~ubuntu-branches/ubuntu/trusty/mysql-5.6/trusty

It is best to make a backup of a table before performing a table repair operation; under some circumstances the operation might cause data loss\&. Possible causes include but are not limited to file system errors\&.

.sp .5v

.RE

.PP

Invoke

\fBmyisamchk\fR

like this:

.sp

.if n \{\

.RS 4

.\}

.nf

shell> \fBmyisamchk [\fR\fB\fIoptions\fR\fR\fB] \fR\fB\fItbl_name\fR\fR\fB \&.\&.\&.\fR

.fi

.if n \{\

.RE

.\}

.PP

The

\fIoptions\fR

specify what you want

\fBmyisamchk\fR

to do\&. They are described in the following sections\&. You can also get a list of options by invoking

\fBmyisamchk \-\-help\fR\&.

100

.PP

101

With no options,

102

\fBmyisamchk\fR

103

simply checks your table as the default operation\&. To get more information or to tell

104

\fBmyisamchk\fR

105

to take corrective action, specify options as described in the following discussion\&.

106

.PP

107

\fItbl_name\fR

108

is the database table you want to check or repair\&. If you run

109

\fBmyisamchk\fR

110

somewhere other than in the database directory, you must specify the path to the database directory, because

111

\fBmyisamchk\fR

112

has no idea where the database is located\&. In fact,

113

\fBmyisamchk\fR

114

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\&.

115

.PP

116

You can name several tables on the

117

\fBmyisamchk\fR

118

command line if you wish\&. You can also specify a table by naming its index file (the file with the

119

\&.MYI

120

suffix)\&. This enables you to specify all tables in a directory by using the pattern

121

*\&.MYI\&. For example, if you are in a database directory, you can check all the

122

MyISAM

123

tables in that directory like this:

124

.sp

125

.if n \{\

126

.RS 4

127

.\}

128

.nf

129

shell> \fBmyisamchk *\&.MYI\fR

130

.fi

131

.if n \{\

132

.RE

133

.\}

134

.PP

135

If you are not in the database directory, you can check all the tables there by specifying the path to the directory:

136

.sp

137

.if n \{\

138

.RS 4

139

.\}

140

.nf

141

shell> \fBmyisamchk \fR\fB\fI/path/to/database_dir/\fR\fR\fB*\&.MYI\fR

142

.fi

143

.if n \{\

144

.RE

145

.\}

146

.PP

147

You can even check all tables in all databases by specifying a wildcard with the path to the MySQL data directory:

148

.sp

149

.if n \{\

150

.RS 4

151

.\}

152

.nf

153

shell> \fBmyisamchk \fR\fB\fI/path/to/datadir/*/*\fR\fR\fB\&.MYI\fR

154

.fi

155

.if n \{\

156

.RE

157

.\}

158

.PP

159

The recommended way to quickly check all

160

MyISAM

161

tables is:

162

.sp

163

.if n \{\

164

.RS 4

165

.\}

166

.nf

167

shell> \fBmyisamchk \-\-silent \-\-fast \fR\fB\fI/path/to/datadir/*/*\fR\fR\fB\&.MYI\fR

168

.fi

169

.if n \{\

170

.RE

171

.\}

172

.PP

173

If you want to check all

174

MyISAM

175

tables and repair any that are corrupted, you can use the following command:

176

.sp

177

.if n \{\

178

.RS 4

179

.\}

180

.nf

181

shell> \fBmyisamchk \-\-silent \-\-force \-\-fast \-\-update\-state \e\fR

182

\fB\-\-key_buffer_size=64M \-\-myisam_sort_buffer_size=64M \e\fR

183

\fB\-\-read_buffer_size=1M \-\-write_buffer_size=1M \e\fR

184

\fB\fI/path/to/datadir/*/*\fR\fR\fB\&.MYI\fR

185

.fi

186

.if n \{\

187

.RE

188

.\}

189

.PP

190

This command assumes that you have more than 64MB free\&. For more information about memory allocation with

191

\fBmyisamchk\fR, see

192

the section called \(lqMYISAMCHK MEMORY USAGE\(rq\&.

193

.PP

194

For additional information about using

195

\fBmyisamchk\fR, see

196

Section\ \&7.6, \(lqMyISAM Table Maintenance and Crash Recovery\(rq\&.

197

.if n \{\

198

.sp

199

.\}

200

.RS 4

201

.it 1 an-trap

202

.nr an-no-space-flag 1

203

.nr an-break-flag 1

204

.br

205

.ps +1

206

\fBImportant\fR

207

.ps -1

208

.br

209

.PP

210

\fIYou must ensure that no other program is using the tables while you are running \fR\fI\fBmyisamchk\fR\fR\&. The most effective means of doing so is to shut down the MySQL server while running

211

\fBmyisamchk\fR, or to lock all tables that

212

\fBmyisamchk\fR

213

is being used on\&.

214

.PP

215

Otherwise, when you run

216

\fBmyisamchk\fR, it may display the following error message:

217

.sp

218

.if n \{\

219

.RS 4

220

.\}

221

.nf

222

warning: clients are using or haven\*(Aqt closed the table properly

223

.fi

224

.if n \{\

225

.RE

226

.\}

227

.PP

228

This means that you are trying to check a table that has been updated by another program (such as the

229

\fBmysqld\fR

230

server) that hasn\*(Aqt yet closed the file or that has died without closing the file properly, which can sometimes lead to the corruption of one or more

231

MyISAM

232

tables\&.

233

.PP

234

235

\fBmysqld\fR

236

is running, you must force it to flush any table modifications that are still buffered in memory by using

237

FLUSH TABLES\&. You should then ensure that no one is using the tables while you are running

238

\fBmyisamchk\fR

239

.PP

240

However, the easiest way to avoid this problem is to use

241

CHECK TABLE

242

instead of

243

\fBmyisamchk\fR

244

to check tables\&. See

245

Section\ \&13.7.2.2, \(lqCHECK TABLE Syntax\(rq\&.

246

.sp .5v

247

.RE

248

.PP

249

\fBmyisamchk\fR

250

supports the following options, which can be specified on the command line or in the

251

[myisamchk]

252

group of an option file\&.

253

\fBmyisamchk\fR

254

also supports the options for processing option files described at

255

Section\ \&4.2.3.4, \(lqCommand-Line Options that Affect Option-File Handling\(rq\&.

256

.SH "MYISAMCHK GENERAL OPTIONS"

257

.\" options: myisamchk

258

.\" myisamchk: options

259

.PP

260

The options described in this section can be used for any type of table maintenance operation performed by

261

\fBmyisamchk\fR\&. The sections following this one describe options that pertain only to specific operations, such as table checking or repairing\&.

262

.sp

263

.RS 4

264

.ie n \{\

265

\h'-04'\(bu\h'+03'\c

266

.\}

267

.el \{\

268

.sp -1

269

.IP \(bu 2.3

270

.\}

271

.\" myisamchk: help option.\" help option: myisamchk\fB\-\-help\fR,

272

\fB\-?\fR

273

.sp

274

Display a help message and exit\&. Options are grouped by type of operation\&.

275

.RE

276

.sp

277

.RS 4

278

.ie n \{\

279

\h'-04'\(bu\h'+03'\c

280

.\}

281

.el \{\

282

.sp -1

283

.IP \(bu 2.3

284

.\}

285

.\" myisamchk: HELP option.\" HELP option: myisamchk\fB\-\-HELP\fR,

286

\fB\-H\fR

287

.sp

288

Display a help message and exit\&. Options are presented in a single list\&.

289

.RE

290

.sp

291

.RS 4

292

.ie n \{\

293

\h'-04'\(bu\h'+03'\c

294

.\}

295

.el \{\

296

.sp -1

297

.IP \(bu 2.3

298

.\}

299

.\" myisamchk: debug option.\" debug option: myisamchk\fB\-\-debug=\fR\fB\fIdebug_options\fR\fR,

300

\fB\-# \fR\fB\fIdebug_options\fR\fR

301

.sp

302

Write a debugging log\&. A typical

303

\fIdebug_options\fR

304

string is

305

\*(Aqd:t:o,\fIfile_name\fR\*(Aq\&. The default is

306

\*(Aqd:t:o,/tmp/myisamchk\&.trace\*(Aq\&.

307

.RE

308

.sp

309

.RS 4

310

.ie n \{\

311

\h'-04'\(bu\h'+03'\c

312

.\}

313

.el \{\

314

.sp -1

315

.IP \(bu 2.3

316

.\}

317

.\" myisamchk: silent option.\" silent option: myisamchk\fB\-\-silent\fR,

318

\fB\-s\fR

319

.sp

320

Silent mode\&. Write output only when errors occur\&. You can use

321

\fB\-s\fR

322

twice (\fB\-ss\fR) to make

323

\fBmyisamchk\fR

324

very silent\&.

325

.RE

326

.sp

327

.RS 4

328

.ie n \{\

329

\h'-04'\(bu\h'+03'\c

330

.\}

331

.el \{\

332

.sp -1

333

.IP \(bu 2.3

334

.\}

335

.\" myisamchk: verbose option.\" verbose option: myisamchk\fB\-\-verbose\fR,

336

\fB\-v\fR

337

.sp

338

Verbose mode\&. Print more information about what the program does\&. This can be used with

339

\fB\-d\fR

340

and

341

\fB\-e\fR\&. Use

342

\fB\-v\fR

343

multiple times (\fB\-vv\fR,

344

\fB\-vvv\fR) for even more output\&.

