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MDEV-22556: Incorrect result for window function when using encrypt-tmp-files=ON

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The issue here is that end_of_file for encrypted temporary IO_CACHE (used by filesort) is updated
using lseek.
Encryption adds storage overhead and hides it from the caller by recalculating offsets and lengths.
Two different IO_CACHE cannot possibly modify the same file
because the encryption key is randomly generated and stored in the IO_CACHE.
So when the tempfiles are encrypted DO NOT use lseek to change end_of_file.

Further observations about updating end_of_file using lseek
1) The end_of_file update is only used for binlog index files
2) The whole point is to update file length when the file was modified via a different file descriptor.
3) The temporary IO_CACHE files can never be modified via a different file descriptor.
4) For encrypted temporary IO_CACHE, end_of_file should not be updated with lseek
This commit is contained in:
Varun Gupta
2020-05-15 02:37:16 +05:30
parent 66f1e288a1
commit 0a5668f512
4 changed files with 47 additions and 2 deletions
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18
mysql-test/suite/encryption/r/tempfiles_encrypted.result Normal file
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#
# Tests when the temporary files are encrypted
#
select @@encrypt_tmp_files;
@@encrypt_tmp_files
1
#
# MDEV-22556: Incorrect result for window function when using encrypt-tmp-files=ON
#
set @save_sort_buffer_size=@@sort_buffer_size;
set sort_buffer_size= 2000;
create table t1( a DECIMAL(12,0) DEFAULT NULL, b VARCHAR(20) DEFAULT NULL, c DECIMAL(12,0) DEFAULT NULL)engine=INNODB;
insert into t1 select seq, seq, seq from seq_1_to_5000;
select count(*) from (select a, b, c, ROW_NUMBER() OVER (PARTITION BY a) FROM t1)q;
count(*)
5000
set @@sort_buffer_size=@save_sort_buffer_size;
drop table t1;