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/* Copyright (C) 2003 MySQL AB
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */
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#ifdef USE_PRAGMA_IMPLEMENTATION
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#pragma implementation // gcc: Class implementation
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#include "mysql_priv.h"
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#if defined(HAVE_ARCHIVE_DB)
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#include "ha_archive.h"
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First, if you want to understand storage engines you should look at
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ha_example.cc and ha_example.h.
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This example was written as a test case for a customer who needed
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a storage engine without indexes that could compress data very well.
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So, welcome to a completely compressed storage engine. This storage
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engine only does inserts. No replace, deletes, or updates. All reads are
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complete table scans. Compression is done through gzip (bzip compresses
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better, but only marginally, if someone asks I could add support for
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it too, but beaware that it costs a lot more in CPU time then gzip).
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We keep a file pointer open for each instance of ha_archive for each read
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but for writes we keep one open file handle just for that. We flush it
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only if we have a read occur. gzip handles compressing lots of records
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at once much better then doing lots of little records between writes.
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It is possible to not lock on writes but this would then mean we couldn't
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handle bulk inserts as well (that is if someone was trying to read at
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the same time since we would want to flush).
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A "meta" file is kept alongside the data file. This file serves two purpose.
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The first purpose is to track the number of rows in the table. The second
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purpose is to determine if the table was closed properly or not. When the
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meta file is first opened it is marked as dirty. It is opened when the table
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itself is opened for writing. When the table is closed the new count for rows
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is written to the meta file and the file is marked as clean. If the meta file
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is opened and it is marked as dirty, it is assumed that a crash occured. At
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this point an error occurs and the user is told to rebuild the file.
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A rebuild scans the rows and rewrites the meta file. If corruption is found
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in the data file then the meta file is not repaired.
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At some point a recovery method for such a drastic case needs to be divised.
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Locks are row level, and you will get a consistant read.
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For performance as far as table scans go it is quite fast. I don't have
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good numbers but locally it has out performed both Innodb and MyISAM. For
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Innodb the question will be if the table can be fit into the buffer
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pool. For MyISAM its a question of how much the file system caches the
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MyISAM file. With enough free memory MyISAM is faster. Its only when the OS
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doesn't have enough memory to cache entire table that archive turns out
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to be any faster. For writes it is always a bit slower then MyISAM. It has no
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internal limits though for row length.
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Examples between MyISAM (packed) and Archive.
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Table with 76695844 identical rows:
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29680807 a_archive.ARZ
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Table with 8991478 rows (all of Slashdot's comments):
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1922964506 comment_archive.ARZ
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2944970297 comment_text.MYD
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Add bzip optional support.
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Allow users to set compression level.
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Add truncate table command.
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Implement versioning, should be easy.
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Allow for errors, find a way to mark bad rows.
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Talk to the gzip guys, come up with a writable format so that updates are doable
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without switching to a block method.
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Add optional feature so that rows can be flushed at interval (which will cause less
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compression but may speed up ordered searches).
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Checkpoint the meta file to allow for faster rebuilds.
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Dirty open (right now the meta file is repaired if a crash occured).
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Option to allow for dirty reads, this would lower the sync calls, which would make
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inserts a lot faster, but would mean highly arbitrary reads.
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Notes on file formats.
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The Meta file is layed out as:
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check - Just an int of 254 to make sure that the the file we are opening was
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version - The current version of the file format.
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rows - This is an unsigned long long which is the number of rows in the data
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check point - Reserved for future use
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dirty - Status of the file, whether or not its values are the latest. This
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flag is what causes a repair to occur
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check - Just an int of 254 to make sure that the the file we are opening was
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version - The current version of the file format.
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data - The data is stored in a "row +blobs" format.
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/* If the archive storage engine has been inited */
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static bool archive_inited= FALSE;
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/* Variables for archive share methods */
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pthread_mutex_t archive_mutex;
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static HASH archive_open_tables;
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static z_off_t max_zfile_size;
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static int zoffset_size;
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/* The file extension */
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#define ARZ ".ARZ" // The data file
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#define ARN ".ARN" // Files used during an optimize call
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#define ARM ".ARM" // Meta file
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uchar + uchar + ulonglong + ulonglong + uchar
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#define META_BUFFER_SIZE 19 // Size of the data used in the meta file
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#define DATA_BUFFER_SIZE 2 // Size of the data used in the data file
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#define ARCHIVE_CHECK_HEADER 254 // The number we use to determine corruption
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Number of rows that will force a bulk insert.
