1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249 1250 1251 1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262 1263 1264 1265 1266 1267 1268 1269 1270 1271 1272 1273 1274 1275 1276 1277 1278 1279 1280 1281 1282 1283 1284 1285 1286 1287 1288 1289 1290 1291 1292 1293 1294 1295 1296 1297 1298 1299 1300 1301 1302 1303 1304 1305 1306 1307 1308 1309 1310 1311 1312 1313 1314 1315 1316 1317 1318 1319 1320 1321 1322 1323 1324 1325 1326 1327 1328 1329 1330 1331 1332 1333 1334 1335 1336 1337 1338 1339 1340 1341 1342 1343 1344 1345 1346 1347 1348 1349 1350 1351 1352 1353 1354 1355 1356 1357 1358 1359 1360 1361 1362 1363 1364 1365 1366 1367 1368 1369 1370 1371 1372 1373 1374 1375 1376 1377 1378 1379 1380 1381 1382 1383 1384 1385 1386 1387 1388 1389 1390 1391 1392 1393 1394 1395 1396 1397 1398 1399 1400 1401 1402 1403 1404 1405 1406 1407 1408 1409 1410 1411 1412 1413 1414 1415 1416 1417 1418 1419 1420 1421 1422 1423 1424 1425 1426 1427 1428 1429 1430 1431 1432 1433 1434 1435 1436 1437 1438 1439 1440 1441 1442 1443 1444 1445 1446 1447 1448 1449 1450 1451 1452 1453 1454 1455 1456 1457 1458 1459 1460 1461 1462 1463 1464 1465 1466 1467 1468 1469 1470 1471 1472 1473 1474 1475 1476 1477 1478 1479 1480 1481 1482 1483 1484 1485 1486 1487 1488 1489 1490 1491 1492 1493 1494 1495 1496 1497 1498 1499 1500 1501 1502 1503 1504 1505 1506 1507 1508 1509 1510 1511 1512 1513 1514 1515 1516 1517 1518 1519 1520 1521 1522 1523 1524 1525 1526 1527 1528 1529 1530 1531 1532 1533 1534 1535 1536 1537 1538 1539 1540 1541 1542 1543 1544 1545 1546 1547 1548 1549 1550 1551 1552 1553 1554 1555 1556 1557 1558 1559 1560 1561 1562 1563 1564 1565 1566 1567 1568 1569 1570 1571 1572 1573 1574 1575 1576 1577 1578 1579 1580 1581 1582 1583 1584 1585 1586 1587 1588 1589 1590 1591 1592 1593 1594 1595 1596 1597 1598 1599 1600 1601 1602 1603 1604 1605 1606 1607 1608 1609 1610 1611 1612 1613 1614 1615 1616 1617 1618 1619 1620 1621 1622 1623 1624 1625 1626 1627 1628 1629 1630 1631 1632 1633 1634 1635 1636 1637 1638 1639 1640 1641 1642 1643 1644 1645 1646 1647 1648 1649 1650 1651 1652 1653 1654 1655 1656 1657 1658 1659 1660 1661 1662 1663 1664 1665 1666 1667 1668 1669 1670 1671 1672 1673 1674 1675 1676 1677 1678 1679 1680 1681 1682 1683 1684 1685 1686 1687 1688 1689 1690 1691 1692 1693 1694 1695 1696 1697 1698 1699 1700 1701 1702 1703 1704 1705 1706 1707 1708 1709 1710 1711 1712 1713 1714 1715 1716 1717 1718 1719 1720 1721 1722 1723 1724 1725 1726 1727 1728 1729 1730 1731 1732 1733 1734 1735 1736 1737 1738 1739 1740 1741 1742 1743 1744 1745 1746 1747 1748 1749 1750 1751 1752 1753 1754 1755 1756 1757 1758 1759 1760 1761 1762 1763 1764 1765 1766 1767 1768 1769 1770 1771 1772 1773 1774 1775 1776 1777 1778 1779 1780 1781 1782 1783 1784 1785 1786 1787 1788 1789 1790 1791 1792 1793 1794 1795 1796 1797 1798 1799 1800 1801 1802 1803 1804 1805 1806 1807 1808 1809 1810 1811 1812 1813 1814 1815 1816 1817 1818 1819 1820 1821 1822 1823 1824 1825 1826 1827 1828 1829 1830 1831 1832 1833 1834 1835 1836 1837 1838 1839 1840 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 1851 1852 1853 1854 1855 1856 1857 1858 