345

.RE

346

.sp

347

.RS 4

348

.ie n \{\

349

\h'-04'\(bu\h'+03'\c

350

.\}

351

.el \{\

352

.sp -1

353

.IP \(bu 2.3

354

.\}

355

.\" myisamchk: version option.\" version option: myisamchk\fB\-\-version\fR,

356

\fB\-V\fR

357

.sp

358

Display version information and exit\&.

359

.RE

360

.sp

361

.RS 4

362

.ie n \{\

363

\h'-04'\(bu\h'+03'\c

364

.\}

365

.el \{\

366

.sp -1

367

.IP \(bu 2.3

368

.\}

369

.\" myisamchk: wait option.\" wait option: myisamchk\fB\-\-wait\fR,

370

\fB\-w\fR

371

.sp

372

Instead of terminating with an error if the table is locked, wait until the table is unlocked before continuing\&. If you are running

373

\fBmysqld\fR

374

with external locking disabled, the table can be locked only by another

375

\fBmyisamchk\fR

376

command\&.

377

.RE

378

.PP

379

You can also set the following variables by using

380

\fB\-\-\fR\fB\fIvar_name\fR\fR\fB=\fR\fB\fIvalue\fR\fR

381

syntax:

382

.\" decode_bits myisamchk variable

383

.\" ft_max_word_len myisamchk variable

384

.\" ft_min_word_len myisamchk variable

385

.\" ft_stopword_file myisamchk variable

386

.\" key_buffer_size myisamchk variable

387

.\" myisam_block_size myisamchk variable

388

.\" read_buffer_size myisamchk variable

389

.\" sort_buffer_size myisamchk variable

390

.\" myisam_sort_buffer_size myisamchk variable

391

.\" sort_key_blocks myisamchk variable

392

.\" stats_method myisamchk variable

393

.\" write_buffer_size myisamchk variable

394

.TS

395

allbox tab(:);

396

lB lB.

397

398

Variable

399

T}:T{

400

Default Value

401

402

.T&

403

l l

404

l l

405

l l

406

l l

407

l l

408

l l

409

l l

410

l l

411

l l

412

l l

413

l l

414

l l.

415

416

decode_bits

417

T}:T{

418

419

420

421

ft_max_word_len

422

T}:T{

423

version\-dependent

424

425

426

ft_min_word_len

427

T}:T{

428

429

430

431

ft_stopword_file

432

T}:T{

433

built\-in list

434

435

436

key_buffer_size

437

T}:T{

438

523264

439

440

441

myisam_block_size

442

T}:T{

443

1024

444

445

446

myisam_sort_key_blocks

447

T}:T{

448

449

450

451

read_buffer_size

452

T}:T{

453

262136

454

455

456

sort_buffer_size

457

T}:T{

458

2097144

459

460

461

sort_key_blocks

462

T}:T{

463

464

465

466

stats_method

467

T}:T{

468

nulls_unequal

469

470

471

write_buffer_size

472

T}:T{

473

262136

474

475

.TE

476

.sp 1

477

.PP

478

The possible

479

\fBmyisamchk\fR

480

variables and their default values can be examined with

481

\fBmyisamchk \-\-help\fR:

482

.PP

483

sort_buffer_size

484

is used when the keys are repaired by sorting keys, which is the normal case when you use

485

\fB\-\-recover\fR\&. As of MySQL 5\&.6\&.9,

486

myisam_sort_buffer_size

487

is available as an alternative name to

488

sort_buffer_size\&.

489

myisam_sort_buffer_size

490

is preferable to

491

sort_buffer_size

492

because its name corresponds to the

493

myisam_sort_buffer_size

494

server system variable that has a similar meaning\&.

495

sort_buffer_size

496

should be considered deprecated\&.

497

.PP

498

key_buffer_size

499

is used when you are checking the table with

500

\fB\-\-extend\-check\fR

501

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:

502

.sp

503

.RS 4

504

.ie n \{\

505

\h'-04'\(bu\h'+03'\c

506

.\}

507

.el \{\

508

.sp -1

509

.IP \(bu 2.3

510

.\}

511

You use

512

\fB\-\-safe\-recover\fR\&.

513

.RE

514

.sp

515

.RS 4

516

.ie n \{\

517

\h'-04'\(bu\h'+03'\c

518

.\}

519

.el \{\

520

.sp -1

521

.IP \(bu 2.3

522

.\}

523

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

524

CHAR,

525

VARCHAR, or

526

TEXT

527

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

528

\fBmyisamchk\fR

529

to repair by sorting, you can use the

530

\fB\-\-sort\-recover\fR

531

option\&.

532

.RE

533

.PP

534

Repairing through the key buffer takes much less disk space than using sorting, but is also much slower\&.

535

.PP

536

If you want a faster repair, set the

537

key_buffer_size

538

and

539

myisam_sort_buffer_size

540

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\&.

541

.PP

542

myisam_block_size

543

is the size used for index blocks\&.

544

.PP

545

stats_method

546

influences how

547

NULL

548

values are treated for index statistics collection when the

549

\fB\-\-analyze\fR

550

option is given\&. It acts like the

551

myisam_stats_method

552

system variable\&. For more information, see the description of

553

myisam_stats_method

554

555

Section\ \&5.1.4, \(lqServer System Variables\(rq, and

556

Section\ \&8.3.7, \(lqInnoDB and MyISAM Index Statistics Collection\(rq\&.

557

.PP

558

ft_min_word_len

559

and

560

ft_max_word_len

561

indicate the minimum and maximum word length for

562

FULLTEXT

563

indexes on

564

MyISAM

565

tables\&.

566

ft_stopword_file

567

names the stopword file\&. These need to be set under the following circumstances\&.

568

.PP

569

If you use

570

\fBmyisamchk\fR

571

to perform an operation that modifies table indexes (such as repair or analyze), the

572

FULLTEXT

573

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\&.

574

.PP

575

The problem occurs because these parameters are known only by the server\&. They are not stored in

576

MyISAM

577

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

578

ft_min_word_len,

579

ft_max_word_len, and

580

ft_stopword_file

581

values to

582

\fBmyisamchk\fR

583

that you use for

584

\fBmysqld\fR\&. For example, if you have set the minimum word length to 3, you can repair a table with

585

\fBmyisamchk\fR

586

like this:

587

.sp

588

.if n \{\

589

.RS 4

590

.\}

591

.nf

592

shell> \fBmyisamchk \-\-recover \-\-ft_min_word_len=3 \fR\fB\fItbl_name\fR\fR\fB\&.MYI\fR

593

.fi

594

.if n \{\

595

.RE

596

.\}

597

.PP

598

To ensure that

599

\fBmyisamchk\fR

600

and the server use the same values for full\-text parameters, you can place each one in both the

601

[mysqld]

602

and

603

[myisamchk]

604

sections of an option file:

605

.sp

606

.if n \{\

607

.RS 4

608

.\}

609

.nf

610

[mysqld]

611

ft_min_word_len=3

612

[myisamchk]

613

ft_min_word_len=3

614

.fi

615

.if n \{\

616

.RE

617

.\}

618

.PP

619

An alternative to using

620

\fBmyisamchk\fR

621

is to use the

622

REPAIR TABLE,

623

ANALYZE TABLE,

624

OPTIMIZE TABLE, or

625

ALTER TABLE\&. These statements are performed by the server, which knows the proper full\-text parameter values to use\&.

626

.SH "MYISAMCHK CHECK OPTIONS"

627

.\" check options: myisamchk

628

.\" tables: checking

629

.PP

630

\fBmyisamchk\fR

631

supports the following options for table checking operations:

632

.sp

633

.RS 4

634

.ie n \{\

635

\h'-04'\(bu\h'+03'\c

636

.\}

637

.el \{\

638

.sp -1

639

.IP \(bu 2.3

640

.\}

641

.\" myisamchk: check option.\" check option: myisamchk\fB\-\-check\fR,

642

\fB\-c\fR

643

.sp

644

Check the table for errors\&. This is the default operation if you specify no option that selects an operation type explicitly\&.

645

.RE

646

.sp

647

.RS 4

648

.ie n \{\

649

\h'-04'\(bu\h'+03'\c

650

.\}

651

.el \{\

652

.sp -1

653

.IP \(bu 2.3

654

.\}

655

.\" myisamchk: check-only-changed option.\" check-only-changed option: myisamchk\fB\-\-check\-only\-changed\fR,

656

\fB\-C\fR

657

.sp

658

Check only tables that have changed since the last check\&.

659

.RE

660

.sp

661

.RS 4

662

.ie n \{\

663

\h'-04'\(bu\h'+03'\c

664

.\}

665

.el \{\

666

.sp -1

667

.IP \(bu 2.3

668

.\}

669

.\" myisamchk: extend-check option.\" extend-check option: myisamchk\fB\-\-extend\-check\fR,

670

\fB\-e\fR

671

.sp

672

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,

673

\fBmyisamchk\fR

674

675

\fBmyisamchk \-\-medium\-check\fR

676

should be able to determine whether there are any errors in the table\&.

