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, 72 insertions, 1 deletions

diff --git a/mysql-test/t/gis.test b/mysql-test/t/gis.test
index 1b355b70bc6..9b3dc69a7d1 100644
--- a/mysql-test/t/gis.test
+++ b/mysql-test/t/gis.test
@@ -1789,7 +1789,7 @@ CALL p1('CREATE TABLE t1 (a ENUM(0x61), b Point)');
 CALL p1('CREATE TABLE t1 (a SET(0x61), b Point)');
 --enable_query_log
 
---echo # This does not preserve geometry type (MDEV-9405)
+--echo # This does not preserve geometry type (MDEV-12560)
 CREATE TABLE t1 AS SELECT COALESCE(NULL, Point(1,1));
 SHOW CREATE TABLE t1;
 DROP TABLE t1;
@@ -1870,6 +1870,77 @@ DROP PROCEDURE p2;
 
 
 --echo #
+--echo # MDEV-12506 Split Item_func_min_max::fix_length_and_dec() into methods in Type_handler
+--echo #
+
+DELIMITER $$;
+CREATE PROCEDURE p2(query TEXT)
+BEGIN
+  DECLARE errcount INT DEFAULT 0;
+  DECLARE CONTINUE HANDLER FOR SQLEXCEPTION
+  BEGIN
+    SET errcount = errcount+1;
+    #SHOW WARNINGS;
+    GET DIAGNOSTICS CONDITION 1 @p= MESSAGE_TEXT;
+    SELECT @p AS `ERROR: `;
+  END;
+  SELECT query AS ``;
+  EXECUTE IMMEDIATE query;
+  IF errcount = 0
+  THEN
+    SHOW CREATE TABLE t2;
+    DROP TABLE t2;
+  END IF;
+END;
+$$
+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;
+$$
+DELIMITER ;$$
+
+--disable_query_log
+CALL p1('CREATE TABLE t1 (a CHAR(10), b Point)');
+CALL p1('CREATE TABLE t1 (a VARCHAR(10), b Point)');
+CALL p1('CREATE TABLE t1 (a TINYTEXT, b Point)');
+CALL p1('CREATE TABLE t1 (a TEXT, b Point)');
+CALL p1('CREATE TABLE t1 (a MEDIUMTEXT, b Point)');
+CALL p1('CREATE TABLE t1 (a LONGTEXT, b Point)');
+
+CALL p1('CREATE TABLE t1 (a TINYINT, b Point)');
+CALL p1('CREATE TABLE t1 (a SMALLINT, b Point)');
+CALL p1('CREATE TABLE t1 (a MEDIUMINT, b Point)');
+CALL p1('CREATE TABLE t1 (a INT, b Point)');
+CALL p1('CREATE TABLE t1 (a BIGINT, b Point)');
+CALL p1('CREATE TABLE t1 (a FLOAT, b Point)');
+CALL p1('CREATE TABLE t1 (a DOUBLE, b Point)');
+CALL p1('CREATE TABLE t1 (a DECIMAL(10,2), b Point)');
+CALL p1('CREATE TABLE t1 (a BIT(8), b Point)');
+
+CALL p1('CREATE TABLE t1 (a TIME, b Point)');
+CALL p1('CREATE TABLE t1 (a DATE, b Point)');
+CALL p1('CREATE TABLE t1 (a DATETIME, b Point)');
+CALL p1('CREATE TABLE t1 (a TIMESTAMP, b Point)');
+CALL p1('CREATE TABLE t1 (a YEAR, b Point)');
+
+--echo # This LEAST(ENUM,GEOMETRY) creates BLOB, but fails on error with UNION (see MDEV-12503)
+CALL p1('CREATE TABLE t1 (a ENUM(0x61), b Point)');
+CALL p1('CREATE TABLE t1 (a SET(0x61), b Point)');
+--enable_query_log
+
+--echo # This does not preserve geometry type (MDEV-9405)
+CREATE TABLE t1 AS SELECT LEAST(NULL, Point(1,1));
+SHOW CREATE TABLE t1;
+DROP TABLE t1;
+
+DROP PROCEDURE p1;
+DROP PROCEDURE p2;
+
+--echo #
 --echo # MDEV-12001 Split Item_func_round::fix_length_and_dec to virtual methods in Type_handler
 --echo #