1859 1860 1861 1862 1863 1864 1865 1866 1867 1868 1869 1870 1871 1872 1873 1874 1875 1876 1877 1878 1879 1880 1881 1882 1883 1884 1885 1886 1887 1888 1889 1890 1891 1892 1893 1894 1895 1896 1897 1898 1899 1900 1901 1902 1903 1904 1905 1906 1907 1908 1909 1910 1911 1912 1913 1914 1915 1916 1917 1918 1919 1920 1921 1922 1923 1924 1925 1926 1927 1928 1929 1930 1931 1932 1933 1934 1935 1936 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 1947 1948 1949 1950 1951 1952 1953 1954 1955 1956 1957 1958 1959 1960 1961 1962 1963 1964 1965 1966 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 2031 2032 2033 2034 2035 2036 2037 2038 2039 2040 2041 2042 2043 2044 2045 2046 2047 2048 2049 2050 2051 2052 2053 2054 2055 2056 2057 2058 2059 2060 2061 2062 2063 2064 2065 2066 2067 2068 2069 2070 2071 2072 2073 2074 2075 2076 2077 2078 2079 2080 2081 2082 2083 2084 2085 2086 2087 2088 2089 2090 2091 2092 2093 2094 2095 2096 2097 2098 2099 2100 2101 2102 2103 2104 2105 2106 2107 2108 2109 2110 2111 2112 2113 2114 2115 2116 2117 2118 2119 2120 2121 2122 2123 2124 2125 2126 2127 2128 2129 2130 2131 2132 2133 2134 2135 2136 2137 2138 2139 2140 2141 2142 2143 2144 2145 2146 2147 2148 2149 2150 2151 2152 2153 2154 2155 2156 2157 2158 2159 2160 2161 2162 2163 2164 2165 2166 2167 2168 2169 2170 2171 2172 2173 2174 2175 2176 2177 2178 2179 2180 2181 2182 2183 2184 2185 2186 2187 2188 2189 2190 2191 2192 2193 2194 2195 2196 2197 2198 2199 2200 2201 2202 2203 2204 2205 2206 2207 2208 2209 2210 2211 2212 2213 2214 2215 2216 2217 2218 2219 2220 2221 2222 2223 2224 2225 2226 2227 2228 2229 2230 2231 2232 2233 2234 2235 2236 2237 2238 2239 2240 2241 2242 2243 2244 2245 2246 2247 2248 2249 2250 2251 2252 2253 2254 2255 2256 2257 2258 2259 2260 2261 2262 2263 2264 2265 2266 2267 2268 2269 2270 2271 2272 2273 2274 2275 2276 2277 2278 2279 2280 2281 2282 2283 2284 2285 2286 2287 2288 2289 2290 2291 2292 2293 2294 2295 2296 2297 2298 2299 2300 2301 2302 2303 2304 2305 2306 2307 2308 2309 2310 2311 2312 2313 2314 2315 2316 2317 2318 2319 2320 2321 2322 2323 2324 2325 2326 2327 2328 2329 2330 2331 2332 2333 2334 2335 2336 2337 2338 2339 2340 2341 2342 2343 2344 2345 2346 2347 2348 2349 2350 2351 2352 2353 2354 2355 2356 2357 2358 2359 2360 2361 2362 2363 2364 2365 2366 2367 2368 2369 2370 2371 2372 2373 2374 2375 2376 2377 2378 2379 2380 2381 2382 2383 2384 2385 2386 2387 2388 2389 2390 2391 2392 2393 2394 2395 2396 2397 2398 2399 2400 2401 2402 2403 2404 2405 2406 2407 2408 2409 2410 2411 2412 2413 2414 2415 2416 2417 2418 2419 2420 2421 2422 2423 2424 2425 2426 2427 2428 2429 2430 2431 2432 2433 2434 2435 2436 2437 2438 2439 2440 2441 2442 2443 2444 2445 2446 2447 2448 2449 2450 2451 2452 2453 2454 2455 2456 2457 2458 2459 2460
|
'\" t
.\" 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: 04/06/2010
.\" Manual: MySQL Database System
.\" Source: MySQL 5.1
.\" Language: English
.\"
.TH "\FBMYISAMCHK\FR" "1" "04/06/2010" "MySQL 5\&.1" "MySQL Database System"
.\" -----------------------------------------------------------------
.\" * set default formatting
