RENAME TABLE log_table TO log_table_old, log_table_new TO log_table Instead of: TRUNCATE log_tableĭo: CREATE TABLE log_table_new LIKE log_table What’s faster than TRUNCATE, then? If you don’t have triggers nor FOREIGN KEYs, a RENAME TABLE can come to the rescue. TRUNCATE on tables with no FOREIGN KEYs should act fast: it translate to dropping the table and creating a new one (and it all depends on the MySQL version, see the manual). The TRUNCATE hanged nothing else would work minutes pass. But sometimes it just hangs I’ve has several such uncheerful events with InnoDB (Plugin) tables which were extensively written to. To preserve the size of these two core data structures.TRUNCATE is usually a fast operation (much faster than DELETE FROM). Several enums used in buf_block_t and buf_page_t to uint8_t. Rearranged the bug_page_t data members to get rid of holes and changed the type of "inherited" from the m_space->m_version when we init a page. Version number of the page to check for stale pages. Pointer to the fil_space_t instance that the page belongs to be deleted if the reference count is greater than zero. Reference count of how many pages point to this instance. or delete we bump up the version number. Version number of the instance, not persistent. We have to handle the impact on flushing when dealing with stale pages. Lazily before the old instance's memory can be freed. Very frequent) and we must ensure any stale pages are purged from the buffer pool The buffer pool from a dropped/truncated undo or temporary tablespace.Īdditionally temporary tablespaces reuse the tablespace ID on truncate (which is Theory can be reused therefore we must ensure that there must not be any page in Undo and Temporary tablespaces IDs are part of a smaller pool and in Tablespace ID therefore we can't have any reads of dropped/truncated user
For user tablespaces we do a drop/create which will change the This is required for temporary and undo tablespaces but not for user Each time we set buf_page_t::m_space we increment a reference count inįil_space_t. The pointer to the fil_space_t instance embedded in buf_page_t is referenceĬounted.
To reduce the stale page check overhead we will store a pointer to the Should be very cheap otherwise it will cost us on each page fetch from the buffer If the page is stale then weįree the page and force a disk read. Pool we need to detect if the page is stale or not. When a caller tries to fetch a page from the buffer Persistent store it must have a version number >= DVER. Referred toĭVER (Drop/Truncate version number) from now on. Structure (fil_space_t) when the tablespace is dropped or truncated. The idea is to increment the version number in the tablespace in memory data Tablespaces is not necessary if we can lazily remove the pages and get rid of the Scanning large LRU and FLUSH lists to remove pages from dropped/truncated That requires a separate fix and will need to be coordinated with Note: This doesn't fix the problem of physically unlinking a large file taking a There are several blogs out there describing the pain and the general problem.
Mysql truncate table free#
Afterwards, we will lazily free all pages from the Buffer Pool, that were referencing this tablespace, as we encounter them one by one. On tablespace drop or truncation we mark it as deleted, delete its file and report back to user the operation is finished. To solve this problem we generalize the solution from WL#11819 so that it can beĪpplied to all tablespaces and not just UNDO. Tablespaces reuses the same tablespace ID we cannot use the DROP/CREATE trick from OnĬonnection disconnect this can cause long stalls. Problem is exacerbated with the use of a pool of temporary tablespaces. Table is otherwise empty or has only one page in the buffer pool (or none).
Mysql truncate table full#
It gets worse, since InnoDB doesn't know how many pagesįrom a tablespace are in the buffer pool it will scan the full list even if the Pools, where large can be anything > 32G, this full list scan can slow down the
Tablespace from the LRU/FLUSH list to the buffer pool FREE list. Pages) list and moves all the pages that belong to the truncated/dropped When a table space is truncated or dropped InnoDB scans the LRU and FLUSH (dirty
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