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#define ARCHIVE_MIN_ROWS_TO_USE_BULK_INSERT 2
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/* dummy handlerton - only to have something to return from archive_db_init */
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handlerton archive_hton = {
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"Archive storage engine",
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0, /* savepoint size. */
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NULL, /* close_connection */
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NULL, /* savepoint */
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NULL, /* rollback to savepoint */
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NULL, /* releas savepoint */
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NULL, /* commit_by_xid */
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NULL, /* rollback_by_xid */
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NULL, /* create_cursor_read_view */
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NULL, /* set_cursor_read_view */
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NULL, /* close_cursor_read_view */
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Used for hash table that tracks open tables.
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static byte* archive_get_key(ARCHIVE_SHARE *share,uint *length,
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my_bool not_used __attribute__((unused)))
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*length=share->table_name_length;
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return (byte*) share->table_name;
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Initialize the archive handler.
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bool archive_db_init()
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DBUG_ENTER("archive_db_init");
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if (pthread_mutex_init(&archive_mutex, MY_MUTEX_INIT_FAST))
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if (hash_init(&archive_open_tables, system_charset_info, 32, 0, 0,
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(hash_get_key) archive_get_key, 0, 0))
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VOID(pthread_mutex_destroy(&archive_mutex));
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zoffset_size= 2 << ((zlibCompileFlags() >> 6) & 3);
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switch (sizeof(z_off_t)) {
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max_zfile_size= INT_MAX16;
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max_zfile_size= (z_off_t) LONGLONG_MAX;
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max_zfile_size= INT_MAX32;
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archive_inited= TRUE;
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have_archive_db= SHOW_OPTION_DISABLED; // If we couldn't use handler
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Release the archive handler.
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bool archive_db_end()
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hash_free(&archive_open_tables);
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VOID(pthread_mutex_destroy(&archive_mutex));
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ha_archive::ha_archive(TABLE *table_arg)
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:handler(&archive_hton, table_arg), delayed_insert(0), bulk_insert(0)
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/* Set our original buffer from pre-allocated memory */
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buffer.set((char *)byte_buffer, IO_SIZE, system_charset_info);
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/* The size of the offset value we will use for position() */
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ref_length = zoffset_size;
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DBUG_ASSERT(ref_length <= sizeof(z_off_t));
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This method reads the header of a datafile and returns whether or not it was successful.
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int ha_archive::read_data_header(gzFile file_to_read)
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uchar data_buffer[DATA_BUFFER_SIZE];
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DBUG_ENTER("ha_archive::read_data_header");
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if (gzrewind(file_to_read) == -1)
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DBUG_RETURN(HA_ERR_CRASHED_ON_USAGE);
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if (gzread(file_to_read, data_buffer, DATA_BUFFER_SIZE) != DATA_BUFFER_SIZE)
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DBUG_RETURN(errno ? errno : -1);
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DBUG_PRINT("ha_archive::read_data_header", ("Check %u", data_buffer[0]));
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DBUG_PRINT("ha_archive::read_data_header", ("Version %u", data_buffer[1]));
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if ((data_buffer[0] != (uchar)ARCHIVE_CHECK_HEADER) &&
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(data_buffer[1] != (uchar)ARCHIVE_VERSION))
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DBUG_RETURN(HA_ERR_CRASHED_ON_USAGE);
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This method writes out the header of a datafile and returns whether or not it was successful.
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int ha_archive::write_data_header(gzFile file_to_write)
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uchar data_buffer[DATA_BUFFER_SIZE];
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DBUG_ENTER("ha_archive::write_data_header");
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data_buffer[0]= (uchar)ARCHIVE_CHECK_HEADER;
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data_buffer[1]= (uchar)ARCHIVE_VERSION;
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if (gzwrite(file_to_write, &data_buffer, DATA_BUFFER_SIZE) !=
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DBUG_PRINT("ha_archive::write_data_header", ("Check %u", (uint)data_buffer[0]));
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DBUG_PRINT("ha_archive::write_data_header", ("Version %u", (uint)data_buffer[1]));
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This method reads the header of a meta file and returns whether or not it was successful.
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*rows will contain the current number of rows in the data file upon success.
