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[linuxjm/LDP_man-pages.git] / draft / man3 / btree.3

.\" Copyright (c) 1990, 1993
.\"     The Regents of the University of California.  All rights reserved.
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.\" modification, are permitted provided that the following conditions
.\" are met:
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.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\" 3. All advertising materials mentioning features or use of this software
.\"    must display the following acknowledgement:
.\"     This product includes software developed by the University of
.\"     California, Berkeley and its contributors.
.\" 4. Neither the name of the University nor the names of its contributors
.\"    may be used to endorse or promote products derived from this software
.\"    without specific prior written permission.
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\"     @(#)btree.3     8.4 (Berkeley) 8/18/94
.\"
.\" Japanese Version Copyright (c) 1999 Shouichi Saito
.\"     all rights reserved.
.\" Translated Mon Jul 26 21:43:11 JST 1999
.\"     by Shouichi Saito <ss236rx@ymg.urban.ne.jp>
.\" Proofed Mon Aug 16 1999 by NAKANO Takeo <nakano@apm.seikei.ac.jp>
.\"
.\"WORD:        access method           ¥¢¥¯¥»¥¹¥á¥½¥Ã¥É
.\"WORD:        prefix (comparison)     Á°ÃÖÈæ³Ó
.TH BTREE 3 1994-08-18 "" "Linux Programmer's Manual"
.UC 7
.SH ̾Á°
.\"O btree \- btree database access method
btree \- btree ¥Ç¡¼¥¿¥Ù¡¼¥¹¤Ø¤Î¥¢¥¯¥»¥¹¥á¥½¥Ã¥É
.SH ½ñ¼°
.nf
.ft B
#include <sys/types.h>
#include <db.h>
.ft R
.fi
.SH ÀâÌÀ
.\"O The routine
.\"O .BR dbopen (3)
.\"O is the library interface to database files.
¥ë¡¼¥Á¥ó
.BR dbopen (3)
¤Ï¥Ç¡¼¥¿¥Ù¡¼¥¹¥Õ¥¡¥¤¥ë¤ËÂФ¹¤ë¥é¥¤¥Ö¥é¥ê¥¤¥ó¥¿¡¼¥Õ¥§¡¼¥¹¤Ç¤¢¤ë¡£
.\"O One of the supported file formats is btree files.
.\"O The general description of the database access methods is in
.\"O .BR dbopen (3),
.\"O this manual page describes only the btree specific information.
¥µ¥Ý¡¼¥È¤µ¤ì¤Æ¤¤¤ë¥Õ¥¡¥¤¥ë¥Õ¥©¡¼¥Þ¥Ã¥È¤Î¤Ò¤È¤Ä¤Ë btree ¥Õ¥¡¥¤¥ë¤¬¤¢¤ë¡£
¥Ç¡¼¥¿¥Ù¡¼¥¹¤Ø¤Î¥¢¥¯¥»¥¹¥á¥½¥Ã¥É¤Ë´Ø¤¹¤ë°ìÈÌŪ¤Êµ­½Ò¤Ï
.BR dbopen (3)
¤Ë½ñ¤«¤ì¤Æ¤¤¤ë¡£
¤³¤Î¥Þ¥Ë¥å¥¢¥ë¥Ú¡¼¥¸¤Ç¤Ï btree ÆÃÍ­¤Î¾ðÊó¤Ë¤Ä¤¤¤Æ¤Î¤ßµ­½Ò¤¹¤ë¡£
.PP
.\"O The btree data structure is a sorted, balanced tree structure storing
.\"O associated key/data pairs.
