NFC: refactor Field::is_equal() and related stuff

Make Field::is_equal() const and return bool as it's a naturally fitting
type for it. Also it's agrument was narrowed to Column_definition.

InnoDB can change type of some columns by itself. InnoDB-specific code used to
reside in Field_xxx:is_equal() methods. Now engine-specific stuff was
moved to a virtual methods of handler::can_convert{string,varstring,blob,geom}.
These methods are called by Field::can_be_converted_by_engine() which is a
double dispatch pattern.

Some InnoDB-specific code still resides in compare_keys_but_name(). It should
be moved from here someday to handler::compare_key_parts(...) or similar.

IS_EQUAL_WITH_REINTERPRET_COMPATIBLE_CHARSET
IS_EQUAL_WITH_REINTERPRET_COMPATIBLE_CHARSET_BUT_COLLATE: both was removed

IS_EQUAL_NO, IS_EQUAL_YES are not needed now and should be removed
along with deprecated handler::check_if_incompatible_data().

HA_EXTENDED_TYPES_CONVERSION: was removed as such logic is not needed now by
server code.

ALTER_COLUMN_EQUAL_PACK_LENGTH: was renamed to a more generic
ALTER_COLUMN_TYPE_CHANGE_BY_ENGINE

3 files changed, 152 insertions, 9 deletions

diff --git a/storage/innobase/handler/ha_innodb.cc b/storage/innobase/handler/ha_innodb.cc
index 88ea6f5e642..107fcac762a 100644
--- a/storage/innobase/handler/ha_innodb.cc
+++ b/storage/innobase/handler/ha_innodb.cc
@@ -54,6 +54,7 @@ this program; if not, write to the Free Software Foundation, Inc.,
 #include <my_bitmap.h>
 #include <mysql/service_thd_alloc.h>
 #include <mysql/service_thd_wait.h>
+#include "field.h"
 
 // MYSQL_PLUGIN_IMPORT extern my_bool lower_case_file_system;
 // MYSQL_PLUGIN_IMPORT extern char mysql_unpacked_real_data_home[];
@@ -6141,11 +6142,6 @@ no_such_table:
 		DBUG_RETURN(HA_ERR_NO_SUCH_TABLE);
 	}
 
-	if (!ib_table->not_redundant()) {
-		m_int_table_flags |= HA_EXTENDED_TYPES_CONVERSION;
-		cached_table_flags |= HA_EXTENDED_TYPES_CONVERSION;
-	}
-
 	size_t n_fields = omits_virtual_cols(*table_share)
 		? table_share->stored_fields : table_share->fields;
 	size_t n_cols = dict_table_get_n_user_cols(ib_table)
@@ -20875,6 +20871,146 @@ bool ha_innobase::rowid_filter_push(Rowid_filter* pk_filter)
 	DBUG_RETURN(false);
 }
 
