operation 'least'
+-------------------------------------
+CREATE TABLE t1 (a BIGINT, b Point)
+
+CREATE TABLE t2 AS SELECT LEAST(a,b) FROM t1
+ERROR: 
+Illegal parameter data types bigint and geometry for operation 'least'
+-------------------------------------
+CREATE TABLE t1 (a FLOAT, b Point)
+
+CREATE TABLE t2 AS SELECT LEAST(a,b) FROM t1
+ERROR: 
+Illegal parameter data types float and geometry for operation 'least'
+-------------------------------------
+CREATE TABLE t1 (a DOUBLE, b Point)
+
+CREATE TABLE t2 AS SELECT LEAST(a,b) FROM t1
+ERROR: 
+Illegal parameter data types double and geometry for operation 'least'
+-------------------------------------
+CREATE TABLE t1 (a DECIMAL(10,2), b Point)
+
+CREATE TABLE t2 AS SELECT LEAST(a,b) FROM t1
+ERROR: 
+Illegal parameter data types decimal and geometry for operation 'least'
+-------------------------------------
+CREATE TABLE t1 (a BIT(8), b Point)
+
+CREATE TABLE t2 AS SELECT LEAST(a,b) FROM t1
+ERROR: 
+Illegal parameter data types bit and geometry for operation 'least'
+-------------------------------------
+CREATE TABLE t1 (a TIME, b Point)
+
+CREATE TABLE t2 AS SELECT LEAST(a,b) FROM t1
+ERROR: 
+Illegal parameter data types time and geometry for operation 'least'
+-------------------------------------
+CREATE TABLE t1 (a DATE, b Point)
+
+CREATE TABLE t2 AS SELECT LEAST(a,b) FROM t1
+ERROR: 
+Illegal parameter data types date and geometry for operation 'least'
+-------------------------------------
+CREATE TABLE t1 (a DATETIME, b Point)
+
+CREATE TABLE t2 AS SELECT LEAST(a,b) FROM t1
+ERROR: 
+Illegal parameter data types datetime and geometry for operation 'least'
+-------------------------------------
+CREATE TABLE t1 (a TIMESTAMP, b Point)
+
+CREATE TABLE t2 AS SELECT LEAST(a,b) FROM t1
+ERROR: 
+Illegal parameter data types timestamp and geometry for operation 'least'
+-------------------------------------
+CREATE TABLE t1 (a YEAR, b Point)
+
+CREATE TABLE t2 AS SELECT LEAST(a,b) FROM t1
+ERROR: 
+Illegal parameter data types year and geometry for operation 'least'
+# This LEAST(ENUM,GEOMETRY) creates BLOB, but fails on error with UNION (see MDEV-12503)
+-------------------------------------
+CREATE TABLE t1 (a ENUM(0x61), b Point)
+
+CREATE TABLE t2 AS SELECT LEAST(a,b) FROM t1
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `LEAST(a,b)` longblob DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+-------------------------------------
+CREATE TABLE t1 (a SET(0x61), b Point)
+
+CREATE TABLE t2 AS SELECT LEAST(a,b) FROM t1
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `LEAST(a,b)` longblob DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+# This does not preserve geometry type (MDEV-9405)
+CREATE TABLE t1 AS SELECT LEAST(NULL, Point(1,1));
+SHOW CREATE TABLE t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `LEAST(NULL, Point(1,1))` geometry DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+DROP TABLE t1;
+DROP PROCEDURE p1;
+DROP PROCEDURE p2;
+#
 # MDEV-12001 Split Item_func_round::fix_length_and_dec to virtual methods in Type_handler
 #
 CREATE TABLE t1 (a GEOMETRY);