677

.sp

678

If you are using

679

\fB\-\-extend\-check\fR

680

and have plenty of memory, setting the

681

key_buffer_size

682

variable to a large value helps the repair operation run faster\&.

683

.sp

684

See also the description of this option under table repair options\&.

685

.sp

686

For a description of the output format, see

687

the section called \(lqOBTAINING TABLE INFORMATION WITH MYISAMCHK\(rq\&.

688

.RE

689

.sp

690

.RS 4

691

.ie n \{\

692

\h'-04'\(bu\h'+03'\c

693

.\}

694

.el \{\

695

.sp -1

696

.IP \(bu 2.3

697

.\}

698

.\" myisamchk: fast option.\" fast option: myisamchk\fB\-\-fast\fR,

699

\fB\-F\fR

700

.sp

701

Check only tables that haven\*(Aqt been closed properly\&.

702

.RE

703

.sp

704

.RS 4

705

.ie n \{\

706

\h'-04'\(bu\h'+03'\c

707

.\}

708

.el \{\

709

.sp -1

710

.IP \(bu 2.3

711

.\}

712

.\" myisamchk: force option.\" force option: myisamchk\fB\-\-force\fR,

713

\fB\-f\fR

714

.sp

715

Do a repair operation automatically if

716

\fBmyisamchk\fR

717

finds any errors in the table\&. The repair type is the same as that specified with the

718

\fB\-\-recover\fR

719

720

\fB\-r\fR

721

option\&.

722

.RE

723

.sp

724

.RS 4

725

.ie n \{\

726

\h'-04'\(bu\h'+03'\c

727

.\}

728

.el \{\

729

.sp -1

730

.IP \(bu 2.3

731

.\}

732

.\" myisamchk: information option.\" information option: myisamchk\fB\-\-information\fR,

733

\fB\-i\fR

734

.sp

735

Print informational statistics about the table that is checked\&.

736

.RE

737

.sp

738

.RS 4

739

.ie n \{\

740

\h'-04'\(bu\h'+03'\c

741

.\}

742

.el \{\

743

.sp -1

744

.IP \(bu 2.3

745

.\}

746

.\" myisamchk: medium-check option.\" medium-check option: myisamchk\fB\-\-medium\-check\fR,

747

\fB\-m\fR

748

.sp

749

Do a check that is faster than an

750

\fB\-\-extend\-check\fR

751

operation\&. This finds only 99\&.99% of all errors, which should be good enough in most cases\&.

752

.RE

753

.sp

754

.RS 4

755

.ie n \{\

756

\h'-04'\(bu\h'+03'\c

757

.\}

758

.el \{\

759

.sp -1

760

.IP \(bu 2.3

761

.\}

762

.\" myisamchk: read-only option.\" read-only option: myisamchk\fB\-\-read\-only\fR,

763

\fB\-T\fR

764

.sp

765

Do not mark the table as checked\&. This is useful if you use

766

\fBmyisamchk\fR

767

to check a table that is in use by some other application that does not use locking, such as

768

\fBmysqld\fR

769

when run with external locking disabled\&.

770

.RE

771

.sp

772

.RS 4

773

.ie n \{\

774

\h'-04'\(bu\h'+03'\c

775

.\}

776

.el \{\

777

.sp -1

778

.IP \(bu 2.3

779

.\}

780

.\" myisamchk: update-state option.\" update-state option: myisamchk\fB\-\-update\-state\fR,

781

\fB\-U\fR

782

.sp

783

Store information in the

784

\&.MYI

785

file to indicate when the table was checked and whether the table crashed\&. This should be used to get full benefit of the

786

\fB\-\-check\-only\-changed\fR

787

option, but you shouldn\*(Aqt use this option if the

788

\fBmysqld\fR

789

server is using the table and you are running it with external locking disabled\&.

790

.RE

791

.SH "MYISAMCHK REPAIR OPTIONS"

792

.\" repair options: myisamchk

793

.\" files: repairing

794

.PP

795

\fBmyisamchk\fR

796

supports the following options for table repair operations (operations performed when an option such as

797

\fB\-\-recover\fR

798

799

\fB\-\-safe\-recover\fR

800

is given):

801

.sp

802

.RS 4

803

.ie n \{\

804

\h'-04'\(bu\h'+03'\c

805

.\}

806

.el \{\

807

.sp -1

808

.IP \(bu 2.3

809

.\}

810

.\" myisamchk: backup option.\" backup option: myisamchk\fB\-\-backup\fR,

811

\fB\-B\fR

812

.sp

813

Make a backup of the

814

\&.MYD

815

file as

816

\fIfile_name\fR\-\fItime\fR\&.BAK

817

.RE

818

.sp

819

.RS 4

820

.ie n \{\

821

\h'-04'\(bu\h'+03'\c

822

.\}

823

.el \{\

824

.sp -1

825

.IP \(bu 2.3

826

.\}

827

.\" myisamchk: character-sets-dir option.\" character-sets-dir option: myisamchk\fB\-\-character\-sets\-dir=\fR\fB\fIpath\fR\fR

828

.sp

829

The directory where character sets are installed\&. See

830

Section\ \&10.5, \(lqCharacter Set Configuration\(rq\&.

831

.RE

832

.sp

833

.RS 4

834

.ie n \{\

835

\h'-04'\(bu\h'+03'\c

836

.\}

837

.el \{\

838

.sp -1

839

.IP \(bu 2.3

840

.\}

841

.\" myisamchk: correct-checksum option.\" correct-checksum option: myisamchk\fB\-\-correct\-checksum\fR

842

.sp

843

Correct the checksum information for the table\&.

844

.RE

845

.sp

846

.RS 4

847

.ie n \{\

848

\h'-04'\(bu\h'+03'\c

849

.\}

850

.el \{\

851

.sp -1

852

.IP \(bu 2.3

853

.\}

854

.\" myisamchk: data-file-length option.\" data-file-length option: myisamchk\fB\-\-data\-file\-length=\fR\fB\fIlen\fR\fR,

855

\fB\-D \fR\fB\fIlen\fR\fR

856

.sp

857

The maximum length of the data file (when re\-creating data file when it is

858

\(lqfull\(rq)\&.

859

.RE

860

.sp

861

.RS 4

862

.ie n \{\

863

\h'-04'\(bu\h'+03'\c

864

.\}

865

.el \{\

866

.sp -1

867

.IP \(bu 2.3

868

.\}

869

.\" myisamchk: extend-check option.\" extend-check option: myisamchk\fB\-\-extend\-check\fR,

870

\fB\-e\fR

871

.sp

872

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\&.

873

.sp

874

See also the description of this option under table checking options\&.

875

.sp

876

For a description of the output format, see

877

the section called \(lqOBTAINING TABLE INFORMATION WITH MYISAMCHK\(rq\&.

878

.RE

879

.sp

880

.RS 4

881

.ie n \{\

882

\h'-04'\(bu\h'+03'\c

883

.\}

884

.el \{\

885

.sp -1

886

.IP \(bu 2.3

887

.\}

888

.\" myisamchk: force option.\" force option: myisamchk\fB\-\-force\fR,

889

\fB\-f\fR

890

.sp

891

Overwrite old intermediate files (files with names like

892

\fItbl_name\fR\&.TMD) instead of aborting\&.

893

.RE

894

.sp

895

.RS 4

896

.ie n \{\

897

\h'-04'\(bu\h'+03'\c

898

.\}

899

.el \{\

900

.sp -1

901

.IP \(bu 2.3

902

.\}

903

.\" myisamchk: keys-used option.\" keys-used option: myisamchk\fB\-\-keys\-used=\fR\fB\fIval\fR\fR,

904

\fB\-k \fR\fB\fIval\fR\fR

905

.sp

906

For

907

\fBmyisamchk\fR, 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\&. 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

908

\fBmyisamchk \-r\fR\&.

909

.RE

910

.sp

911

.RS 4

912

.ie n \{\

913

\h'-04'\(bu\h'+03'\c

914

.\}

915

.el \{\

916

.sp -1

917

.IP \(bu 2.3

918

.\}

919

.\" myisamchk: no-symlinks option.\" no-symlinks option: myisamchk\fB\-\-no\-symlinks\fR,

920

\fB\-l\fR

921

.sp

922

Do not follow symbolic links\&. Normally

923

\fBmyisamchk\fR

924

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\&.

925

.RE

926

.sp

927

.RS 4

928

.ie n \{\

929

\h'-04'\(bu\h'+03'\c

930

.\}

931

.el \{\

932

.sp -1

933

.IP \(bu 2.3

934

.\}

935

.\" myisamchk: max-record-length option.\" max-record-length option: myisamchk\fB\-\-max\-record\-length=\fR\fB\fIlen\fR\fR

936

.sp

937

Skip rows larger than the given length if

938

\fBmyisamchk\fR

939

cannot allocate memory to hold them\&.

940

.RE

941

.sp

942

.RS 4

943

.ie n \{\

944

\h'-04'\(bu\h'+03'\c

945

.\}

946

.el \{\

947

.sp -1

948

.IP \(bu 2.3

949

.\}

950

.\" myisamchk: parallel-recover option.\" parallel-recover option: myisamchk\fB\-\-parallel\-recover\fR,

951

\fB\-p\fR

952

.sp

953

Use the same technique as

954

\fB\-r\fR

955

and

956

\fB\-n\fR, but create all the keys in parallel, using different threads\&.

