AnyData(3) User Contributed Perl Documentation AnyData(3)NAMEAnyData-- easy access to data in many formats
SYNOPSIS
$table = adTie( 'CSV','my_db.csv','o', # create a table
{col_names=>'name,country,sex'}
);
$table->{Sue} = {country=>'de',sex=>'f'}; # insert a row
delete $table->{Tom}; # delete a single row
$str = $table->{Sue}->{country}; # select a single value
while ( my $row = each %$table ) { # loop through table
print $row->{name} if $row->{sex} eq 'f';
}
$rows = $table->{{age=>'> 25'}} # select multiple rows
delete $table->{{country=>qr/us|mx|ca/}}; # delete multiple rows
$table->{{country=>'Nz'}}={country=>'nz'}; # update multiple rows
my $num = adRows( $table, age=>'< 25' ); # count matching rows
my @names = adNames( $table ); # get column names
my @cars = adColumn( $table, 'cars' ); # group a column
my @formats = adFormats(); # list available parsers
adExport( $table, $format, $file, $flags ); # save in specified format
print adExport( $table, $format, $flags ); # print to screen in format
print adDump($table); # dump table to screen
undef $table; # close the table
adConvert( $format1, $file1, $format2, $file2 ); # convert btwn formats
print adConvert( $format1, $file1, $format2 ); # convert to screen
DESCRIPTION
The rather wacky idea behind this module and its sister module
DBD::AnyData is that any data, regardless of source or format should be
accessable and modifiable with the same simple set of methods. This
module provides a multi-dimensional tied hash interface to data in a
dozen different formats. The DBD::AnyData module adds a DBI/SQL
interface for those same formats.
Both modules provide built-in protections including appropriate
flocking() for all I/O and (in most cases) record-at-a-time access to
files rather than slurping of entire files.
Currently supported formats include general format flatfiles (CSV,
Fixed Length, etc.), specific formats (passwd files, httpd logs, etc.),
and a variety of other kinds of formats (XML, Mp3, HTML tables). The
number of supported formats will continue to grow rapidly since there
is an open API making it easy for any author to create additional
format parsers which can be plugged in to AnyData itself and thereby be
accessible by either the tiedhash or DBI/SQL interface.
PREREQUISITES
The AnyData.pm module itself is pure Perl and does not depend on
anything other than modules that come standard with Perl. Some formats
and some advanced features require additional modules: to use the
remote ftp/http features, you must have the LWP bundle installed; to
use the XML format, you must have XML::Parser and XML::Twig installed;
to use the HTMLtable format for reading, you must have HTML::Parser and
HTML::TableExtract installed but you can use the HTMLtable for writing
with just the standard CGI module. To use DBI/SQL commands, you must
have DBI, DBD::AnyData, SQL::Statement and DBD::File installed.
USAGE
The AnyData module imports eight methods (functions):
adTie()-- create a new table or open an existing table
adExport()-- save an existing table in a specified format
adConvert()-- convert data in one format into another format
adFormats()-- list available formats
adNames()-- get the column names of a table
adRows()-- get the number of rows in a table or query
adDump()-- display the data formatted as an array of rows
adColumn()-- group values in a single column
The adTie() command returns a special tied hash. The tied hash can
then be used to access and/or modify data. See below for details
With the exception of the XML, HTMLtable, and ARRAY formats, the
adTie() command saves all modifications of the data directly to file
as they are made. With XML and HTMLtable, you must make your
modifications in memory and then explicitly save them to file with
adExport().
adTie()
my $table = adTie( $format, $data, $open_mode, $flags );
The adTie() command creates a reference to a multi-dimensional tied
hash. In its simplest form, it simply reads a file in a specified
format into the tied hash:
my $table = adTie( $format, $file );
$format is the name of any supported format 'CSV','Fixed','Passwd', etc.
$file is the name of a relative or absolute path to a local file
e.g. my $table = adTie( 'CSV', '/usr/me/myfile.csv' );
this creates a tied hash called $table by reading data in the
CSV (comma separated values) format from the file 'myfile.csv'.
The hash reference resulting from adTie() can be accessed and modified
as follows:
use AnyData;
my $table = adTie( $format, $file );
$table->{$key}->{$column} # select a value
$table->{$key} = {$col1=>$val1,$col2=>$val2...} # update a row
delete $table->{$key} # delete a row
while(my $row = each %$table) { # loop through rows
print $row->{$col1} if $row->{$col2} ne 'baz';
}
The thing returned by adTie ($table in the example) is not an object,
it is a reference to a tied hash. This means that hash operations such
as exists, values, keys, may be used, keeping in mind that this is a
*reference* to a tied hash so the syntax would be
for( keys %$table ) {...}
for( values %$table ) {...}
Also keep in mind that if the table is really large, you probably do
not want to use keys and values because they create arrays in memory
containng data from every row in the table. Instead use 'each' as
shown above since that cycles through the file one record at a time and
never puts the entire table into memory.
