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1 | .\" Copyright (c) 1990, 1993 | |
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28 | .\" @(#)recno.3 8.5 (Berkeley) 8/18/94 | |
29 | .\" $FreeBSD: src/lib/libc/db/man/recno.3,v 1.9 2007/01/09 00:27:51 imp Exp $ | |
30 | .\" | |
31 | .Dd August 18, 1994 | |
32 | .Dt RECNO 3 | |
33 | .Os | |
34 | .Sh NAME | |
35 | .Nm recno | |
36 | .Nd "record number database access method" | |
37 | .Sh SYNOPSIS | |
38 | .In sys/types.h | |
39 | .In db.h | |
40 | .Sh DESCRIPTION | |
41 | The routine | |
42 | .Fn dbopen | |
43 | is the library interface to database files. | |
44 | One of the supported file formats is record number files. | |
45 | The general description of the database access methods is in | |
46 | .Xr dbopen 3 , | |
47 | this manual page describes only the | |
48 | .Nm | |
49 | specific information. | |
50 | .Pp | |
51 | The record number data structure is either variable or fixed-length | |
52 | records stored in a flat-file format, accessed by the logical record | |
53 | number. | |
54 | The existence of record number five implies the existence of records | |
55 | one through four, and the deletion of record number one causes | |
56 | record number five to be renumbered to record number four, as well | |
57 | as the cursor, if positioned after record number one, to shift down | |
58 | one record. | |
59 | .Pp | |
60 | The | |
61 | .Nm | |
62 | access method specific data structure provided to | |
63 | .Fn dbopen | |
64 | is defined in the | |
65 | .In db.h | |
66 | include file as follows: | |
67 | .Bd -literal | |
68 | typedef struct { | |
69 | u_long flags; | |
70 | u_int cachesize; | |
71 | u_int psize; | |
72 | int lorder; | |
73 | size_t reclen; | |
74 | u_char bval; | |
75 | char *bfname; | |
76 | } RECNOINFO; | |
77 | .Ed | |
78 | .Pp | |
79 | The elements of this structure are defined as follows: | |
80 | .Bl -tag -width indent | |
81 | .It Va flags | |
82 | The flag value is specified by | |
83 | .Em or Ns 'ing | |
84 | any of the following values: | |
85 | .Bl -tag -width indent | |
86 | .It Dv R_FIXEDLEN | |
87 | The records are fixed-length, not byte delimited. | |
88 | The structure element | |
89 | .Va reclen | |
90 | specifies the length of the record, and the structure element | |
91 | .Va bval | |
92 | is used as the pad character. | |
93 | Any records, inserted into the database, that are less than | |
94 | .Va reclen | |
95 | bytes long are automatically padded. | |
96 | .It Dv R_NOKEY | |
97 | In the interface specified by | |
98 | .Fn dbopen , | |
99 | the sequential record retrieval fills in both the caller's key and | |
100 | data structures. | |
101 | If the | |
102 | .Dv R_NOKEY | |
103 | flag is specified, the | |
104 | .Em cursor | |
105 | routines are not required to fill in the key structure. | |
106 | This permits applications to retrieve records at the end of files without | |
107 | reading all of the intervening records. | |
108 | .It Dv R_SNAPSHOT | |
109 | This flag requires that a snapshot of the file be taken when | |
110 | .Fn dbopen | |
111 | is called, instead of permitting any unmodified records to be read from | |
112 | the original file. | |
113 | .El | |
114 | .It Va cachesize | |
115 | A suggested maximum size, in bytes, of the memory cache. | |
116 | This value is | |
117 | .Em only | |
118 | advisory, and the access method will allocate more memory rather than fail. | |
119 | If | |
120 | .Va cachesize | |
121 | is 0 (no size is specified) a default cache is used. | |
122 | .It Va psize | |
123 | The | |
124 | .Nm | |
125 | access method stores the in-memory copies of its records | |
