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Diffstat (limited to 'man/myisamchk.1')
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diff --git a/man/myisamchk.1 b/man/myisamchk.1 index 7a9f6931d65..d3f6a9f1670 100644 --- a/man/myisamchk.1 +++ b/man/myisamchk.1 @@ -2,12 +2,12 @@ .\" Title: \fBmyisamchk\fR .\" Author: [FIXME: author] [see http://docbook.sf.net/el/author] .\" Generator: DocBook XSL Stylesheets v1.75.2 <http://docbook.sf.net/> -.\" Date: 08/12/2009 +.\" Date: 11/04/2009 .\" Manual: MySQL Database System .\" Source: MySQL 5.1 .\" Language: English .\" -.TH "\FBMYISAMCHK\FR" "1" "08/12/2009" "MySQL 5\&.1" "MySQL Database System" +.TH "\FBMYISAMCHK\FR" "1" "11/04/2009" "MySQL 5\&.1" "MySQL Database System" .\" ----------------------------------------------------------------- .\" * set default formatting .\" ----------------------------------------------------------------- @@ -275,7 +275,8 @@ Display a help message and exit\&. Options are presented in a single list\&. .\} .\" myisamchk: debug option .\" debug option: myisamchk -\fB\-\-debug=\fR\fB\fIdebug_options\fR\fR\fB, \-# \fR\fB\fIdebug_options\fR\fR +\fB\-\-debug=\fR\fB\fIdebug_options\fR\fR, +\fB\-# \fR\fB\fIdebug_options\fR\fR .sp Write a debugging log\&. A typical \fIdebug_options\fR @@ -520,7 +521,7 @@ system variable\&. For more information, see the description of myisam_stats_method in Section\ \&5.1.4, \(lqServer System Variables\(rq, and -Section\ \&7.4.6, \(lqMyISAM Index Statistics Collection\(rq\&. For MySQL 5\&.1, +Section\ \&7.4.7, \(lqMyISAM Index Statistics Collection\(rq\&. For MySQL 5\&.1, stats_method was added in MySQL 5\&.0\&.14\&. For older versions, the statistics collection method is equivalent to nulls_equal\&. @@ -662,6 +663,9 @@ If you are using and have plenty of memory, setting the key_buffer_size variable to a large value helps the repair operation run faster\&. +.sp +For a description of the output format, see +the section called \(lqMYISAMCHK TABLE INFORMATION\(rq\&. .RE .sp .RS 4 @@ -782,7 +786,11 @@ server is using the table and you are running it with external locking disabled\ .\" files: repairing .PP \fBmyisamchk\fR -supports the following options for table repair operations: +supports the following options for table repair operations (operations performed when an option such as +\fB\-\-recover\fR +or +\fB\-\-safe\-recover\fR +is given): .sp .RS 4 .ie n \{\ @@ -844,7 +852,8 @@ Correct the checksum information for the table\&. .\} .\" myisamchk: data-file-length option .\" data-file-length option: myisamchk -\fB\-\-data\-file\-length=\fR\fB\fIlen\fR\fR\fB, \-D \fR\fB\fIlen\fR\fR +\fB\-\-data\-file\-length=\fR\fB\fIlen\fR\fR, +\fB\-D \fR\fB\fIlen\fR\fR .sp The maximum length of the data file (when re\-creating data file when it is \(lqfull\(rq)\&. @@ -864,6 +873,9 @@ The maximum length of the data file (when re\-creating data file when it is \fB\-e\fR .sp Do a repair that tries to recover every possible row from the data file\&. Normally, this also finds a lot of garbage rows\&. Do not use this option unless you are desperate\&. +.sp +For a description of the output format, see +the section called \(lqMYISAMCHK TABLE INFORMATION\(rq\&. .RE .sp .RS 4 @@ -1172,7 +1184,10 @@ Find the record that a block at the given offset belongs to\&. \fB\-\-description\fR, \fB\-d\fR .sp -Print some descriptive information about the table\&. +Print some descriptive information about the table\&. Specifying the +\fB\-\-verbose\fR +option once or twice produces additional information\&. See +the section called \(lqMYISAMCHK TABLE INFORMATION\(rq\&. .RE .sp .RS 4 @@ -1243,6 +1258,1068 @@ sorts and moves records, it just overwrites record offsets in the index\&. If ke \fBmyisamchk\fR 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\&.) .RE +.SH "MYISAMCHK TABLE INFORMATION" +.\" table description: myisamchk +.\" tables: information +.\" examples: myisamchk output +.