fbbd9655e5
Renumber cluase 4 to 3, per what everybody else did when BSD granted them permission to remove clause 3. My insistance on keeping the same numbering for legal reasons is too pedantic, so give up on that point. Submitted by: Jan Schaumann <jschauma@stevens.edu> Pull Request: https://github.com/freebsd/freebsd/pull/96
229 lines
6.6 KiB
Groff
229 lines
6.6 KiB
Groff
.\" Copyright (c) 1990, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. Neither the name of the University nor the names of its contributors
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.\" may be used to endorse or promote products derived from this software
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.\" without specific prior written permission.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)recno.3 8.5 (Berkeley) 8/18/94
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.\" $FreeBSD$
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.\"
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.Dd August 18, 1994
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.Dt RECNO 3
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.Os
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.Sh NAME
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.Nm recno
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.Nd "record number database access method"
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.Sh SYNOPSIS
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.In sys/types.h
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.In db.h
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.Sh DESCRIPTION
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The routine
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.Fn dbopen
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is the library interface to database files.
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One of the supported file formats is record number files.
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The general description of the database access methods is in
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.Xr dbopen 3 ,
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this manual page describes only the
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.Nm
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specific information.
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.Pp
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The record number data structure is either variable or fixed-length
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records stored in a flat-file format, accessed by the logical record
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number.
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The existence of record number five implies the existence of records
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one through four, and the deletion of record number one causes
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record number five to be renumbered to record number four, as well
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as the cursor, if positioned after record number one, to shift down
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one record.
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.Pp
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The
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.Nm
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access method specific data structure provided to
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.Fn dbopen
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is defined in the
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.In db.h
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include file as follows:
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.Bd -literal
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typedef struct {
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u_long flags;
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u_int cachesize;
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u_int psize;
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int lorder;
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size_t reclen;
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u_char bval;
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char *bfname;
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} RECNOINFO;
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.Ed
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.Pp
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The elements of this structure are defined as follows:
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.Bl -tag -width indent
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.It Va flags
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The flag value is specified by
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.Em or Ns 'ing
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any of the following values:
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.Bl -tag -width indent
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.It Dv R_FIXEDLEN
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The records are fixed-length, not byte delimited.
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The structure element
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.Va reclen
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specifies the length of the record, and the structure element
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.Va bval
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is used as the pad character.
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Any records, inserted into the database, that are less than
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.Va reclen
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bytes long are automatically padded.
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.It Dv R_NOKEY
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In the interface specified by
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.Fn dbopen ,
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the sequential record retrieval fills in both the caller's key and
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data structures.
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If the
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.Dv R_NOKEY
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flag is specified, the
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.Em cursor
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routines are not required to fill in the key structure.
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This permits applications to retrieve records at the end of files without
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reading all of the intervening records.
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.It Dv R_SNAPSHOT
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This flag requires that a snapshot of the file be taken when
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.Fn dbopen
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is called, instead of permitting any unmodified records to be read from
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the original file.
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.El
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.It Va cachesize
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A suggested maximum size, in bytes, of the memory cache.
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This value is
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.Em only
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advisory, and the access method will allocate more memory rather than fail.
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If
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.Va cachesize
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is 0 (no size is specified) a default cache is used.
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.It Va psize
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The
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.Nm
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access method stores the in-memory copies of its records
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in a btree.
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This value is the size (in bytes) of the pages used for nodes in that tree.
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If
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.Va psize
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is 0 (no page size is specified) a page size is chosen based on the
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underlying file system I/O block size.
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See
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.Xr btree 3
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for more information.
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.It Va lorder
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The byte order for integers in the stored database metadata.
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The number should represent the order as an integer; for example,
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big endian order would be the number 4,321.
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If
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.Va lorder
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is 0 (no order is specified) the current host order is used.
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.It Va reclen
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The length of a fixed-length record.
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.It Va bval
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The delimiting byte to be used to mark the end of a record for
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variable-length records, and the pad character for fixed-length
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records.
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If no value is specified, newlines
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.Pq Dq \en
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are used to mark the end
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of variable-length records and fixed-length records are padded with
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spaces.
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.It Va bfname
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The
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.Nm
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access method stores the in-memory copies of its records
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in a btree.
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If
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.Va bfname
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is
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.No non\- Ns Dv NULL ,
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it specifies the name of the btree file,
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as if specified as the file name for a
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.Fn dbopen
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of a btree file.
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.El
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.Pp
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The data part of the key/data pair used by the
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.Nm
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access method
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is the same as other access methods.
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The key is different.
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The
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.Va data
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field of the key should be a pointer to a memory location of type
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.Ft recno_t ,
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as defined in the
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.In db.h
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include file.
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This type is normally the largest unsigned integral type available to
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the implementation.
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The
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.Va size
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field of the key should be the size of that type.
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.Pp
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Because there can be no meta-data associated with the underlying
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.Nm
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access method files, any changes made to the default values
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(e.g.\& fixed record length or byte separator value) must be explicitly
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specified each time the file is opened.
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.Pp
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In the interface specified by
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.Fn dbopen ,
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using the
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.Va put
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interface to create a new record will cause the creation of multiple,
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empty records if the record number is more than one greater than the
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largest record currently in the database.
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.Sh ERRORS
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The
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.Nm
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access method routines may fail and set
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.Va errno
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for any of the errors specified for the library routine
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.Xr dbopen 3
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or the following:
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.Bl -tag -width Er
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.It Bq Er EINVAL
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An attempt was made to add a record to a fixed-length database that
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was too large to fit.
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.El
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.Sh SEE ALSO
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.Xr btree 3 ,
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.Xr dbopen 3 ,
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.Xr hash 3 ,
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.Xr mpool 3
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.Rs
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.%T "Document Processing in a Relational Database System"
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.%A Michael Stonebraker
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.%A Heidi Stettner
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.%A Joseph Kalash
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.%A Antonin Guttman
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.%A Nadene Lynn
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.%R "Memorandum No. UCB/ERL M82/32"
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.%D May 1982
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.Re
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.Sh BUGS
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Only big and little endian byte order is supported.
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