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int ha_archive::read_meta_file(File meta_file, ha_rows *rows)
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uchar meta_buffer[META_BUFFER_SIZE];
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ulonglong check_point;
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DBUG_ENTER("ha_archive::read_meta_file");
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VOID(my_seek(meta_file, 0, MY_SEEK_SET, MYF(0)));
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if (my_read(meta_file, (byte*)meta_buffer, META_BUFFER_SIZE, 0) != META_BUFFER_SIZE)
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Parse out the meta data, we ignore version at the moment
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*rows= (ha_rows)uint8korr(meta_buffer + 2);
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check_point= uint8korr(meta_buffer + 10);
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DBUG_PRINT("ha_archive::read_meta_file", ("Check %d", (uint)meta_buffer[0]));
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DBUG_PRINT("ha_archive::read_meta_file", ("Version %d", (uint)meta_buffer[1]));
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DBUG_PRINT("ha_archive::read_meta_file", ("Rows %lu", (ulong) *rows));
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DBUG_PRINT("ha_archive::read_meta_file", ("Checkpoint %lu", (ulong) check_point));
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DBUG_PRINT("ha_archive::read_meta_file", ("Dirty %d", (int)meta_buffer[18]));
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if ((meta_buffer[0] != (uchar)ARCHIVE_CHECK_HEADER) ||
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((bool)meta_buffer[18] == TRUE))
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DBUG_RETURN(HA_ERR_CRASHED_ON_USAGE);
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my_sync(meta_file, MYF(MY_WME));
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This method writes out the header of a meta file and returns whether or not it was successful.
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By setting dirty you say whether or not the file represents the actual state of the data file.
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Upon ::open() we set to dirty, and upon ::close() we set to clean.
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int ha_archive::write_meta_file(File meta_file, ha_rows rows, bool dirty)
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uchar meta_buffer[META_BUFFER_SIZE];
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ulonglong check_point= 0; //Reserved for the future
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DBUG_ENTER("ha_archive::write_meta_file");
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meta_buffer[0]= (uchar)ARCHIVE_CHECK_HEADER;
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meta_buffer[1]= (uchar)ARCHIVE_VERSION;
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int8store(meta_buffer + 2, (ulonglong)rows);
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int8store(meta_buffer + 10, check_point);
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*(meta_buffer + 18)= (uchar)dirty;
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DBUG_PRINT("ha_archive::write_meta_file", ("Check %d", (uint)ARCHIVE_CHECK_HEADER));
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DBUG_PRINT("ha_archive::write_meta_file", ("Version %d", (uint)ARCHIVE_VERSION));
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DBUG_PRINT("ha_archive::write_meta_file", ("Rows %lu", (ulong)rows));
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DBUG_PRINT("ha_archive::write_meta_file", ("Checkpoint %lu", (ulong) check_point));
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DBUG_PRINT("ha_archive::write_meta_file", ("Dirty %d", (uint)dirty));
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VOID(my_seek(meta_file, 0, MY_SEEK_SET, MYF(0)));
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if (my_write(meta_file, (byte *)meta_buffer, META_BUFFER_SIZE, 0) != META_BUFFER_SIZE)
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my_sync(meta_file, MYF(MY_WME));
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We create the shared memory space that we will use for the open table.
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No matter what we try to get or create a share. This is so that a repair
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table operation can occur.
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See ha_example.cc for a longer description.
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ARCHIVE_SHARE *ha_archive::get_share(const char *table_name,
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TABLE *table, int *rc)
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ARCHIVE_SHARE *share;
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char meta_file_name[FN_REFLEN];
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DBUG_ENTER("ha_archive::get_share");
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pthread_mutex_lock(&archive_mutex);
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length=(uint) strlen(table_name);
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if (!(share=(ARCHIVE_SHARE*) hash_search(&archive_open_tables,
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if (!my_multi_malloc(MYF(MY_WME | MY_ZEROFILL),
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&share, sizeof(*share),
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pthread_mutex_unlock(&archive_mutex);
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*rc= HA_ERR_OUT_OF_MEM;
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share->table_name_length= length;
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share->table_name= tmp_name;
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share->crashed= FALSE;
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share->archive_write_open= FALSE;
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fn_format(share->data_file_name,table_name,"",ARZ,MY_REPLACE_EXT|MY_UNPACK_FILENAME);
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fn_format(meta_file_name,table_name,"",ARM,MY_REPLACE_EXT|MY_UNPACK_FILENAME);
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strmov(share->table_name,table_name);
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We will use this lock for rows.