957

\fIThis is beta\-quality code\&. Use at your own risk!\fR

958

.RE

959

.sp

960

.RS 4

961

.ie n \{\

962

\h'-04'\(bu\h'+03'\c

963

.\}

964

.el \{\

965

.sp -1

966

.IP \(bu 2.3

967

.\}

968

.\" myisamchk: quick option.\" quick option: myisamchk\fB\-\-quick\fR,

969

\fB\-q\fR

970

.sp

971

Achieve a faster repair by modifying only the index file, not the data file\&. You can specify this option twice to force

972

\fBmyisamchk\fR

973

to modify the original data file in case of duplicate keys\&.

974

.RE

975

.sp

976

.RS 4

977

.ie n \{\

978

\h'-04'\(bu\h'+03'\c

979

.\}

980

.el \{\

981

.sp -1

982

.IP \(bu 2.3

983

.\}

984

.\" myisamchk: recover option.\" recover option: myisamchk\fB\-\-recover\fR,

985

\fB\-r\fR

986

.sp

987

Do a repair that can fix almost any problem except unique keys that are not unique (which is an extremely unlikely error with

988

MyISAM

989

tables)\&. If you want to recover a table, this is the option to try first\&. You should try

990

\fB\-\-safe\-recover\fR

991

only if

992

\fBmyisamchk\fR

993

reports that the table cannot be recovered using

994

\fB\-\-recover\fR\&. (In the unlikely case that

995

\fB\-\-recover\fR

996

fails, the data file remains intact\&.)

997

.sp

998

If you have lots of memory, you should increase the value of

999

myisam_sort_buffer_size\&.

1000

.RE

1001

.sp

1002

.RS 4

1003

.ie n \{\

1004

\h'-04'\(bu\h'+03'\c

1005

.\}

1006

.el \{\

1007

.sp -1

1008

.IP \(bu 2.3

1009

.\}

1010

.\" myisamchk: safe-recover option.\" safe-recover option: myisamchk\fB\-\-safe\-recover\fR,

1011

\fB\-o\fR

1012

.sp

1013

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

1014

\fB\-\-recover\fR, but can handle a couple of very unlikely cases that

1015

\fB\-\-recover\fR

1016

cannot\&. This recovery method also uses much less disk space than

1017

\fB\-\-recover\fR\&. Normally, you should repair first using

1018

\fB\-\-recover\fR, and then with

1019

\fB\-\-safe\-recover\fR

1020

only if

1021

\fB\-\-recover\fR

1022

fails\&.

1023

.sp

1024

If you have lots of memory, you should increase the value of

1025

key_buffer_size\&.

1026

.RE

1027

.sp

1028

.RS 4

1029

.ie n \{\

1030

\h'-04'\(bu\h'+03'\c

1031

.\}

1032

.el \{\

1033

.sp -1

1034

.IP \(bu 2.3

1035

.\}

1036

.\" myisamchk: set-character-set option.\" set-character-set option: myisamchk\fB\-\-set\-character\-set=\fR\fB\fIname\fR\fR

1037

.sp

1038

Change the character set used by the table indexes\&. This option was replaced by

1039

\fB\-\-set\-collation\fR

1040

in MySQL 5\&.0\&.3\&.

1041

.RE

1042

.sp

1043

.RS 4

1044

.ie n \{\

1045

\h'-04'\(bu\h'+03'\c

1046

.\}

1047

.el \{\

1048

.sp -1

1049

.IP \(bu 2.3

1050

.\}

1051

.\" myisamchk: set-collation option.\" set-collation option: myisamchk\fB\-\-set\-collation=\fR\fB\fIname\fR\fR

1052

.sp

1053

Specify the collation to use for sorting table indexes\&. The character set name is implied by the first part of the collation name\&.

1054

.RE

1055

.sp

1056

.RS 4

1057

.ie n \{\

1058

\h'-04'\(bu\h'+03'\c

1059

.\}

1060

.el \{\

1061

.sp -1

1062

.IP \(bu 2.3

1063

.\}

1064

.\" myisamchk: sort-recover option.\" sort-recover option: myisamchk\fB\-\-sort\-recover\fR,

1065

\fB\-n\fR

1066

.sp

1067

Force

1068

\fBmyisamchk\fR

1069

to use sorting to resolve the keys even if the temporary files would be very large\&.

1070

.RE

1071

.sp

1072

.RS 4

1073

.ie n \{\

1074

\h'-04'\(bu\h'+03'\c

1075

.\}

1076

.el \{\

1077

.sp -1

1078

.IP \(bu 2.3

1079

.\}

1080

.\" myisamchk: tmpdir option.\" tmpdir option: myisamchk\fB\-\-tmpdir=\fR\fB\fIpath\fR\fR,

1081

\fB\-t \fR\fB\fIpath\fR\fR

1082

.sp

1083

The path of the directory to be used for storing temporary files\&. If this is not set,

1084

\fBmyisamchk\fR

1085

uses the value of the

1086

TMPDIR

1087

environment variable\&.

1088

\fB\-\-tmpdir\fR

1089

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 is the colon (\(lq:\(rq) on Unix and the semicolon (\(lq;\(rq) on Windows\&.

1090

.RE

1091

.sp

1092

.RS 4

1093

.ie n \{\

1094

\h'-04'\(bu\h'+03'\c

1095

.\}

1096

.el \{\

1097

.sp -1

1098

.IP \(bu 2.3

1099

.\}

1100

.\" myisamchk: unpack option.\" unpack option: myisamchk\fB\-\-unpack\fR,

1101

\fB\-u\fR

1102

.sp

1103

Unpack a table that was packed with

1104

\fBmyisampack\fR\&.

1105

.RE

1106

.SH "OTHER MYISAMCHK OPTIONS"

1107

.PP

1108

\fBmyisamchk\fR

1109

supports the following options for actions other than table checks and repairs:

1110

.sp

1111

.RS 4

1112

.ie n \{\

1113

\h'-04'\(bu\h'+03'\c

1114

.\}

1115

.el \{\

1116

.sp -1

1117

.IP \(bu 2.3

1118

.\}

1119

.\" myisamchk: analyze option.\" analyze option: myisamchk\fB\-\-analyze\fR,

1120

\fB\-a\fR

1121

.sp

1122

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

1123

\fBmyisamchk \-\-description \-\-verbose \fR\fB\fItbl_name\fR\fR

1124

command or the

1125

SHOW INDEX FROM \fItbl_name\fR

1126

statement\&.

1127

.RE

1128

.sp

1129

.RS 4

1130

.ie n \{\

1131

\h'-04'\(bu\h'+03'\c

1132

.\}

1133

.el \{\

1134

.sp -1

1135

.IP \(bu 2.3

1136

.\}

1137

.\" myisamchk: block-search option.\" block-search option: myisamchk\fB\-\-block\-search=\fR\fB\fIoffset\fR\fR,

1138

\fB\-b \fR\fB\fIoffset\fR\fR

1139

.sp

1140

Find the record that a block at the given offset belongs to\&.

1141

.RE

1142

.sp

1143

.RS 4

1144

.ie n \{\

1145

\h'-04'\(bu\h'+03'\c

1146

.\}

1147

.el \{\

1148

.sp -1

1149

.IP \(bu 2.3

1150

.\}

1151

.\" myisamchk: description option.\" description option: myisamchk\fB\-\-description\fR,

1152

\fB\-d\fR

1153

.sp

1154

Print some descriptive information about the table\&. Specifying the

1155

\fB\-\-verbose\fR

1156

option once or twice produces additional information\&. See

1157

the section called \(lqOBTAINING TABLE INFORMATION WITH MYISAMCHK\(rq\&.

1158

.RE

1159

.sp

1160

.RS 4

1161

.ie n \{\

1162

\h'-04'\(bu\h'+03'\c

1163

.\}

1164

.el \{\

1165

.sp -1

1166

.IP \(bu 2.3

1167

.\}

1168

.\" myisamchk: set-auto-increment[ option.\" set-auto-increment[ option: myisamchk\fB\-\-set\-auto\-increment[=\fR\fB\fIvalue\fR\fR\fB]\fR,

1169

\fB\-A[\fR\fB\fIvalue\fR\fR\fB]\fR

1170

.sp

1171

Force

1172

AUTO_INCREMENT

1173

numbering for new records to start at the given value (or higher, if there are existing records with

1174

AUTO_INCREMENT

1175

values this large)\&. If

1176

\fIvalue\fR

1177

is not specified,

1178

AUTO_INCREMENT

1179

numbers for new records begin with the largest value currently in the table, plus one\&.

1180

.RE

1181

.sp

1182

.RS 4

1183

.ie n \{\

1184

\h'-04'\(bu\h'+03'\c

1185

.\}

1186

.el \{\

1187

.sp -1

1188

.IP \(bu 2.3

1189

.\}

1190

.\" myisamchk: sort-index option.\" sort-index option: myisamchk\fB\-\-sort\-index\fR,

1191

\fB\-S\fR

1192

.sp

1193

Sort the index tree blocks in high\-low order\&. This optimizes seeks and makes table scans that use indexes faster\&.