\" myisamchk: example output +.PP +To obtain a description of a +MyISAM +table or statistics about it, use the commands shown here\&. The output from these commands is explained later in this section\&. +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +\fBmyisamchk \-d \fR\fB\fItbl_name\fR\fR +.sp +Runs +\fBmyisamchk\fR +in +\(lqdescribe mode\(rq +to produce a description of your table\&. If you start the MySQL server with external locking disabled, +\fBmyisamchk\fR +may report an error for a table that is updated while it runs\&. However, because +\fBmyisamchk\fR +does not change the table in describe mode, there is no risk of destroying data\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +\fBmyisamchk \-dv \fR\fB\fItbl_name\fR\fR +.sp +Adding +\fB\-v\fR +runs +\fBmyisamchk\fR +in verbose mode so that it produces more information about the table\&. Adding +\fB\-v\fR +a second time produces even more information\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +\fBmyisamchk \-eis \fR\fB\fItbl_name\fR\fR +.sp +Shows only the most important information from a table\&. This operation is slow because it must read the entire table\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +\fBmyisamchk \-eiv \fR\fB\fItbl_name\fR\fR +.sp +This is like +\fB\-eis\fR, but tells you what is being done\&. +.RE +.PP +The +\fItbl_name\fR +argument can be either the name of a +MyISAM +table or the name of its index file, as described in +\fBmyisamchk\fR(1)\&. Multiple +\fItbl_name\fR +arguments can be given\&. +.PP +Suppose that a table named +person +has the following structure\&. (The +MAX_ROWS +table option is included so that in the example output from +\fBmyisamchk\fR +shown later, some values are smaller and fit the output format more easily\&.) +.sp +.if n \{\ +.RS 4 +.\} +.nf +CREATE TABLE person +( + id INT NOT NULL AUTO_INCREMENT, + last_name VARCHAR(20) NOT NULL, + first_name VARCHAR(20) NOT NULL, + birth DATE, + death DATE, + PRIMARY KEY (id), + INDEX (last_name, first_name), + INDEX (birth) +) MAX_ROWS = 1000000; +.fi +.if n \{\ +.RE +.\} +.PP +Suppose also that the table has these data and index file sizes: +.sp +.if n \{\ +.RS 4 +.\} +.nf +\-rw\-rw\-\-\-\- 1 mysql mysql 9347072 Aug 19 11:47 person\&.MYD +\-rw\-rw\-\-\-\- 1 mysql mysql 6066176 Aug 19 11:47 person\&.MYI +.fi +.if n \{\ +.RE +.\} +.PP +Example of +\fBmyisamchk \-dvv\fR +output: +.sp +.if n \{\ +.RS 4 +.\} +.nf +MyISAM file: person +Record format: Packed +Character set: latin1_swedish_ci (8) +File\-version: 1 +Creation time: 2009\-08\-19 16:47:41 +Recover time: 2009\-08\-19 16:47:56 +Status: checked,analyzed,optimized keys +Auto increment key: 1 Last value: 306688 +Data records: 306688 Deleted blocks: 0 +Datafile parts: 306688 Deleted data: 0 +Datafile pointer (bytes): 4 Keyfile pointer (bytes): 3 +Datafile length: 9347072 Keyfile length: 6066176 +Max datafile length: 4294967294 Max keyfile length: 17179868159 +Recordlength: 54 +table description: +Key Start Len Index Type Rec/key Root Blocksize +1 2 4 unique long 1 99328 1024 +2 6 20 multip\&. varchar prefix 512 3563520 1024 + 27 20 varchar 512 +3 48 3 multip\&. uint24 NULL 306688 6065152 1024 +Field Start Length Nullpos Nullbit Type +1 1 1 +2 2 4 no zeros +3 6 21 varchar +4 27 21 varchar +5 48 3 1 1 no zeros +6 51 3 1 2 no zeros +.fi +.if n \{\ +.RE +.\} +.PP +Explanations for the types of information +\fBmyisamchk\fR +produces are given here\&. +\(lqKeyfile\(rq +refers to the index file\&. +\(lqRecord\(rq +and +\(lqrow\(rq +are synonymous, as are +\(lqfield\(rq +and +\(lqcolumn\&.\(rq +.PP +The initial part of the table description contains these values: +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +MyISAM file +.sp +Name of the +MyISAM +(index) file\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Record format +.sp +The format used to store table rows\&. The preceding examples use +Fixed length\&. Other possible values are +Compressed +and +Packed\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Chararacter set +.sp +The table default character set\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +File\-version +.sp +Version of +MyISAM +format\&. Currently always 1\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Creation time +.sp +When the data file was created\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Recover time +.sp +When the index/data file was last reconstructed\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Status +.sp +Table status flags\&. Possible values are +crashed, +open, +changed, +analyzed, +optimized keys, and +sorted index pages\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Auto increment key, +Last value +.sp +The key number associated the table\'s +AUTO_INCREMENT +column, and the most recently generated value for this column\&. These fields do not appear if there is no such column\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Data records +.sp +The number of rows in the table\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Deleted blocks +.sp +How many deleted blocks still have reserved space\&. You can optimize your table to minimize this space\&. See +Section\ \&6.4.4, \(lqTable