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VOID(pthread_mutex_init(&share->mutex,MY_MUTEX_INIT_FAST));
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if ((share->meta_file= my_open(meta_file_name, O_RDWR, MYF(0))) == -1)
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share->crashed= TRUE;
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After we read, we set the file to dirty. When we close, we will do the
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opposite. If the meta file will not open we assume it is crashed and
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leave it up to the user to fix.
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if (read_meta_file(share->meta_file, &share->rows_recorded))
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share->crashed= TRUE;
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VOID(my_hash_insert(&archive_open_tables, (byte*) share));
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thr_lock_init(&share->lock);
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DBUG_PRINT("info", ("archive table %.*s has %d open handles now",
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share->table_name_length, share->table_name,
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*rc= HA_ERR_CRASHED_ON_USAGE;
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pthread_mutex_unlock(&archive_mutex);
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See ha_example.cc for a description.
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int ha_archive::free_share(ARCHIVE_SHARE *share)
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DBUG_ENTER("ha_archive::free_share");
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DBUG_PRINT("info", ("archive table %.*s has %d open handles on entrance",
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share->table_name_length, share->table_name,
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pthread_mutex_lock(&archive_mutex);
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if (!--share->use_count)
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hash_delete(&archive_open_tables, (byte*) share);
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thr_lock_delete(&share->lock);
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VOID(pthread_mutex_destroy(&share->mutex));
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(void)write_meta_file(share->meta_file, share->rows_recorded, TRUE);
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(void)write_meta_file(share->meta_file, share->rows_recorded, FALSE);
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if (share->archive_write_open)
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if (gzclose(share->archive_write) == Z_ERRNO)
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if (my_close(share->meta_file, MYF(0)))
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my_free((gptr) share, MYF(0));
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pthread_mutex_unlock(&archive_mutex);
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int ha_archive::init_archive_writer()
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DBUG_ENTER("ha_archive::init_archive_writer");
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(void)write_meta_file(share->meta_file, share->rows_recorded, TRUE);
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It is expensive to open and close the data files and since you can't have
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a gzip file that can be both read and written we keep a writer open
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that is shared amoung all open tables.
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if ((share->archive_write= gzopen(share->data_file_name, "ab")) == NULL)
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share->crashed= TRUE;
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share->archive_write_open= TRUE;
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info(HA_STATUS_TIME);
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share->approx_file_size= (ulong) data_file_length;
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We just implement one additional file extension.
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static const char *ha_archive_exts[] = {
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const char **ha_archive::bas_ext() const
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return ha_archive_exts;
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When opening a file we:
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Create/get our shared structure.
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We open the file we will read from.
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int ha_archive::open(const char *name, int mode, uint open_options)
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DBUG_ENTER("ha_archive::open");
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DBUG_PRINT("info", ("archive table was opened for crash %s",
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(open_options & HA_OPEN_FOR_REPAIR) ? "yes" : "no"));
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share= get_share(name, table, &rc);
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if (rc == HA_ERR_CRASHED_ON_USAGE && !(open_options & HA_OPEN_FOR_REPAIR))
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else if (rc == HA_ERR_OUT_OF_MEM)
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thr_lock_data_init(&share->lock,&lock,NULL);
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if ((archive= gzopen(share->data_file_name, "rb")) == NULL)
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if (errno == EROFS || errno == EACCES)
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DBUG_RETURN(my_errno= errno);
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DBUG_RETURN(HA_ERR_CRASHED_ON_USAGE);
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DBUG_PRINT("info", ("archive table was crashed %s",
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rc == HA_ERR_CRASHED_ON_USAGE ? "yes" : "no"));
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if (rc == HA_ERR_CRASHED_ON_USAGE && open_options & HA_OPEN_FOR_REPAIR)
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We first close this storage engines file handle to the archive and
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then remove our reference count to the table (and possibly free it
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int ha_archive::close(void)
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DBUG_ENTER("ha_archive::close");
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/* First close stream */
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if (gzclose(archive) == Z_ERRNO)
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/* then also close share */
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rc|= free_share(share);
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We create our data file here. The format is pretty simple.
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You can read about the format of the data file above.
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Unlike other storage engines we do not "pack" our data. Since we
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are about to do a general compression, packing would just be a waste of
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CPU time. If the table has blobs they are written after the row in the order
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int ha_archive::create(const char *name, TABLE *table_arg,
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HA_CREATE_INFO *create_info)
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File create_file; // We use to create the datafile and the metafile
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char name_buff[FN_REFLEN];
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DBUG_ENTER("ha_archive::create");
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if ((create_file= my_create(fn_format(name_buff,name,"",ARM,
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MY_REPLACE_EXT|MY_UNPACK_FILENAME),0,
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O_RDWR | O_TRUNC,MYF(MY_WME))) < 0)
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write_meta_file(create_file, 0, FALSE);
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my_close(create_file,MYF(0));
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We reuse name_buff since it is available.