.\" -----------------------------------------------------------------
.\" disable hyphenation
.nh
.\" disable justification (adjust text to left margin only)
.ad l
.\" -----------------------------------------------------------------
.\" * MAIN CONTENT STARTS HERE *
.\" -----------------------------------------------------------------
.\" myisamchk
.SH "NAME"
myisamchk \- MyISAM table\-maintenance utility
.SH "SYNOPSIS"
.HP \w'\fBmyisamchk\ [\fR\fB\fIoptions\fR\fR\fB]\ \fR\fB\fItbl_name\fR\fR\fB\ \&.\&.\&.\fR\ 'u
\fBmyisamchk [\fR\fB\fIoptions\fR\fR\fB] \fR\fB\fItbl_name\fR\fR\fB \&.\&.\&.\fR
.SH "DESCRIPTION"
.PP
The
\fBmyisamchk\fR
utility gets information about your database tables or checks, repairs, or optimizes them\&.
\fBmyisamchk\fR
works with
MyISAM
tables (tables that have
\&.MYD
and
\&.MYI
files for storing data and indexes)\&.
.PP
The use of
\fBmyisamchk\fR
with partitioned tables is not supported\&.
.if n \{\
.sp
.\}
.RS 4
.it 1 an-trap
.nr an-no-space-flag 1
.nr an-break-flag 1
.br
.ps +1
\fBCaution\fR
.ps -1
.br
.PP
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\&.
.PP
With no options,
\fBmyisamchk\fR
simply checks your table as the default operation\&. To get more information or to tell
\fBmyisamchk\fR
to take corrective action, specify options as described in the following discussion\&.
.PP
\fItbl_name\fR
is the database table you want to check or repair\&. If you run
\fBmyisamchk\fR
somewhere other than in the database directory, you must specify the path to the database directory, because
\fBmyisamchk\fR
has no idea where the database is located\&. In fact,
\fBmyisamchk\fR
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\&.
.PP
You can name several tables on the
\fBmyisamchk\fR
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:
.sp
.if n \{\
.RS 4
.\}
.nf
shell> \fBmyisamchk *\&.MYI\fR
.fi
.if n \{\
.RE
.\}
.PP
If you are not in the database directory, you can check all the tables there by specifying the path to the directory:
.sp
.if n \{\
.RS 4
.\}
.nf
shell> \fBmyisamchk \fR\fB\fI/path/to/database_dir/\fR\fR\fB*\&.MYI\fR
.fi
.if n \{\
.RE
.\}
.PP
You can even check all tables in all databases by specifying a wildcard with the path to the MySQL data directory:
.sp
.if n \{\
.RS 4
.\}
.nf
shell> \fBmyisamchk \fR\fB\fI/path/to/datadir/*/*\fR\fR\fB\&.MYI\fR
.fi
.if n \{\
.RE
.\}
.PP
The recommended way to quickly check all
MyISAM
tables is:
.sp
.if n \{\
.RS 4
.\}
.nf
shell> \fBmyisamchk \-\-silent \-\-fast \fR\fB\fI/path/to/datadir/*/*\fR\fR\fB\&.MYI\fR
.fi
.if n \{\
.RE
.\}
.PP
If you want to check all
MyISAM
tables and repair any that are corrupted, you can use the following command:
.sp
.if n \{\
.RS 4
.\}
.nf
shell> \fBmyisamchk \-\-silent \-\-force \-\-fast \-\-update\-state \e\fR
\fB\-\-key_buffer_size=64M \-\-sort_buffer_size=64M \e\fR
\fB\-\-read_buffer_size=1M \-\-write_buffer_size=1M \e\fR
\fB\fI/path/to/datadir/*/*\fR\fR\fB\&.MYI\fR
.fi
.if n \{\
.RE
.\}
.PP
This command assumes that you have more than 64MB free\&. For more information about memory allocation with
\fBmyisamchk\fR, see
the section called \(lqMYISAMCHK MEMORY USAGE\(rq\&.
