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diff --git a/lib/libc/db/man/btree.3 b/lib/libc/db/man/btree.3 deleted file mode 100644 index 8284b21..0000000 --- a/lib/libc/db/man/btree.3 +++ /dev/null @@ -1,233 +0,0 @@ -.\" Copyright (c) 1990, 1993 -.\" The Regents of the University of California. All rights reserved. -.\" -.\" Redistribution and use in source and binary forms, with or without -.\" modification, are permitted provided that the following conditions -.\" are met: -.\" 1. Redistributions of source code must retain the above copyright -.\" notice, this list of conditions and the following disclaimer. -.\" 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. -.\" -.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND -.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE -.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE -.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE -.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL -.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS -.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) -.\" 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 -.\" -.TH BTREE 3 "August 18, 1994" -.\".UC 7 -.SH NAME -btree \- btree database access method -.SH SYNOPSIS -.nf -.ft B -#include <sys/types.h> -#include <db.h> -.ft R -.fi -.SH DESCRIPTION -The routine -.IR dbopen -is the library interface to database files. -One of the supported file formats is btree files. -The general description of the database access methods is in -.IR dbopen (3), -this manual page describes only the btree specific information. -.PP -The btree data structure is a sorted, balanced tree structure storing -associated key/data pairs. -.PP -The btree access method specific data structure provided to -.I dbopen -is defined in the <db.h> include file as follows: -.PP -typedef struct { -.RS -u_long flags; -.br -u_int cachesize; -.br -int maxkeypage; -.br -int minkeypage; -.br -u_int psize; -.br -int (*compare)(const DBT *key1, const DBT *key2); -.br -size_t (*prefix)(const DBT *key1, const DBT *key2); -.br -int lorder; -.RE -} BTREEINFO; -.PP -The elements of this structure are as follows: -.TP -flags -The flag value is specified by -.IR or 'ing -any of the following values: -.RS -.TP -R_DUP -Permit duplicate keys in the tree, i.e. permit insertion if the key to be -inserted already exists in the tree. -The default behavior, as described in -.IR dbopen (3), -is to overwrite a matching key when inserting a new key or to fail if -the R_NOOVERWRITE flag is specified. -The R_DUP flag is overridden by the R_NOOVERWRITE flag, and if the -R_NOOVERWRITE flag is specified, attempts to insert duplicate keys into -the tree will fail. -.IP -If the database contains duplicate keys, the order of retrieval of -key/data pairs is undefined if the -.I get -routine is used, however, -.I seq -routine calls with the R_CURSOR flag set will always return the logical -``first'' of any group of duplicate keys. -.RE -.TP -cachesize -A suggested maximum size (in bytes) of the memory cache. -This value is -.B only -advisory, and the access method will allocate more memory rather than fail. -Since every search examines the root page of the tree, caching the most -recently used pages substantially improves access time. -In addition, physical writes are delayed as long as possible, so a moderate -cache can reduce the number of I/O operations significantly. -Obviously, using a cache increases (but only increases) the likelihood of -corruption or lost data if the system crashes while a tree is being modified. -If -.I cachesize -is 0 (no size is specified) a default cache is used. -.TP -maxkeypage -The maximum number of keys which will be stored on any single page. -Not currently implemented. -.\" 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 -minkeypage -The minimum number of keys which will be stored on any single page. -This value is used to determine which keys will be stored on overflow -pages, i.e. if a key or data item is longer than the pagesize divided -by the minkeypage value, it will be stored on overflow pages instead -of in the page itself. -If -.I minkeypage -is 0 (no minimum number of keys is specified) a value of 2 is used. -.TP -psize -Page size is the size (in bytes) of the pages used for nodes in the tree. -The minimum page size is 512 bytes and the maximum page size is 64K. -If -.I psize -is 0 (no page size is specified) a page size is chosen based on the -underlying file system I/O block size. -.TP -compare -Compare is the key comparison function. -It must return an integer less than, equal to, or greater than zero if the -first key argument is considered to be respectively less than, equal to, -or greater than the second key argument. -The same comparison function must be used on a given tree every time it -is opened. -If -.I compare -is NULL (no comparison function is specified), the keys are compared -lexically, with shorter keys considered less than longer keys. -.TP -prefix -Prefix is the prefix comparison function. -If specified, this routine must return the number of bytes of the second key -argument which are necessary to determine that it is greater than the first -key argument. -If the keys are equal, the key length should be returned. -Note, the usefulness of this routine is very data dependent, but, in some -data sets can produce significantly reduced tree sizes and search times. -If -.I prefix -is NULL (no prefix function is specified), -.B and -no comparison function is specified, a default lexical comparison routine -is used. -If -.I prefix -is NULL and a comparison routine is specified, no prefix comparison is -done. -.TP -lorder -The byte order for integers in the stored database metadata. -The number should represent the order as an integer; for example, -big endian order would be the number 4,321. -If -.I lorder -is 0 (no order is specified) the current host order is used. -.PP -If the file already exists (and the O_TRUNC flag is not specified), the -values specified for the parameters flags, lorder and psize are ignored -in favor of the values used when the tree was created. -.PP -Forward sequential scans of a tree are from the least key to the greatest. -.PP -Space freed up by deleting key/data pairs from the tree is never reclaimed, -although it is normally made available for reuse. -This means that the btree storage structure is grow-only. -The only solutions are to avoid excessive deletions, or to create a fresh -tree periodically from a scan of an existing one. -.PP -Searches, insertions, and deletions in a btree will all complete in -O lg base N where base is the average fill factor. -Often, inserting ordered data into btrees results in a low fill factor. -This implementation has been modified to make ordered insertion the best -case, resulting in a much better than normal page fill factor. -.SH ERRORS -The -.I btree -access method routines may fail and set -.I errno -for any of the errors specified for the library routine -.IR dbopen (3). -.SH "SEE ALSO" -.IR dbopen (3), -.IR hash (3), -.IR mpool (3), -.IR 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. -.SH BUGS -Only big and little endian byte order is supported. |