btree ¥Ç¡¼¥¿¹½Â¤¤Ç¤Ï¡¢¥½¡¼¥È¤µ¤ì¤¿¥Ð¥é¥ó¥¹¥Ä¥ê¡¼¹½Â¤¤Ë
¸ß¤¤¤Ë´ØÏ¢¤Å¤±¤é¤ì¤¿¥­¡¼/¥Ç¡¼¥¿ÂФò³ÊǼ¤·¤Æ¤¤¤ë¡£
.PP
.\"O The btree access method specific data structure provided to
.\"O .BR dbopen (3)
.\"O is defined in the
.\"O .I <db.h>
.\"O include file as follows:
.BR dbopen (3)
¤ËÅϤµ¤ì¤ë btree ¥¢¥¯¥»¥¹¥á¥½¥Ã¥É¤ËÆÃÍ­¤Î¥Ç¡¼¥¿¹½Â¤ÂΤϡ¢
.I <db.h>
¥¤¥ó¥¯¥ë¡¼¥É¥Õ¥¡¥¤¥ë¤Ç¼¡¤Î¤è¤¦¤ËÄêµÁ¤µ¤ì¤Æ¤¤¤ë¡£
.sp
.in +4n
.nf

typedef struct {
    unsigned long flags;
    unsigned int  cachesize;
    int           maxkeypage;
    int           minkeypage;
    unsigned int  psize;
    int         (*compare)(const DBT *key1, const DBT *key2);
    size_t      (*prefix)(const DBT *key1, const DBT *key2);
    int           lorder;
} BTREEINFO;
.fi
.in
.sp
.\"O The elements of this structure are as follows:
¤³¤Î¹½Â¤ÂΤÎÍ×ÁǤò°Ê²¼¤Ë¼¨¤¹¡£
.TP
.I flags
.\"O The flag value is specified by
.\"O .IR or 'ing
.\"O any of the following values:
.I flags
¤ÎÃͤϰʲ¼¤ÎÃͤΤ¤¤º¤ì¤«¤«¡¢¤³¤ì¤é¤ÎÏÀÍýϤǻØÄꤵ¤ì¤ë¡£
.RS
.TP
.B R_DUP
.\"O Permit duplicate keys in the tree, that is,
.\"O permit insertion if the key to be
.\"O inserted already exists in the tree.
.\"O The default behavior, as described in
.\"O .BR dbopen (3),
.\"O is to overwrite a matching key when inserting a new key or to fail if
.\"O the
.\"O .B R_NOOVERWRITE
.\"O flag is specified.
¥Ä¥ê¡¼¤ÎÃæ¤Ë¥­¡¼¤Î½ÅÊ£¤òµö¤¹¡£¤¹¤Ê¤ï¤Á¥Ä¥ê¡¼¤ÎÃæ¤ËÁÞÆþ¤µ¤ì¤è¤¦¤È¤·¤Æ¤¤¤ë
¥­¡¼¤¬´û¤Ë¸ºß¤·¤Æ¤¤¤Æ¤â¡¢¤½¤ÎÁÞÆþ¤òµö²Ä¤¹¤ë¡£¥Ç¥Õ¥©¥ë¥È¤ÎÆ°ºî¤Ï
.BR dbopen (3)
¤Ëµ­½Ò¤µ¤ì¤Æ¤¤¤ë¤è¤¦¤Ë¡¢¿·¤·¤¤¥­¡¼¤¬ÁÞÆþ¤µ¤ì¤ë¤È°ìÃפ·¤¿¥­¡¼¤ò¾å½ñ¤­¤¹¤ë¡£
¤¢¤ë¤¤¤Ï
.B R_NOOVERWRITE
¥Õ¥é¥°¤¬»ØÄꤵ¤ì¤Æ¤¤¤ë¤ÈÁÞÆþ¤Ë¼ºÇÔ¤¹¤ë¡£
.\"O The
.\"O .B R_DUP
.\"O flag is overridden by the
.\"O .B R_NOOVERWRITE
.\"O flag, and if the
.\"O .B R_NOOVERWRITE
.\"O flag is specified, attempts to insert duplicate keys into
.\"O the tree will fail.
.B R_DUP
¥Õ¥é¥°¤Ï
.B R_NOOVERWRITE
¥Õ¥é¥°¤Ë¤è¤Ã¤Æ¾å½ñ¤­¤µ¤ì¤ë¡£¤Ä¤Þ¤ê
.B R_NOOVERWRITE
¥Õ¥é¥°¤¬»ØÄꤵ¤ì¤¿¾ì¹ç¡¢¥Ä¥ê¡¼¤ËÊ£À½¥­¡¼¤òÁÞÆþ¤·¤è¤¦¤È¤¹¤ë¤È¼ºÇÔ¤¹¤ë¡£
.IP
.\"O If the database contains duplicate keys, the order of retrieval of
.\"O key/data pairs is undefined if the
.\"O .I get
.\"O routine is used, however,
.\"O .I seq
.\"O routine calls with the
.\"O .B R_CURSOR
.\"O flag set will always return the logical
.\"O "first" of any group of duplicate keys.