1194

.RE

1195

.sp

1196

.RS 4

1197

.ie n \{\

1198

\h'-04'\(bu\h'+03'\c

1199

.\}

1200

.el \{\

1201

.sp -1

1202

.IP \(bu 2.3

1203

.\}

1204

.\" myisamchk: sort-records option.\" sort-records option: myisamchk\fB\-\-sort\-records=\fR\fB\fIN\fR\fR,

1205

\fB\-R \fR\fB\fIN\fR\fR

1206

.sp

1207

Sort records according to a particular index\&. This makes your data much more localized and may speed up range\-based

1208

SELECT

1209

and

1210

ORDER BY

1211

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\*(Aqs index numbers, use

1212

SHOW INDEX, which displays a table\*(Aqs indexes in the same order that

1213

\fBmyisamchk\fR

1214

sees them\&. Indexes are numbered beginning with 1\&.

1215

.sp

1216

If keys are not packed (PACK_KEYS=0), they have the same length, so when

1217

\fBmyisamchk\fR

1218

sorts and moves records, it just overwrites record offsets in the index\&. If keys are packed (PACK_KEYS=1),

1219

\fBmyisamchk\fR

1220

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\&.)

1221

.RE

1222

.SH "OBTAINING TABLE INFORMATION WITH MYISAMCHK"

1223

.\" table description: myisamchk

1224

.\" tables: information

1225

.\" examples: myisamchk output

1226

.\" myisamchk: example output

1227

.PP

1228

To obtain a description of a

1229

MyISAM

1230

table or statistics about it, use the commands shown here\&. The output from these commands is explained later in this section\&.

1231

.sp

1232

.RS 4

1233

.ie n \{\

1234

\h'-04'\(bu\h'+03'\c

1235

.\}

1236

.el \{\

1237

.sp -1

1238

.IP \(bu 2.3

1239

.\}

1240

\fBmyisamchk \-d \fR\fB\fItbl_name\fR\fR

1241

.sp

1242

Runs

1243

\fBmyisamchk\fR

1244

1245

\(lqdescribe mode\(rq

1246

to produce a description of your table\&. If you start the MySQL server with external locking disabled,

1247

\fBmyisamchk\fR

1248

may report an error for a table that is updated while it runs\&. However, because

1249

\fBmyisamchk\fR

1250

does not change the table in describe mode, there is no risk of destroying data\&.

1251

.RE

1252

.sp

1253

.RS 4

1254

.ie n \{\

1255

\h'-04'\(bu\h'+03'\c

1256

.\}

1257

.el \{\

1258

.sp -1

1259

.IP \(bu 2.3

1260

.\}

1261

\fBmyisamchk \-dv \fR\fB\fItbl_name\fR\fR

1262

.sp

1263

Adding

1264

\fB\-v\fR

1265

runs

1266

\fBmyisamchk\fR

1267

in verbose mode so that it produces more information about the table\&. Adding

1268

\fB\-v\fR

1269

a second time produces even more information\&.

1270

.RE

1271

.sp

1272

.RS 4

1273

.ie n \{\

1274

\h'-04'\(bu\h'+03'\c

1275

.\}

1276

.el \{\

1277

.sp -1

1278

.IP \(bu 2.3

1279

.\}

1280

\fBmyisamchk \-eis \fR\fB\fItbl_name\fR\fR

1281

.sp

1282

Shows only the most important information from a table\&. This operation is slow because it must read the entire table\&.

1283

.RE

1284

.sp

1285

.RS 4

1286

.ie n \{\

1287

\h'-04'\(bu\h'+03'\c

1288

.\}

1289

.el \{\

1290

.sp -1

1291

.IP \(bu 2.3

1292

.\}

1293

\fBmyisamchk \-eiv \fR\fB\fItbl_name\fR\fR

1294

.sp

1295

This is like

1296

\fB\-eis\fR, but tells you what is being done\&.

1297

.RE

1298

.PP

1299

The

1300

\fItbl_name\fR

1301

argument can be either the name of a

1302

MyISAM

1303

table or the name of its index file, as described in

1304

\fBmyisamchk\fR(1)\&. Multiple

1305

\fItbl_name\fR

1306

arguments can be given\&.

1307

.PP

1308

Suppose that a table named

1309

person

1310

has the following structure\&. (The

1311

MAX_ROWS

1312

table option is included so that in the example output from

1313

\fBmyisamchk\fR

1314

shown later, some values are smaller and fit the output format more easily\&.)

1315

.sp

1316

.if n \{\

1317

.RS 4

1318

.\}

1319

.nf

1320

CREATE TABLE person

1321

(

1322

id INT NOT NULL AUTO_INCREMENT,

1323

last_name VARCHAR(20) NOT NULL,

1324

first_name VARCHAR(20) NOT NULL,

1325

birth DATE,

1326

death DATE,

1327

PRIMARY KEY (id),

1328

INDEX (last_name, first_name),

1329

INDEX (birth)

1330

) MAX_ROWS = 1000000;

1331

.fi

1332

.if n \{\

1333

.RE

1334

.\}

1335

.PP

1336

Suppose also that the table has these data and index file sizes:

1337

.sp

1338

.if n \{\

1339

.RS 4

1340

.\}

1341

.nf

1342

\-rw\-rw\-\-\-\- 1 mysql mysql 9347072 Aug 19 11:47 person\&.MYD

1343

\-rw\-rw\-\-\-\- 1 mysql mysql 6066176 Aug 19 11:47 person\&.MYI

1344

.fi

1345

.if n \{\

1346

.RE

1347

.\}

1348

.PP

1349

Example of

1350

\fBmyisamchk \-dvv\fR

1351

output:

1352

.sp

1353

.if n \{\

1354

.RS 4

1355

.\}

1356

.nf

1357

MyISAM file: person

1358

Record format: Packed

1359

Character set: latin1_swedish_ci (8)

1360

File\-version: 1

1361

Creation time: 2009\-08\-19 16:47:41

1362

Recover time: 2009\-08\-19 16:47:56

1363

Status: checked,analyzed,optimized keys

1364

Auto increment key: 1 Last value: 306688

1365

Data records: 306688 Deleted blocks: 0

1366

Datafile parts: 306688 Deleted data: 0

1367

Datafile pointer (bytes): 4 Keyfile pointer (bytes): 3

1368

Datafile length: 9347072 Keyfile length: 6066176

1369

Max datafile length: 4294967294 Max keyfile length: 17179868159

1370

Recordlength: 54

1371

table description:

1372

Key Start Len Index Type Rec/key Root Blocksize

1373

1 2 4 unique long 1 99328 1024

1374

2 6 20 multip\&. varchar prefix 512 3563520 1024

1375

27 20 varchar 512

1376

3 48 3 multip\&. uint24 NULL 306688 6065152 1024

1377

Field Start Length Nullpos Nullbit Type

1378

1 1 1

1379

2 2 4 no zeros

1380

3 6 21 varchar

1381

4 27 21 varchar

1382

5 48 3 1 1 no zeros

1383

6 51 3 1 2 no zeros

1384

.fi

1385

.if n \{\

1386

.RE

1387

.\}

1388

.PP

1389

Explanations for the types of information

1390

\fBmyisamchk\fR

1391

produces are given here\&.

1392

\(lqKeyfile\(rq

1393

refers to the index file\&.

1394

\(lqRecord\(rq

1395

and

1396

\(lqrow\(rq

1397

are synonymous, as are

1398

\(lqfield\(rq

1399

and

1400

\(lqcolumn\&.\(rq

1401

.PP

1402

The initial part of the table description contains these values:

1403

.sp

1404

.RS 4

1405

.ie n \{\

1406

\h'-04'\(bu\h'+03'\c

1407

.\}

1408

.el \{\

1409

.sp -1

1410

.IP \(bu 2.3

1411

.\}

1412

MyISAM file

1413

.sp

1414

Name of the

1415

MyISAM

1416

(index) file\&.

1417

.RE

1418

.sp

1419

.RS 4

1420

.ie n \{\

1421

\h'-04'\(bu\h'+03'\c

1422

.\}

1423

.el \{\

1424

.sp -1

1425

.IP \(bu 2.3

1426

.\}

1427

Record format

1428

.sp

1429

The format used to store table rows\&. The preceding examples use

1430

Fixed length\&. Other possible values are

1431

Compressed

1432

and

1433

Packed\&. (Packed

1434

corresponds to what

1435

SHOW TABLE STATUS

1436

reports as

1437

Dynamic\&.)

1438

.RE

1439

.sp

1440

.RS 4

1441

.ie n \{\

1442

\h'-04'\(bu\h'+03'\c

1443

.\}

1444

.el \{\

1445

.sp -1

1446

.IP \(bu 2.3

1447

.\}

1448

Chararacter set

1449

.sp

1450

The table default character set\&.

1451

.RE

1452

.sp

1453

.RS 4

1454

.ie n \{\

1455

\h'-04'\(bu\h'+03'\c

1456

.\}

1457

.el \{\

1458

.sp -1

1459

.IP \(bu 2.3

1460

.\}

1461

File\-version

1462

.sp

1463

Version of

1464

MyISAM

1465

format\&. Currently always 1\&.

1466

.RE

1467

.sp

1468

.RS 4

1469

.ie n \{\

1470

\h'-04'\(bu\h'+03'\c

1471

.\}

1472

.el \{\

1473

.sp -1

1474

.IP \(bu 2.3

1475

.\}

1476

Creation time

1477

.sp

1478

When the data file was created\&.

