recno


SYNOPSIS
       #include <sys/types.h>
       #include <db.h>

DESCRIPTION
       The  routine dbopen(3) is the library interface to database files.  One
       of the supported file formats is  record  number  files.   The  general
       description of the database access methods is in dbopen(3), this manual
       page describes only the recno specific information.

       The record number data structure is  either  variable  or  fixed-length
       records  stored  in  a flat-file format, accessed by the logical record
       number.  The existence of record number five implies the  existence  of
       records  one through four, and the deletion of record number one causes
       record number five to be renumbered to record number four, as  well  as
       the  cursor,  if  positioned after record number one, to shift down one
       record.

       The recno access method specific data structure provided  to  dbopen(3)
       is defined in the <db.h> include file as follows:

           typedef struct {
               unsigned long flags;
               unsigned int  cachesize;
               unsigned int  psize;
               int           lorder;
               size_t        reclen;
               unsigned char bval;
               char         *bfname;
           } RECNOINFO;

       The elements of this structure are defined as follows:

       flags  The  flag value is specified by or'ing any of the following val-
              ues:

              R_FIXEDLEN
                     The records are fixed-length, not  byte  delimited.   The
                     structure  element  reclen  specifies  the  length of the
                     record, and the structure element bval is used as the pad
                     character.  Any records, inserted into the database, that
                     are less than reclen bytes long are automatically padded.

              R_NOKEY
                     In the interface specified by dbopen(3),  the  sequential
                     record  retrieval fills in both the caller's key and data
                     structures.  If the R_NOKEY flag is specified, the cursor
                     routines  are  not required to fill in the key structure.
                     This permits applications to retrieve records at the  end
                     of files without reading all of the intervening records.

              R_SNAPSHOT
                     This  flag  requires that a snapshot of the file be taken

              is specified) a page size is chosen based on the underlying file
              system I/O block size.  See btree(3) for more information.

       lorder The byte order for integers in  the  stored  database  metadata.
              The  number  should represent the order as an integer; for exam-
              ple, big endian order would be the number 4,321.  If lorder is 0
              (no order is specified) the current host order is used.

       reclen The length of a fixed-length record.

       bval   The  delimiting  byte to be used to mark the end of a record for
              variable-length records, and the pad character for  fixed-length
              records.   If no value is specified, newlines ("\n") are used to
              mark the end of variable-length records and fixed-length records
              are padded with spaces.

       bfname The  recno  access  method  stores  the  in-memory copies of its
              records in a btree.  If bfname is  non-NULL,  it  specifies  the
              name  of  the  btree file, as if specified as the filename for a
              dbopen(3) of a btree file.

       The data part of the key/data pair used by the recno access  method  is
       the  same  as  other  access  methods.  The key is different.  The data
       field of the key should be a pointer  to  a  memory  location  of  type
       recno_t,  as  defined in th <db.h> include file.  This type is normally
       the largest unsigned integral type  available  to  the  implementation.
       The size field of the key should be the size of that type.

       Because  there  can be no metadata associated with the underlying recno
       access method files, any changes made  to  the  default  values  (e.g.,
       fixed  record length or byte separator value) must be explicitly speci-
       fied each time the file is opened.

       In the interface specified by dbopen(3), using  the  put  interface  to
       create  a new record will cause the creation of multiple, empty records
       if the record number is more than one greater than the  largest  record
       currently in the database.

ERRORS
       The  recno access method routines may fail and set errno for any of the
       errors specified for the library routine dbopen(3) or the following:

       EINVAL An attempt was made to add a record to a  fixed-length  database
              that was too large to fit.

BUGS
       Only big and little endian byte order is supported.

SEE ALSO
       btree(3), dbopen(3), hash(3), mpool(3)

       Document  Processing  in  a  Relational Database System, Michael Stone-
       braker, Heidi Stettner, Joseph Kalash, Antonin  Guttman,  Nadene  Lynn,
       Memorandum No. UCB/ERL M82/32, May 1982.
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