NAME

    Kx - Perl extension for Kdb+ http://kx.com

SYNOPSIS

        use Kx;
    
        my $k = Kx->new(host=>'localhost', port=>2222);
        $k->connect() or die "Can't connect to Kdb+ server";
    
        my $rtn = $k->cmd('til 8');
        my $sum = $k->cmd('{x+y}', $k->int(5)->kval, $k->int(7)->kval);
    
        my $lst = $k->listof(5, Kx::KI());
        for (0 .. 4) {
            $lst->at($_, $_);
        }
        my $ktyp = Kx::kType($lst->kval);
        my $lst_perl = $lst->val;

DESCRIPTION

    Alpha code. Create a wrapper around Kdb+ and Q in Perl using the C
    interface to Kdb+

EXPORT

    None by default.

METHODS

 New

        my $k = Kx->new(name=>'local22', host=>'localhost', port=>2222);

    Create a new Kx object. Set the connection paramaters to conect to
    'host' and 'port' as specified.

    No connection is made to the server until you call $k->connect()

    If you don't define a name it defaults to 'default'. Each subsequent
    call to new() will use the same 'default' connection.

    So once you make a connection later calls to new() with the same name
    will use the same connection without further connect() calls required.

        my $k = Kx->new(host=>'localhost', port=>2222);
        $k->connect() or die "Can't connect to Kdb+ server";
    
        # picks up previous default connection to localhost port 2222 and
        # will use it as well.
        my $k1 = Kx->new();

    Also username and passwords are supported. Just add the userpass
    attribute thus:

        $k = Kx->new(name=>'local22', 
                     host=>'localhost', 
                     port=>2222,
                     userpass=>'user:pass');

 Connect

    To connect to the 'default' server.

        unless($k->connect()) {
            warn "Can't connect to Kdb+ server\n";
        }

    To connect to a defined server say 'local22'

        unless($k->connect('local22')) {
            warn "Can't connect to local22 Kdb+ server\n";
        }
     

 Environment

    There are a number of environment details you can glean from the Kdb+
    server you are connected to. They are:

        my $arrayref = $k->tables;     # The tables defined
        my $arrayref = $k->funcs;      # The functions defined
        my $arrayref = $k->views;      # The views defined
        my $arrayref = $k->variables;  # The variables defined
        my $arrayref = $k->memory;     # The memory details \w
    
        my $dir = $k->cwd;              # The current working directory
        my $dir = $k->chdir($newdir);   # Set the cwd
        my $num = $k->GMToffset;        # Offset from GMT for times

    If you make changes that effects these environmental details then call
    the env() method to update what is known. This module doesn't
    continually hassle the server for these details.

        my @details = $k->env;  # Get the environment from the server
    
        $details[0] => [ tables     ]
        $details[1] => [ funcs      ]
        $details[2] => [ views      ]
        $details[3] => [ variables  ]
        $details[4] => 'GMToffset'
        $details[5] => 'releasedate'
        $details[6] => 'gmt'
        $details[7] => 'localtime'
        $details[8] => [ memory     ]
        $details[7] => 'cwd'

    You can also execute OS commands on the server end and gather the
    results like this.

        $arref = $k->oscmd("ls -l /");

 TABLES

    You don't need to use this just use the cmd() interface if you like.
    However if your lazy like me.... read on

    Each of these accessors have a method name starting with 'T'. To help
    distinguish them as cooperating methods.

    Create a new table in Kdb+ named mytab with 3 columns col1, col2 and
    col3. The keys will be on col1 and col3 This equates to the Q command

        # Q command
        q)mytab:([col1:;col3:] col2:)
    
        # The long winded Perl way
        $k->Tnew(name=>'mytab',keys=>['col1','col3'],cols=>['col2']);

    To add data use Tinsert(). Each row is added in the order defined
    above. This line adds 1 into col1, 2 into col3 and 3 into col2 as the
    keys are always defined before the other columns.

        $k->Tinsert('mytab',1,2,3);

    To do a select over a table use Tselect(). Tselect() takes a variable
    name as its first argument. The select will be executed and assigned to
    the variable you define. This way no data is passed from Kdb+ to the
    client until it is needed.