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if ((create_file= my_create(fn_format(name_buff,name,"",ARZ,
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MY_REPLACE_EXT|MY_UNPACK_FILENAME),0,
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O_RDWR | O_TRUNC,MYF(MY_WME))) < 0)
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if ((archive= gzdopen(dup(create_file), "wb")) == NULL)
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if (write_data_header(archive))
643
if (gzclose(archive))
649
my_close(create_file, MYF(0));
654
/* We already have an error, so ignore results of gzclose. */
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(void)gzclose(archive);
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my_close(create_file, MYF(0));
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/* Return error number, if we got one */
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DBUG_RETURN(error ? error : -1);
665
This is where the actual row is written out.
667
int ha_archive::real_write_row(byte *buf, gzFile writer)
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z_off_t written, total_row_length;
671
DBUG_ENTER("ha_archive::real_write_row");
672
total_row_length= table->s->reclength;
673
for (ptr= table->s->blob_field, end= ptr + table->s->blob_fields;
675
total_row_length+= ((Field_blob*) table->field[*ptr])->get_length();
676
if (share->approx_file_size > max_zfile_size - total_row_length)
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info(HA_STATUS_TIME);
679
share->approx_file_size= (ulong) data_file_length;
680
if (share->approx_file_size > max_zfile_size - total_row_length)
681
DBUG_RETURN(HA_ERR_RECORD_FILE_FULL);
683
share->approx_file_size+= total_row_length;
684
written= gzwrite(writer, buf, table->s->reclength);
685
DBUG_PRINT("ha_archive::real_write_row", ("Wrote %d bytes expected %lu", (int) written,
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table->s->reclength));
687
if (!delayed_insert || !bulk_insert)
690
if (written != (z_off_t)table->s->reclength)
691
DBUG_RETURN(errno ? errno : -1);
693
We should probably mark the table as damagaged if the record is written
696
for (ptr= table->s->blob_field, end= ptr + table->s->blob_fields ;
701
uint32 size= ((Field_blob*) table->field[*ptr])->get_length();
705
((Field_blob*) table->field[*ptr])->get_ptr(&data_ptr);
706
written= gzwrite(writer, data_ptr, (unsigned)size);
707
if (written != (z_off_t)size)
708
DBUG_RETURN(errno ? errno : -1);
716
Look at ha_archive::open() for an explanation of the row format.
717
Here we just write out the row.
719
Wondering about start_bulk_insert()? We don't implement it for
720
archive since it optimizes for lots of writes. The only save
721
for implementing start_bulk_insert() is that we could skip
722
setting dirty to true each time.
724
int ha_archive::write_row(byte *buf)
727
DBUG_ENTER("ha_archive::write_row");
730
DBUG_RETURN(HA_ERR_CRASHED_ON_USAGE);
732
statistic_increment(table->in_use->status_var.ha_write_count, &LOCK_status);
733
if (table->timestamp_field_type & TIMESTAMP_AUTO_SET_ON_INSERT)
734
table->timestamp_field->set_time();
735
pthread_mutex_lock(&share->mutex);
736
if (!share->archive_write_open)
737
if (init_archive_writer())
738
DBUG_RETURN(HA_ERR_CRASHED_ON_USAGE);
741
Varchar structures are constant in size but are not cleaned up request
742
to request. The following sets all unused space to null to improve
745
for (Field **field=table->field ; *field ; field++)
747
DBUG_PRINT("archive",("Pack is %d\n", (*field)->pack_length()));
748
DBUG_PRINT("archive",("MyPack is %d\n", (*field)->data_length((char*) buf + (*field)->offset())));
749
if ((*field)->real_type() == MYSQL_TYPE_VARCHAR)
751
uint actual_length= (*field)->data_length((char*) buf + (*field)->offset());
752
uint offset= (*field)->offset() + actual_length +
753
(actual_length > 255 ? 2 : 1);
754
DBUG_PRINT("archive",("Offset is %d -> %d\n", actual_length, offset));
756
if ((*field)->pack_length() + (*field)->offset() != offset)
757
bzero(buf + offset, (size_t)((*field)->pack_length() + (actual_length > 255 ? 2 : 1) - (*field)->data_length));
762
share->rows_recorded++;
763
rc= real_write_row(buf, share->archive_write);
764
pthread_mutex_unlock(&share->mutex);
770
All calls that need to scan the table start with this method. If we are told
771
that it is a table scan we rewind the file to the beginning, otherwise
772
we assume the position will be set.
