MDEV-28699 Shrink temporary tablespaces without restart
- Introduced the variable "innodb_truncate_temporary_tablespace_now" to shrink the temporary tablespace. Steps for shrinking the temporary tablespace: 1) Find the last used extent in temporary tablespace by iterating through the BITMAP in extent descriptor pages 2) If the last used extent is lesser than user specified size then set desired target size to user specified size 3) Store the page contents of "to be modified" extent descriptor pages, latches the "to be modified" extent descriptor pages and check for buffer pool memory availability 4) Update the FSP_SIZE and FSP_FREE_LIMIT in header page 5) Remove the "to be truncated" pages from FSP_FREE and FSP_FREE_FRAG list 6) Reset the bitmap in the last descriptor pages for the "to be truncated" pages. 7) Clear the freed range in temporary tablespace which are to be truncated. 8) Evict the "to be truncated" temporary tablespace pages from LRU list. 9) In case of multiple files, calculate the truncated last file size and do truncation in last file 10) Commit the mini-transaction for shrinking the tablespace
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