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| author | Sergei Golubchik <sergii@pisem.net> | 2014-02-21 00:52:50 +0100 |
|---|---|---|
| committer | Sergei Golubchik <sergii@pisem.net> | 2014-02-21 00:52:50 +0100 |
| commit | e840d323e22b5737a8594c497209b7147154e912 (patch) | |
| tree | 20b321b70871bcf56bcd5085e9d65f22ec8fd1b6 /storage/federatedx | |
| parent | 62f355239007efc4546ea2d774ddb9ce1aa585f5 (diff) | |
| download | mariadb-git-e840d323e22b5737a8594c497209b7147154e912.tar.gz | |
MDEV-5698 Using ORDER BY in a FederatedX table is abnormally slow
In ::position() federated needs to know an element before the
current ("data_cursor") in the single-linked list. Replace list
traversal for every ::position() call (which is O(n^2)) with remembering
the current element before it's advanced by mysql_fetch_row().
storage/federatedx/federatedx_io_mysql.cc:
mdev:5698
Diffstat (limited to 'storage/federatedx')
| -rw-r--r-- | storage/federatedx/federatedx_io_mysql.cc | 17 |
1 files changed, 5 insertions, 12 deletions
diff --git a/storage/federatedx/federatedx_io_mysql.cc b/storage/federatedx/federatedx_io_mysql.cc index 8df54f9c6f2..c6a5732c564 100644 --- a/storage/federatedx/federatedx_io_mysql.cc +++ b/storage/federatedx/federatedx_io_mysql.cc @@ -62,6 +62,7 @@ struct mysql_position class federatedx_io_mysql :public federatedx_io { MYSQL mysql; /* MySQL connection */ + MYSQL_ROWS *current; DYNAMIC_ARRAY savepoints; bool requested_autocommit; bool actual_autocommit; @@ -510,7 +511,9 @@ my_ulonglong federatedx_io_mysql::get_num_rows(FEDERATEDX_IO_RESULT *io_result) FEDERATEDX_IO_ROW *federatedx_io_mysql::fetch_row(FEDERATEDX_IO_RESULT *io_result) { - return (FEDERATEDX_IO_ROW *) mysql_fetch_row((MYSQL_RES *) io_result); + MYSQL_RES *result= (MYSQL_RES*)io_result; + current= result->data_cursor; + return (FEDERATEDX_IO_ROW *) mysql_fetch_row(result); } @@ -619,19 +622,9 @@ size_t federatedx_io_mysql::get_ref_length() const void federatedx_io_mysql::mark_position(FEDERATEDX_IO_RESULT *io_result, void *ref) { - MYSQL_ROWS *tmp= 0; mysql_position& pos= *reinterpret_cast<mysql_position*>(ref); pos.result= (MYSQL_RES *) io_result; - - if (pos.result && pos.result->data) - { - for (tmp= pos.result->data->data; - tmp && (tmp->next != pos.result->data_cursor); - tmp= tmp->next) - {} - } - - pos.offset= tmp; + pos.offset= current; } int federatedx_io_mysql::seek_position(FEDERATEDX_IO_RESULT **io_result, |