.if n \{\
.sp
.\}
.RS 4
.it 1 an-trap
.nr an-no-space-flag 1
.nr an-break-flag 1
.br
.ps +1
\fBImportant\fR
.ps -1
.br
.PP
\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
\fBmyisamchk\fR, or to lock all tables that
\fBmyisamchk\fR
is being used on\&.
.PP
Otherwise, when you run
\fBmyisamchk\fR, it may display the following error message:
.sp
.if n \{\
.RS 4
.\}
.nf
warning: clients are using or haven\'t closed the table properly
.fi
.if n \{\
.RE
.\}
.PP
This means that you are trying to check a table that has been updated by another program (such as the
\fBmysqld\fR
server) that hasn\'t yet closed the file or that has died without closing the file properly, which can sometimes lead to the corruption of one or more
MyISAM
tables\&.
.PP
If
\fBmysqld\fR
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
\fBmyisamchk\fR
.PP
However, the easiest way to avoid this problem is to use
CHECK TABLE
instead of
\fBmyisamchk\fR
to check tables\&. See
Section\ \&12.4.2.3, \(lqCHECK TABLE Syntax\(rq\&.
.sp .5v
.RE
.PP
\fBmyisamchk\fR
supports the following options, which can be specified on the command line or in the
[myisamchk]
option file group\&.
\fBmyisamchk\fR
also supports the options for processing option files described at
Section\ \&4.2.3.3.1, \(lqCommand-Line Options that Affect Option-File Handling\(rq\&.
.SH "MYISAMCHK GENERAL OPTIONS"
.\" options: myisamchk
.\" myisamchk: options
.PP
The options described in this section can be used for any type of table maintenance operation performed by
\fBmyisamchk\fR\&. The sections following this one describe options that pertain only to specific operations, such as table checking or repairing\&.
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: help option
.\" help option: myisamchk
\fB\-\-help\fR,
\fB\-?\fR
.sp
Display a help message and exit\&. Options are grouped by type of operation\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: HELP option
.\" HELP option: myisamchk
\fB\-\-HELP\fR,
\fB\-H\fR
.sp
Display a help message and exit\&. Options are presented in a single list\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: debug option
.\" debug option: myisamchk
\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
string is
\'d:t:o,\fIfile_name\fR\'\&. The default is
\'d:t:o,/tmp/myisamchk\&.trace\'\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: silent option
.\" silent option: myisamchk
\fB\-\-silent\fR,
\fB\-s\fR
.sp
Silent mode\&. Write output only when errors occur\&. You can use
\fB\-s\fR
twice (\fB\-ss\fR) to make
\fBmyisamchk\fR
very silent\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: verbose option
.\" verbose option: myisamchk
\fB\-\-verbose\fR,
\fB\-v\fR
.sp
Verbose mode\&. Print more information about what the program does\&. This can be used with
\fB\-d\fR
and
\fB\-e\fR\&. Use
\fB\-v\fR
multiple times (\fB\-vv\fR,
\fB\-vvv\fR) for even more output\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: version option
.\" version option: myisamchk
\fB\-\-version\fR,
\fB\-V\fR
.sp
Display version information and exit\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: wait option
.\" wait option: myisamchk
\fB\-\-wait\fR,
\fB\-w\fR
.sp
Instead of terminating with an error if the table is locked, wait until the table is unlocked before continuing\&. If you are running
\fBmysqld\fR
with external locking disabled, the table can be locked only by another
\fBmyisamchk\fR
command\&.
