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/*-
* See the file LICENSE for redistribution information.
*
* Copyright (c) 2005,2008 Oracle. All rights reserved.
*
* $Id: README,v 1.22 2008/01/08 20:58:23 bostic Exp $
*/
The "comma-separated value" (csv) directory is a suite of three programs:
csv_code: write "helper" code on which to build applications,
csv_load: import csv files into a Berkeley DB database,
csv_query: query databases created by csv_load.
The goal is to allow programmers to easily build applications for using
csv databases.
You can build the three programs, and run a sample application in this
directory.
First, there's the sample.csv file:
Adams,Bob,01/02/03,green,apple,37
Carter,Denise Ann,04/05/06,blue,banana,38
Eidel,Frank,07/08/09,red,cherry,38
Grabel,Harriet,10/11/12,purple,date,40
Indals,Jason,01/03/05,pink,orange,32
Kilt,Laura,07/09/11,yellow,grape,38
Moreno,Nancy,02/04/06,black,strawberry,38
Octon,Patrick,08/10/12,magenta,kiwi,15
The fields are:
Last name,
First name,
Birthdate,
Favorite color,
Favorite fruit,
Age
Second, there's a "description" of that csv file in sample.desc:
version 1 {
LastName string
FirstName string
BirthDate
Color string index
Fruit string index
Age unsigned_long index
}
The DESCRIPTION file maps one-to-one to the fields in the csv file, and
provides a data type for any field the application wants to use. (If
the application doesn't care about a field, don't specify a data type
and the csv code will ignore it.) The string "index" specifies there
should be a secondary index based on the field.
The "field" names in the DESCRIPTION file don't have to be the same as
the ones in the csv file (and, as they may not have embedded spaces,
probably won't be).
To build in the sample directory, on POSIX-like systems, type "make".
This first builds the program csv_code, which it then run, with the file
DESCRIPTION as an input. Running csv_code creates two additional files:
csv_local.c and csv_local.h. Those two files are then used as part of
the build process for two more programs: csv_load and csv_query.
You can load now load the csv file into a Berkeley DB database with the
following command:
% ./csv_load -h TESTDIR < sample.csv
The csv_load command will create a directory and four databases:
primary primary database
Age secondary index on Age field
Color secondary index on Color field
Fruit secondary index on Fruit field
You can then query the database:
% ./csv_query -h TESTDIR
Query: id=2
Record: 2:
LastName: Carter
FirstName: Denise
Color: blue
Fruit: banana
Age: 38
Query: color==green
Record: 1:
LastName: Adams
FirstName: Bob
Color: green
Fruit: apple
Age: 37
and so on.
The csv_code process also creates source code modules that support
building your own applications based on this database. First, there
is the local csv_local.h include file:
/*
* DO NOT EDIT: automatically built by csv_code.
*
* Record structure.
*/
typedef struct __DbRecord {
u_int32_t recno; /* Record number */
/*
* Management fields
*/
void *raw; /* Memory returned by DB */
char *record; /* Raw record */
size_t record_len; /* Raw record length */
u_int32_t field_count; /* Field count */
u_int32_t version; /* Record version */
u_int32_t *offset; /* Offset table */
/*
* Indexed fields
*/
#define CSV_INDX_LASTNAME 1
char *LastName;
#define CSV_INDX_FIRSTNAME 2
char *FirstName;
#define CSV_INDX_COLOR 4
char *Color;
#define CSV_INDX_FRUIT 5
char *Fruit;
#define CSV_INDX_AGE 6
u_long Age;
} DbRecord;
This defines the DbRecord structure that is the primary object for this
csv file. As you can see, the intersting fields in the csv file have
mappings in this structure.
Also, there are routines in the Dbrecord.c file your application can use
to handle DbRecord structures. When you retrieve a record from the
database the DbRecord structure will be filled in based on that record.
Here are the helper routines:
int
DbRecord_print(DbRecord *recordp, FILE *fp)
Display the contents of a DbRecord structure to the specified
output stream.
int
DbRecord_init(const DBT *key, DBT *data, DbRecord *recordp)
Fill in a DbRecord from a returned database key/data pair.
int
DbRecord_read(u_long key, DbRecord *recordp)
Read the specified record (DbRecord_init will be called
to fill in the DbRecord).
int
DbRecord_discard(DbRecord *recordp)
Discard the DbRecord structure (must be called after the
DbRecord_read function), when the application no longer
needs the returned DbRecord.
int
DbRecord_search_field_name(char *field, char *value, OPERATOR op)
Display the DbRecords where the field (named by field) has
the specified relationship to the value. For example:
DbRecord_search_field_name("Age", "35", GT)
would search for records with a "Age" field greater than
35.
int
DbRecord_search_field_number(
u_int32_t fieldno, char *value, OPERATOR op)
Display the DbRecords where the field (named by field)
has the specified relationship to the value. The field
number used as an argument comes from the csv_local.h
file, for example, CSV_INDX_AGE is the field index for
the "Age" field in this csv file. For example:
DbRecord_search_field_number(CSV_INDX_AGE, 35, GT)
would search for records with a "Age" field greater than
35.
Currently, the csv code only supports three types of data:
strings, unsigned longs and doubles. Others can easily be
added.
The usage of the csv_code program is as follows:
usage: csv_code [-v] [-c source-file] [-f input] [-h header-file]
-c output C source code file
-h output C header file
-f input file
-v verbose (defaults to off)
-c A file to which to write the C language code. By default,
the file "csv_local.c" is used.
