InnoDB: commit after every 10000 rows in ALTER TABLE

innobase/include/lock0lock.h

@@ -463,6 +463,14 @@ lock_rec_hash(
 	ulint	space,	/* in: space */
 	ulint	page_no);/* in: page number */
 /*************************************************************************
+Gets the table covered by an IX table lock. */
+
+dict_table_t*
+lock_get_ix_table(
+/*==============*/
+			/* out: the table covered by the lock */
+	lock_t*	lock);	/* in: table lock */
+/*************************************************************************
 Checks that a transaction id is sensible, i.e., not in the future. */
 
 ibool

innobase/include/row0mysql.h

@@ -175,8 +175,12 @@ int
 row_lock_table_for_mysql(
 /*=====================*/
 					/* out: error code or DB_SUCCESS */
-	row_prebuilt_t*	prebuilt);	/* in: prebuilt struct in the MySQL
+	row_prebuilt_t*	prebuilt,	/* in: prebuilt struct in the MySQL
 					table handle */
+	dict_table_t*	table);		/* in: table to LOCK_IX, or NULL
+					if prebuilt->table should be
+					locked as LOCK_TABLE_EXP |
+					prebuilt->select_lock_type */
 /*************************************************************************
 Does an insert for MySQL. */
 

innobase/lock/lock0lock.c

@@ -395,6 +395,19 @@ lock_rec_get_nth_bit(
 	return(ut_bit_get_nth(b, bit_index));
 }	
 
+/*************************************************************************
+Gets the table covered by an IX table lock. */
+
+dict_table_t*
+lock_get_ix_table(
+/*==============*/
+			/* out: the table covered by the lock */
+	lock_t*	lock)	/* in: table lock */
+{
+	ut_a(lock->type_mode == (LOCK_TABLE | LOCK_IX));
+	return(lock->un_member.tab_lock.table);
+}
+
 /*************************************************************************/
 
 #define lock_mutex_enter_kernel()	mutex_enter(&kernel_mutex)

innobase/row/row0mysql.c

@@ -779,8 +779,12 @@ int
 row_lock_table_for_mysql(
 /*=====================*/
 					/* out: error code or DB_SUCCESS */
-	row_prebuilt_t*	prebuilt)	/* in: prebuilt struct in the MySQL
+	row_prebuilt_t*	prebuilt,	/* in: prebuilt struct in the MySQL
 					table handle */
+	dict_table_t*	table)		/* in: table to LOCK_IX, or NULL
+					if prebuilt->table should be
+					locked as LOCK_TABLE_EXP |
+					prebuilt->select_lock_type */
 {
 	trx_t*		trx 		= prebuilt->trx;
 	que_thr_t*	thr;
@@ -813,8 +817,12 @@ run_again:
 
 	trx_start_if_not_started(trx);
 
-	err = lock_table(LOCK_TABLE_EXP, prebuilt->table,
-		prebuilt->select_lock_type, thr);
+	if (table) {
+		err = lock_table(0, table, LOCK_IX, thr);
+	} else {
+		err = lock_table(LOCK_TABLE_EXP, prebuilt->table,
+			prebuilt->select_lock_type, thr);
+	}
 
 	trx->error_state = err;
 

sql/ha_innodb.cc

@@ -2314,7 +2314,31 @@ ha_innobase::write_row(
         if (table->timestamp_field_type & TIMESTAMP_AUTO_SET_ON_INSERT)
                 table->timestamp_field->set_time();
 
+	num_write_row++;
+
+	if (user_thd->lex->sql_command == SQLCOM_ALTER_TABLE
+	    && num_write_row > 10000) {
+		/* ALTER TABLE is COMMITted at every 10000 copied rows.
+		The IX table lock for the original table has to be re-issued.
+		As this method will be called on a temporary table where the
+		contents of the original table is being copied to, it is
+		a bit tricky to determine the source table.  The cursor
+		position in the source table need not be adjusted after the
+		intermediate COMMIT, since writes by other transactions are
+		being blocked by a MySQL table lock TL_WRITE_ALLOW_READ. */
+		ut_a(prebuilt->trx->mysql_n_tables_locked == 2);
+		ut_a(UT_LIST_GET_LEN(prebuilt->trx->trx_locks) >= 2);
+		dict_table_t* table = lock_get_ix_table(
+				UT_LIST_GET_FIRST(prebuilt->trx->trx_locks));
+		num_write_row = 0;
+		innobase_commit(user_thd, prebuilt->trx);
+		user_thd->transaction.all.innodb_active_trans = 1;
+		row_lock_table_for_mysql(prebuilt, table);
+		goto new_trx;
+	}
+
 	if (last_query_id != user_thd->query_id) {
+	new_trx:
 	        prebuilt->sql_stat_start = TRUE;
                 last_query_id = user_thd->query_id;
 
@@ -4986,7 +5010,7 @@ ha_innobase::external_lock(
 			if (thd->in_lock_tables &&
 			    thd->variables.innodb_table_locks) {
 				ulint	error;
-				error = row_lock_table_for_mysql(prebuilt);
+				error = row_lock_table_for_mysql(prebuilt, 0);
 
 				if (error != DB_SUCCESS) {
 					error = convert_error_code_to_mysql(

sql/ha_innodb.h

@@ -64,6 +64,7 @@ class ha_innobase: public handler
 	uint		last_match_mode;/* match mode of the latest search:
 					ROW_SEL_EXACT, ROW_SEL_EXACT_PREFIX,
 					or undefined */
+	uint		num_write_row;	/* number of write_row() calls */
 	longlong	auto_inc_counter_for_this_stat;
 	ulong max_supported_row_length(const byte *buf);
 
@@ -85,7 +86,8 @@ class ha_innobase: public handler
 			  HA_PRIMARY_KEY_IN_READ_INDEX |
 			  HA_TABLE_SCAN_ON_INDEX),
 	  last_dup_key((uint) -1),
-	  start_of_scan(0)
+	  start_of_scan(0),
+	  num_write_row(0)
   	{
   	}
   	~ha_innobase() {}