¥Ç¡¼¥¿¥Ù¡¼¥¹¤Ë¥­¡¼¤Î½ÅÊ£¤¬¤¢¤ë¤È¡¢
.I get
¥ë¡¼¥Á¥ó¤ò»È¤Ã¤¿¾ì¹ç¤Î¥­¡¼/¥Ç¡¼¥¿ÂФμèÆÀ½ç¤Ï̤ÄêµÁ¤Ç¤¢¤ë¡£¤½¤ì¤ËÂФ·¡¢
.B R_CURSOR
¥Õ¥é¥°¤ò¥»¥Ã¥È¤·¤Æ
.I seq
¥ë¡¼¥Á¥ó¤ò»È¤¦¤È¡¢Ê£À½¥­¡¼¤Î¥°¥ë¡¼¥×¤ÎÃæ¤Î
ÏÀÍýŪ¤Ë¡ÖºÇ½é¡×¤Î¥­¡¼¤òɬ¤ºÊÖ¤·¤Æ¤¯¤ë¡£
.RE
.TP
.I cachesize
.\"O A suggested maximum size (in bytes) of the memory cache.
ÁÛÄꤵ¤ì¤ë¥á¥â¥ê¥­¥ã¥Ã¥·¥å¤ÎºÇÂ祵¥¤¥º (¥Ð¥¤¥Èñ°Ì)¡£
.\"O This value is
.\"O .I only
.\"O advisory, and the access method will allocate more memory rather than fail.
.\"O Since every search examines the root page of the tree, caching the most
.\"O recently used pages substantially improves access time.
¤³¤ÎÃͤÏ
.I ¤¢¤¯¤Þ¤Ç
»²¹Í¤Ç¤¢¤ê¡¢¥¢¥¯¥»¥¹¥á¥½¥Ã¥É¤Ï¤³¤ÎÃͤò±Û¤¨¤¿¥á¥â¥ê¤Î
³ä¤êÅö¤Æ¤ËÀ®¸ù¤¹¤ë¤³¤È¤â¤¢¤ë¡£
.\"O In addition, physical writes are delayed as long as possible, so a moderate
.\"O cache can reduce the number of I/O operations significantly.
²Ã¤¨¤Æ¡¢ÊªÍýŪ¤Ê½ñ¤­¹þ¤ß¤Ï²Äǽ¤Ê¸Â¤êÃٱ䤵¤ì¤ë¤Î¤Ç¡¢
¥­¥ã¥Ã¥·¥å¤ÎÂ礭¤µ¤òŬÅ٤ˤ·¤Æ¤ª¤±¤Ð I/O Áàºî¤Î²ó¿ô¤ò¤«¤Ê¤ê¸º¤é¤¹¤³¤È
¤¬¤Ç¤­¤ë¡£
.\"O Obviously, using a cache increases (but only increases) the likelihood of
.\"O corruption or lost data if the system crashes while a tree is being modified.
¤¢¤­¤é¤«¤Ë¥­¥ã¥Ã¥·¥å¤ò»È¤¦¤È¡¢¥Ä¥ê¡¼¤¬Êѹ¹¤µ¤ì¤Æ¤¤¤ëÅÓÃæ¤Ç
¥·¥¹¥Æ¥à¤¬¥¯¥é¥Ã¥·¥å¤·¤¿¾ì¹ç¤Î¥Ç¡¼¥¿Ç˲õ¤ä¥Ç¡¼¥¿¥í¥¹¥È¤Î²ÄǽÀ­¤Ï
Áý¤¨¤ë (¤Þ¤¢¤Ç¤â¤½¤ì¤À¤±¤Î¤³¤È)¡£
.\"O If
.I cachesize
.\"O is 0 (no size is specified) a default cache is used.