        $k->Tselect('a','select from mytab where col1>4');

    This is really just the same as

        # q command
        a:select from mytab where col1>4

    To get the details of the stored selection

        my $numrows = $k->Tnumrows('a');
        my $numcols = $k->Tnumcols('a');

    This only works on variables that are tables returned from a selection.

    Tget() Tindex() Tcol() and Theader() are only useful once you have done
    a Tget().

    Remember it is probably better to only pull back small tables less than
    say a few tens of thousand of rows as you'll eat up memory fast.

    You may have run a number of Tselects() and now wish to pull back the
    data. To do this use Tget()

        $k->Tget('table');   # table must be a table in the server

    Tget() can also be used with select type queries that return a table as
    their result. It also handles indexed tables better than the cmd()
    method.

    To get access to random values in the returned table from Tget().

        $val = $k->Tindex(row,col);

    This only works for simple tables holding scalars in each row. Don't
    try this if the index would point to a mulit-valued list. Actually it
    sort of works for lists and when it does $val is an array reference. If
    you have troubles use Tcol().

    To get the list of column names as Kdb+ knows them.

        my $header = $k->Theader();
            print "@$header\n";

    To get the meta data for a table as defined in KDB do this.

        my @meta = $k->Tmeta($table);
        foreach(@meta)
        {
            print "(name type) => (@$_)\n";
        }

    To get a Perl reference to a column of data from the table (as K is
    column oriented) do the following:

        my $colref = $k->Tcol(0);   # get the zeroth column
        print "Column 0 data is: @$colref\n";

    I advise against using this on large columns or tables as it is very
    memory inefficent. Better to use $k->cmd() interface to pull back
    exactly what you want first. The column reference above is a Perl copy
    of the data structure held in Kdb+ memory format in the client. This
    can be over 3 times larger in core than the Kdb+ data.

    If you need to access data via rows then use $k->Trow(). Given a row
    number it will return a reference to the row. The first row is at zero
    0.

        my $row = $k->Trow(0);   # get the zeroth row
        print "Row 0 data is: @$row\n";

    Finally to delete or remove a table by name from the server:

        $k->Tdelete('table');

    Here is a list of the complete table methods we have so far:

        $k->Tnew(name=>'thename',keys=>[],cols=>[]);
        $k->Tinsert('table',1,2,3);
        $k->Tbulkinsert('table',col1=>[],col2=>[],...);
        $k->Tget('select statement');
        $scalar = $k->Tindex($row,$col);
        $arref  = $k->Tcol(2);      # 3rd col vector
        $arref  = $k->Trow(2);      # 3rd row
        $arref  = $k->Theader;
        $x      = $k->Tnumrows;
        $y      = $k->Tnumcols;
        $k->Tselect('table','select statement');
        $k->Tsave('table','file');
        $k->Tappend('table','file');
        $k->Tload('table','file');
        $k->Tdelete('table');

    If you want a faster bulk insert function use:

        $k->Tfastbulkinsert('mytab',$col1,$col2,$col3...);

    Here col1 col2 etc are infact in core Kdb+ structures and must be in
    the same order as the declaration use when you used Tnew(). This is
    almost 3 times faster than Tbulkinsert but uses more memory in the
    client. See the test files that came with this module for more details
    on how it is used.

 COMMANDS

    Execute the code on an already accessable Kdb+ server. The query is
    executed and the results are held in K structures in RAM. Example

        $return = $k->cmd('b:til 100');

    If you just what to send a command to the Kdb+ server and not wait then
    use the following. No return value is provided.

        $k->whenever('b:til 100');

    The cmd() method also allows up to two extra arguments that are
    normally K objects. You normally call cmd() this way when you have a
    function to call. Here is a dodgy example.

        my $data = $k->listof(length($arrsym), Kx::KG());  # list of bytes
        $data->setbin($arrsym);
    
        $result = $k->cmd('{[x]insert[`mytab](0;x;.z.z)}', $data->kval);

    The cmd() function will return a reference to an array if the Q command
    returns a list. It will return a simple scalar if the result is a
    scalar response from Q. It will return a hash reference if the return
    result from Q is either table/keyed table/dictionary. You need to know
    what you are doing so can know what the result is (or use Perl's
    ref()).