-f A file to read for a description of the fields in the
csv file. By default, csv_code reads from stdin.
-h A file to which to write the C language header structures.
By default, the file "csv_local.h" is used.
-v The -v verbose flag outputs potentially useful debugging
information.
There are two applications built on top of the code produced by
csv_code, csv_load and csv_query.
The usage of the csv_load program is as follows:
usage: csv_load [-v] [-F format] [-f csv-file] [-h home] [-V version]
-F format (currently supports "excel")
-f input file
-h database environment home directory
-v verbose (defaults to off)
-F See "Input format" below.
-f If an input file is specified using the -f flag, the file
is read and the records in the file are stored into the
database. By default, csv_load reads from stdin.
-h If a database environment home directory is specified
using the -h flag, that directory is used as the
Berkeley DB directory. The default for -h is the
current working directory or the value of the DB_HOME
environment variable.
-V Specify a version number for the input (the default is 1).
-v The -v verbose flag outputs potentially useful debugging
information. It can be specified twice for additional
information.
The usage of csv_query program is as follows:
usage: csv_query [-v] [-c cmd] [-h home]
-c A command to run, otherwise csv_query will enter
interactive mode and prompt for user input.
-h If a database environment home directory is specified
using the -h flag, that directory is used as the
Berkeley DB directory. The default for -h is the
current working directory or the value of the DB_HOME
environment variable.
-v The -v verbose flag outputs potentially useful debugging
information. It can be specified twice for additional
information.
The query program currently supports the following commands:
? Display help screen
exit Exit program
fields Display list of field names
help Display help screen
quit Exit program
version Display database format version
field[op]value Display fields by value (=, !=, <, <=, >, >=, ~, !~)
The "field[op]value" command allows you to specify a field and a
relationship to a value. For example, you could run the query:
csv_query -c "price < 5"
to list all of the records with a "price" field less than "5".
Field names and all string comparisons are case-insensitive.
The operators ~ and !~ do match/no-match based on the IEEE Std 1003.2
(POSIX.2) Basic Regular Expression standard.
As a special case, every database has the field "Id", which matches the
record number of the primary key.
Input format:
The input to the csv_load utility is a text file, containing
lines of comma-separated fields.
Blank lines are ignored. All non-blank lines must be comma-separated
lists of fields.
By default:
<nul> (\000) bytes and unprintable characters are stripped,
input lines are <nl> (\012) separated,
commas cannot be escaped.
If "-F excel" is specified:
<nul> (\000) bytes and unprintable characters are stripped,
input lines are <cr> (\015) separated,
<nl> bytes (\012) characters are stripped from the input,
commas surrounded by double-quote character (") are not
treated as field separators.
Storage format:
Records in the primary database are stored with a 32-bit unsigned
record number as the key.
Key/Data pair 0 is of the format:
[version] 32-bit unsigned int
[field count] 32-bit unsigned int
[raw record] byte array
For example:
[1]
[5]
[field1,field2,field3,field4,field5]
All other Key/Data pairs are of the format:
[version] 32-bit unsigned int
[offset to field 1] 32-bit unsigned int
[offset to field 2] 32-bit unsigned int
[offset to field 3] 32-bit unsigned int
... 32-bit unsigned int
[offset to field N] 32-bit unsigned int
[offset past field N] 32-bit unsigned int
[raw record] byte array
For example:
[1]
[0]
[2]
[5]
[9]
[14]
[19]
[a,ab,abc,abcd,abcde]
012345678901234567890 << byte offsets
0 1 2
So, field 3 of the data can be directly accessed by using
the "offset to field 3", and the length of the field is
the "((offset to field 4) - (offset to field 3)) - 1".
Limits:
The csv program stores the primary key in a 32-bit unsigned
value, limiting the number of records in the database. New
records are inserted after the last existing record, that is,
new records are not inserted into gaps left by any deleted
records. This will limit the total number of records stored in
any database.
Versioning:
Versioning is when a database supports multiple versions of the
records. This is likely to be necessary when dealing with large
applications and databases, as record fields change over time.
The csv application suite does not currently support versions,
although all of the necessary hooks are there.
The way versioning will work is as follows:
The XXX.desc file needs to support multiple version layouts.
The generated C language structure defined should be a superset
of all of the interesting fields from all of the version
layouts, regardless of which versions of the csv records those
fields exist in.
When the csv layer is asked for a record, the record's version
will provide a lookup into a separate database of field lists.
That is, there will be another database which has key/data pairs
where the key is a version number, and the data is the field
list. At that point, it's relatively easy to map the fields
to the structure as is currently done, except that some of the
fields may not be filled in.
To determine if a field is filled in, in the structure, the
application has to have an out-of-band value to put in that
field during DbRecord initialization. If that's a problem, the
alternative would be to add an additional field for each listed
field -- if the additional field is set to 1, the listed field
has been filled in, otherwise it hasn't. The csv code will
support the notion of required fields, so in most cases the
application won't need to check before simply using the field,
it's only if a field isn't required and may be filled in that
the check will be necessary.
TODO:
Csv databases are not portable between machines of different
byte orders. To make them portable, all of the 32-bit unsigned
int fields currently written into the database should be
converted to a standard byte order. This would include the
version number and field count in the column-map record, and the
version and field offsets in the other records.
Add Extended RE string matches.
Add APIs to replace the reading of a schema file, allow users to
fill in a DbRecord structure and do a put on it. (Hard problem:
how to flag fields that aren't filled in.)
Add a second sample file, and write the actual versioning code.
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