¤¬ 0 (¥µ¥¤¥º¤¬»ØÄꤵ¤ì¤Æ¤¤¤Ê¤¤) ¤Î¾ì¹ç¡¢¥Ç¥Õ¥©¥ë¥È¤Î¥­¥ã¥Ã¥·¥å¤¬»È¤ï¤ì¤ë¡£
.TP
.I maxkeypage
.\"O The maximum number of keys which will be stored on any single page.
.\"O Not currently implemented.
ñ°ì¥Ú¡¼¥¸¤ËǼ¤á¤é¤ì¤ëºÇÂ祭¡¼¿ô¤Ç¤¢¤ë¡£¸½ºß¼ÂÁõ¤µ¤ì¤Æ¤¤¤Ê¤¤¡£
.\" The maximum number of keys which will be stored on any single page.
.\" Because of the way the btree data structure works,
.\" .I maxkeypage
.\" must always be greater than or equal to 2.
.\" If
.\" .I maxkeypage
.\" is 0 (no maximum number of keys is specified) the page fill factor is
.\" made as large as possible (which is almost invariably what is wanted).
.TP
.I minkeypage
.\"O The minimum number of keys which will be stored on any single page.
.\"O This value is used to determine which keys will be stored on overflow
.\"O pages, that is, if a key or data item is longer than the pagesize divided
.\"O by the minkeypage value, it will be stored on overflow pages instead
.\"O of in the page itself.
ñ°ì¥Ú¡¼¥¸¤ËǼ¤á¤é¤ì¤ëºÇ¾®¥­¡¼¿ô¤Ç¤¢¤ë¡£¤³¤ÎÃͤϡ¢¤É¤Î¥­¡¼¤ò
¥ª¡¼¥Ð¡¼¥Õ¥í¡¼¥Ú¡¼¥¸
¤ËǼ¤á¤ë¤«·è¤á¤ë¤Î¤Ë»È¤ï¤ì¤ë¡£¤¹¤Ê¤ï¤Á¥­¡¼¤Þ¤¿¤Ï¥Ç¡¼¥¿¤¬
minkeypage ¤ÎÃͤÇʬ³ä¤µ¤ì¤¿¥Ú¡¼¥¸¥µ¥¤¥º¤è¤êÂ礭¤¤»þ¡¢¤½¤Î¥Ú¡¼¥¸¤ËǼ¤á
¤ëÂå¤ï¤ê¤Ë¥ª¡¼¥Ð¡¼¥Õ¥í¡¼¥Ú¡¼¥¸¤ËǼ¤á¤ë¤È¤¤¤¦¤³¤È¤Ç¤¢¤ë¡£
.\"O If
.I minkeypage
.\"O is 0 (no minimum number of keys is specified) a value of 2 is used.
¤¬ 0 (¥­¡¼¤ÎºÇ¾®Ãͤ¬»ØÄꤵ¤ì¤Æ¤¤¤Ê¤¤) ¤Î¾ì¹ç¡¢ÃͤȤ·¤Æ 2 ¤¬»È¤ï¤ì¤ë¡£
.TP
.I psize
.\"O Page size is the size (in bytes) of the pages used for nodes in the tree.
.\"O The minimum page size is 512 bytes and the maximum page size is 64K.
¥Ä¥ê¡¼¤ÎÃæ¤Î¥Î¡¼¥É¤Ë»È¤ï¤ì¤ë¥Ú¡¼¥¸¥µ¥¤¥º (¥Ð¥¤¥Èñ°Ì)¡£
ºÇ¾®ÃÍ¤Ï 512 ¥Ð¥¤¥È¤Ç¡¢ºÇÂçÃÍ¤Ï 64K ¤Ç¤¢¤ë¡£
.\"O If
.I psize
.\"O is 0 (no page size is specified) a page size is chosen based on the
.\"O underlying file system I/O block size.