1479

.RE

1480

.sp

1481

.RS 4

1482

.ie n \{\

1483

\h'-04'\(bu\h'+03'\c

1484

.\}

1485

.el \{\

1486

.sp -1

1487

.IP \(bu 2.3

1488

.\}

1489

Recover time

1490

.sp

1491

When the index/data file was last reconstructed\&.

1492

.RE

1493

.sp

1494

.RS 4

1495

.ie n \{\

1496

\h'-04'\(bu\h'+03'\c

1497

.\}

1498

.el \{\

1499

.sp -1

1500

.IP \(bu 2.3

1501

.\}

1502

Status

1503

.sp

1504

Table status flags\&. Possible values are

1505

crashed,

1506

open,

1507

changed,

1508

analyzed,

1509

optimized keys, and

1510

sorted index pages\&.

1511

.RE

1512

.sp

1513

.RS 4

1514

.ie n \{\

1515

\h'-04'\(bu\h'+03'\c

1516

.\}

1517

.el \{\

1518

.sp -1

1519

.IP \(bu 2.3

1520

.\}

1521

Auto increment key,

1522

Last value

1523

.sp

1524

The key number associated the table\*(Aqs

1525

AUTO_INCREMENT

1526

column, and the most recently generated value for this column\&. These fields do not appear if there is no such column\&.

1527

.RE

1528

.sp

1529

.RS 4

1530

.ie n \{\

1531

\h'-04'\(bu\h'+03'\c

1532

.\}

1533

.el \{\

1534

.sp -1

1535

.IP \(bu 2.3

1536

.\}

1537

Data records

1538

.sp

1539

The number of rows in the table\&.

1540

.RE

1541

.sp

1542

.RS 4

1543

.ie n \{\

1544

\h'-04'\(bu\h'+03'\c

1545

.\}

1546

.el \{\

1547

.sp -1

1548

.IP \(bu 2.3

1549

.\}

1550

Deleted blocks

1551

.sp

1552

How many deleted blocks still have reserved space\&. You can optimize your table to minimize this space\&. See

1553

Section\ \&7.6.4, \(lqMyISAM Table Optimization\(rq\&.

1554

.RE

1555

.sp

1556

.RS 4

1557

.ie n \{\

1558

\h'-04'\(bu\h'+03'\c

1559

.\}

1560

.el \{\

1561

.sp -1

1562

.IP \(bu 2.3

1563

.\}

1564

Datafile parts

1565

.sp

1566

For dynamic\-row format, this indicates how many data blocks there are\&. For an optimized table without fragmented rows, this is the same as

1567

Data records\&.

1568

.RE

1569

.sp

1570

.RS 4

1571

.ie n \{\

1572

\h'-04'\(bu\h'+03'\c

1573

.\}

1574

.el \{\

1575

.sp -1

1576

.IP \(bu 2.3

1577

.\}

1578

Deleted data

1579

.sp

1580

How many bytes of unreclaimed deleted data there are\&. You can optimize your table to minimize this space\&. See

1581

Section\ \&7.6.4, \(lqMyISAM Table Optimization\(rq\&.

1582

.RE

1583

.sp

1584

.RS 4

1585

.ie n \{\

1586

\h'-04'\(bu\h'+03'\c

1587

.\}

1588

.el \{\

1589

.sp -1

1590

.IP \(bu 2.3

1591

.\}

1592

Datafile pointer

1593

.sp

1594

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\&.

1595

.RE

1596

.sp

1597

.RS 4

1598

.ie n \{\

1599

\h'-04'\(bu\h'+03'\c

1600

.\}

1601

.el \{\

1602

.sp -1

1603

.IP \(bu 2.3

1604

.\}

1605

Keyfile pointer

1606

.sp

1607

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\&.

1608

.RE

1609

.sp

1610

.RS 4

1611

.ie n \{\

1612

\h'-04'\(bu\h'+03'\c

1613

.\}

1614

.el \{\

1615

.sp -1

1616

.IP \(bu 2.3

1617

.\}

1618

Max datafile length

1619

.sp

1620

How long the table data file can become, in bytes\&.

1621

.RE

1622

.sp

1623

.RS 4

1624

.ie n \{\

1625

\h'-04'\(bu\h'+03'\c

1626

.\}

1627

.el \{\

1628

.sp -1

1629

.IP \(bu 2.3

1630

.\}

1631

Max keyfile length

1632

.sp

1633

How long the table index file can become, in bytes\&.

1634

.RE

1635

.sp

1636

.RS 4

1637

.ie n \{\

1638

\h'-04'\(bu\h'+03'\c

1639

.\}

1640

.el \{\

1641

.sp -1

1642

.IP \(bu 2.3

1643

.\}

1644

Recordlength

1645

.sp

1646

How much space each row takes, in bytes\&.

1647

.RE

1648

.PP

1649

The

1650

table description

1651

part of the output includes a list of all keys in the table\&. For each key,

1652

\fBmyisamchk\fR

1653

displays some low\-level information:

1654

.sp

1655

.RS 4

1656

.ie n \{\

1657

\h'-04'\(bu\h'+03'\c

1658

.\}

1659

.el \{\

1660

.sp -1

1661

.IP \(bu 2.3

1662

.\}

1663

Key

1664

.sp

1665

This key\*(Aqs 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

1666

table description

1667

lines for the second index\&. This indicates that it is a multiple\-part index with two parts\&.

1668

.RE

1669

.sp

1670

.RS 4

1671

.ie n \{\

1672

\h'-04'\(bu\h'+03'\c

1673

.\}

1674

.el \{\

1675

.sp -1

1676

.IP \(bu 2.3

1677

.\}

1678

Start

1679

.sp

1680

Where in the row this portion of the index starts\&.

1681

.RE

1682

.sp

1683

.RS 4

1684

.ie n \{\

1685

\h'-04'\(bu\h'+03'\c

1686

.\}

1687

.el \{\

1688

.sp -1

1689

.IP \(bu 2.3

1690

.\}

1691

Len

1692

.sp

1693

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

1694

Len

1695

values for all key parts\&.

1696

.RE

1697

.sp

1698

.RS 4

1699

.ie n \{\

1700

\h'-04'\(bu\h'+03'\c

1701

.\}

1702

.el \{\

1703

.sp -1

1704

.IP \(bu 2.3

1705

.\}

1706

Index

1707

.sp

1708

Whether a key value can exist multiple times in the index\&. Possible values are

1709

unique

1710

1711

multip\&.

1712

(multiple)\&.

1713

.RE

1714

.sp

1715

.RS 4

1716

.ie n \{\

1717

\h'-04'\(bu\h'+03'\c

1718

.\}

1719

.el \{\

1720

.sp -1

1721

.IP \(bu 2.3

1722

.\}

1723

Type

1724

.sp

1725

What data type this portion of the index has\&. This is a

1726

MyISAM

1727

data type with the possible values

1728

packed,

1729

stripped, or

1730

empty\&.

1731

.RE

1732

.sp

1733

.RS 4

1734

.ie n \{\

1735

\h'-04'\(bu\h'+03'\c

1736

.\}

1737

.el \{\

1738

.sp -1

1739

.IP \(bu 2.3

1740

.\}

1741

Root

1742

.sp

1743

Address of the root index block\&.

1744

.RE

1745

.sp

1746

.RS 4

1747

.ie n \{\

1748

\h'-04'\(bu\h'+03'\c

1749

.\}

1750

.el \{\

1751

.sp -1

1752

.IP \(bu 2.3

1753

.\}

1754

Blocksize

1755

.sp

1756

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\&.

1757

.RE

1758

.sp

1759

.RS 4

1760

.ie n \{\

1761

\h'-04'\(bu\h'+03'\c

1762

.\}

1763

.el \{\

1764

.sp -1

1765

.IP \(bu 2.3

1766

.\}

1767

Rec/key

1768

.sp

1769

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

1770

\fBmyisamchk \-a\fR\&. If this is not updated at all, a default value of 30 is given\&.

1771

.RE

1772

.PP

1773

The last part of the output provides information about each column:

1774

.sp

1775

.RS 4

1776

.ie n \{\

1777

\h'-04'\(bu\h'+03'\c

1778

.\}

1779

.el \{\

1780

.sp -1

1781

.IP \(bu 2.3

1782

.\}

1783

Field

1784

.sp

1785

The column number\&.

1786

.RE

1787

.sp

1788

.RS 4

1789

.ie n \{\

1790

\h'-04'\(bu\h'+03'\c

1791

.\}

1792

.el \{\

1793

.sp -1

1794

.IP \(bu 2.3

1795

.\}

1796

Start

1797

.sp

1798

The byte position of the column within table rows\&.

1799

.RE

1800

.sp

1801

.RS 4

1802

.ie n \{\

1803

\h'-04'\(bu\h'+03'\c

1804

.\}

1805

.el \{\

1806

.sp -1

1807

.IP \(bu 2.3

1808

.\}

1809

Length

1810

.sp

1811

The length of the column in bytes\&.

1812

.RE

1813

.sp

1814

.RS 4

1815

.ie n \{\

1816

\h'-04'\(bu\h'+03'\c

1817

.\}

1818

.el \{\

1819

.sp -1

1820

.IP \(bu 2.3

1821

.\}

1822

Nullpos,

1823

Nullbit

1824

.sp

1825

For columns that can be

1826

NULL,

1827

MyISAM

1828

stores

1829

NULL

1830

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

1831

Nullpos

1832

and

1833

Nullbit

1834

values, if nonempty, indicate which byte and bit contains that flag indicating whether the column is

1835

NULL\&.