It is also possible to use more advanced searching on the hash, see
"Multiple Row Operations" below.
In addition to the simple adTie($format,$file), there are other ways to
specify additional information in the adTie() command. The full syntax
is:
my $table = adTie( $format, $data, $open_mode, $flags );
The $data parameter allows you to read data from remote files accessible by
http or ftp, see "Using Remote Files" below. It also allows you to treat
strings and arrays as data sources without needing a file at all, see
"Working with Strings and Arrays" below.
The optional $mode parameter defaults to 'r' if none is supplied or
must be one of
'r' read # read only access
'u' update # read/write access
'c' create # create a new file unless it already exists
'o' overwrite # create a new file, overwriting any that already exist
The $flags parameter allows you to specify additional information such
as column names. See the sections in "Further Details" below.
With the exception of the XML, HTMLtable, and ARRAY formats, the
adTie() command saves all modifications of the data directly to file as
they are made. With XML and HTMLtable, you must make your
modifications in memory and then explicitly save them to file with
adExport().
adConvert()
adConvert( $format1, $data1, $format2, $file2, $flags1, $flags2 );
or
print adConvert( $format1, $data1, $format2, undef, $flags1, $flags2 );
or
my $aryref = adConvert( $format1, $data1, 'ARRAY', undef, $flags1 );
This method converts data in any supported format into any other supported
format. The resulting data may either be saved to a file (if $file2 is
supplied as a parameter) or sent back as a string to e.g. print the data
to the screen in the new format (if no $file2 is supplied), or sent back
as an array reference if $format2 is 'ARRAY'.
Some examples:
# convert a CSV file into an XML file
#
adConvert('CSV','foo.csv','XML','foo.xml');
# convert a CSV file into an HTML table and print it to the screen
#
print adConvert('CSV','foo.csv','HTMLtable');
# convert an XML string into a CSV file
#
adConvert('XML', ["<x><motto id='perl'>TIMTOWTDI</motto></x>"],
'CSV','foo.csv'
);
# convert an array reference into an XML file
#
adConvert('ARRAY', [['id','motto'],['perl','TIMTOWTDI']],
'XML','foo.xml'
);
# convert an XML file into an array reference
#
my $aryref = adConvert('XML','foo.xml','ARRAY');
See section below "Using strings and arrays" for details.
adExport()
adExport( $table, $format, $file, $flags );
or
print adExport( $table, $format );
or
my $aryref = adExport( $table, 'ARRAY' );
This method converts an existing tied hash into another format and/or
saves the tied hash as a file in the specified format.
Some examples:
all assume a previous call to my $table= adTie(...);
# export table to an XML file
#
adExport($table','XML','foo.xml');
# export table to an HTML string and print it to the screen
#
print adExport($table,'HTMLtable');
# export the table to an array reference
#
my $aryref = adExport($table,'ARRAY');
See section below "Using strings and arrays" for details.
adNames()
my $table = adTie(...);
my @column_names = adNames($table);
This method returns an array of the column names for the specified
table.
adRows()
my $table = adTie(...);
adRows( $table, %search_hash );
This method takes an AnyData tied hash created with adTie() and counts
the rows in the table that match the search hash.
For example, this snippet returns a count of the rows in the file that
contain the specified page in the request column
my $hits = adTie( 'Weblog', 'access.log');
print adRows( $hits , request => 'mypage.html' );
The search hash may contain multiple search criteria, see the section
on mltiple row operations below.
If the search_hash is omitted, it returns a count of all rows.
adColumn()
my @col_vals = adColumn( $table, $column_name, $distinct_flag );
This method returns an array of values taken from the specified column.
If there is a distinct_flag parameter, duplicates will be eliminated
from the list.
For example, this snippet returns a unique list of the values in the
'player' column of the table.
my $game = adTie( 'Pipe','games.db' );
my @players = adColumn( $game, 'player', 1 );
adDump()
my $table = adTie(...);
print adDump($table);
This method prints the raw data in the table. Column names are printed
inside angle brackets and separated by colons on the first line, then
each row is printed as a list of values inside sqaure brackets.
adFormats()
print "$_\n for adFormats();
This method shows the available format parsers, e.g. 'CSV', 'XML', etc.