Optimization\(rq\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Datafile parts +.sp +For dynamic\-row format, this indicates how many data blocks there are\&. For an optimized table without fragmented rows, this is the same as +Data records\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Deleted data +.sp +How many bytes of unreclaimed deleted data there are\&. You can optimize your table to minimize this space\&. See +Section\ \&6.4.4, \(lqTable Optimization\(rq\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Datafile pointer +.sp +The size of the data file pointer, in bytes\&. It is usually 2, 3, 4, or 5 bytes\&. Most tables manage with 2 bytes, but this cannot be controlled from MySQL yet\&. For fixed tables, this is a row address\&. For dynamic tables, this is a byte address\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Keyfile pointer +.sp +The size of the index file pointer, in bytes\&. It is usually 1, 2, or 3 bytes\&. Most tables manage with 2 bytes, but this is calculated automatically by MySQL\&. It is always a block address\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Max datafile length +.sp +How long the table data file can become, in bytes\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Max keyfile length +.sp +How long the table index file can become, in bytes\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Recordlength +.sp +How much space each row takes, in bytes\&. +.RE +.PP +The +table description +part of the output includes a list of all keys in the table\&. For each key, +\fBmyisamchk\fR +displays some low\-level information: +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Key +.sp +This key\'s number\&. This value is shown only for the first column of the key\&. If this value is missing, the line corresponds to the second or later column of a multiple\-column key\&. For the table shown in the example, there are two +table description +lines for the second index\&. This indicates that it is a multiple\-part index with two parts\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Start +.sp +Where in the row this portion of the index starts\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Len +.sp +How long this portion of the index is\&. For packed numbers, this should always be the full length of the column\&. For strings, it may be shorter than the full length of the indexed column, because you can index a prefix of a string column\&. The total length of a multiple\-part key is the sum of the +Len +values for all key parts\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Index +.sp +Whether a key value can exist multiple times in the index\&. Possible values are +unique +or +multip\&. +(multiple)\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Type +.sp +What data type this portion of the index has\&. This is a +MyISAM +data type with the possible values +packed, +stripped, or +empty\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Root +.sp +Address of the root index block\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Blocksize +.sp +The size of each index block\&. By default this is 1024, but the value may be changed at compile time when MySQL is built from source\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Rec/key +.sp +This is a statistical value used by the optimizer\&. It tells how many rows there are per value for this index\&. A unique index always has a value of 1\&. This may be updated after a table is loaded (or greatly changed) with +\fBmyisamchk \-a\fR\&. If this is not updated at all, a default value of 30 is given\&. +.RE +.PP +The last part of the output provides information about each column: +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Field +.sp +The column number\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Start +.sp +The byte position of the column within table rows\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Length +.sp +The length of the column in bytes\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Nullpos, +Nullbit +.sp +For columns that can be +NULL, +MyISAM +stores +NULL +values as a flag in a byte\&. Depending on how many nullable columns there are, there can be one or more bytes used for this purpose\&. The +Nullpos +and +Nullbit +values, if nonempty, indicate which byte and bit contains that flag indicating whether the column is +NULL\&. +.sp +The position and number of bytes used to store +NULL +flags is shown in the line for field 1\&. This is why there are six +Field +lines for the +person +table even though it has only five