diff options
Diffstat (limited to 'sql/examples/ha_archive.cc')
| -rw-r--r-- | sql/examples/ha_archive.cc | 27 |
1 files changed, 15 insertions, 12 deletions
diff --git a/sql/examples/ha_archive.cc b/sql/examples/ha_archive.cc index 436c72702a0..b33b5102e69 100644 --- a/sql/examples/ha_archive.cc +++ b/sql/examples/ha_archive.cc @@ -43,18 +43,20 @@ handle bulk inserts as well (that is if someone was trying to read at the same time since we would want to flush). - A "meta" file is kept. All this file does is contain information on - the number of rows. + A "meta" file is kept alongside the data file. This file serves two purpose. + The first purpose is to track the number of rows in the table. The second + purpose is to determine if the table was closed properly or not. When the + meta file is first opened it is marked as dirty. It is opened when the table + itself is opened for writing. When the table is closed the new count for rows + is written to the meta file and the file is marked as clean. If the meta file + is opened and it is marked as dirty, it is assumed that a crash occured. At + this point an error occurs and the user is told to rebuild the file. + A rebuild scans the rows and rewrites the meta file. If corruption is found + in the data file then the meta file is not repaired. - No attempts at durability are made. You can corrupt your data. A repair - method was added to repair the meta file that stores row information, - but if your data file gets corrupted I haven't solved that. I could - create a repair that would solve this, but do you want to take a - chance of loosing your data? + At some point a recovery method for such a drastic case needs to be divised. - Locks are row level, and you will get a consistant read. Transactions - will be added later (they are not that hard to add at this - stage). + Locks are row level, and you will get a consistant read. For performance as far as table scans go it is quite fast. I don't have good numbers but locally it has out performed both Innodb and MyISAM. For @@ -89,7 +91,6 @@ compression but may speed up ordered searches). Checkpoint the meta file to allow for faster rebuilds. Dirty open (right now the meta file is repaired if a crash occured). - Transactions. Option to allow for dirty reads, this would lower the sync calls, which would make inserts a lot faster, but would mean highly arbitrary reads. @@ -347,6 +348,7 @@ ARCHIVE_SHARE *ha_archive::get_share(const char *table_name, TABLE *table) share->crashed= TRUE; else (void)write_meta_file(share->meta_file, share->rows_recorded, TRUE); + /* It is expensive to open and close the data files and since you can't have a gzip file that can be both read and written we keep a writer open @@ -393,7 +395,8 @@ int ha_archive::free_share(ARCHIVE_SHARE *share) (void)write_meta_file(share->meta_file, share->rows_recorded, FALSE); if (gzclose(share->archive_write) == Z_ERRNO) rc= 1; - my_close(share->meta_file,MYF(0)); + if (my_close(share->meta_file, MYF(0))) + rc= 1; my_free((gptr) share, MYF(0)); } pthread_mutex_unlock(&archive_mutex); |