It looks in your @INC for the .../AnyData/Format directory and prints
the names of format parsing files there. If the parser requires
further modules (e.g. XML requires XML::Parser) and you do not have the
additonal modules installed, the format will not work even if listed by
this command. Otherwise, all formats should work as described in this
documentation.
FURTHER DETAILS
Column Names
Column names may be assigned in three ways:
* pre -- The format parser pre-assigns column
names (e.g. Passwd files automatically have
columns named 'username', 'homedir', 'GID', etc.).
* user -- The user specifies the column names as a comma
separated string associated with the key 'cols':
my $table = adTie( $format,
$file,
$mode,
{cols=>'name,age,gender'}
);
* auto -- If there is no pre-assigned list of column names
and none defined by the user, the first line of
the file is treated as a list of column names;
the line is parsed according to the specific
format (e.g. CSV column names are a comma-separated
list, Tab column names are a tab separated list);
When creating a new file in a format that does not pre-assign column
names, the user *must* manually assign them as shown above.
Some formats have special rules for assigning column names
(XML,Fixed,HTMLtable), see the sections below on those formats.
Key Columns
The AnyData modules support tables that have a single key column that
uniquely identifies each row as well as tables that do not have such
keys. For tables where there is a unique key, that key may be assigned
in three ways:
* pre -- The format parser automatically pre-assigns the
key column name e.g. Passwd files automatically
have 'username' as the key column.
* user -- The user specifies the key column name:
my $table = adTie( $format,
$file,
$mode,
{key=>'country'}
);
* auto If there is no pre-assigned key column and the user
does not define one, the first column becomes the
default key column
Format Specific Details
For full details, see the documentation for AnyData::Format::Foo
where Foo is any of the formats listed in the adFormats() command
e.g. 'CSV', 'XML', etc.
Included below are only some of the more important details of the
specific parsers.
Fixed Format
When using the Fixed format for fixed length records you must
always specify a pattern indicating the lengths of the fields.
This should be a string as would be passed to the unpack() function
to unpack the records in your Fixed length definition:
my $t = adTie( 'Fixed', $file, 'r', {pattern=>'A3 A7 A9'} );
If you want the column names to appear on the first line of a Fixed
file, they should be in comma-separated format, not in Fixed
format. This is different from other formats which use their own
format to display the column names on the first line. This is
necessary because the name of the column might be longer than the
length of the column.
XML Format
The XML format does not allow you to specify column names as a flag,
rather you specify a "record_tag" and the column names are determined
from the contents of the tag. If no record_tag is specified, the
record tag will be assumed to be the first child of the root of the
XML tree. That child and its structure will be determined from the
DTD if there is one, or from the first occurring record if there is
no DTD.
For simple XML, no flags are necessary:
<table>
<row row_id="1"><name>Joe</name><location>Seattle</location></row>
<row row_id="2"><name>Sue</name><location>Portland</location></row>
</table>
The record_tag will default to the first child, namely "row". The
column names will be generated from the attributes of the record
tag and all of the tags included under the record tag, so the
column names in this example will be "row_id","name","location".
If the record_tag is not the first child, you will need to specify
it. For example:
<db>
<table table_id="1">
<row row_id="1"><name>Joe</name><location>Seattle</location></row>
<row row_id="2"><name>Sue</name><location>Portland</location></row>
</table>
<table table_id="2">
<row row_id="1"><name>Bob</name><location>Boise</location></row>
<row row_id="2"><name>Bev</name><location>Billings</location></row>
</table>
</db>
In this case you will need to specify "row" as the record_tag since
it is not the first child of the tree. The column names will be
generated from the attributes of row's parent (if the parent is not
the root), from row's attributes and sub tags, i.e.
"table_id","row_id","name","location".
When exporting XML, you can specify a DTD to control the output.
For example, if you import a table from CSV or from an Array, you
can output as XML and specify which of the columns become tags and
which become attributes and also specify the nesting of the tags in
your DTD.
The XML format parser is built on top of Michel Rodriguez's
excellent XML::Twig which is itslef based on XML::Parser.
Parameters to either of those modules may be passed in the flags
for adTie() and the other commands including the "prettyPrint" flag
to specify how the output XML is displayed and things like
ProtocolEncoding. ProtocolEncoding defaults to 'ISO-8859-1', all
other flags keep the defaults of XML::Twig and XML::Parser. See
the documentation of those modules for details;
CAUTION: Unlike other formats, the XML format does not save changes to
the file as they are entered, but only saves the changes when you explicitly
request them to be saved with the adExport() command.