.RE
.PP
You can also set the following variables by using
\fB\-\-\fR\fB\fIvar_name\fR\fR\fB=\fR\fB\fIvalue\fR\fR
syntax:
.\" decode_bits myisamchk variable
.\" ft_max_word_len myisamchk variable
.\" ft_min_word_len myisamchk variable
.\" ft_stopword_file myisamchk variable
.\" key_buffer_size myisamchk variable
.\" myisam_block_size myisamchk variable
.\" read_buffer_size myisamchk variable
.\" sort_buffer_size myisamchk variable
.\" sort_key_blocks myisamchk variable
.\" stats_method myisamchk variable
.\" write_buffer_size myisamchk variable
.TS
allbox tab(:);
l l
l l
l l
l l
l l
l l
l l
l l
l l
l l
l l
l l.
T{
\fBVariable\fR
T}:T{
\fBDefault Value\fR
T}
T{
decode_bits
T}:T{
9
T}
T{
ft_max_word_len
T}:T{
version\-dependent
T}
T{
ft_min_word_len
T}:T{
4
T}
T{
ft_stopword_file
T}:T{
built\-in list
T}
T{
key_buffer_size
T}:T{
523264
T}
T{
myisam_block_size
T}:T{
1024
T}
T{
read_buffer_size
T}:T{
262136
T}
T{
sort_buffer_size
T}:T{
2097144
T}
T{
sort_key_blocks
T}:T{
16
T}
T{
stats_method
T}:T{
nulls_unequal
T}
T{
write_buffer_size
T}:T{
262136
T}
.TE
.sp 1
.PP
The possible
\fBmyisamchk\fR
variables and their default values can be examined with
\fBmyisamchk \-\-help\fR:
.PP
sort_buffer_size
is used when the keys are repaired by sorting keys, which is the normal case when you use
\fB\-\-recover\fR\&.
.PP
key_buffer_size
is used when you are checking the table with
\fB\-\-extend\-check\fR
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:
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
You use
\fB\-\-safe\-recover\fR\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
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
\fBmyisamchk\fR
to repair by sorting, you can use the
\fB\-\-sort\-recover\fR
option\&.
.RE
.PP
Repairing through the key buffer takes much less disk space than using sorting, but is also much slower\&.
.PP
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\&.
.PP
myisam_block_size
is the size used for index blocks\&.
.PP
stats_method
influences how
NULL
values are treated for index statistics collection when the
\fB\-\-analyze\fR
option is given\&. It acts like the
myisam_stats_method
system variable\&. For more information, see the description of
myisam_stats_method
in
Section\ \&5.1.4, \(lqServer System Variables\(rq, and
Section\ \&7.4.7, \(lqMyISAM Index Statistics Collection\(rq\&.
.PP
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\&.
.PP
If you use
\fBmyisamchk\fR
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\&.
.PP
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
\fBmyisamchk\fR
that you use for
\fBmysqld\fR\&. For example, if you have set the minimum word length to 3, you can repair a table with
\fBmyisamchk\fR
like this:
.sp
.if n \{\
.RS 4
.\}
.nf
shell> \fBmyisamchk \-\-recover \-\-ft_min_word_len=3 \fR\fB\fItbl_name\fR\fR\fB\&.MYI\fR
.fi
.if n \{\
.RE
.\}
.PP
To ensure that
\fBmyisamchk\fR
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:
.sp
.if n \{\
.RS 4
.\}
.nf
[mysqld]
ft_min_word_len=3
[myisamchk]
ft_min_word_len=3
.fi
.if n \{\
.RE
.\}
.PP
An alternative to using
\fBmyisamchk\fR
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\&.