¤¬ 0 (¥Ú¡¼¥¸¥µ¥¤¥º¤¬»ØÄꤵ¤ì¤Æ¤¤¤Ê¤¤) ¤Î¾ì¹ç¡¢
¥Õ¥¡¥¤¥ë¥·¥¹¥Æ¥à¤Î I/O ¥Ö¥í¥Ã¥¯¥µ¥¤¥º¤Ë´ð¤Å¤¤¤Æ·è¤á¤é¤ì¤ë¡£
.TP
.I compare
.\"O Compare is the key comparison function.
.I compare
¤Ï¥­¡¼¤ÎÈæ³Ó´Ø¿ô¤Ç¤¢¤ë¡£
.\"O It must return an integer less than, equal to, or greater than zero if the
.\"O first key argument is considered to be respectively less than, equal to,
.\"O or greater than the second key argument.
ºÇ½é¤Î¥­¡¼°ú¿ô¤ËÂФ·¡¢ÆóÈÖÌܤΥ­¡¼°ú¿ô¤¬Â礭¤¤¾ì¹ç¤Ë¤ÏÀµ¤ÎÀ°¿ô¤ò¡¢
Ʊ¤¸¾ì¹ç¤Ë¤Ï¥¼¥í¤ò¡¢¾®¤µ¤¤¾ì¹ç¤Ë¤ÏÉé¤ÎÀ°¿ô¤òÊÖ¤¹¡£
.\"O The same comparison function must be used on a given tree every time it
.\"O is opened.
¥Ä¥ê¡¼¤ò³«¤¯ºÝ¤Ë¤Ï¡¢¾ï¤ËƱ¤¸Èæ³Ó´Ø¿ô¤¬»È¤ï¤ì¤Ê¤±¤ì¤Ð¤Ê¤é¤Ê¤¤¡£
.\"O If
.I compare
.\"O is NULL (no comparison function is specified), the keys are compared
.\"O lexically, with shorter keys considered less than longer keys.
¤¬ NULL (Èæ³Ó´Ø¿ô¤¬»ØÄꤵ¤ì¤Æ¤¤¤Ê¤¤) ¤Î¾ì¹ç¡¢
¼­½ñŪ¤ËÈæ³Ó¤µ¤ì¤ë¡£Ã»¤¤¥­¡¼¤ÏŤ¤¥­¡¼¤è¤ê¾®¤µ¤¤¤³¤È¤Ë¤Ê¤ë¡£
.TP
.I prefix
.\"O Prefix is the prefix comparison function.
.I prefix
¤ÏÁ°ÃÖÈæ³Ó´Ø¿ô¤Ç¤¢¤ë¡£
.\"O If specified, this routine must return the number of bytes of the second key
.\"O argument which are necessary to determine that it is greater than the first
.\"O key argument.
¤³¤Î¥ë¡¼¥Á¥ó¤Ï (»ØÄꤵ¤ì¤¿¾ì¹ç¤Ë¤Ï)¡¢ÆóÈÖÌܤΥ­¡¼°ú¿ô¤Î
¥Ð¥¤¥È¿ô¤òÊÖ¤µ¤Ê¤¯¤Æ¤Ï¤Ê¤é¤Ê¤¤¡£¤³¤ì¤ÏÆóÈÖÌܤΥ­¡¼°ú¿ô¤¬
°ìÈÖÌܤΥ­¡¼°ú¿ô¤è¤êÂ礭¤¤¤«¤É¤¦¤«·è¤á¤ë¤Î¤ËɬÍפǤ¢¤ë¡£
.\"NAKANO ¤Á¤ç¤Ã¤È°ÕÌ£¤ï¤«¤é¤ó...
.\"O If the keys are equal, the key length should be returned.
.\"O Note, the usefulness of this routine is very data-dependent, but, in some
.\"O data sets can produce significantly reduced tree sizes and search times.