columns\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Type +.sp +The data type\&. The value may contain any of the following descriptors: +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +constant +.sp +All rows have the same value\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +no endspace +.sp +Do not store endspace\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +no endspace, not_always +.sp +Do not store endspace and do not do endspace compression for all values\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +no endspace, no empty +.sp +Do not store endspace\&. Do not store empty values\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +table\-lookup +.sp +The column was converted to an +ENUM\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +zerofill(\fIN\fR) +.sp +The most significant +\fIN\fR +bytes in the value are always 0 and are not stored\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +no zeros +.sp +Do not store zeros\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +always zero +.sp +Zero values are stored using one bit\&. +.RE +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Huff tree +.sp +The number of the Huffman tree associated with the column\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Bits +.sp +The number of bits used in the Huffman tree\&. +.RE +.PP +The +Huff tree +and +Bits +fields are displayed if the table has been compressed with +\fBmyisampack\fR\&. See +\fBmyisampack\fR(1), for an example of this information\&. +.PP +Example of +\fBmyisamchk \-eiv\fR +output: +.sp +.if n \{\ +.RS 4 +.\} +.nf +Checking MyISAM file: person +Data records: 306688 Deleted blocks: 0 +\- check file\-size +\- check record delete\-chain +No recordlinks +\- check key delete\-chain +block_size 1024: +\- check index reference +\- check data record references index: 1 +Key: 1: Keyblocks used: 98% Packed: 0% Max levels: 3 +\- check data record references index: 2 +Key: 2: Keyblocks used: 99% Packed: 97% Max levels: 3 +\- check data record references index: 3 +Key: 3: Keyblocks used: 98% Packed: \-14% Max levels: 3 +Total: Keyblocks used: 98% Packed: 89% +\- check records and index references +\fI*** LOTS OF ROW NUMBERS DELETED ***\fR +Records: 306688 M\&.recordlength: 25 Packed: 83% +Recordspace used: 97% Empty space: 2% Blocks/Record: 1\&.00 +Record blocks: 306688 Delete blocks: 0 +Record data: 7934464 Deleted data: 0 +Lost space: 256512 Linkdata: 1156096 +User time 43\&.08, System time 1\&.68 +Maximum resident set size 0, Integral resident set size 0 +Non\-physical pagefaults 0, Physical pagefaults 0, Swaps 0 +Blocks in 0 out 7, Messages in 0 out 0, Signals 0 +Voluntary context switches 0, Involuntary context switches 0 +Maximum memory usage: 1046926 bytes (1023k) +.fi +.if n \{\ +.RE +.\} +.PP +\fBmyisamchk \-eiv\fR +output includes the following information: +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Data records +.sp +The number of rows in the table\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Deleted blocks +.sp +How many deleted blocks still have reserved space\&. You can optimize your table to minimize this space\&. See +Section\ \&6.4.4, \(lqTable Optimization\(rq\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Key +.sp +The key number\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Keyblocks used +.sp +What percentage of the keyblocks are used\&. When a table has just been reorganized with +\fBmyisamchk\fR, the values are very high (very near theoretical maximum)\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Packed +.sp +MySQL tries to pack key values that have a common suffix\&. This can only be used for indexes on +CHAR +and +VARCHAR +columns\&. For long indexed strings that have similar leftmost parts, this can significantly reduce the space used\&. In the preceding example, the second key is 40 bytes long and a 97% reduction in space is achieved\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Max levels +.sp +How deep the B\-tree for this key is\&. Large tables with long key values get high values\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Records +.sp +How many rows are in the table\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +M\&.recordlength +.sp +The average row length\&. This is the exact row length for tables with fixed\-length rows, because all rows have the same length\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Packed +.sp +MySQL strips spaces from the end of strings\&. The +Packed +value indicates the percentage of savings achieved by doing