.SH "MYISAMCHK CHECK OPTIONS"
.\" check options: myisamchk
.\" tables: checking
.PP
\fBmyisamchk\fR
supports the following options for table checking operations:
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: check option
.\" check option: myisamchk
\fB\-\-check\fR,
\fB\-c\fR
.sp
Check the table for errors\&. This is the default operation if you specify no option that selects an operation type explicitly\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: check-only-changed option
.\" check-only-changed option: myisamchk
\fB\-\-check\-only\-changed\fR,
\fB\-C\fR
.sp
Check only tables that have changed since the last check\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: extend-check option
.\" extend-check option: myisamchk
\fB\-\-extend\-check\fR,
\fB\-e\fR
.sp
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,
\fBmyisamchk\fR
or
\fBmyisamchk \-\-medium\-check\fR
should be able to determine whether there are any errors in the table\&.
.sp
If you are using
\fB\-\-extend\-check\fR
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
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: fast option
.\" fast option: myisamchk
\fB\-\-fast\fR,
\fB\-F\fR
.sp
Check only tables that haven\'t been closed properly\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: force option
.\" force option: myisamchk
\fB\-\-force\fR,
\fB\-f\fR
.sp
Do a repair operation automatically if
\fBmyisamchk\fR
finds any errors in the table\&. The repair type is the same as that specified with the
\fB\-\-recover\fR
or
\fB\-r\fR
option\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: information option
.\" information option: myisamchk
\fB\-\-information\fR,
\fB\-i\fR
.sp
Print informational statistics about the table that is checked\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: medium-check option
.\" medium-check option: myisamchk
\fB\-\-medium\-check\fR,
\fB\-m\fR
.sp
Do a check that is faster than an
\fB\-\-extend\-check\fR
operation\&. This finds only 99\&.99% of all errors, which should be good enough in most cases\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: read-only option
.\" read-only option: myisamchk
\fB\-\-read\-only\fR,
\fB\-T\fR
.sp
Do not mark the table as checked\&. This is useful if you use
\fBmyisamchk\fR
to check a table that is in use by some other application that does not use locking, such as
\fBmysqld\fR
when run with external locking disabled\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: update-state option
.\" update-state option: myisamchk
\fB\-\-update\-state\fR,
\fB\-U\fR
.sp
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
\fB\-\-check\-only\-changed\fR
option, but you shouldn\'t use this option if the
\fBmysqld\fR
server is using the table and you are running it with external locking disabled\&.
.RE
.SH "MYISAMCHK REPAIR OPTIONS"
.\" repair options: myisamchk
.\" files: repairing
.PP
\fBmyisamchk\fR
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 \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: backup option
.\" backup option: myisamchk
\fB\-\-backup\fR,
\fB\-B\fR
.sp
Make a backup of the
\&.MYD
file as
\fIfile_name\fR\-\fItime\fR\&.BAK
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: character-sets-dir option
.\" character-sets-dir option: myisamchk
\fB\-\-character\-sets\-dir=\fR\fB\fIpath\fR\fR
.sp
The directory where character sets are installed\&. See
Section\ \&9.5, \(lqCharacter Set Configuration\(rq\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: correct-checksum option
.\" correct-checksum option: myisamchk
\fB\-\-correct\-checksum\fR
.sp
Correct the checksum information for the table\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" 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
.sp
The maximum length of the data file (when re\-creating data file when it is
\(lqfull\(rq)\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: extend-check option
.\" extend-check option: myisamchk
\fB\-\-extend\-check\fR,
\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
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: force option
.\" force option: myisamchk
\fB\-\-force\fR,
\fB\-f\fR
.sp
Overwrite old intermediate files (files with names like
\fItbl_name\fR\&.TMD) instead of aborting\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: keys-used option
.\" keys-used option: myisamchk
\fB\-\-keys\-used=\fR\fB\fIval\fR\fR,
\fB\-k \fR\fB\fIval\fR\fR
.sp
For
\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
\fBmyisamchk \-r\fR\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: no-symlinks option
.\" no-symlinks option: myisamchk
\fB\-\-no\-symlinks\fR,
\fB\-l\fR
.sp
Do not follow symbolic links\&. Normally
\fBmyisamchk\fR
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\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: max-record-length option
.\" max-record-length option: myisamchk
\fB\-\-max\-record\-length=\fR\fB\fIlen\fR\fR
.sp
Skip rows larger than the given length if
\fBmyisamchk\fR
cannot allocate memory to hold them\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: parallel-recover option
.\" parallel-recover option: myisamchk
\fB\-\-parallel\-recover\fR,
\fB\-p\fR
.sp
Use the same technique as
\fB\-r\fR
and
\fB\-n\fR, but create all the keys in parallel, using different threads\&.
