Table of Contents
There are many different MySQL client programs that connect to the server to access databases or perform administrative tasks. Other utilities are available as well. These do not establish a client connection with the server but perform MySQL-related operations.
This chapter provides a brief overview of these programs and then a more detailed description of each one. Each program's description indicates its invocation syntax and the options that it understands. See Chapter 4, Using MySQL Programs, for general information on invoking programs and specifying program options.
The following list briefly describes the MySQL client programs and utilities:
A utility that displays information about full-text indexes in
MyISAM tables. See
Section 8.2, myisam_ftdump Display Full-Text Index information.
A utility to describe, check, optimize, and repair
MyISAM tables. isamchk
is a similar program for ISAM tables. See
Section 8.3, myisamchk MyISAM Table-Maintenance Utility.
Utilities that process the contents of a
MyISAM or ISAM log file.
See Section 8.4, myisamlog Display MyISAM Log File Contents.
Utilities that compress MyISAM or
ISAM tables to produce smaller read-only
tables. See Section 8.5, myisampack Generate Compressed, Read-Only MyISAM Tables.
The command-line tool for interactively entering SQL statements or executing them from a file in batch mode. See Section 8.6, mysql The MySQL Command-Line Tool.
A utility that analyzes queries in the MySQL query log using
EXPLAIN See
Section 8.7, mysql_explain_log Use EXPLAIN on Statements in Query Log.
A script that checks the access privileges for a hostname, username, and database combination. See Section 8.8, mysqlaccess Client for Checking Access Privileges.
A client that performs administrative operations, such as creating or dropping databases, reloading the grant tables, flushing tables to disk, and reopening log files. mysqladmin can also be used to retrieve version, process, and status information from the server. See Section 8.9, mysqladmin Client for Administering a MySQL Server.
A utility for reading statements from a binary log. The log of executed statements contained in the binary log files can be used to help recover from a crash. See Section 8.10, mysqlbinlog Utility for Processing Binary Log Files.
A table-maintenance client that checks, repairs, analyzes, and optimizes tables. See Section 8.11, mysqlcheck A Table Maintenance and Repair Program.
A client that dumps a MySQL database into a file as SQL, text, or XML. See Section 8.12, mysqldump A Database Backup Program.
A utility that quickly makes backups of
MyISAM or ISAM tables
while the server is running. See
Section 8.13, mysqlhotcopy A Database Backup Program.
A client that imports text files into their respective tables
using LOAD DATA INFILE. See
Section 8.14, mysqlimport A Data Import Program.
A client that displays information about databases, tables, columns, and indexes. See Section 8.15, mysqlshow Display Database, Table, and Column Information.
A utility that kills processes that match a pattern. Section 8.16, mysql_zap Kill Processes That Match a Pattern.
A utility that displays the meaning of system or MySQL error codes. See Section 8.17, perror Explain Error Codes.
A utility program that performs string replacement in the input text. See Section 8.18, replace A String-Replacement Utility.
MySQL AB also provides a number of GUI tools for administering and otherwise working with MySQL servers. For basic information about these, see Chapter 4, Using MySQL Programs.
Each MySQL program takes many different options. Most programs
provide a --help option that you can use to get a
full description of the program's different options. For example,
try mysql --help.
MySQL client programs that communicate with the server using the MySQL client/server library use the following environment variables:
MYSQL_UNIX_PORT | The default Unix socket file; used for connections to
localhost |
MYSQL_TCP_PORT | The default port number; used for TCP/IP connections |
MYSQL_PWD | The default password |
MYSQL_DEBUG | Debug trace options when debugging |
TMPDIR | The directory where temporary tables and files are created |
Use of MYSQL_PWD is insecure. See
Section 5.8.6, Keeping Your Password Secure.
You can override the default option values or values specified in environment variables for all standard programs by specifying options in an option file or on the command line. See Section 4.3, Specifying Program Options.
myisam_ftdump displays information about
FULLTEXT indexes in
MyISAM tables. It reads the
MyISAM index file directly, so it must be
run on the server host where the table is located
Invoke myisam_ftdump like this:
shell> myisam_ftdump [options] tbl_name index_num
The tbl_name argument should be the
name of a MyISAM table. You can also
specify a table by naming its index file (the file with the
.MYI suffix). If you do not invoke
myisam_ftdump in the directory where the
table files are located, the table or index file name name
must be preceded by the pathname to the table's database
directory. Index numbers begin with 0.
Example: Suppose that the test database
contains a table named mytexttablel that
has the following definition:
CREATE TABLE mytexttable ( id INT NOT NULL, txt TEXT NOT NULL, PRIMARY KEY (id), FULLTEXT (txt) );
The index on id is index 0 and the
FULLTEXT index on txt is
index 1. If your working directory is the
test database directory, invoke
myisam_ftdump as follows:
shell> myisam_ftdump mytexttable 1
If the pathname to the test database
directory is /usr/local/mysql/data/test,
you can also specify the table name argument using that
pathname. This is useful if you do not invoke
myisam_ftdump in the database directory:
shell> myisam_ftdump /usr/local/mysql/data/test/mytexttable 1
myisam_ftdump understands the following options:
Display a help message and exit.
