| hash.3 (84306) | hash.3 (108087) |
|---|---|
| 1.\" Copyright (c) 1990, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. --- 16 unchanged lines hidden (view full) --- 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)hash.3 8.6 (Berkeley) 8/18/94 | 1.\" Copyright (c) 1990, 1993 2.\" The Regents of the University of California. All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. --- 16 unchanged lines hidden (view full) --- 25.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30.\" SUCH DAMAGE. 31.\" 32.\" @(#)hash.3 8.6 (Berkeley) 8/18/94 |
| 33.\" $FreeBSD: head/lib/libc/db/man/hash.3 84306 2001-10-01 16:09:29Z ru $ | 33.\" $FreeBSD: head/lib/libc/db/man/hash.3 108087 2002-12-19 09:40:28Z ru $ |
| 34.\" 35.Dd August 18, 1994 36.Dt HASH 3 37.Os 38.Sh NAME 39.Nm hash 40.Nd "hash database access method" 41.Sh SYNOPSIS --- 30 unchanged lines hidden (view full) --- 72 u_int32_t (*hash)(const void *, size_t); 73 int lorder; 74} HASHINFO; 75.Ed 76.Pp 77The elements of this structure are as follows: 78.Bl -tag -width indent 79.It Va bsize | 34.\" 35.Dd August 18, 1994 36.Dt HASH 3 37.Os 38.Sh NAME 39.Nm hash 40.Nd "hash database access method" 41.Sh SYNOPSIS --- 30 unchanged lines hidden (view full) --- 72 u_int32_t (*hash)(const void *, size_t); 73 int lorder; 74} HASHINFO; 75.Ed 76.Pp 77The elements of this structure are as follows: 78.Bl -tag -width indent 79.It Va bsize |
| 80.Va Bsize | 80The 81.Va bsize 82element |
| 81defines the 82.Nm 83table bucket size, and is, by default, 256 bytes. 84It may be preferable to increase the page size for disk-resident tables 85and tables with large data items. 86.It Va ffactor | 83defines the 84.Nm 85table bucket size, and is, by default, 256 bytes. 86It may be preferable to increase the page size for disk-resident tables 87and tables with large data items. 88.It Va ffactor |
| 87.Va Ffactor | 89The 90.Va ffactor 91element |
| 88indicates a desired density within the 89.Nm 90table. 91It is an approximation of the number of keys allowed to accumulate in any 92one bucket, determining when the 93.Nm 94table grows or shrinks. 95The default value is 8. 96.It Va nelem | 92indicates a desired density within the 93.Nm 94table. 95It is an approximation of the number of keys allowed to accumulate in any 96one bucket, determining when the 97.Nm 98table grows or shrinks. 99The default value is 8. 100.It Va nelem |
| 97.Va Nelem | 101The 102.Va nelem 103element |
| 98is an estimate of the final size of the 99.Nm 100table. 101If not set or set too low, 102.Nm 103tables will expand gracefully as keys 104are entered, although a slight performance degradation may be noticed. 105The default value is 1. 106.It Va cachesize 107A suggested maximum size, in bytes, of the memory cache. 108This value is 109.Em only 110advisory, and the access method will allocate more memory rather 111than fail. 112.It Va hash | 104is an estimate of the final size of the 105.Nm 106table. 107If not set or set too low, 108.Nm 109tables will expand gracefully as keys 110are entered, although a slight performance degradation may be noticed. 111The default value is 1. 112.It Va cachesize 113A suggested maximum size, in bytes, of the memory cache. 114This value is 115.Em only 116advisory, and the access method will allocate more memory rather 117than fail. 118.It Va hash |
| 113.Va Hash | 119The 120.Va hash 121element |
| 114is a user defined 115.Nm 116function. 117Since no 118.Nm 119function performs equally well on all possible data, the 120user may find that the built-in 121.Nm --- 14 unchanged lines hidden (view full) --- 136is 0 (no order is specified) the current host order is used. 137If the file already exists, the specified value is ignored and the 138value specified when the tree was created is used. 139.El 140.Pp 141If the file already exists (and the 142.Dv O_TRUNC 143flag is not specified), the | 122is a user defined 123.Nm 124function. 125Since no 126.Nm 127function performs equally well on all possible data, the 128user may find that the built-in 129.Nm --- 14 unchanged lines hidden (view full) --- 144is 0 (no order is specified) the current host order is used. 145If the file already exists, the specified value is ignored and the 146value specified when the tree was created is used. 147.El 148.Pp 149If the file already exists (and the 150.Dv O_TRUNC 151flag is not specified), the |
| 144values specified for the parameters | 152values specified for the |
| 145.Va bsize , ffactor , lorder 146and 147.Va nelem | 153.Va bsize , ffactor , lorder 154and 155.Va nelem |
| 156arguments |
|
| 148are 149ignored and the values specified when the tree was created are used. 150.Pp 151If a 152.Nm 153function is specified, 154.Fn hash_open 155will attempt to determine if the --- 36 unchanged lines hidden --- | 157are 158ignored and the values specified when the tree was created are used. 159.Pp 160If a 161.Nm 162function is specified, 163.Fn hash_open 164will attempt to determine if the --- 36 unchanged lines hidden --- |