¥­¡¼¤¬Æ±¤¸¾ì¹ç¡¢¥­¡¼¤ÎŤµ¤¬Ê֤롣¤³¤Î¥ë¡¼¥Á¥ó¤¬Í­ÍѤ«¤É¤¦¤«¤Ï¡¢
¥Ç¡¼¥¿¤Ë¶¯¤¯°Í¸¤¹¤ë¡£¤·¤«¤·¥Ç¡¼¥¿¥»¥Ã¥È¤Ë¤è¤Ã¤Æ¤Ï¡¢ÌÀ¤é¤«¤Ë¥Ä¥ê¡¼
¤Î¥µ¥¤¥º¤È¸¡º÷»þ´Ö¤ò¸º¤é¤·¤Æ¤¯¤ì¤ë¡£
.\"O If
.\"O .I prefix
.\"O is NULL (no prefix function is specified),
.\"O .I and
.\"O no comparison function is specified, a default lexical comparison routine
.\"O is used.
.I prefix
¤¬ NULL (prefix ´Ø¿ô¤¬»ØÄꤵ¤ì¤Æ¤¤¤Ê¤¤) ¤Ç¡¢
.I ¤«¤Ä
Èæ³Ó´Ø¿ô¤¬»ØÄꤵ¤ì¤Æ¤¤¤Ê¤¤¤È¡¢¥Ç¥Õ¥©¥ë¥È¤Î¼­½ñÈæ³Ó¥ë¡¼¥Á¥ó¤¬»È¤ï¤ì¤ë¡£
.\"O If
.\"O .I prefix
.\"O is NULL and a comparison routine is specified, no prefix comparison is
.\"O done.
.I prefix
¤¬ NULL ¤ÇÈæ³Ó´Ø¿ô¤¬»ØÄꤵ¤ì¤Æ¤¤¤ë¾ì¹ç¤Ï¡¢Á°ÃÖÈæ³Ó¤Ï¹Ô¤ï¤ì¤Ê¤¤¡£
.TP
.I lorder
.\"O The byte order for integers in the stored database metadata.
.\"O The number should represent the order as an integer; for example,
.\"O big endian order would be the number 4,321.
.\"O If
.\"O .I lorder
.\"O is 0 (no order is specified) the current host order is used.
¥Ç¡¼¥¿¥Ù¡¼¥¹¤Ë³ÊǼ¤µ¤ì¤Æ¤¤¤ë¥á¥¿¥Ç¡¼¥¿¤ÎÀ°¿ôÃͤΥХ¤¥È¥ª¡¼¥À¡¼¡£
¤³¤Î¿ô»ú¤Ï¡¢½ç½ø¤òÀ°¿ô¤Çɽ¤·¤¿¤â¤Î¤Ç¤¢¤ë¡£
Î㤨¤Ð¥Ó¥Ã¥°¥¨¥ó¥Ç¥£¥¢¥ó¤Ê¤é¡¢¤³¤Î¿ôÃÍ¤Ï 4,321 ¤È¤Ê¤ë¡£
.I lorder
¤¬ 0 (»ØÄꤵ¤ì¤Æ¤¤¤Ê¤¤) ¤Î¾ì¹ç¡¢¸½ºß¤Î¥Û¥¹¥È
¤Ç»È¤ï¤ì¤Æ¤¤¤ë¥Ð¥¤¥È¥ª¡¼¥À¡¼¤¬»È¤ï¤ì¤ë¡£
.PP
.\"O If the file already exists (and the
.\"O .B O_TRUNC
.\"O flag is not specified), the
.\"O values specified for the arguments
.\"O .IR flags ,
.\"O .I lorder
.\"O and
.\"O .I psize
.\"O are ignored
.\"O in favor of the values used when the tree was created.
¥Õ¥¡¥¤¥ë¤¬´û¤Ë¸ºß¤·¤Æ¤¤¤ë (¤Þ¤¿¤Ï
.B O_TRUCT
¥Õ¥é¥°¤¬»ØÄꤵ¤ì¤Æ¤¤¤Ê¤¤) ¤È¡¢
°ú¤­¿ô
.IR flag ,
.IR lorder ,
.I psize
¤Ë»ØÄꤵ¤ì¤¿ÃͤÏ̵»ë¤µ¤ì¡¢
¥Ä¥ê¡¼¤¬ºî¤é¤ì¤¿»þ¤Ë»È¤Ã¤¿Ãͤ¬ÍѤ¤¤é¤ì¤ë¡£
.PP
.\"O Forward sequential scans of a tree are from the least key to the greatest.