+static bool
+is_part_of_a_primary_key(const Field* field)
+{
+	const TABLE_SHARE* s = field->table->s;
+
+	return s->primary_key != MAX_KEY
+	       && field->part_of_key.is_set(s->primary_key);
+}
+
+bool
+ha_innobase::can_convert_string(const Field_string* field,
+				const Column_definition& new_type) const
+{
+	DBUG_ASSERT(!field->compression_method());
+	if (new_type.type_handler() != field->type_handler()) {
+		return false;
+	}
+
+	if (new_type.char_length < field->char_length()) {
+		return false;
+	}
+
+	if (new_type.charset != field->charset()) {
+		if (new_type.length != field->max_display_length()
+		    && !m_prebuilt->table->not_redundant()) {
+			return IS_EQUAL_NO;
+		}
+
+		Charset field_cs(field->charset());
+		if (!field_cs.encoding_allows_reinterpret_as(
+			new_type.charset)) {
+			return false;
+		}
+
+		if (!field_cs.eq_collation_specific_names(new_type.charset)) {
+			return !is_part_of_a_primary_key(field);
+		}
+
+		return true;
+	}
+
+	if (new_type.length != field->max_display_length()) {
+		return false;
+	}
+
+	return true;
+}
+
+static bool
+supports_enlarging(const dict_table_t* table, const Field_varstring* field,
+		   const Column_definition& new_type)
+{
+	return field->field_length <= 127 || new_type.length <= 255
+	       || field->field_length > 255 || !table->not_redundant();
+}
+
+bool
+ha_innobase::can_convert_varstring(const Field_varstring* field,
+				   const Column_definition& new_type) const
+{
+	if (new_type.length < field->field_length) {
+		return false;
+	}
+
+	if (new_type.char_length < field->char_length()) {
+		return false;
+	}
+
+	if (!new_type.compression_method() != !field->compression_method()) {
+		return false;
+	}
+
+	if (new_type.type_handler() != field->type_handler()) {
+		return false;
+	}
+
+	if (new_type.charset != field->charset()) {
+		if (!supports_enlarging(m_prebuilt->table, field, new_type)) {
+			return false;
+		}
+
+		Charset field_cs(field->charset());
+		if (!field_cs.encoding_allows_reinterpret_as(
+			new_type.charset)) {
+			return false;
+		}
+
+		if (!field_cs.eq_collation_specific_names(new_type.charset)) {
+			return !is_part_of_a_primary_key(field);
+		}
+
+		return true;
+	}
+
+	if (new_type.length != field->field_length) {
+		if (!supports_enlarging(m_prebuilt->table, field, new_type)) {
+			return false;
+		}
+
+		return true;
+	}
+
+	return true;
+}
+
+bool
+ha_innobase::can_convert_blob(const Field_blob* field,
+			      const Column_definition& new_type) const
+{
+	if (new_type.type_handler() != field->type_handler()) {
+		return false;
+	}
+
+	if (!new_type.compression_method() != !field->compression_method()) {
+		return false;
+	}
+
+	if (new_type.pack_length != field->pack_length()) {
+		return false;
+	}
+
+	if (new_type.charset != field->charset()) {
+		Charset field_cs(field->charset());
+		if (!field_cs.encoding_allows_reinterpret_as(
+			new_type.charset)) {
+			return false;
+		}
+
+		if (!field_cs.eq_collation_specific_names(new_type.charset)) {
+			bool is_part_of_a_key
+			    = !field->part_of_key.is_clear_all();
+			return !is_part_of_a_key;
+		}
+
+		return true;
+	}
+
+	return true;
+}
+
 /******************************************************************//**
 Use this when the args are passed to the format string from
 errmsg-utf8.txt directly as is.
diff --git a/storage/innobase/handler/ha_innodb.h b/storage/innobase/handler/ha_innodb.h
index 11b69974558..60c560f9bc7 100644
--- a/storage/innobase/handler/ha_innodb.h
+++ b/storage/innobase/handler/ha_innodb.h
@@ -437,6 +437,13 @@ public:
 	@retval	false if pushed (always) */
 	bool rowid_filter_push(Rowid_filter *rowid_filter);
 
+	bool can_convert_string(const Field_string* field,
+				const Column_definition& new_field) const;
+	bool can_convert_varstring(const Field_varstring* field,
+				   const Column_definition& new_field) const;
+	bool can_convert_blob(const Field_blob* field,
+			      const Column_definition& new_field) const;
+
 protected:
 	/**
 	MySQL calls this method at the end of each statement. This method
diff --git a/storage/innobase/handler/handler0alter.cc b/storage/innobase/handler/handler0alter.cc
index e4f5a04f668..08e549629fd 100644
--- a/storage/innobase/handler/handler0alter.cc
+++ b/storage/innobase/handler/handler0alter.cc
@@ -131,7 +131,7 @@ static const alter_table_operations INNOBASE_ALTER_INSTANT
 	| ALTER_COLUMN_NAME
 	| ALTER_ADD_VIRTUAL_COLUMN
 	| INNOBASE_FOREIGN_OPERATIONS
-	| ALTER_COLUMN_EQUAL_PACK_LENGTH
+	| ALTER_COLUMN_TYPE_CHANGE_BY_ENGINE
 	| ALTER_COLUMN_UNVERSIONED
 	| ALTER_RENAME_INDEX
 	| ALTER_DROP_VIRTUAL_COLUMN;
@@ -8332,7 +8332,7 @@ ok_exit:
 	rebuild_templ
 	     = ctx->need_rebuild()
 	       || ((ha_alter_info->handler_flags
-		& ALTER_COLUMN_EQUAL_PACK_LENGTH)
+		& ALTER_COLUMN_TYPE_CHANGE_BY_ENGINE)
 		&& alter_templ_needs_rebuild(
 		   altered_table, ha_alter_info, ctx->new_table));
 
@@ -9194,7 +9194,7 @@ innobase_rename_or_enlarge_columns_try(
 	DBUG_ENTER("innobase_rename_or_enlarge_columns_try");
 
 	if (!(ha_alter_info->handler_flags
-	      & (ALTER_COLUMN_EQUAL_PACK_LENGTH
+	      & (ALTER_COLUMN_TYPE_CHANGE_BY_ENGINE
 		 | ALTER_COLUMN_NAME))) {
 		DBUG_RETURN(false);
 	}
@@ -9242,7 +9242,7 @@ innobase_rename_or_enlarge_columns_cache(
 	dict_table_t*		user_table)
 {
 	if (!(ha_alter_info->handler_flags
-	      & (ALTER_COLUMN_EQUAL_PACK_LENGTH
+	      & (ALTER_COLUMN_TYPE_CHANGE_BY_ENGINE
 		 | ALTER_COLUMN_NAME))) {
 		return;
 	}