xref: /dragonfly/lib/libc/db/man/recno.3 (revision 8a7bdfea) 
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28.\"	@(#)recno.3	8.5 (Berkeley) 8/18/94
29.\" $FreeBSD: src/lib/libc/db/man/recno.3,v 1.4.2.2 2001/12/14 18:33:49 ru Exp $
30.\" $DragonFly: src/lib/libc/db/man/recno.3,v 1.5 2007/08/18 20:48:47 swildner Exp $
31.\"
32.Dd August 18, 1994
33.Dt RECNO 3
34.Os
35.Sh NAME
36.Nm recno
37.Nd "record number database access method"
38.Sh LIBRARY
39.Lb libc
40.Sh SYNOPSIS
41.In sys/types.h
42.In db.h
43.Sh DESCRIPTION
44The routine
45.Fn dbopen
46is the library interface to database files.
47One of the supported file formats is record number files.
48The general description of the database access methods is in
49.Xr dbopen 3 ,
50this manual page describes only the
51.Nm
52specific information.
53.Pp
54The record number data structure is either variable or fixed-length
55records stored in a flat-file format, accessed by the logical record
56number.
57The existence of record number five implies the existence of records
58one through four, and the deletion of record number one causes
59record number five to be renumbered to record number four, as well
60as the cursor, if positioned after record number one, to shift down
61one record.
62.Pp
63The
64.Nm
65access method specific data structure provided to
66.Fn dbopen
67is defined in the
68.In db.h
69include file as follows:
70.Bd -literal
71typedef struct {
72	u_long flags;
73	u_int cachesize;
74	u_int psize;
75	int lorder;
76	size_t reclen;
77	u_char bval;
78	char *bfname;
79} RECNOINFO;
80.Ed
81.Pp
82The elements of this structure are defined as follows:
83.Bl -tag -width indent
84.It Va flags
85The flag value is specified by
86.Em or Ns 'ing
87any of the following values:
88.Bl -tag -width indent
89.It Dv R_FIXEDLEN
90The records are fixed-length, not byte delimited.
91The structure element
92.Va reclen
93specifies the length of the record, and the structure element
94.Va bval
95is used as the pad character.
96Any records, inserted into the database, that are less than
97.Va reclen
98bytes long are automatically padded.
99.It Dv R_NOKEY
100In the interface specified by
101.Fn dbopen ,
102the sequential record retrieval fills in both the caller's key and
103data structures.
104If the
105.Dv R_NOKEY
106flag is specified, the
107.Em cursor
108routines are not required to fill in the key structure.
109This permits applications to retrieve records at the end of files without
110reading all of the intervening records.
111.It Dv R_SNAPSHOT
112This flag requires that a snapshot of the file be taken when
113.Fn dbopen
114is called, instead of permitting any unmodified records to be read from
115the original file.
116.El
117.It Va cachesize
118A suggested maximum size, in bytes, of the memory cache.
119This value is
120.Em only
121advisory, and the access method will allocate more memory rather than fail.
122If
123.Va cachesize
124is 0 (no size is specified) a default cache is used.
125.It Va psize
126The
127.Nm
128access method stores the in-memory copies of its records
129in a btree.
130This value is the size (in bytes) of the pages used for nodes in that tree.
131If
132.Va psize
133is 0 (no page size is specified) a page size is chosen based on the
134underlying file system I/O block size.
135See
136.Xr btree 3
137for more information.
138.It Va lorder
139The byte order for integers in the stored database metadata.
140The number should represent the order as an integer; for example,
141big endian order would be the number 4,321.
142If
143.Va lorder
144is 0 (no order is specified) the current host order is used.
145.It Va reclen
146The length of a fixed-length record.
147.It Va bval
148The delimiting byte to be used to mark the end of a record for
149variable-length records, and the pad character for fixed-length
150records.
151If no value is specified, newlines
152.Pq Dq \en
153are used to mark the end
154of variable-length records and fixed-length records are padded with
155spaces.
156.It Va bfname
157The
158.Nm
159access method stores the in-memory copies of its records
160in a btree.
161If
162.Va bfname
163is
164.No non\- Ns Dv NULL ,
165it specifies the name of the btree file,
166as if specified as the file name for a
167.Fn dbopen
168of a btree file.
169.El
170.Pp
171The data part of the key/data pair used by the
172.Nm
173access method
174is the same as other access methods.
175The key is different.
176The
177.Va data
178field of the key should be a pointer to a memory location of type
179.Ft recno_t ,
180as defined in the
181.In db.h
182include file.
183This type is normally the largest unsigned integral type available to
184the implementation.
185The
186.Va size
187field of the key should be the size of that type.
188.Pp
189Because there can be no meta-data associated with the underlying
190.Nm
191access method files, any changes made to the default values
192(e.g. fixed record length or byte separator value) must be explicitly
193specified each time the file is opened.
194.Pp
195In the interface specified by
196.Fn dbopen ,
197using the
198.Va put
199interface to create a new record will cause the creation of multiple,
200empty records if the record number is more than one greater than the
201largest record currently in the database.
202.Sh ERRORS
203The
204.Nm
205access method routines may fail and set
206.Va errno
207for any of the errors specified for the library routine
208.Xr dbopen 3
209or the following:
210.Bl -tag -width Er
211.It Bq Er EINVAL
212An attempt was made to add a record to a fixed-length database that
213was too large to fit.
214.El
215.Sh SEE ALSO
216.Xr btree 3 ,
217.Xr dbopen 3 ,
218.Xr hash 3 ,
219.Xr mpool 3
220.Rs
221.%T "Document Processing in a Relational Database System"
222.%A Michael Stonebraker
223.%A Heidi Stettner
224.%A Joseph Kalash
225.%A Antonin Guttman
226.%A Nadene Lynn
227.%R "Memorandum No. UCB/ERL M82/32"
228.%D May 1982
229.Re
230.Sh BUGS
231Only big and little endian byte order is supported.
232