¥Ä¥ê¡¼¤ÎÁ°Êý½ç¸¡º÷¤Ï¡¢ºÇ¾®¥­¡¼¤«¤éºÇÂ祭¡¼¤Ë¸þ¤«¤Ã¤Æ¹Ô¤ï¤ì¤ë¡£
.PP
.\"O Space freed up by deleting key/data pairs from the tree is never reclaimed,
.\"O although it is normally made available for reuse.
.\"O This means that the btree storage structure is grow-only.
.\"O The only solutions are to avoid excessive deletions, or to create a fresh
.\"O tree periodically from a scan of an existing one.
¥Ä¥ê¡¼¤«¤é¥­¡¼/¥Ç¡¼¥¿ÂФ¬ºï½ü¤µ¤ì¤ë¤³¤È¤Ë¤è¤Ã¤Æ¤Ç¤­¤¿¥¹¥Ú¡¼¥¹¤Ï¡¢
Ä̾ïºÆÍøÍѤǤ­¤ë·Á¤Ë¤Ê¤Ã¤Æ¤¤¤ë¤¬ºÆÍøÍѤµ¤ì¤ë¤³¤È¤Ï̵¤¤¡£
¤Ä¤Þ¤ê brtee µ­²±¹½Â¤¤ÏÈîÂ礹¤ë°ìÊý¤Ç¤¢¤ë¡£
Âкö¤Ï²áÅ٤κï½ü¤òÈò¤±¤ë¤«¡¢
¸ºß¤¹¤ë¥Ä¥ê¡¼¤òÄ´¤Ù¤ÆÄê´üŪ¤Ë¿·¤·¤¤¥Ä¥ê¡¼¤òºî¤ë¤«¡¢¤À¤±¤Ç¤¢¤ë¡£
.PP
.\"O Searches, insertions, and deletions in a btree will all complete in
.\"O O lg base N where base is the average fill factor.
.\"O Often, inserting ordered data into btrees results in a low fill factor.
.\"O This implementation has been modified to make ordered insertion the best
.\"O case, resulting in a much better than normal page fill factor.
.SH ¥¨¥é¡¼
.\"O The
.\"O .I btree
.\"O access method routines may fail and set
.\"O .I errno
.\"O for any of the errors specified for the library routine
.\"O .BR dbopen (3).
.I btree
¥¢¥¯¥»¥¹¥á¥½¥Ã¥É¥ë¡¼¥Á¥ó¤Ï¼ºÇÔ¤¹¤ë¤È¡¢¥é¥¤¥Ö¥é¥ê¥ë¡¼¥Á¥ó
.BR dbopen (3)
¤ÇÄêµÁ¤µ¤ì¤Æ¤¤¤ë¥¨¥é¡¼¤Î¤¤¤º¤ì¤«¤ò
.I errno
¤È¤·¤ÆÊÖ¤¹¡£
.\"O .SH BUGS
.SH ¥Ð¥°
.\"O Only big and little endian byte order is supported.
¥Ð¥¤¥È¥ª¡¼¥À¡¼¤È¤·¤Æ¤Ï¥Ó¥Ã¥°¥¨¥ó¥Ç¥£¥¢¥ó¤È¥ê¥È¥ë¥¨¥ó¥Ç¥£¥¢¥ó¤Î¤ß¤¬
¥µ¥Ý¡¼¥È¤µ¤ì¤Æ¤¤¤ë¡£
.SH ´ØÏ¢¹àÌÜ
.BR dbopen (3),
.BR hash (3),
.BR mpool (3),
.BR recno (3)
.sp
.IR "The Ubiquitous B-tree" ,
Douglas Comer, ACM Comput. Surv. 11, 2 (June 1979), 121-138.
.sp
.IR "Prefix B-trees" ,
Bayer and Unterauer, ACM Transactions on Database Systems, Vol. 2, 1
(March 1977), 11-26.
.sp
.IR "The Art of Computer Programming Vol. 3: Sorting and Searching" ,
D.E. Knuth, 1968, pp 471-480.