this\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Recordspace used +.sp +What percentage of the data file is used\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Empty space +.sp +What percentage of the data file is unused\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Blocks/Record +.sp +Average number of blocks per row (that is, how many links a fragmented row is composed of)\&. This is always 1\&.0 for fixed\-format tables\&. This value should stay as close to 1\&.0 as possible\&. If it gets too large, you can reorganize the table\&. See +Section\ \&6.4.4, \(lqTable Optimization\(rq\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Recordblocks +.sp +How many blocks (links) are used\&. For fixed\-format tables, this is the same as the number of rows\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Deleteblocks +.sp +How many blocks (links) are deleted\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Recorddata +.sp +How many bytes in the data file are used\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Deleted data +.sp +How many bytes in the data file are deleted (unused)\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Lost space +.sp +If a row is updated to a shorter length, some space is lost\&. This is the sum of all such losses, in bytes\&. +.RE +.sp +.RS 4 +.ie n \{\ +\h'-04'\(bu\h'+03'\c +.\} +.el \{\ +.sp -1 +.IP \(bu 2.3 +.\} +Linkdata +.sp +When the dynamic table format is used, row fragments are linked with pointers (4 to 7 bytes each)\&. +Linkdata +is the sum of the amount of storage used by all such pointers\&. +.RE .SH "MYISAMCHK MEMORY USAGE" .\" memory usage: myisamchk .PP @@ -1259,8 +2336,10 @@ to operate faster\&. For example, if you have more than 32MB RAM, you could use .RS 4 .\} .nf -shell> \fBmyisamchk \-\-sort_buffer_size=16M \-\-key_buffer_size=16M \e\fR - \fB\-\-read_buffer_size=1M \-\-write_buffer_size=1M \&.\&.\&.\fR +shell> \fBmyisamchk \-\-sort_buffer_size=16M \e\fR + \fB\-\-key_buffer_size=16M \e\fR + \fB\-\-read_buffer_size=1M \e\fR + \fB\-\-write_buffer_size=1M \&.\&.\&.\fR .fi .if n \{\ .RE @@ -1275,13 +2354,13 @@ Be aware that uses temporary files in TMPDIR\&. If TMPDIR -points to a memory file system, you may easily get out of memory errors\&. If this happens, run +points to a memory file system, out of memory errors can easily occur\&. If this happens, run \fBmyisamchk\fR with the \fB\-\-tmpdir=\fR\fB\fIpath\fR\fR -option to specify some directory located on a file system that has more space\&. +option to specify a directory located on a file system that has more space\&. .PP -When repairing, +When performing repair operations, \fBmyisamchk\fR also needs a lot of disk space: .sp @@ -1293,7 +2372,7 @@ also needs a lot of disk space: .sp -1 .IP \(bu 2.3 .\} -Double the size of the data file (the original file and a copy)\&. This space is not needed if you do a repair with +Twice the size of the data file (the original file and a copy)\&. This space is not needed if you do a repair with \fB\-\-quick\fR; in this case, only the index file is re\-created\&. \fIThis space must be available on the same file system as the original data file\fR, as the copy is created in the same directory as the original\&. .RE @@ -1322,7 +2401,10 @@ When using or \fB\-\-sort\-recover\fR (but not when using -\fB\-\-safe\-recover\fR), you need space for a sort buffer\&. The following formula yields the amount of space required: +\fB\-\-safe\-recover\fR), you need space on disk for sorting\&. This space is allocated in the temporary directory (specified by +TMPDIR +or +\fB\-\-tmpdir=\fR\fB\fIpath\fR\fR)\&. The following formula yields the amount of space required: .sp .if n \{\ .RS 4 @@ -1335,12 +2417,27 @@ or .\} .sp You can check the length of the keys and the -row_pointer_length +\fIrow_pointer_length\fR with -\fBmyisamchk \-dv \fR\fB\fItbl_name\fR\fR\&. This space is allocated in the temporary directory (specified by -TMPDIR -or -\fB\-\-tmpdir=\fR\fB\fIpath\fR\fR)\&. +\fBmyisamchk \-dv \fR\fB\fItbl_name\fR\fR +(see +the section called \(lqMYISAMCHK TABLE INFORMATION\(rq)\&. The +\fIrow_pointer_length\fR +and +\fInumber_of_rows\fR +values are the +Datafile pointer +and +Data records +values in the table description\&. To determine the +\fIlargest_key\fR +value, check the +Key +lines in the table description\&. The +Len +column indicates the number of bytes for each key part\&. For a multiple\-column index, the key size is the sum of the +Len +values for all key parts\&. .RE .PP If you have a problem with disk space during repair, you can try |