A few days ago, when executing DROP TABLE in MySQL, all processes including DDL and DML were hung until DROP TABLE was completed. I am confused about this phenomenon.
I have reviewed the source codes of MySQL to check how MySQL internally handle DROP TABLE.
When user trigger DROP TABLE command:
########################MySQL SERVER drop table########################
/* Sql_table.cc delete (drop) tables. */
bool mysql_rm_table( )
/* Execute the drop of a normal or temporary table */
int mysql_rm_table_part2 ()
/* Remove matching tables from the HANDLER’s hash table. */
void mysql_ha_rm_tables ()
/* Mark all entries with the table as deleted to force an reopen of the table */
remove_table_from_cache ()
/* remove engine files */ LINE 2024
int handler::ha_delete_table(const char *name)
file->ha_delete_table(path) line 1991
int handler::delete_table(const char *name) //Delete data table
/* Here INNODB inherits parent class handler ，
it actually calls int ha_innobase::delete_table
go to next #### INNODB handle drop table ####
if it's other engine, directly delete data file, continue*/
int mysys::my_delete_with_symlink(const char *name, myf MyFlags)
int mysys::my_delete(const char *name, myf MyFlags)
/* Delete the table definition file */ LINE 2042
int mysys::my_delete()
/* clear query cache*/
query_cache_invalidate3
/* writes to BINLOG */
############# INNODB handle drop table ##################
/* Drops a table from an InnoDB database. */
int ha_innobase::delete_table( const char* name) ; // Drop table with INNODB
int row_drop_table_for_mysql()
/* Serialize data dictionary operations with dictionary mutex:
row_mysql_lock_data_dictionary(trx);
/* Update dictionary table (MEMDB,information_schema), line 3178 */
que_eval_sql(info, “PROCEDURE DROP_TABLE_PROC () IS\n”
/*Here using a PROCEDURE*/
/* update dictionary table(CACHE) */
void dict_table_remove_from_cache(dict_table_t* table))
/* Delete data file
/* Deletes a single-table tablespace */
ibool fil_delete_tablespace()
/* Frees a space object from the tablespace memory cache*/
ibool fil_space_free ()
/* Deletes a file. The file has to be closed before calling this. */
ibool os_file_delete ()
unlink((const char*)name);
/* release the lock */
row_mysql_unlock_data_dictionary(trx);
Source : http://www.mysqlops.com/2011/02/18/mysql-drop-table-%e5%a4%84%e7%90%86%e8%bf%87%e7%a8%8b.html