    Do not execute queries that return large 'keyed' tables as a copy of
    the table in unkeyed form is held to convert to a Perl Hash before
    being freed.

    Note: cmd() does not convert a keyed table to an unkeyed table in
    memory. It holds onto what was passed back from KDB+ as is. If you want
    get at the underlying K structure and change it use Tget() instead.
    Tget() will convert a keyed table to an unkeyed table and hold it in
    memory.

    If you have a Q script that you wish to run against the Kdb+ server you
    can use the do(file) method. Any error in your script that is caught
    will stop do(file) from proceeding. If you don't care when it is done
    then use dolater(file).

    Both do() and dolater() don't return anything useful. They just blindly
    execute each line of Q against the server. If you want to check each
    command and do stuff as a result then use cmd() and check the result.

    An example file name foo.txt holds the lines:

        t:([]a:();b:())
        insert[`t](`a;10.70)
        insert[`t](`b;-5.6)
        insert[`t](`c;21.73)

    You can run that file by doing this:

        $k->do("foo.txt");

 ATOMS and STRUCTURES

    To create Kdb+ atoms locally in RAM use the following calls.

        my $d;
        $d=$k->bool(0);           # boolean
        $d=$k->byte(100);         # char
        $d=$k->char(ord('a'));    # char
        $d=$k->short(20);
        $d=$k->int(70);
        $d=$k->long(93939);
        $d=$k->real(20.44);        # remember 20.44 may look close as a real
        $d=$k->float(20.44);       # should look closer to 20.44 as a float
        $d=$k->sym('mysymbol');    # A Kdb+ symbol
        $d=$k->date(2007,4,22);    # integer encoded date year, month, day
        $d=$k->dt(time());         # Kdb+ datetime from Unix epoch
        $d=$k->tm(100);            # Time type in milliseconds

    These allow for fine grained control over the 'type' of K object you
    want. If you don't mind particularly about the type conversions then
    you can use perl2K() like this.

        $d = $k->perl2K('mysymbol');
        $d = $k->perl2K([qw/this will be a K list of symbols/]);
        $d = $k->perl2K({this => 1, that => 2, 'is a' => 'dict'});

    To get a Perl value back from a Kdb+ atom try this;

        my $val = $d->val();

    To get the internal value back from a Kdb+ atom try this;

        my $kval = $k->kval;  # used in $x->cmd('func', $kval)

    As a further comment on the date() method. When you look at the value
    retuned from a date() call it is in epoch seconds.

        my $date = $k->date(2007,4,22);
        print scalar localtime($date->val),"\n";

    Further more, KDB+ Datetimes are held as a C double in memory. The
    integral part is the number of days since 1/1/2000 and the fractional
    part is the fraction of the day. You have some control over how
    datetimes are returned from KDB+ back into Perl data structures. By
    default a conversion to Unix epoch seconds will be made. You can also
    get epoch seconds with milliseconds and you can also turn off
    conversion all together.

        Kx::__Z2epoch(0);   # turn off Kdb+ to Unix epoch conversion
        Kx::__Z2epoch(1);   # turn on Kdb+ to Unix epoch conversion (default)
        Kx::__Z2epoch(2);   # turn on Kdb+ to Unix epoch conversion plus millisecs

    These have immediate effects on how datetimes are converted into Perl
    data structures. These do not effect what is held in RAM after a call
    to KDB+ has been made, just how they are converted into Perl.

    These methods use the underlying functions as listed below. Don't use
    these unless you know what your doing. They are listed here for
    completeness and so you can use them if you really want. But don't.