Calculate per-word statistics (counts and global weights).
Dump the index, including data offsets and word weights.
Report the length distribution.
Report global index statistics. This is the default operation if no other operation is specified.
Verbose mode. Print more output about what the program does.
The myisamchk utility gets information
about your database tables or checks, repairs, or optimizes
them. myisamchk works with
MyISAM tables (tables that have
.MYD and .MYI files
for storing data and indexes). A related utility,
isamchk, works with ISAM
tables (tables that have .ISD and
.ISM files for storing data and indexes).
Invoke myisamchk like this:
shell> myisamchk [options] tbl_name ...
The options specify what you want
myisamchk to do. They are described in the
following sections. You can also get a list of options by
invoking myisamchk --help.
With no options, myisamchk simply checks your table as the default operation. To get more information or to tell myisamchk to take corrective action, specify options as described in the following discussion.
tbl_name is the database table you
want to check or repair. If you run
myisamchk somewhere other than in the
database directory, you must specify the path to the database
directory, because myisamchk has no idea
where the database is located. In fact,
myisamchk does not actually care whether
the files you are working on are located in a database
directory. You can copy the files that correspond to a
database table into some other location and perform recovery
operations on them there.
You can name several tables on the
myisamchk command line if you wish. You can
also specify a table by naming its index file (the file with
the .MYI suffix). This allows you to
specify all tables in a directory by using the pattern
*.MYI. For example, if you are in a
database directory, you can check all the
MyISAM tables in that directory like this:
shell> myisamchk *.MYI
If you are not in the database directory, you can check all the tables there by specifying the path to the directory:
shell> myisamchk /path/to/database_dir/*.MYI
You can even check all tables in all databases by specifying a wildcard with the path to the MySQL data directory:
shell> myisamchk /path/to/datadir/*/*.MYI
The recommended way to quickly check all
MyISAM and ISAM tables
is:
shell>myisamchk --silent --fastshell>/path/to/datadir/*/*.MYIisamchk --silent/path/to/datadir/*/*.ISM
If you want to check all MyISAM and
ISAM tables and repair any that are
corrupted, you can use the following commands:
shell>myisamchk --silent --force --fast --update-state \--key_buffer_size=64M --sort_buffer_size=64M \--read_buffer_size=1M --write_buffer_size=1M \shell>/path/to/datadir/*/*.MYIisamchk --silent --force --key_buffer_size=64M \--sort_buffer_size=64M --read_buffer_size=1M --write_buffer_size=1M \/path/to/datadir/*/*.ISM
These commands assume that you have more than 64MB free. For more information about memory allocation with myisamchk, see Section 8.3.5, myisamchk Memory Usage.
You must ensure that no other program is using the tables while you are running myisamchk. Otherwise, when you run myisamchk, it may display the following error message:
warning: clients are using or haven't closed the table properly
This means that you are trying to check a table that has been updated by another program (such as the mysqld server) that hasn't yet closed the file or that has died without closing the file properly.
If mysqld is running, you must force it to
flush any table modifications that are still buffered in
memory by using FLUSH TABLES. You should
then ensure that no one is using the tables while you are
running myisamchk. The easiest way to avoid
this problem is to use CHECK TABLE instead
of myisamchk to check tables.
The options described in this section can be used for any type of table maintenance operation performed by myisamchk. The sections following this one describe options that pertain only to specific operations, such as table checking or repairing.
Display a help message and exit.
--debug=
debug_options,
-# debug_options
Write a debugging log. The
debug_options string often is
'd:t:o,.
file_name'
Silent mode. Write output only when errors occur. You can
use -s twice (-ss) to
make myisamchk very silent.
Verbose mode. Print more information about what the
program does. This can be used with -d
and -e. Use -v multiple
times (-vv, -vvv) for
even more output.
Display version information and exit.
Instead of terminating with an error if the table is locked, wait until the table is unlocked before continuing. Note that if you are running mysqld with external locking disabled, the table can be locked only by another myisamchk command.
You can also set the following variables by using
--
syntax:
var_name=value
| Variable | Default Value |
decode_bits | 9 |
ft_max_word_len | version-dependent |
ft_min_word_len | 4 |
ft_stopword_file | built-in list |
key_buffer_size | 523264 |
myisam_block_size | 1024 |
read_buffer_size | 262136 |
sort_buffer_size | 2097144 |
sort_key_blocks | 16 |
stats_method | nulls_unequal |
write_buffer_size | 262136 |
It is also possible to set variables by using
--set-variable=
or var_name=value-O
syntax. However, this syntax is deprecated as of MySQL 4.0.
var_name=value
The possible myisamchk variables and their default values can be examined with myisamchk --help:
sort_buffer_size is used when the keys are
repaired by sorting keys, which is the normal case when you
use --recover.
key_buffer_size is used when you are
checking the table with --extend-check or
when the keys are repaired by inserting keys row by row into
the table (like when doing normal inserts). Repairing through
the key buffer is used in the following cases:
You use --safe-recover.