HTMLtable Format
This format is based on Matt Sisk's excelletn HTML::TableExtract.
It can be used to read an existing table from an html page, or to
create a new HTML table from any data source.
You may control which table in an HTML page is used with the column_names,
depth and count flags.
If a column_names flag is passed, the first table that contains those names
as the cells in a row will be selected.
If depth and or count parameters are passed, it will look for tables as
specified in the HTML::TableExtract documentation.
If none of column_names, depth, or count flags are passed, the first table
encountered in the file will be the table selected and its first row will
be used to determine the column names for the table.
When exporting to an HTMLtable, you may pass flags to specify properties
of the whole table (table_flags), the top row containing the column names
(top_row_flags), and the data rows (data_row_flags). These flags follow
the syntax of CGI.pm table constructors, e.g.:
print adExport( $table, 'HTMLtable', {
table_flags => {Border=>3,bgColor=>'blue'};
top_row_flags => {bgColor=>'red'};
data_row_flags => {valign='top'};
});
The table_flags will default to {Border=>1,bgColor=>'white'} if none
are specified.
The top_row_flags will default to {bgColor=>'#c0c0c0'} if none are
specified;
The data_row_flags will be empty if none are specified.
In other words, if no flags are specified the table will print out with
a border of 1, the column headings in gray, and the data rows in white.
CAUTION: This module will *not* preserve anything in the html file except
the selected table so if your file contains more than the selected table,
you will want to use adTie() to read the table and then adExport() to write
the table to a different file. When using the HTMLtable format, this is the
only way to preserve changes to the data, the adTie() command will *not*
write to a file.
Multiple Row Operations
The AnyData hash returned by adTie() may use either single values as
keys, or a reference to a hash of comparisons as a key. If the key to
the hash is a single value, the hash operates on a single row but if
the key to the hash is itself a hash reference, the hash operates on a
group of rows.
my $num_deleted = delete $table->{Sue};
This example deletes a single row where the key column has the value
'Sue'. If multiple rows have the value 'Sue' in that column, only the
first is deleted. It uses a simple string as a key, therefore it
operates on only a single row.
my $num_deleted = delete $table->{ {name=>'Sue'} };
This example deletes all rows where the column 'name' is equal to
'Sue'. It uses a hashref as a key and therefore operates on multiple
rows.
The hashref used in this example is a single column comparison but the
hashref could also include multiple column comparisons. This deletes
all rows where the the values listed for the country, gender, and age
columns are equal to those specified:
my $num_deleted = delete $table->{{ country => 'us',
gender => 'm',
age => '25'
}}
In addition to simple strings, the values may be specified as regular
expressions or as numeric or alphabetic comparisons. This will delete
all North American males under the age of 25:
my $num_deleted = delete $table->{{ country => qr/mx|us|ca/,
gender => 'm',
age => '< 25'
}}
If numeric or alphabetic comparisons are used, they should be a string
with the comparison operator separated from the value by a space, e.g.
'> 4' or 'lt b'.
This kind of search hashref can be used not only to delete multiple
rows, but also to update rows. In fact you *must* use a hashref key in
order to update your table. Updating is the only operation that can
not be done with a single string key.
The search hashref can be used with a select statement, in which case
it returns a reference to an array of rows matching the criteria:
my $male_players = $table->{{gender=>'m'}};
for my $player( @$male_players ) { print $player->{name},"\n" }
This should be used with caution with a large table since it gathers
all of the selected rows into an array in memory. Again, 'each' is a
much better way for large tables. This accomplishes the same thing as
the example above, but without ever pulling more than a row into memory
at a time:
while( my $row= each %$table ) {
print $row->{name}, "\n" if $row->{gender}=>'m';
}
Search criteria for multiple rows can also be used with the adRows()
function:
my $num_of_women = adRows( $table, gender => 'w' );
That does *not* pull the entire table into memory, it counts the rows a
record at a time.
Using Remote Files
If the first file parameter of adTie() or adConvert() begins with
"http://" or "ftp://", the file is treated as a remote URL and the LWP
module is called behind the scenes to fetch the file. If the files are
in an area that requires authentication, that may be supplied in the
$flags parameter.
