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1 perry 1 RECNO
2 !!!RECNO
3 NAME
4 SYNOPSIS
5 DESCRIPTION
6 ERRORS
7 SEE ALSO
8 BUGS
9 ----
10 !!NAME
11
12
13 recno - record number database access method
14 !!SYNOPSIS
15
16
17 __#include
18 __
19 !!DESCRIPTION
20
21
22 The routine ''dbopen'' is the library interface to
23 database files. One of the supported file formats is record
24 number files. The general description of the database access
25 methods is in dbopen(3), this manual page describes
26 only the recno specific information.
27
28
29 The record number data structure is either variable or
30 fixed-length records stored in a flat-file format, accessed
31 by the logical record number. The existence of record number
32 five implies the existence of records one through four, and
33 the deletion of record number one causes record number five
34 to be renumbered to record number four, as well as the
35 cursor, if positioned after record number one, to shift down
36 one record.
37
38
39 The recno access method specific data structure provided to
40 ''dbopen'' is defined in the
41 ''
42
43
44 typedef struct {
45
46
47 u_long flags;
48 u_int cachesize;
49 u_int psize;
50 int lorder;
51 size_t reclen;
52 u_char bval;
53 char *bfname;
54
55
56 } RECNOINFO;
57
58
59 The elements of this structure are defined as
60 follows:
61
62
63 flags
64
65
66 The flag value is specified by ''or'''ing any of the
67 following values:
68
69
70 R_FIXEDLEN
71
72
73 The records are fixed-length, not byte delimited. The
74 structure element ''reclen'' specifies the length of the
75 record, and the structure element ''bval'' is used as the
76 pad character. Any records, inserted into the database, that
77 are less than ''reclen'' bytes long are automatically
78 padded.
79
80
81 R_NOKEY
82
83
84 In the interface specified by ''dbopen'', the sequential
85 record retrieval fills in both the caller's key and data
86 structures. If the R_NOKEY flag is specified, the
87 ''cursor'' routines are not required to fill in the key
88 structure. This permits applications to retrieve records at
89 the end of files without reading all of the intervening
90 records.
91
92
93 R_SNAPSHOT
94
95
96 This flag requires that a snapshot of the file be taken when
97 ''dbopen'' is called, instead of permitting any
98 unmodified records to be read from the original
99 file.
100
101
102 cachesize
103
104
105 A suggested maximum size, in bytes, of the memory cache.
106 This value is __only__ advisory, and the access method
107 will allocate more memory rather than fail. If
108 ''cachesize'' is 0 (no size is specified) a default cache
109 is used.
110
111
112 psize
113
114
115 The recno access method stores the in-memory copies of its
116 records in a btree. This value is the size (in bytes) of the
117 pages used for nodes in that tree. If ''psize'' is 0 (no
118 page size is specified) a page size is chosen based on the
119 underlying file system I/O block size. See btree(3)
120 for more information.
121
122
123 lorder
124
125
126 The byte order for integers in the stored database metadata.
127 The number should represent the order as an integer; for
128 example, big endian order would be the number 4,321. If
129 ''lorder'' is 0 (no order is specified) the current host
130 order is used.
131
132
133 reclen
134
135
136 The length of a fixed-length record.
137
138
139 bval
140
141
142 The delimiting byte to be used to mark the end of a record
143 for variable-length records, and the pad character for
144 fixed-length records. If no value is specified, newlines
145 (``n'') are used to mark the end of variable-length records
146 and fixed-length records are padded with
147 spaces.
148
149
150 bfname
151
152
153 The recno access method stores the in-memory copies of its
154 records in a btree. If bfname is non-NULL, it specifies the
155 name of the btree file, as if specified as the file name for
156 a dbopen of a btree file.
157
158
159 The data part of the key/data pair used by the recno access
160 method is the same as other access methods. The key is
161 different. The ''data'' field of the key should be a
162 pointer to a memory location of type ''recno_t'', as
163 defined in the
164 ''size'' field of the key should be
165 the size of that type.
166
167
168 Because there can be no meta-data associated with the
169 underlying recno access method files, any changes made to
170 the default values (e.g. fixed record length or byte
171 separator value) must be explicitly specified each time the
172 file is opened.
173
174
175 In the interface specified by ''dbopen'', using the
176 ''put'' interface to create a new record will cause the
177 creation of multiple, empty records if the record number is
178 more than one greater than the largest record currently in
179 the database.
180 !!ERRORS
181
182
183 The ''recno'' access method routines may fail and set
184 ''errno'' for any of the errors specified for the library
185 routine dbopen(3) or the following:
186
187
188 [[EINVAL]
189
190
191 An attempt was made to add a record to a fixed-length
192 database that was too large to fit.
193 !!SEE ALSO
194
195
196 btree(3) dbopen(3), hash(3),
197 mpool(3),
198
199
200 ''Document Processing in a Relational Database System'',
201 Michael Stonebraker, Heidi Stettner, Joseph Kalash, Antonin
202 Guttman, Nadene Lynn, Memorandum No. UCB/ERL M82/32, May
203 1982.
204 !!BUGS
205
206
207 Only big and little endian byte order is
208 supported.
209 ----
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