775
int ha_archive::rnd_init(bool scan)
777
DBUG_ENTER("ha_archive::rnd_init");
780
DBUG_RETURN(HA_ERR_CRASHED_ON_USAGE);
782
/* We rewind the file so that we can read from the beginning if scan */
785
scan_rows= share->rows_recorded;
786
DBUG_PRINT("info", ("archive will retrieve %lu rows", (ulong) scan_rows));
790
If dirty, we lock, and then reset/flush the data.
791
I found that just calling gzflush() doesn't always work.
793
if (share->dirty == TRUE)
795
pthread_mutex_lock(&share->mutex);
796
if (share->dirty == TRUE)
798
DBUG_PRINT("info", ("archive flushing out rows for scan"));
799
gzflush(share->archive_write, Z_SYNC_FLUSH);
802
pthread_mutex_unlock(&share->mutex);
805
if (read_data_header(archive))
806
DBUG_RETURN(HA_ERR_CRASHED_ON_USAGE);
814
This is the method that is used to read a row. It assumes that the row is
815
positioned where you want it.
817
int ha_archive::get_row(gzFile file_to_read, byte *buf)
819
int read; // Bytes read, gzread() returns int
822
size_t total_blob_length= 0;
823
DBUG_ENTER("ha_archive::get_row");
825
read= gzread(file_to_read, buf, table->s->reclength);
826
DBUG_PRINT("ha_archive::get_row", ("Read %d bytes expected %lu", (int) read,
827
table->s->reclength));
829
if (read == Z_STREAM_ERROR)
830
DBUG_RETURN(HA_ERR_CRASHED_ON_USAGE);
832
/* If we read nothing we are at the end of the file */
834
DBUG_RETURN(HA_ERR_END_OF_FILE);
837
If the record is the wrong size, the file is probably damaged, unless
838
we are dealing with a delayed insert or a bulk insert.
840
if ((ulong) read != table->s->reclength)
841
DBUG_RETURN(HA_ERR_END_OF_FILE);
843
/* Calculate blob length, we use this for our buffer */
844
for (ptr= table->s->blob_field, end=ptr + table->s->blob_fields ;
847
total_blob_length += ((Field_blob*) table->field[*ptr])->get_length();
849
/* Adjust our row buffer if we need be */
850
buffer.alloc(total_blob_length);
851
last= (char *)buffer.ptr();
853
/* Loop through our blobs and read them */
854
for (ptr= table->s->blob_field, end=ptr + table->s->blob_fields ;
858
size_t size= ((Field_blob*) table->field[*ptr])->get_length();
861
read= gzread(file_to_read, last, size);
862
if ((size_t) read != size)
863
DBUG_RETURN(HA_ERR_END_OF_FILE);
864
((Field_blob*) table->field[*ptr])->set_ptr(size, last);
873
Called during ORDER BY. Its position is either from being called sequentially
874
or by having had ha_archive::rnd_pos() called before it is called.
877
int ha_archive::rnd_next(byte *buf)
880
DBUG_ENTER("ha_archive::rnd_next");
883
DBUG_RETURN(HA_ERR_CRASHED_ON_USAGE);
886
DBUG_RETURN(HA_ERR_END_OF_FILE);
889
statistic_increment(table->in_use->status_var.ha_read_rnd_next_count,
891
current_position= gztell(archive);
892
rc= get_row(archive, buf);
895
if (rc != HA_ERR_END_OF_FILE)
903
Thanks to the table flag HA_REC_NOT_IN_SEQ this will be called after
904
each call to ha_archive::rnd_next() if an ordering of the rows is
908
void ha_archive::position(const byte *record)
910
DBUG_ENTER("ha_archive::position");
911
my_store_ptr(ref, ref_length, current_position);
917
This is called after a table scan for each row if the results of the
918
scan need to be ordered. It will take *pos and use it to move the
919
cursor in the file so that the next row that is called is the
920
correctly ordered row.