The temporary files needed to sort the keys would be more
than twice as big as when creating the key file directly.
This is often the case when you have large key values for
CHAR, VARCHAR, or
TEXT columns, because the sort
operation needs to store the complete key values as it
proceeds. If you have lots of temporary space and you can
force myisamchk to repair by sorting,
you can use the --sort-recover option.
Repairing through the key buffer takes much less disk space than using sorting, but is also much slower.
If you want a faster repair, set the
key_buffer_size and
sort_buffer_size variables to about 25% of
your available memory. You can set both variables to large
values, because only one of them is used at a time.
myisam_block_size is the size used for
index blocks. It is available as of MySQL 4.0.0.
stats_method influences how
NULL values are treated for index
statistics collection when the --analyze
option is given. It acts like the
myisam_stats_method system variable. For
more information, see the description of
myisam_stats_method in
Section 5.2.2, System Variables, and
Section 7.4.7, MyISAM Index Statistics Collection.
stats_method was added in MySQL
4.1.15/5.0.14. For older versions, the statistics collection
method is equivalent to nulls_equal.
The ft_min_word_len and
ft_max_word_len variables are available as
of MySQL 4.0.0. ft_stopword_file is
available as of MySQL 4.0.19.
ft_min_word_len and
ft_max_word_len indicate the minimum and
maximum word length for FULLTEXT indexes.
ft_stopword_file names the stopword file.
These need to be set under the following circumstances.
If you use myisamchk to perform an
operation that modifies table indexes (such as repair or
analyze), the FULLTEXT indexes are rebuilt
using the default full-text parameter values for minimum and
maximum word length and the stopword file unless you specify
otherwise. This can result in queries failing.
The problem occurs because these parameters are known only by
the server. They are not stored in MyISAM
index files. To avoid the problem if you have modified the
minimum or maximum word length or the stopword file in the
server, specify the same ft_min_word_len,
ft_max_word_len, and
ft_stopword_file values to
myisamchk that you use for
mysqld. For example, if you have set the
minimum word length to 3, you can repair a table with
myisamchk like this:
shell> myisamchk --recover --ft_min_word_len=3 tbl_name.MYI
To ensure that myisamchk and the server use
the same values for full-text parameters, you can place each
one in both the [mysqld] and
[myisamchk] sections of an option file:
[mysqld] ft_min_word_len=3 [myisamchk] ft_min_word_len=3
An alternative to using myisamchk is to use
the REPAIR TABLE, ANALYZE
TABLE, OPTIMIZE TABLE, or
ALTER TABLE. These statements are performed
by the server, which knows the proper full-text parameter
values to use.
myisamchk supports the following options for table checking operations:
Check the table for errors. This is the default operation if you specify no option that selects an operation type explicitly.
Check only tables that have changed since the last check.
Check the table very thoroughly. This is quite slow if the table has many indexes. This option should only be used in extreme cases. Normally, myisamchk or myisamchk --medium-check should be able to determine whether there are any errors in the table.
If you are using --extend-check and have
plenty of memory, setting the
key_buffer_size variable to a large
value helps the repair operation run faster.
Check only tables that haven't been closed properly.
Do a repair operation automatically if
myisamchk finds any errors in the
table. The repair type is the same as that specified with
the --recover or -r
option.
Print informational statistics about the table that is checked.
Do a check that is faster than an
--extend-check operation. This finds only
99.99% of all errors, which should be good enough in most
cases.
Don't mark the table as checked. This is useful if you use myisamchk to check a table that is in use by some other application that does not use locking, such as mysqld when run with external locking disabled.
Store information in the .MYI file to
indicate when the table was checked and whether the table
crashed. This should be used to get full benefit of the
--check-only-changed option, but you
shouldn't use this option if the mysqld
server is using the table and you are running it with
external locking disabled.
myisamchk supports the following options for table repair operations:
Make a backup of the .MYD file as
file_name-time.BAK
The directory where character sets are installed. See Section 5.10.1, The Character Set Used for Data and Sorting.
Correct the checksum information for the table.
--data-file-length=
len,
-D len
Maximum length of the data file (when re-creating data file when it is full).
Do a repair that tries to recover every possible row from the data file. Normally, this also finds a lot of garbage rows. Don't use this option unless you are totally desperate.