1836

.sp

1837

The position and number of bytes used to store

1838

NULL

1839

flags is shown in the line for field 1\&. This is why there are six

1840

Field

1841

lines for the

1842

person

1843

table even though it has only five columns\&.

1844

.RE

1845

.sp

1846

.RS 4

1847

.ie n \{\

1848

\h'-04'\(bu\h'+03'\c

1849

.\}

1850

.el \{\

1851

.sp -1

1852

.IP \(bu 2.3

1853

.\}

1854

Type

1855

.sp

1856

The data type\&. The value may contain any of the following descriptors:

1857

.sp

1858

.RS 4

1859

.ie n \{\

1860

\h'-04'\(bu\h'+03'\c

1861

.\}

1862

.el \{\

1863

.sp -1

1864

.IP \(bu 2.3

1865

.\}

1866

constant

1867

.sp

1868

All rows have the same value\&.

1869

.RE

1870

.sp

1871

.RS 4

1872

.ie n \{\

1873

\h'-04'\(bu\h'+03'\c

1874

.\}

1875

.el \{\

1876

.sp -1

1877

.IP \(bu 2.3

1878

.\}

1879

no endspace

1880

.sp

1881

Do not store endspace\&.

1882

.RE

1883

.sp

1884

.RS 4

1885

.ie n \{\

1886

\h'-04'\(bu\h'+03'\c

1887

.\}

1888

.el \{\

1889

.sp -1

1890

.IP \(bu 2.3

1891

.\}

1892

no endspace, not_always

1893

.sp

1894

Do not store endspace and do not do endspace compression for all values\&.

1895

.RE

1896

.sp

1897

.RS 4

1898

.ie n \{\

1899

\h'-04'\(bu\h'+03'\c

1900

.\}

1901

.el \{\

1902

.sp -1

1903

.IP \(bu 2.3

1904

.\}

1905

no endspace, no empty

1906

.sp

1907

Do not store endspace\&. Do not store empty values\&.

1908

.RE

1909

.sp

1910

.RS 4

1911

.ie n \{\

1912

\h'-04'\(bu\h'+03'\c

1913

.\}

1914

.el \{\

1915

.sp -1

1916

.IP \(bu 2.3

1917

.\}

1918

table\-lookup

1919

.sp

1920

The column was converted to an

1921

ENUM\&.

1922

.RE

1923

.sp

1924

.RS 4

1925

.ie n \{\

1926

\h'-04'\(bu\h'+03'\c

1927

.\}

1928

.el \{\

1929

.sp -1

1930

.IP \(bu 2.3

1931

.\}

1932

zerofill(\fIN\fR)

1933

.sp

1934

The most significant

1935

\fIN\fR

1936

bytes in the value are always 0 and are not stored\&.

1937

.RE

1938

.sp

1939

.RS 4

1940

.ie n \{\

1941

\h'-04'\(bu\h'+03'\c

1942

.\}

1943

.el \{\

1944

.sp -1

1945

.IP \(bu 2.3

1946

.\}

1947

no zeros

1948

.sp

1949

Do not store zeros\&.

1950

.RE

1951

.sp

1952

.RS 4

1953

.ie n \{\

1954

\h'-04'\(bu\h'+03'\c

1955

.\}

1956

.el \{\

1957

.sp -1

1958

.IP \(bu 2.3

1959

.\}

1960

always zero

1961

.sp

1962

Zero values are stored using one bit\&.

1963

.RE

1964

.RE

1965

.sp

1966

.RS 4

1967

.ie n \{\

1968

\h'-04'\(bu\h'+03'\c

1969

.\}

1970

.el \{\

1971

.sp -1

1972

.IP \(bu 2.3

1973

.\}

1974

Huff tree

1975

.sp

1976

The number of the Huffman tree associated with the column\&.

1977

.RE

1978

.sp

1979

.RS 4

1980

.ie n \{\

1981

\h'-04'\(bu\h'+03'\c

1982

.\}

1983

.el \{\

1984

.sp -1

1985

.IP \(bu 2.3

1986

.\}

1987

Bits

1988

.sp

1989

The number of bits used in the Huffman tree\&.

1990

.RE

1991

.PP

1992

The

1993

Huff tree

1994

and

1995

Bits

1996

fields are displayed if the table has been compressed with

1997

\fBmyisampack\fR\&. See

1998

\fBmyisampack\fR(1), for an example of this information\&.

1999

.PP

2000

Example of

2001

\fBmyisamchk \-eiv\fR

2002

output:

2003

.sp

2004

.if n \{\

2005

.RS 4

2006

.\}

2007

.nf

2008

Checking MyISAM file: person

2009

Data records: 306688 Deleted blocks: 0

2010

\- check file\-size

2011

\- check record delete\-chain

2012

No recordlinks

2013

\- check key delete\-chain

2014

block_size 1024:

2015

\- check index reference

2016

\- check data record references index: 1

2017

Key: 1: Keyblocks used: 98% Packed: 0% Max levels: 3

2018

\- check data record references index: 2

2019

Key: 2: Keyblocks used: 99% Packed: 97% Max levels: 3

2020

\- check data record references index: 3

2021

Key: 3: Keyblocks used: 98% Packed: \-14% Max levels: 3

2022

Total: Keyblocks used: 98% Packed: 89%

2023

\- check records and index references

2024

\fI*** LOTS OF ROW NUMBERS DELETED ***\fR

2025

Records: 306688 M\&.recordlength: 25 Packed: 83%

2026

Recordspace used: 97% Empty space: 2% Blocks/Record: 1\&.00

2027

Record blocks: 306688 Delete blocks: 0

2028

Record data: 7934464 Deleted data: 0

2029

Lost space: 256512 Linkdata: 1156096

2030

User time 43\&.08, System time 1\&.68

2031

Maximum resident set size 0, Integral resident set size 0

2032

Non\-physical pagefaults 0, Physical pagefaults 0, Swaps 0

2033

Blocks in 0 out 7, Messages in 0 out 0, Signals 0

2034

Voluntary context switches 0, Involuntary context switches 0

2035

Maximum memory usage: 1046926 bytes (1023k)

2036

.fi

2037

.if n \{\

2038

.RE

2039

.\}

2040

.PP

2041

\fBmyisamchk \-eiv\fR

2042

output includes the following information:

2043

.sp

2044

.RS 4

2045

.ie n \{\

2046

\h'-04'\(bu\h'+03'\c

2047

.\}

2048

.el \{\

2049

.sp -1

2050

.IP \(bu 2.3

2051

.\}

2052

Data records

2053

.sp

2054

The number of rows in the table\&.

2055

.RE

2056

.sp

2057

.RS 4

2058

.ie n \{\

2059

\h'-04'\(bu\h'+03'\c

2060

.\}

2061

.el \{\

2062

.sp -1

2063

.IP \(bu 2.3

2064

.\}

2065

Deleted blocks

2066

.sp

2067

How many deleted blocks still have reserved space\&. You can optimize your table to minimize this space\&. See

2068

Section\ \&7.6.4, \(lqMyISAM Table Optimization\(rq\&.

2069

.RE

2070

.sp

2071

.RS 4

2072

.ie n \{\

2073

\h'-04'\(bu\h'+03'\c

2074

.\}

2075

.el \{\

2076

.sp -1

2077

.IP \(bu 2.3

2078

.\}

2079

Key

2080

.sp

2081

The key number\&.

2082

.RE

2083

.sp

2084

.RS 4

2085

.ie n \{\

2086

\h'-04'\(bu\h'+03'\c

2087

.\}

2088

.el \{\

2089

.sp -1

2090

.IP \(bu 2.3

2091

.\}

2092

Keyblocks used

2093

.sp

2094

What percentage of the keyblocks are used\&. When a table has just been reorganized with

2095

\fBmyisamchk\fR, the values are very high (very near theoretical maximum)\&.

2096

.RE

2097

.sp

2098

.RS 4

2099

.ie n \{\

2100

\h'-04'\(bu\h'+03'\c

2101

.\}

2102

.el \{\

2103

.sp -1

2104

.IP \(bu 2.3

2105

.\}

2106

Packed

2107

.sp

2108

MySQL tries to pack key values that have a common suffix\&. This can only be used for indexes on

2109

CHAR

2110

and

2111

VARCHAR

2112

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\&.

2113

.RE

2114

.sp

2115

.RS 4

2116

.ie n \{\

2117

\h'-04'\(bu\h'+03'\c

2118

.\}

2119

.el \{\

2120

.sp -1

2121

.IP \(bu 2.3

2122

.\}

2123

Max levels

2124

.sp

2125

How deep the B\-tree for this key is\&. Large tables with long key values get high values\&.

2126

.RE

2127

.sp

2128

.RS 4

2129

.ie n \{\

2130

\h'-04'\(bu\h'+03'\c

2131

.\}

2132

.el \{\

2133

.sp -1

2134

.IP \(bu 2.3

2135

.\}

2136

Records

2137

.sp

2138

How many rows are in the table\&.

