MDEV-17831 TRUNCATE TABLE removes ROW_FORMAT=COMPRESSED

If a table had a KEY_BLOCK_SIZE attribute, but no ROW_FORMAT,
it would be created as ROW_FORMAT=COMPRESSED in InnoDB.
However, TRUNCATE TABLE would lose the KEY_BLOCK_SIZE attribute
and create the table with the innodb_default_row_format (DYNAMIC).

This is a regression that was introduced by MDEV-13564.

update_create_info_from_table(): Copy also KEY_BLOCK_SIZE.

mysql-test/suite/innodb/r/truncate.result

@@ -18,3 +18,12 @@ SELECT * FROM t1;
 c
 character
 DROP TABLE t1;
+#
+# MDEV-17831 TRUNCATE TABLE removes ROW_FORMAT=COMPRESSED
+#
+CREATE TABLE t1 (a SERIAL) ENGINE=InnoDB KEY_BLOCK_SIZE=4;
+TRUNCATE TABLE t1;
+SHOW TABLE STATUS;
+Name	Engine	Version	Row_format	Rows	Avg_row_length	Data_length	Max_data_length	Index_length	Data_free	Auto_increment	Create_time	Update_time	Check_time	Collation	Checksum	Create_options	Comment
+t1	InnoDB	#	Compressed	#	#	#	#	#	#	1	#	#	NULL	latin1_swedish_ci	NULL	key_block_size=4	
+DROP TABLE t1;

mysql-test/suite/innodb/t/truncate.test

@@ -27,3 +27,12 @@ ALTER TABLE t1 ROW_FORMAT=REDUNDANT;
 TRUNCATE TABLE t1;
 SELECT * FROM t1;
 DROP TABLE t1;
+
+--echo #
+--echo # MDEV-17831 TRUNCATE TABLE removes ROW_FORMAT=COMPRESSED
+--echo #
+CREATE TABLE t1 (a SERIAL) ENGINE=InnoDB KEY_BLOCK_SIZE=4;
+TRUNCATE TABLE t1;
+--replace_column 3 # 5 # 6 # 7 # 8 # 9 # 10 # 12 # 13 #
+SHOW TABLE STATUS;
+DROP TABLE t1;

sql/table.cc

@@ -3830,6 +3830,7 @@ void update_create_info_from_table(HA_CREATE_INFO *create_info, TABLE *table)
   create_info->table_options= share->db_create_options;
   create_info->avg_row_length= share->avg_row_length;
   create_info->row_type= share->row_type;
+  create_info->key_block_size= share->key_block_size;
   create_info->default_table_charset= share->table_charset;
   create_info->table_charset= 0;
   create_info->comment= share->comment;