Overwrite old intermediate files (files with names like
tbl_name.TMD
For myisamchk, the option value is a
bit-value that indicates which indexes to update. Each
binary bit of the option value corresponds to a table
index, where the first index is bit 0. For
isamchk, the option value indicates
that only the first val of the
table indexes should be updated. In either case, an option
value of 0 disables updates to all indexes, which can be
used to get faster inserts. Deactivated indexes can be
reactivated by using myisamchk -r or
(isamchk -r).
Do not follow symbolic links. Normally myisamchk repairs the table that a symlink points to. This option does not exist as of MySQL 4.0 because versions from 4.0 on do not remove symlinks during repair operations.
Skip rows larger than the given length if myisamchk cannot allocate memory to hold them. This option was added in MySQL 4.1.1.
Uses the same technique as -r and
-n, but creates all the keys in parallel,
using different threads. This option was added in MySQL
4.0.2. This is beta-quality code; use at your
own risk!.
Achieve a faster repair by not modifying the data file. You can specify this option twice to force myisamchk to modify the original data file in case of duplicate keys.
Do a repair that can fix almost any problem except unique
keys that are not unique (which is an extremely unlikely
error with
ISAM/MyISAM tables).
If you want to recover a table, this is the option to try
first. You should try --safe-recover only
if myisamchk reports that the table
cannot be recovered by --recover. (In the
unlikely case that --recover fails, the
data file remains intact.)
If you have lots of memory, you should increase the value
of sort_buffer_size.
Do a repair using an old recovery method that reads
through all rows in order and updates all index trees
based on the rows found. This is an order of magnitude
slower than --recover, but can handle a
couple of very unlikely cases that
--recover cannot. This recovery method
also uses much less disk space than
--recover. Normally, you should repair
first using --recover, and then with
--safe-recover only if
--recover fails.
If you have lots of memory, you should increase the value
of key_buffer_size.
Change the character set used by the table indexes. This
option was replaced by --set-collation in
MySQL 4.1.1.
Specify the collation to use for sorting table indexes. The character set name is implied by the first part of the collation name. This option was added in MySQL 4.1.11.
Force myisamchk to use sorting to resolve the keys even if the temporary files should be very big.
Path of the directory to be used for storing temporary
files. If this is not set, myisamchk
uses the value of the TMPDIR
environment variable. Starting from MySQL 4.1,
tmpdir can be set to a list of
directory paths that are used successively in round-robin
fashion for creating temporary files. The separator
character between directory names should be colon
(:) on Unix and semicolon
(;) on Windows, NetWare,
and OS/2.
Unpack a table that was packed with myisampack.
myisamchk supports the following options for actions other than table checks and repairs:
Analyze the distribution of key values. This improves join
performance by enabling the join optimizer to better
choose the order in which to join the tables and which
indexes it should use. To obtain information about the key
distribution, use a myisamchk --description
--verbose tbl_name
command or the SHOW INDEX FROM
statement.
tbl_name
--block-search=,
offset-b
offset
Find the record that a block at the given offset belongs to.
Print some descriptive information about the table.
--set-auto-increment[=,
value]-A[
value]
Force AUTO_INCREMENT numbering for new
records to start at the given value (or higher, if there
are existing records with
AUTO_INCREMENT values this large). If
value is not specified,
AUTO_INCREMENT numbers for new records
begin with the largest value currently in the table, plus
one.
Sort the index tree blocks in high-low order. This optimizes seeks and makes table scans that use indexes faster.
Sort records according to a particular index. This makes
your data much more localized and may speed up range-based
SELECT and ORDER BY
operations that use this index. (The first time you use
this option to sort a table, it may be very slow.) To
determine a table's index numbers, use SHOW
INDEX, which displays a table's indexes in the
same order that myisamchk sees them.
Indexes are numbered beginning with 1.
If keys are not packed (PACK_KEYS=0)),
they have the same length, so when
myisamchk sorts and moves records, it
just overwrites record offsets in the index. If keys are
packed (PACK_KEYS=1),
myisamchk must unpack key blocks first,
then re-create indexes and pack the key blocks again. (In
this case, re-creating indexes is faster than updating
offsets for each index.)
Memory allocation is important when you run myisamchk. myisamchk uses no more memory than its memory-related variables are set to. If you are going to use myisamchk on very large tables, you should first decide how much memory you want it to use. The default is to use only about 3MB to perform repairs. By using larger values, you can get myisamchk to operate faster. For example, if you have more than 32MB RAM, you could use options such as these (in addition to any other options you might specify):
shell>myisamchk --sort_buffer_size=16M --key_buffer_size=16M \--read_buffer_size=1M --write_buffer_size=1M ...
Using --sort_buffer_size=16M should probably
be enough for most cases.