        Kx::kb(integer)     => Create boolean 0|1
        Kx::kg(integer)     => Create a byte/char
        Kx::kh(integer)     => Create a short
        Kx::ki(integer)     => Create and integer
        Kx::kj(longval)     => Create a long
        Kx::ke(realval)     => Create a real
        Kx::kf(floatval)    => Create a float
        Kx::kc(charval)     => Create a char from an int ord()
        Kx::ks(symbol)      => Create a symbol from a string
        Kx::kd(date)        => Create a date - See K dates
        Kx::kz(datetime)    => Create a datetime - See K dates
        Kx::kt(time)        => Create a time
    
        Kx::p2k($ref)       => return a K structure describing the Reference
        Kx::k2p(K)          => return a Perl structure from a Kdb+ structure
    
        Kx::k2pscalar(K)    => return a scalar from a Kdb+ atom
        Kx::k2parray(K)     => return an array from a Kdb+ list
        Kx::k2phash(K)      => return a hash from a Kdb+ dict/table
    
        Kx::phash2k($href)  => return a Kdb+ dict from a Perl hash ref
        Kx::parray2k($aref) => return a Kdb+ list from a Perl array ref
        Kx::pscalar2k($srf) => return a Kdb+ atom from a Perl scalar ref

    Example:

        # Simple create
        my $bool = $k->bool(0);
        print "My boolean in K is ",$bool->val,"\n";

 LISTS

  Simple Lists

    These list functions create in memory local lists outside of any 'q'
    running process. These will allow you to create very large simple lists
    without blowing out all your memory.

    To create a simple Kdb+ list of a single type use the listof()
    function. The type of the list is passed in as the second aregument and
    can be one of:

        Kx::KC()  char
        Kx::KD()  date yyyy mm dd
        Kx::KE()  real
        Kx::KF()  float
        Kx::KG()  byte
        Kx::KH()  short
        Kx::KI()  integer
        Kx::KJ()  long
        Kx::KM()  month
        Kx::KS()  symbol (internalised string)
        Kx::KT()  time
        Kx::KU()  minute
        Kx::KV()  second
        Kx::KZ()  datetime epoch seconds

    Example simple lists:

        my $list = $k->listof(20,Kx::KS());      # List of 20 symbols
        for( my $i=0; $i < 20; $i++)
        {
            $list->at($i,"symbol$i");
        }
    
        # To get at the 4th element
        my $sym = $list->at(3);     # symbol3
    
        my $perl_list = $list->list;
        print "Symbols are @$perl_list\n";
    
        # dates
        $d = $k->listof(20,Kx::KD());
        for( my $i=0; $i < 20; $i++)
        {
            $d->at($i,2007,4,$i+1);  # 20070401 -> 20070421
        }
    
        # Add an extra date to the end of the list
        my $day = $k->date(2007,4,30);
        $d->joinatom($day->kval);

    There is also another method defined setbin() that sets binary data
    into a list of bytes. You can use this to save serialised Perl data
    structures into Kdb+ tables (much like a blob or text field in SQL
    DBs). Here is an example:

        use Kx;
        use Compress::Zlib qw/compress uncompress/;
        use Data::Dumper;
        $Data::Dumper::Indent = 0; # no newlines, important
        
        my $k = Kx->new(host=>"localhost", port=>2222, check_for_errors=>1);
        $k->connect() or die "Can't connect to Kdb+ server";
        
        # create new table in q
        $k->Tnew(name=>'mytab',cols=>[qw/id data ts/]);
        
        # Build a large complicated Perl structure.
        my $arr = { a=>['a','b','c',1,2,3], b=>'this is a test'};
        for (0..10000) {
            $arr->{$_} = {$_ => $_};
            $arr->{"a$_"} = [$_, $_];
        }
        
        # Serialise it as a compressed piece of data
        my $arrsym =  Dumper($arr);
        print "Dumper size is: ", length $arrsym, "\n";
        $arrsym = compress( $arrsym );
        print "Compress Dumper size is: ", length $arrsym, "\n";
        
        # An in memory Kdb+ list of bytes to hold the compressed data
        my $data = $k->listof(length($arrsym),Kx::KG());  # list of length bytes
        $data->setbin($arrsym);
        
        # Insert it into a table using a function call.
        $k->cmd('{[x]insert[`mytab](0;x;.z.z)}',$data->kval);
        
        # Select a single row from the table, and return it's data
        $binary = $k->cmd('(select data from mytab where id=0)[0;`data]');
        
        # Get the data back into Perl string form
        $arrsym = uncompress($binary);
        #print $arrsym,"\n";
        
        # Eval the string into a Perl data structure the hard way
        my $VAR1;
        eval $arrsym;
        print $VAR1->{'b'},"\n";

  Mixed Lists

        # The zero in line below says its to be a mixed list
        my $list = $k->listof(40,0); # mixed list 40 elements
        $list->at(0,$k->float(22.22));
    
        $list->at(1,$k->sym('this is a test'));
        .
        .
        $list->at(39,$k->date(2007,2,28));

    This is handy for creating multiple arguments to a KDB+ function call.