126 | in a btree. | |
127 | This value is the size (in bytes) of the pages used for nodes in that tree. | |
128 | If | |
129 | .Va psize | |
130 | is 0 (no page size is specified) a page size is chosen based on the | |
131 | underlying file system I/O block size. | |
132 | See | |
133 | .Xr btree 3 | |
134 | for more information. | |
135 | .It Va lorder | |
136 | The byte order for integers in the stored database metadata. | |
137 | The number should represent the order as an integer; for example, | |
138 | big endian order would be the number 4,321. | |
139 | If | |
140 | .Va lorder | |
141 | is 0 (no order is specified) the current host order is used. | |
142 | .It Va reclen | |
143 | The length of a fixed-length record. | |
144 | .It Va bval | |
145 | The delimiting byte to be used to mark the end of a record for | |
146 | variable-length records, and the pad character for fixed-length | |
147 | records. | |
148 | If no value is specified, newlines | |
149 | .Pq Dq \en | |
150 | are used to mark the end | |
151 | of variable-length records and fixed-length records are padded with | |
152 | spaces. | |
153 | .It Va bfname | |
154 | The | |
155 | .Nm | |
156 | access method stores the in-memory copies of its records | |
157 | in a btree. | |
158 | If | |
159 | .Va bfname | |
160 | is | |
161 | .No non\- Ns Dv NULL , | |
162 | it specifies the name of the btree file, | |
163 | as if specified as the file name for a | |
164 | .Fn dbopen | |
165 | of a btree file. | |
166 | .El | |
167 | .Pp | |
168 | The data part of the key/data pair used by the | |
169 | .Nm | |
170 | access method | |
171 | is the same as other access methods. | |
172 | The key is different. | |
173 | The | |
174 | .Va data | |
175 | field of the key should be a pointer to a memory location of type | |
176 | .Ft recno_t , | |
177 | as defined in the | |
178 | .In db.h | |
179 | include file. | |
180 | This type is normally the largest unsigned integral type available to | |
181 | the implementation. | |
182 | The | |
183 | .Va size | |
184 | field of the key should be the size of that type. | |
185 | .Pp | |
186 | Because there can be no meta-data associated with the underlying | |
187 | .Nm | |
188 | access method files, any changes made to the default values | |
189 | (e.g.\& fixed record length or byte separator value) must be explicitly | |
190 | specified each time the file is opened. | |
191 | .Pp | |
192 | In the interface specified by | |
193 | .Fn dbopen , | |
194 | using the | |
195 | .Va put | |
196 | interface to create a new record will cause the creation of multiple, | |
197 | empty records if the record number is more than one greater than the | |
198 | largest record currently in the database. | |
199 | .Sh ERRORS | |
200 | The | |
201 | .Nm | |
202 | access method routines may fail and set | |
203 | .Va errno | |
204 | for any of the errors specified for the library routine | |
205 | .Xr dbopen 3 | |
206 | or the following: | |
207 | .Bl -tag -width Er | |
208 | .It Bq Er EINVAL | |
209 | An attempt was made to add a record to a fixed-length database that | |
210 | was too large to fit. | |
211 | .El | |
212 | .Sh SEE ALSO | |
213 | .Xr btree 3 , | |
214 | .Xr dbopen 3 , | |
215 | .Xr hash 3 , | |
216 | .Xr mpool 3 | |
217 | .Rs | |
218 | .%T "Document Processing in a Relational Database System" | |
219 | .%A Michael Stonebraker | |
220 | .%A Heidi Stettner | |
221 | .%A Joseph Kalash | |
222 | .%A Antonin Guttman | |
223 | .%A Nadene Lynn | |
224 | .%R "Memorandum No. UCB/ERL M82/32" | |
225 | .%D May 1982 | |
226 | .Re | |
227 | .Sh BUGS | |
228 | Only big and little endian byte order is supported. |