\fIThis is beta\-quality code\&. Use at your own risk!\fR
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: quick option
.\" quick option: myisamchk
\fB\-\-quick\fR,
\fB\-q\fR
.sp
Achieve a faster repair by modifying only the index file, not the data file\&. You can specify this option twice to force
\fBmyisamchk\fR
to modify the original data file in case of duplicate keys\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: recover option
.\" recover option: myisamchk
\fB\-\-recover\fR,
\fB\-r\fR
.sp
Do a repair that can fix almost any problem except unique keys that are not unique (which is an extremely unlikely error with
MyISAM
tables)\&. If you want to recover a table, this is the option to try first\&. You should try
\fB\-\-safe\-recover\fR
only if
\fBmyisamchk\fR
reports that the table cannot be recovered using
\fB\-\-recover\fR\&. (In the unlikely case that
\fB\-\-recover\fR
fails, the data file remains intact\&.)
.sp
If you have lots of memory, you should increase the value of
sort_buffer_size\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: safe-recover option
.\" safe-recover option: myisamchk
\fB\-\-safe\-recover\fR,
\fB\-o\fR
.sp
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
\fB\-\-recover\fR, but can handle a couple of very unlikely cases that
\fB\-\-recover\fR
cannot\&. This recovery method also uses much less disk space than
\fB\-\-recover\fR\&. Normally, you should repair first using
\fB\-\-recover\fR, and then with
\fB\-\-safe\-recover\fR
only if
\fB\-\-recover\fR
fails\&.
.sp
If you have lots of memory, you should increase the value of
key_buffer_size\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: set-character-set option
.\" set-character-set option: myisamchk
\fB\-\-set\-character\-set=\fR\fB\fIname\fR\fR
.sp
Change the character set used by the table indexes\&. This option was replaced by
\fB\-\-set\-collation\fR
in MySQL 5\&.0\&.3\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: set-collation option
.\" set-collation option: myisamchk
\fB\-\-set\-collation=\fR\fB\fIname\fR\fR
.sp
Specify the collation to use for sorting table indexes\&. The character set name is implied by the first part of the collation name\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: sort-recover option
.\" sort-recover option: myisamchk
\fB\-\-sort\-recover\fR,
\fB\-n\fR
.sp
Force
\fBmyisamchk\fR
to use sorting to resolve the keys even if the temporary files would be very large\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: tmpdir option
.\" tmpdir option: myisamchk
\fB\-\-tmpdir=\fR\fB\fIpath\fR\fR,
\fB\-t \fR\fB\fIpath\fR\fR
.sp
The path of the directory to be used for storing temporary files\&. If this is not set,
\fBmyisamchk\fR
uses the value of the
TMPDIR
environment variable\&.
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 is the colon (\(lq:\(rq) on Unix and the semicolon (\(lq;\(rq) on Windows, NetWare, and OS/2\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: unpack option
.\" unpack option: myisamchk
\fB\-\-unpack\fR,
\fB\-u\fR
.sp
Unpack a table that was packed with
\fBmyisampack\fR\&.