 Utility Methods

    $k->dump0() will return a string describing the under lying K
    structure.

    Kx::dump($k) will print out the K structure of $k

    $sym = Kx::makesym("string") will convert a simple string into a quoted
    symbol suitable for usage in KDB+

    make_C() will convert its argument into a suitable string quoted as a
    KDB+ character list.

        my $c = Kx::make_C("now is\tthe \n time for \n help");

    There is also make_s():

        my $sym = Kx::make_s("a symbol"); # `$"a symbol"
        my $sym = Kx::make_s(undef);      # a null symbol `

Kx::LIST

    You may wish to tie a Perl array to a Kdb+ variable. Well, you can do
    that as well. Try something like this:

        use Kx;
        
        my %config = (
            host=>"localhost",
            port=>2222,
            userpass=>'user:pass',    # optional
            type=>'symbol',
            list=>'d',
            create=>1
        );
        tie(@a, 'Kx::LIST', %config);
        
        # push lost of stuff on an array
        my @array = (qw/aaaa bbbbb ccccc ddddddddd e f j h i j k l/) x 30000
        ;
        push(@a,@array);
        push(@a,@array);
        push(@a,@array);
        print "\@a has ", scalar(@a)," elements\n";
        
        # Store
        $a[3] = "Help me";
        print "Elementt 3 is ",$a[3],"\n";

    All the functions defined in perltie for lists are included.

    Note: 'type' is a Kdb+ type as defined in Types below - it is the type
    for the array. Only simple types are allowed at the moment.

Kx::HASH

    You may wish to tie a Perl hash to a Kdb+ variable. Well, you can do
    that as well. Try something like this:

        use Kx;
    
        my %config = (
                host=>"localhost",
                port=>2222,
                userpass=>'user:pass', # optional
                ktype=>'symbol',
                vtype=>'int',
                dict=>'x',
                create=>1
        );
        tie(%x, 'Kx::HASH', %config);
        
        print "Size of hash x is :". scalar %x ."\n";
        for(0..5) {
            $x{"a$_"} = $_;
        }
        
        %y = %x;
        
        for(0..5) {
            print $y{"a$_"}," " if exists $y{"a$_"};
        }
        print "\n";
        
        while(($k,$v) = each %x) {
            print "Key=>$k is $v\n";
        }
        untie(%x);

    All the functions defined in perltie for hashs are included.

    Note: ktype is a Kdb+ type as defined in Types below - it is the 'key'
    type for the hash. vtype is also defined in Types - it is the value
    type. Only simple types are allowed at the moment.

SEE ALSO

    http://kx.com

    http://code.kx.com

    See the test code under the 't' directory of this module for more
    details on how to call each method.

AUTHORS

      * Mark Pfeiffer <markpf@mlp-consulting.com.au>

      * Stephan Loyd <stephanloyd9@gmail.com>

COPYRIGHT AND LICENSE

    Copyright (C) 2007 by Mark Pfeiffer

    This library is free software; you can redistribute it and/or modify it
    under the same terms as Perl itself, either Perl version 5.8.6 or, at
    your option, any later version of Perl 5 you may have available.

    This code is not affiliated with KxSystems in anyway. It is just a
    simple interface to their code. Any functionality that is of any use is
    due to the hard work of the people at KxSystems.

    This is Alpha code. Use at your own risk. It is availble only for
    testing at the moment. It has not been fully tested. For example nulls,
    inf and the like. Your kms may vary.

    If this code is useful then please drop me a line and let me know. I
    would also like to be acknowledged in any products you may make from
    this. I get a bit of a buzz out of it.

    The LICENSE file in the package is the Perl 5 license.

BUGS

    Plenty and to be expected. Please send me any bugs you find. Patches
    are even better and will always be acknowledged.

    Once the code has been tested for a while I'll move it to beta. Don't
    hold your breath though.

    All spelling mistakes are mine ;-)