Be aware that myisamchk uses temporary
files in TMPDIR. If
TMPDIR points to a memory filesystem, you
may easily get out of memory errors. If this happens, run
myisamchk with the
--tmpdir=
option to specify some directory located on a filesystem that
has more space.
path
When repairing, myisamchk also needs a lot of disk space:
Double the size of the data file (the original file and a
copy). This space is not needed if you do a repair with
--quick; in this case, only the index
file is re-created. This space must be available
on the same filesystem as the original data
file, as the copy is created in the same
directory as the original.
Space for the new index file that replaces the old one. The old index file is truncated at the start of the repair operation, so you usually ignore this space. This space must be available on the same filesystem as the original data file.
When using --recover or
--sort-recover (but not when using
--safe-recover), you need space for a
sort buffer. The following formula yields the amount of
space required:
(largest_key+row_pointer_length) ×number_of_rows× 2
You can check the length of the keys and the
row_pointer_length with
myisamchk -dv
tbl_name. This space
is allocated in the temporary directory (specified by
TMPDIR or
--tmpdir=).
path
If you have a problem with disk space during repair, you can
try --safe-recover instead of
--recover.
myisamlog processes the contents of a
MyISAM log file. isamlog
is similar, but is used with ISAM log
files.
Invoke myisamlog or isamloglike this:
shell>myisamlog [shell>options] [log_file[tbl_name] ...]isamlog [options] [log_file[tbl_name] ...]
The default operation is update (-u). If a
recovery is done (-r), all writes and
possibly updates and deletes are done and errors are only
counted. The default log file name is
myisam.log for
myisamlog and isam.log
for isamlog if no
log_file argument is given. If
tables are named on the command line, only those tables are
updated.
myisamlog and isamlog understand the following options:
-?, -I
Display a help message and exit.
-c
N
Execute only N commands.
-f
N
Specify the maximum number of open files.
-i
Display extra information before exiting.
-o
offset
Specify the starting offset.
-p
N
Remove N components from path.
-r
Perform a recovery operation.
-R
record_pos_file
record_pos
Specify record position file and record position.
-u
Perform an update operation.
-v
Verbose mode. Print more output about what the program does. This option can be given multiple times to produce more and more output.
-w
write_file
Specify the write file.
-V
Display version information.
The myisampack utility compresses
MyISAM tables.
myisampack works by compressing each column
in the table separately. Usually,
myisampack packs the data file 40%-70%.
When the table is used later, the server reads into memory the information needed to decompress columns. This results in much better performance when accessing individual rows, because you only have to uncompress exactly one row.
MySQL uses mmap() when possible to perform
memory mapping on compressed tables. If
mmap() does not work, MySQL falls back to
normal read/write file operations.
A similar utility, pack_isam, compresses
ISAM tables. Because
ISAM tables are deprecated, this section
discusses only myisampack, but the general
procedures for using myisampack are also
true for pack_isam unless otherwise
specified. References to myisamchk should
be read as references to isamchk if you are
using pack_isam.
Please note the following:
If the mysqld server was invoked with external locking disabled, it is not a good idea to invoke myisampack if the table might be updated by the server during the packing process. It is safest to compress tables with the server stopped.
After packing a table, it becomes read-only. This is generally intended (such as when accessing packed tables on a CD). Allowing writes to a packed table is on our TODO list, but with low priority.
myisampack can pack
BLOB or TEXT
columns. (The older pack_isam program
for ISAM tables does not have this
capability.)
Invoke myisampack like this:
shell> myisampack [options] file_name ...
Each filename argument should be the name of an index
(.MYI) file. If you are not in the
database directory, you should specify the pathname to the
file. It is permissible to omit the .MYI
extension.
After you compress a table with myisampack, you should use myisamchk -rq to rebuild its indexes. Section 8.3, myisamchk MyISAM Table-Maintenance Utility.
myisampack supports the following options:
Display a help message and exit.
Make a backup of each table's data file using the name
tbl_name.OLD
The directory where character sets are installed. See Section 5.10.1, The Character Set Used for Data and Sorting.
--debug[=,
debug_options]-#
[
debug_options]
Write a debugging log. The
debug_options string often is
'd:t:o,.
file_name'
Produce a packed table even if it becomes larger than the
original or if the intermediate file from an earlier
invocation of myisampack exists.
(myisampack creates an intermediate
file named
tbl_name.TMD.TMD file might not be deleted.)
Normally, myisampack exits with an
error if it finds that
tbl_name.TMD--force,
myisampack packs the table anyway.
--join=,
big_tbl_name-j
big_tbl_name
Join all tables named on the command line into a single
table big_tbl_name. All tables
that are to be combined must have
identical structure (same column names and types, same
indexes, and so forth).
Specify the row length storage size, in bytes. The value should be 1, 2, or 3. myisampack stores all rows with length pointers of 1, 2, or 3 bytes. In most normal cases, myisampack can determine the correct length value before it begins packing the file, but it may notice during the packing process that it could have used a shorter length. In this case, myisampack prints a note that you could use a shorter row length the next time you pack the same file.