.RE
.SH "OTHER MYISAMCHK OPTIONS"
.PP
\fBmyisamchk\fR
supports the following options for actions other than table checks and repairs:
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: analyze option
.\" analyze option: myisamchk
\fB\-\-analyze\fR,
\fB\-a\fR
.sp
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
\fBmyisamchk \-\-description \-\-verbose \fR\fB\fItbl_name\fR\fR
command or the
SHOW INDEX FROM \fItbl_name\fR
statement\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: block-search option
.\" block-search option: myisamchk
\fB\-\-block\-search=\fR\fB\fIoffset\fR\fR,
\fB\-b \fR\fB\fIoffset\fR\fR
.sp
Find the record that a block at the given offset belongs to\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: description option
.\" description option: myisamchk
\fB\-\-description\fR,
\fB\-d\fR
.sp
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
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: set-auto-increment[ option
.\" set-auto-increment[ option: myisamchk
\fB\-\-set\-auto\-increment[=\fR\fB\fIvalue\fR\fR\fB]\fR,
\fB\-A[\fR\fB\fIvalue\fR\fR\fB]\fR
.sp
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
\fIvalue\fR
is not specified,
AUTO_INCREMENT
numbers for new records begin with the largest value currently in the table, plus one\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: sort-index option
.\" sort-index option: myisamchk
\fB\-\-sort\-index\fR,
\fB\-S\fR
.sp
Sort the index tree blocks in high\-low order\&. This optimizes seeks and makes table scans that use indexes faster\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
.\" myisamchk: sort-records option
.\" sort-records option: myisamchk
\fB\-\-sort\-records=\fR\fB\fIN\fR\fR,
\fB\-R \fR\fB\fIN\fR\fR
.sp
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
\fBmyisamchk\fR
sees them\&. Indexes are numbered beginning with 1\&.
.sp
If keys are not packed (PACK_KEYS=0), they have the same length, so when
\fBmyisamchk\fR
sorts and moves records, it just overwrites record offsets in the index\&. If keys are packed (PACK_KEYS=1),
\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\&. (Packed
corresponds to what
SHOW TABLE STATUS
reports as
Dynamic\&.)
.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\ \&6.6.4, \(lqMyISAM Table 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\ \&6.6.4, \(lqMyISAM Table 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\ \&6.6.4, \(lqMyISAM Table 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\ \&6.6.4, \(lqMyISAM Table 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
Memory allocation is important when you run
\fBmyisamchk\fR\&.
\fBmyisamchk\fR
uses no more memory than its memory\-related variables are set to\&. If you are going to use
\fBmyisamchk\fR
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
\fBmyisamchk\fR
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):
.sp
.if n \{\
.RS 4
.\}
.nf
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
.\}
.PP
Using
\fB\-\-sort_buffer_size=16M\fR
should probably be enough for most cases\&.
.PP
Be aware that
\fBmyisamchk\fR
uses temporary files in
TMPDIR\&. If
TMPDIR
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 a directory located on a file system that has more space\&.
.PP
When performing repair operations,
\fBmyisamchk\fR
also needs a lot of disk space:
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
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
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
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\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
When using
\fB\-\-recover\fR
or
\fB\-\-sort\-recover\fR
(but not when using
\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
.\}
.nf
(\fIlargest_key\fR + \fIrow_pointer_length\fR) \(mu \fInumber_of_rows\fR \(mu 2
.fi
.if n \{\
.RE
.\}
.sp
You can check the length of the keys and the
\fIrow_pointer_length\fR
with
\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
\fB\-\-safe\-recover\fR
instead of
\fB\-\-recover\fR\&.
.SH "COPYRIGHT"
.br
.PP
Copyright 2007-2008 MySQL AB, 2008-2010 Sun Microsystems, Inc.
.PP
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.
.PP
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.
.PP
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/.
.sp
.SH "SEE ALSO"
For more information, please refer to the MySQL Reference Manual,
which may already be installed locally and which is also available
online at http://dev.mysql.com/doc/.
.SH AUTHOR
Sun Microsystems, Inc. (http://www.mysql.com/).
|