For example:
# read a remote file and access it via a tied hash
#
my $table = adTie( 'XML', 'http://www.foo.edu/bar.xml' );
# same with username/password
#
my $table = ( 'XML', 'ftp://www.foo.edu/pub/bar.xml', 'r'
{ user => 'me', pass => 'x7dy4'
);
# read a remote file, convert it to an HTML table, and print it
#
print adConvert( 'XML', 'ftp://www.foo.edu/pub/bar.xml', 'HTMLtable' );
Using Strings and Arrays
Strings and arrays may be used as either the source of data input or as
the target of data output. Strings should be passed as the only
element of an array reference (in other words, insdie square brackets).
Arrays should be a reference to an array whose first element is a
reference to an array of column names and whose succeeding elements are
references to arrays of row values.
For example:
my $table = adTie( 'XML', ["<x><motto id='perl'>TIMTOWTDI</motto></x>"] );
This uses the XML format to parse the supplied string and returns a tied
hash to the resulting table.
my $table = adTie( 'ARRAY', [['id','motto'],['perl','TIMTOWTDI']] );
This uses the column names "id" and "motto" and the supplied row values
and returns a tied hash to the resulting table.
It is also possible to use an empty array to create a new empty tied
hash in any format, for example:
my $table = adTie('XML',[],'c');
creates a new empty tied hash;
See adConvert() and adExport() for further examples of using strings
and arrays.
Ties, Flocks, I/O, and Atomicity
AnyData provides flocking which works under the limitations of flock --
that it only works if other processes accessing the files are also
using flock and only on platforms that support flock. See the flock()
man page for details.
Here is what the user supplied open modes actually do:
r = read only (LOCK_SH) O_RDONLY
u = update (LOCK_EX) O_RDWR
c = create (LOCK_EX) O_CREAT | O_RDWR | O_EXCL
o = overwrite (LOCK_EX) O_CREAT | O_RDWR | O_TRUNC
When you use something like "my $table = adTie(...)", it opens the file
with a lock and leaves the file and lock open until 1) the hash
variable ($table) goes out of scope or 2) the hash is undefined (e.g.
"undef $table") or 3) the hash is re-assigned to another tie. In all
cases the file is closed and the lock released.
If adTie is called without creating a tied hash variable, the file is
closed and the lock released immediately after the call to adTie.
For example: print adTie('XML','foo.xml')->{main_office}->{phone}.
That obtains a shared lock, opens the file, retrieves the one value
requested, closes the file and releases the lock.
These two examples accomplish the same thing but the first example
opens the file once, does all of the deletions, keeping the exclusive
lock in place until they are all done, then closes the file. The
second example opens and closes the file three times, once for each
deletion and releases the exclusive lock between each deletion:
1. my $t = adTie('Pipe','games.db','u');
delete $t->{"user$_"} for (0..3);
undef $t; # closes file and releases lock
2. delete adTie('Pipe','games.db','u')->{"user$_"} for (0..3);
# no undef needed since no hash variable created
Deletions and Packing
In order to save time and to prevent having to do writes anywhere
except at the end of the file, deletions and updates are *not* done at
the time of issuing a delete command. Rather when the user does a
delete, the position of the deleted record is stored in a hash and when
the file is saved to disk, the deletions are only then physically
removed by packing the entire database. Updates are done by inserting
the new record at the end of the file and marking the old record for
deletion. In the normal course of events, all of this should be
transparent and you'll never need to worry about it. However, if your
server goes down after you've made updates or deletions but before
you've saved the file, then the deleted rows will remain in the
database and for updates there will be duplicate rows -- the old
unpdated row and the new updated row. If you are worried about this
kind of event, then use atomic deletes and updates as shown in the
section above. There's still a very small possiblity of a crash in
between the deletion and the save, but in this case it should impact at
most a single row. (BIG thanks to Matthew Wickline for suggestions on
handling deletes)
MORE HELP
See the README file and the test.pl included with the module for
further examples.
See the AnyData/Format/*.pm PODs for further details of specific
formats.
For further support, please use comp.lang.perl.modules
ACKNOWLEDGEMENTS
Special thanks to Andy Duncan, Tom Lowery, Randal Schwartz, Michel
Rodriguez, Jochen Wiedmann, Tim Bunce, Aligator Descartes, Mathew
Persico, Chris Nandor, Malcom Cook and to many others on the DBI
mailing lists and the clp* newsgroups.
AUTHOR & COPYRIGHT
Jeff Zucker <jeff@vpservices.com>
This module is copyright (c), 2000 by Jeff Zucker.
It may be freely distributed under the same terms as Perl itself.
perl v5.14.0 2004-04-19 AnyData(3)