923
int ha_archive::rnd_pos(byte * buf, byte *pos)
925
DBUG_ENTER("ha_archive::rnd_pos");
926
statistic_increment(table->in_use->status_var.ha_read_rnd_next_count,
928
current_position= (z_off_t)my_get_ptr(pos, ref_length);
929
(void)gzseek(archive, current_position, SEEK_SET);
931
DBUG_RETURN(get_row(archive, buf));
935
This method repairs the meta file. It does this by walking the datafile and
936
rewriting the meta file. Currently it does this by calling optimize with
939
int ha_archive::repair(THD* thd, HA_CHECK_OPT* check_opt)
941
DBUG_ENTER("ha_archive::repair");
942
check_opt->flags= T_EXTEND;
943
int rc= optimize(thd, check_opt);
946
DBUG_RETURN(HA_ERR_CRASHED_ON_REPAIR);
948
share->crashed= FALSE;
953
The table can become fragmented if data was inserted, read, and then
954
inserted again. What we do is open up the file and recompress it completely.
956
int ha_archive::optimize(THD* thd, HA_CHECK_OPT* check_opt)
958
DBUG_ENTER("ha_archive::optimize");
961
char writer_filename[FN_REFLEN];
963
/* Open up the writer if we haven't yet */
964
if (!share->archive_write_open)
965
init_archive_writer();
967
/* Flush any waiting data */
968
gzflush(share->archive_write, Z_SYNC_FLUSH);
970
/* Lets create a file to contain the new data */
971
fn_format(writer_filename, share->table_name, "", ARN,
972
MY_REPLACE_EXT|MY_UNPACK_FILENAME);
974
if ((writer= gzopen(writer_filename, "wb")) == NULL)
975
DBUG_RETURN(HA_ERR_CRASHED_ON_USAGE);
978
An extended rebuild is a lot more effort. We open up each row and re-record it.
979
Any dead rows are removed (aka rows that may have been partially recorded).
982
if (check_opt->flags == T_EXTEND)
987
First we create a buffer that we can use for reading rows, and can pass
990
if (!(buf= (byte*) my_malloc(table->s->reclength, MYF(MY_WME))))
992
rc= HA_ERR_OUT_OF_MEM;
997
Now we will rewind the archive file so that we are positioned at the
1000
rc= read_data_header(archive);
1003
Assuming now error from rewinding the archive file, we now write out the
1004
new header for out data file.
1007
rc= write_data_header(writer);
1010
On success of writing out the new header, we now fetch each row and
1011
insert it into the new archive file.
1015
share->rows_recorded= 0;
1016
while (!(rc= get_row(archive, buf)))
1018
real_write_row(buf, writer);
1019
share->rows_recorded++;
1022
DBUG_PRINT("info", ("recovered %lu archive rows",
1023
(ulong) share->rows_recorded));
1025
my_free((char*)buf, MYF(0));
1026
if (rc && rc != HA_ERR_END_OF_FILE)
1032
The quick method is to just read the data raw, and then compress it directly.
1034
int read; // Bytes read, gzread() returns int
1035
char block[IO_SIZE];
1036
if (gzrewind(archive) == -1)
1038
rc= HA_ERR_CRASHED_ON_USAGE;
1042
while ((read= gzread(archive, block, IO_SIZE)))
1043
gzwrite(writer, block, read);
1046
gzflush(writer, Z_SYNC_FLUSH);
1047
share->dirty= FALSE;
1048
gzclose(share->archive_write);
1049
share->archive_write= writer;
1051
my_rename(writer_filename,share->data_file_name,MYF(0));
1054
Now we need to reopen our read descriptor since it has changed.
1057
if ((archive= gzopen(share->data_file_name, "rb")) == NULL)
1059
rc= HA_ERR_CRASHED_ON_USAGE;
1073
Below is an example of how to setup row level locking.
1075
THR_LOCK_DATA **ha_archive::store_lock(THD *thd,
1077
enum thr_lock_type lock_type)
1079
if (lock_type == TL_WRITE_DELAYED)
1080
delayed_insert= TRUE;
1082
delayed_insert= FALSE;
1084
if (lock_type != TL_IGNORE && lock.type == TL_UNLOCK)
1087
Here is where we get into the guts of a row level lock.
1089
If we are not doing a LOCK TABLE or DISCARD/IMPORT
1090
TABLESPACE, then allow multiple writers
1093
if ((lock_type >= TL_WRITE_CONCURRENT_INSERT &&
1094
lock_type <= TL_WRITE) && !thd->in_lock_tables
1095
&& !thd->tablespace_op)
1096
lock_type = TL_WRITE_ALLOW_WRITE;
1099
In queries of type INSERT INTO t1 SELECT ... FROM t2 ...