Silent mode. Write output only when errors occur.
Do not actually pack the table, just test packing it.
Use the named directory as the location where myisampack creates temporary files.
Verbose mode. Write information about the progress of the packing operation and its result.
Display version information and exit.
Wait and retry if the table is in use. If the mysqld server was invoked with external locking disabled, it is not a good idea to invoke myisampack if the table might be updated by the server during the packing process.
The following sequence of commands illustrates a typical table compression session:
shell>ls -l station.*-rw-rw-r-- 1 monty my 994128 Apr 17 19:00 station.MYD -rw-rw-r-- 1 monty my 53248 Apr 17 19:00 station.MYI -rw-rw-r-- 1 monty my 5767 Apr 17 19:00 station.frm shell>myisamchk -dvv stationMyISAM file: station Isam-version: 2 Creation time: 1996-03-13 10:08:58 Recover time: 1997-02-02 3:06:43 Data records: 1192 Deleted blocks: 0 Datafile parts: 1192 Deleted data: 0 Datafile pointer (bytes): 2 Keyfile pointer (bytes): 2 Max datafile length: 54657023 Max keyfile length: 33554431 Recordlength: 834 Record format: Fixed length table description: Key Start Len Index Type Root Blocksize Rec/key 1 2 4 unique unsigned long 1024 1024 1 2 32 30 multip. text 10240 1024 1 Field Start Length Type 1 1 1 2 2 4 3 6 4 4 10 1 5 11 20 6 31 1 7 32 30 8 62 35 9 97 35 10 132 35 11 167 4 12 171 16 13 187 35 14 222 4 15 226 16 16 242 20 17 262 20 18 282 20 19 302 30 20 332 4 21 336 4 22 340 1 23 341 8 24 349 8 25 357 8 26 365 2 27 367 2 28 369 4 29 373 4 30 377 1 31 378 2 32 380 8 33 388 4 34 392 4 35 396 4 36 400 4 37 404 1 38 405 4 39 409 4 40 413 4 41 417 4 42 421 4 43 425 4 44 429 20 45 449 30 46 479 1 47 480 1 48 481 79 49 560 79 50 639 79 51 718 79 52 797 8 53 805 1 54 806 1 55 807 20 56 827 4 57 831 4 shell>myisampack station.MYICompressing station.MYI: (1192 records) - Calculating statistics normal: 20 empty-space: 16 empty-zero: 12 empty-fill: 11 pre-space: 0 end-space: 12 table-lookups: 5 zero: 7 Original trees: 57 After join: 17 - Compressing file 87.14% Remember to run myisamchk -rq on compressed tables shell>ls -l station.*-rw-rw-r-- 1 monty my 127874 Apr 17 19:00 station.MYD -rw-rw-r-- 1 monty my 55296 Apr 17 19:04 station.MYI -rw-rw-r-- 1 monty my 5767 Apr 17 19:00 station.frm shell>myisamchk -dvv stationMyISAM file: station Isam-version: 2 Creation time: 1996-03-13 10:08:58 Recover time: 1997-04-17 19:04:26 Data records: 1192 Deleted blocks: 0 Datafile parts: 1192 Deleted data: 0 Datafile pointer (bytes): 3 Keyfile pointer (bytes): 1 Max datafile length: 16777215 Max keyfile length: 131071 Recordlength: 834 Record format: Compressed table description: Key Start Len Index Type Root Blocksize Rec/key 1 2 4 unique unsigned long 10240 1024 1 2 32 30 multip. text 54272 1024 1 Field Start Length Type Huff tree Bits 1 1 1 constant 1 0 2 2 4 zerofill(1) 2 9 3 6 4 no zeros, zerofill(1) 2 9 4 10 1 3 9 5 11 20 table-lookup 4 0 6 31 1 3 9 7 32 30 no endspace, not_always 5 9 8 62 35 no endspace, not_always, no empty 6 9 9 97 35 no empty 7 9 10 132 35 no endspace, not_always, no empty 6 9 11 167 4 zerofill(1) 2 9 12 171 16 no endspace, not_always, no empty 5 9 13 187 35 no endspace, not_always, no empty 6 9 14 222 4 zerofill(1) 2 9 15 226 16 no endspace, not_always, no empty 5 9 16 242 20 no endspace, not_always 8 9 17 262 20 no endspace, no empty 8 9 18 282 20 no endspace, no empty 5 9 19 302 30 no endspace, no empty 6 9 20 332 4 always zero 2 9 21 336 4 always zero 2 9 22 340 1 3 9 23 341 8 table-lookup 9 0 24 349 8 table-lookup 10 0 25 357 8 always zero 2 9 26 365 2 2 9 27 367 2 no zeros, zerofill(1) 2 9 28 369 4 no zeros, zerofill(1) 2 9 29 373 4 table-lookup 11 0 30 377 1 3 9 31 378 2 no zeros, zerofill(1) 2 9 32 380 8 no zeros 2 9 33 388 4 always zero 2 9 34 392 4 table-lookup 12 0 35 396 4 no zeros, zerofill(1) 13 9 36 400 4 no zeros, zerofill(1) 2 9 37 404 1 2 9 38 405 4 no zeros 2 9 39 409 4 always zero 2 9 40 413 4 no zeros 2 9 41 417 4 always zero 2 9 42 421 4 no zeros 2 9 43 425 4 always zero 2 9 44 429 20 no empty 3 9 45 449 30 no empty 3 9 46 479 1 14 4 47 480 1 14 4 48 481 79 no endspace, no empty 15 9 49 560 79 no empty 2 9 50 639 79 no empty 2 9 51 718 79 no endspace 16 9 52 797 8 no empty 2 9 53 805 1 17 1 54 806 1 3 9 55 807 20 no empty 3 9 56 827 4 no zeros, zerofill(2) 2 9 57 831 4 no zeros, zerofill(1) 2 9
myisampack displays the following kinds of information:
normal
The number of columns for which no extra packing is used.