2139

.RE

2140

.sp

2141

.RS 4

2142

.ie n \{\

2143

\h'-04'\(bu\h'+03'\c

2144

.\}

2145

.el \{\

2146

.sp -1

2147

.IP \(bu 2.3

2148

.\}

2149

M\&.recordlength

2150

.sp

2151

The average row length\&. This is the exact row length for tables with fixed\-length rows, because all rows have the same length\&.

2152

.RE

2153

.sp

2154

.RS 4

2155

.ie n \{\

2156

\h'-04'\(bu\h'+03'\c

2157

.\}

2158

.el \{\

2159

.sp -1

2160

.IP \(bu 2.3

2161

.\}

2162

Packed

2163

.sp

2164

MySQL strips spaces from the end of strings\&. The

2165

Packed

2166

value indicates the percentage of savings achieved by doing this\&.

2167

.RE

2168

.sp

2169

.RS 4

2170

.ie n \{\

2171

\h'-04'\(bu\h'+03'\c

2172

.\}

2173

.el \{\

2174

.sp -1

2175

.IP \(bu 2.3

2176

.\}

2177

Recordspace used

2178

.sp

2179

What percentage of the data file is used\&.

2180

.RE

2181

.sp

2182

.RS 4

2183

.ie n \{\

2184

\h'-04'\(bu\h'+03'\c

2185

.\}

2186

.el \{\

2187

.sp -1

2188

.IP \(bu 2.3

2189

.\}

2190

Empty space

2191

.sp

2192

What percentage of the data file is unused\&.

2193

.RE

2194

.sp

2195

.RS 4

2196

.ie n \{\

2197

\h'-04'\(bu\h'+03'\c

2198

.\}

2199

.el \{\

2200

.sp -1

2201

.IP \(bu 2.3

2202

.\}

2203

Blocks/Record

2204

.sp

2205

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

2206

Section\ \&7.6.4, \(lqMyISAM Table Optimization\(rq\&.

2207

.RE

2208

.sp

2209

.RS 4

2210

.ie n \{\

2211

\h'-04'\(bu\h'+03'\c

2212

.\}

2213

.el \{\

2214

.sp -1

2215

.IP \(bu 2.3

2216

.\}

2217

Recordblocks

2218

.sp

2219

How many blocks (links) are used\&. For fixed\-format tables, this is the same as the number of rows\&.

2220

.RE

2221

.sp

2222

.RS 4

2223

.ie n \{\

2224

\h'-04'\(bu\h'+03'\c

2225

.\}

2226

.el \{\

2227

.sp -1

2228

.IP \(bu 2.3

2229

.\}

2230

Deleteblocks

2231

.sp

2232

How many blocks (links) are deleted\&.

2233

.RE

2234

.sp

2235

.RS 4

2236

.ie n \{\

2237

\h'-04'\(bu\h'+03'\c

2238

.\}

2239

.el \{\

2240

.sp -1

2241

.IP \(bu 2.3

2242

.\}

2243

Recorddata

2244

.sp

2245

How many bytes in the data file are used\&.

2246

.RE

2247

.sp

2248

.RS 4

2249

.ie n \{\

2250

\h'-04'\(bu\h'+03'\c

2251

.\}

2252

.el \{\

2253

.sp -1

2254

.IP \(bu 2.3

2255

.\}

2256

Deleted data

2257

.sp

2258

How many bytes in the data file are deleted (unused)\&.

2259

.RE

2260

.sp

2261

.RS 4

2262

.ie n \{\

2263

\h'-04'\(bu\h'+03'\c

2264

.\}

2265

.el \{\

2266

.sp -1

2267

.IP \(bu 2.3

2268

.\}

2269

Lost space

2270

.sp

2271

If a row is updated to a shorter length, some space is lost\&. This is the sum of all such losses, in bytes\&.

2272

.RE

2273

.sp

2274

.RS 4

2275

.ie n \{\

2276

\h'-04'\(bu\h'+03'\c

2277

.\}

2278

.el \{\

2279

.sp -1

2280

.IP \(bu 2.3

2281

.\}

2282

Linkdata

2283

.sp

2284

When the dynamic table format is used, row fragments are linked with pointers (4 to 7 bytes each)\&.

2285

Linkdata

2286

is the sum of the amount of storage used by all such pointers\&.

2287

.RE

2288

.SH "MYISAMCHK MEMORY USAGE"

2289

.\" memory usage: myisamchk

2290

.PP

2291

Memory allocation is important when you run

2292

\fBmyisamchk\fR\&.

2293

\fBmyisamchk\fR

2294

uses no more memory than its memory\-related variables are set to\&. If you are going to use

2295

\fBmyisamchk\fR

2296

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

2297

\fBmyisamchk\fR

2298

to operate faster\&. For example, if you have more than 512MB RAM available, you could use options such as these (in addition to any other options you might specify):

2299

.sp

2300

.if n \{\

2301

.RS 4

2302

.\}

2303

.nf

2304

shell> \fBmyisamchk \-\-myisam_sort_buffer_size=256M \e\fR

2305

\fB\-\-key_buffer_size=512M \e\fR

2306

\fB\-\-read_buffer_size=64M \e\fR

2307

\fB\-\-write_buffer_size=64M \&.\&.\&.\fR

2308

.fi

2309

.if n \{\

2310

.RE

2311

.\}

2312

.PP

2313

Using

2314

\fB\-\-myisam_sort_buffer_size=16M\fR

2315

is probably enough for most cases\&.

2316

.PP

2317

Be aware that

2318

\fBmyisamchk\fR

2319

uses temporary files in

2320

TMPDIR\&. If

2321

TMPDIR

2322

points to a memory file system, out of memory errors can easily occur\&. If this happens, run

2323

\fBmyisamchk\fR

2324

with the

2325

\fB\-\-tmpdir=\fR\fB\fIpath\fR\fR

2326

option to specify a directory located on a file system that has more space\&.

2327

.PP

2328

When performing repair operations,

2329

\fBmyisamchk\fR

2330

also needs a lot of disk space:

2331

.sp

2332

.RS 4

2333

.ie n \{\

2334

\h'-04'\(bu\h'+03'\c

2335

.\}

2336

.el \{\

2337

.sp -1

2338

.IP \(bu 2.3

2339

.\}

2340

Twice the size of the data file (the original file and a copy)\&. This space is not needed if you do a repair with

2341

\fB\-\-quick\fR; in this case, only the index file is re\-created\&.

2342

\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\&.

2343

.RE

2344

.sp

2345

.RS 4

2346

.ie n \{\

2347

\h'-04'\(bu\h'+03'\c

2348

.\}

2349

.el \{\

2350

.sp -1

2351

.IP \(bu 2.3

2352

.\}

2353

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 file system as the original data file\&.

2354

.RE

2355

.sp

2356

.RS 4

2357

.ie n \{\

2358

\h'-04'\(bu\h'+03'\c

2359

.\}

2360

.el \{\

2361

.sp -1

2362

.IP \(bu 2.3

2363

.\}

2364

When using

2365

\fB\-\-recover\fR

2366

2367

\fB\-\-sort\-recover\fR

2368

(but not when using

2369

\fB\-\-safe\-recover\fR), you need space on disk for sorting\&. This space is allocated in the temporary directory (specified by

2370

TMPDIR

2371

2372

\fB\-\-tmpdir=\fR\fB\fIpath\fR\fR)\&. The following formula yields the amount of space required:

2373

.sp

2374

.if n \{\

2375

.RS 4

2376

.\}

2377

.nf

2378

(\fIlargest_key\fR + \fIrow_pointer_length\fR) * \fInumber_of_rows\fR * 2

2379

.fi

2380

.if n \{\

2381

.RE

2382

.\}

2383

.sp

2384

You can check the length of the keys and the

2385

\fIrow_pointer_length\fR

2386

with

2387

\fBmyisamchk \-dv \fR\fB\fItbl_name\fR\fR

2388

(see

2389

the section called \(lqOBTAINING TABLE INFORMATION WITH MYISAMCHK\(rq)\&. The

2390

\fIrow_pointer_length\fR

2391

and

2392

\fInumber_of_rows\fR

2393

values are the

2394

Datafile pointer

2395

and

2396

Data records

2397

values in the table description\&. To determine the

2398

\fIlargest_key\fR

2399

value, check the

2400

Key

2401

lines in the table description\&. The

2402

Len

2403

column indicates the number of bytes for each key part\&. For a multiple\-column index, the key size is the sum of the

2404

Len

2405

values for all key parts\&.

2406

.RE

2407

.PP

2408

If you have a problem with disk space during repair, you can try

2409

\fB\-\-safe\-recover\fR

2410

instead of

2411

\fB\-\-recover\fR\&.

2412

.SH "COPYRIGHT"

2413

.br

2414

.PP

2415

2416

.PP

2417

This documentation is free software; you can redistribute it and/or modify it only under the terms of the GNU General Public License as published by the Free Software Foundation; version 2 of the License.

2418

.PP

2419

This documentation is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

2420

.PP

2421

You should have received a copy of the GNU General Public License along with the program; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA or see http://www.gnu.org/licenses/.

2422

.sp

2423

.SH "SEE ALSO"

2424

For more information, please refer to the MySQL Reference Manual,

2425

which may already be installed locally and which is also available

2426

online at http://dev.mysql.com/doc/.

2427

.SH AUTHOR

2428

Oracle Corporation (http://dev.mysql.com/).

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