1100
MySQL would use the lock TL_READ_NO_INSERT on t2, and that
1101
would conflict with TL_WRITE_ALLOW_WRITE, blocking all inserts
1102
to t2. Convert the lock to a normal read lock to allow
1103
concurrent inserts to t2.
1106
if (lock_type == TL_READ_NO_INSERT && !thd->in_lock_tables)
1107
lock_type = TL_READ;
1109
lock.type=lock_type;
1119
Hints for optimizer, see ha_tina for more information
1121
int ha_archive::info(uint flag)
1123
DBUG_ENTER("ha_archive::info");
1125
This should be an accurate number now, though bulk and delayed inserts can
1126
cause the number to be inaccurate.
1128
records= share->rows_recorded;
1130
/* Costs quite a bit more to get all information */
1131
if (flag & HA_STATUS_TIME)
1133
MY_STAT file_stat; // Stat information for the data file
1135
VOID(my_stat(share->data_file_name, &file_stat, MYF(MY_WME)));
1137
mean_rec_length= table->s->reclength + buffer.alloced_length();
1138
data_file_length= file_stat.st_size;
1139
create_time= file_stat.st_ctime;
1140
update_time= file_stat.st_mtime;
1141
max_data_file_length= share->rows_recorded * mean_rec_length;
1144
index_file_length=0;
1151
This method tells us that a bulk insert operation is about to occur. We set
1152
a flag which will keep write_row from saying that its data is dirty. This in
1153
turn will keep selects from causing a sync to occur.
1154
Basically, yet another optimizations to keep compression working well.
1156
void ha_archive::start_bulk_insert(ha_rows rows)
1158
DBUG_ENTER("ha_archive::start_bulk_insert");
1159
if (!rows || rows >= ARCHIVE_MIN_ROWS_TO_USE_BULK_INSERT)
1166
Other side of start_bulk_insert, is end_bulk_insert. Here we turn off the bulk insert
1167
flag, and set the share dirty so that the next select will call sync for us.
1169
int ha_archive::end_bulk_insert()
1171
DBUG_ENTER("ha_archive::end_bulk_insert");
1178
We cancel a truncate command. The only way to delete an archive table is to drop it.
1179
This is done for security reasons. In a later version we will enable this by
1180
allowing the user to select a different row format.
1182
int ha_archive::delete_all_rows()
1184
DBUG_ENTER("ha_archive::delete_all_rows");
1185
DBUG_RETURN(HA_ERR_WRONG_COMMAND);
1189
We just return state if asked.
1191
bool ha_archive::is_crashed() const
1193
DBUG_ENTER("ha_archive::is_crashed");
1194
DBUG_RETURN(share->crashed);
1198
Simple scan of the tables to make sure everything is ok.
1201
int ha_archive::check(THD* thd, HA_CHECK_OPT* check_opt)
1205
const char *old_proc_info=thd->proc_info;
1206
ha_rows count= share->rows_recorded;
1207
DBUG_ENTER("ha_archive::check");
1209
thd->proc_info= "Checking table";
1210
/* Flush any waiting data */
1211
gzflush(share->archive_write, Z_SYNC_FLUSH);
1214
First we create a buffer that we can use for reading rows, and can pass
1217
if (!(buf= (byte*) my_malloc(table->s->reclength, MYF(MY_WME))))
1218
rc= HA_ERR_OUT_OF_MEM;
1221
Now we will rewind the archive file so that we are positioned at the
1225
read_data_header(archive);
1228
while (!(rc= get_row(archive, buf)))
1231
my_free((char*)buf, MYF(0));
1233
thd->proc_info= old_proc_info;
1235
if ((rc && rc != HA_ERR_END_OF_FILE) || count)
1237
share->crashed= FALSE;
1238
DBUG_RETURN(HA_ADMIN_CORRUPT);
1242
DBUG_RETURN(HA_ADMIN_OK);
1247
Check and repair the table if needed.
1249
bool ha_archive::check_and_repair(THD *thd)
1251
HA_CHECK_OPT check_opt;
1252
DBUG_ENTER("ha_archive::check_and_repair");
1256
DBUG_RETURN(repair(thd, &check_opt));
1258
#endif /* HAVE_ARCHIVE_DB */
added
removed
libmysqld/ha_archive.cc