empty-space
The number of columns containing values that are only spaces. These occupy one bit.
empty-zero
The number of columns containing values that are only binary zeros. These occupy one bit.
empty-fill
The number of integer columns that do not occupy the full
byte range of their type. These are changed to a smaller
type. For example, a BIGINT column
(eight bytes) can be stored as a
TINYINT column (one byte) if all its
values are in the range from -128 to
127.
pre-space
The number of decimal columns that are stored with leading spaces. In this case, each value contains a count for the number of leading spaces.
end-space
The number of columns that have a lot of trailing spaces. In this case, each value contains a count for the number of trailing spaces.
table-lookup
The column had only a small number of different values,
which were converted to an ENUM before
Huffman compression.
zero
The number of columns for which all values are zero.
Original trees
The initial number of Huffman trees.
After join
The number of distinct Huffman trees left after joining trees to save some header space.
After a table has been compressed, myisamchk -dvv prints additional information about each column:
Type
The data type. The value may contain any of the following descriptors:
constant
All rows have the same value.
no endspace
Do not store endspace.
no endspace, not_always
Do not store endspace and do not do endspace compression for all values.
no endspace, no empty
Do not store endspace. Do not store empty values.
table-lookup
The column was converted to an
ENUM.
zerofill(
N)
The most significant N
bytes in the value are always 0 and are not stored.
no zeros
Do not store zeros.
always zero
Zero values are stored using one bit.
Huff tree
The number of the Huffman tree associated with the column.
Bits
The number of bits used in the Huffman tree.
After you run myisampack, you must run myisamchk to re-create any indexes. At this time, you can also sort the index blocks and create statistics needed for the MySQL optimizer to work more efficiently:
shell> myisamchk -rq --sort-index --analyze tbl_name.MYI
A similar procedure applies for ISAM
tables. After using pack_isam, use
isamchk to re-create the indexes:
shell> isamchk -rq --sort-index --analyze tbl_name.ISM
After you have installed the packed table into the MySQL database directory, you should execute mysqladmin flush-tables to force mysqld to start using the new table.
To unpack a packed table, use the --unpack
option to myisamchk or
isamchk.
mysql is a simple SQL shell (with GNU
readline capabilities). It supports
interactive and non-interactive use. When used interactively,
query results are presented in an ASCII-table format. When
used non-interactively (for example, as a filter), the result
is presented in tab-separated format. The output format can be
changed using command options.
If you have problems due to insufficient memory for large
result sets, use the --quick option. This
forces mysql to retrieve results from the
server a row at a time rather than retrieving the entire
result set and buffering it in memory before displaying it.
This is done by returning the result set using the
mysql_use_result() C API function in the
client/server library rather than
mysql_store_result().
Using mysql is very easy. Invoke it from the prompt of your command interpreter as follows:
shell> mysql db_name
Or:
shell> mysql --user=user_name --password=your_password db_name
Then type an SQL statement, end it with
;, \g, or
\G and press Enter.
You can execute SQL statements in a script file (batch file) like this:
shell> mysql db_name < script.sql > output.tab
mysql supports the following options:
Display a help message and exit.
Enable automatic rehashing. This option is on by default,
which enables table and column name completion. Use
--skip-auto-rehash to disable rehashing.
That causes mysql to start faster, but
you must issue the rehash command if
you want to use table and column name completion.
Print results using tab as the column separator, with each row on a new line. With this option, mysql does not use the history file.
The directory where character sets are installed. See Section 5.10.1, The Character Set Used for Data and Sorting.
Write column names in results.
Compress all information sent between the client and the server if both support compression.
--database=,
db_name-D
db_name
The database to use. This is useful primarily in an option file.
--debug[=,
debug_options]-#
[
debug_options]
Write a debugging log. The
debug_options string often is
'd:t:o,.
The default is
file_name''d:t:o,/tmp/mysql.trace'.
Print some debugging information when the program exits.
--default-character-set=
charset_name
Use charset_name as the default
character set. See Section 5.10.1, The Character Set Used for Data and Sorting.
Set the statement delimiter. The default is the semicolon
character (;).
--execute=,
statement-e
statement
Execute the statement and quit. The default output format
is like that produced with --batch. See
Section 4.3.1, Using Options on the Command Line, for some examples.
Continue even if an SQL error occurs.
--host=,
host_name-h
host_name
Connect to the MySQL server on the given host.
Produce HTML output.
Ignore spaces after function names. The effect of this is
described in the discussion for the
IGNORE_SPACE SQL mode (see
Section 5.2.5, SQL Modes).
Write line numbers for errors. Disable this with
--skip-line-numbers.
Enable or disable LOCAL capability for
LOAD DATA INFILE. With no value, the
option enables LOCAL. The option may be
given as --local-infile=0 or
--local-infile=1 to explicitly disable or
enable LOCAL. Enabling
LOCAL has no effect if the server does
not also support it.
Enable named mysql commands.
Long-format commands are allowed, not just short-format
commands. For example, quit and
\q both are recognized. Use
--skip-named-commands to disable named
commands. See Section 8.6.2, mysql Commands.
Deprecated form of -skip-auto-rehash. See
the description for --auto-rehash.
Do not beep when errors occur.
Disable named commands. Use the \* form
only, or use named commands only at the beginning of a
line ending with a semicolon
(;). As of MySQL 3.23.22,
mysql starts with this option
enabled by default. However, even
with this option, long-format commands still work from the
first line. See Section 8.6.2, mysql Commands.
Deprecated form of --skip-pager. See the
--pager option.
Do not copy output to a file. Section 8.6.2, mysql Commands, discusses tee files further.
Ignore statements except those for the default database named on the command line. This is useful for skipping updates to other databases in the binary log.
Use the given command for paging query output. If the
command is omitted, the default pager is the value of your
PAGER environment variable. Valid
pagers are less,
more, cat [>
filename], and so forth. This option works only
on Unix. It does not work in batch mode. To disable
paging, use --skip-pager.
Section 8.6.2, mysql Commands, discusses output paging
further.
--password[=,
password]-p[
password]
The password to use when connecting to the server. If you
use the short option form (-p), you
cannot have a space between the
option and the password. If you omit the
password value following the
--password or -p option
on the command line, you are prompted for one.
Specifying a password on the command line should be considered insecure. See Section 5.8.6, Keeping Your Password Secure.
The TCP/IP port number to use for the connection.
Set the prompt to the specified format. The default is
mysql>. The special sequences that
the prompt can contain are described in
Section 8.6.2, mysql Commands.
--protocol={TCP|SOCKET|PIPE|MEMORY}
The connection protocol to use. Added in MySQL 4.1.
Do not cache each query result, print each row as it is received. This may slow down the server if the output is suspended. With this option, mysql does not use the history file.
Write column values without escape conversion. Often used
with the --batch option.
If the connection to the server is lost, automatically try
to reconnect. A single reconnect attempt is made each time
the connection is lost. To suppress reconnection behavior,
use --skip-reconnect. Added in MySQL
4.1.0.
--safe-updates,
--i-am-a-dummy, -U
Allow only those UPDATE and
DELETE statements that specify which
rows to modify by using key values. If you have set this
option in an option file, you can override it by using
--safe-updates on the command line. See
Section 8.6.5, mysql Tips, for more information about
this option.
Do not send passwords to the server in old (pre-4.1.1) format. This prevents connections except for servers that use the newer password format. This option was added in MySQL 4.1.1.
Ignore SIGINT signals (typically the
result of typing Control-C). This option was added in
MySQL 4.1.6.
Silent mode. Produce less output. This option can be given multiple times to produce less and less output.
Do not write column names in results.
Do not write line numbers for errors. Useful when you want to compare result files that include error messages.
For connections to localhost, the Unix
socket file to use, or, on Windows, the name of the named
pipe to use.
Options that begin with --ssl specify
whether to connect to the server via SSL and indicate
where to find SSL keys and certificates. See
Section 5.8.7.3, SSL Command Options.
Display output in table format. This is the default for interactive use, but can be used to produce table output in batch mode.
Append a copy of output to the given file. This option does not work in batch mode. in Section 8.6.2, mysql Commands, discusses tee files further.
Flush the buffer after each query.
--user=,
user_name-u
user_name
The MySQL username to use when connecting to the server.
Verbose mode. Produce more output about what the program
does. This option can be given multiple times to produce
more and more output. (For example, -v -v
-v produces table output format even in batch
mode.)