Indulge in some microoptimization

[dbsrgits/DBIx-Class.git] / lib / DBIx / Class / Storage / DBI / Sybase / ASE.pm

package DBIx::Class::Storage::DBI::Sybase::ASE;

use strict;
use warnings;

use base qw/
    DBIx::Class::Storage::DBI::Sybase
    DBIx::Class::Storage::DBI::AutoCast
/;
use mro 'c3';
use Carp::Clan qw/^DBIx::Class/;
use Scalar::Util 'blessed';
use List::Util 'first';
use Sub::Name();
use Data::Dumper::Concise 'Dumper';
use Try::Tiny;
use namespace::clean;

__PACKAGE__->sql_limit_dialect ('RowCountOrGenericSubQ');

__PACKAGE__->mk_group_accessors('simple' =>
    qw/_identity _blob_log_on_update _writer_storage _is_extra_storage
       _bulk_storage _is_bulk_storage _began_bulk_work
       _bulk_disabled_due_to_coderef_connect_info_warned
       _identity_method/
);

my @also_proxy_to_extra_storages = qw/
  connect_call_set_auto_cast auto_cast connect_call_blob_setup
  connect_call_datetime_setup

  disconnect _connect_info _sql_maker _sql_maker_opts disable_sth_caching
  auto_savepoint unsafe cursor_class debug debugobj schema
/;

=head1 NAME

DBIx::Class::Storage::DBI::Sybase::ASE - Sybase ASE SQL Server support for
DBIx::Class

=head1 SYNOPSIS

This subclass supports L<DBD::Sybase> for real (non-Microsoft) Sybase databases.

=head1 DESCRIPTION

If your version of Sybase does not support placeholders, then your storage will
be reblessed to L<DBIx::Class::Storage::DBI::Sybase::ASE::NoBindVars>.
You can also enable that driver explicitly, see the documentation for more
details.

With this driver there is unfortunately no way to get the C<last_insert_id>
without doing a C<SELECT MAX(col)>. This is done safely in a transaction
(locking the table.) See L</INSERTS WITH PLACEHOLDERS>.

A recommended L<connect_info|DBIx::Class::Storage::DBI/connect_info> setting:

  on_connect_call => [['datetime_setup'], ['blob_setup', log_on_update => 0]]

=head1 METHODS

=cut

sub _rebless {
  my $self = shift;

  my $no_bind_vars = __PACKAGE__ . '::NoBindVars';

  if ($self->using_freetds) {
    carp <<'EOF' unless $ENV{DBIC_SYBASE_FREETDS_NOWARN};

You are using FreeTDS with Sybase.

We will do our best to support this configuration, but please consider this
support experimental.

TEXT/IMAGE columns will definitely not work.

You are encouraged to recompile DBD::Sybase with the Sybase Open Client libraries
instead.

See perldoc DBIx::Class::Storage::DBI::Sybase::ASE for more details.

To turn off this warning set the DBIC_SYBASE_FREETDS_NOWARN environment
variable.
EOF

    if (not $self->_use_typeless_placeholders) {
      if ($self->_use_placeholders) {
        $self->auto_cast(1);
      }
      else {
        $self->ensure_class_loaded($no_bind_vars);
        bless $self, $no_bind_vars;
        $self->_rebless;
      }
    }
  }

  elsif (not $self->_get_dbh->{syb_dynamic_supported}) {
    # not necessarily FreeTDS, but no placeholders nevertheless
    $self->ensure_class_loaded($no_bind_vars);
    bless $self, $no_bind_vars;
    $self->_rebless;
  }
  # this is highly unlikely, but we check just in case
  elsif (not $self->_use_typeless_placeholders) {
    $self->auto_cast(1);
  }
}

sub _init {
  my $self = shift;
  $self->_set_max_connect(256);

# create storage for insert/(update blob) transactions,
# unless this is that storage
  return if $self->_is_extra_storage;

  my $writer_storage = (ref $self)->new;

  $writer_storage->_is_extra_storage(1);
  $writer_storage->connect_info($self->connect_info);
  $writer_storage->auto_cast($self->auto_cast);

  $self->_writer_storage($writer_storage);

# create a bulk storage unless connect_info is a coderef
  return if ref($self->_dbi_connect_info->[0]) eq 'CODE';

  my $bulk_storage = (ref $self)->new;

  $bulk_storage->_is_extra_storage(1);
  $bulk_storage->_is_bulk_storage(1); # for special ->disconnect acrobatics
  $bulk_storage->connect_info($self->connect_info);

# this is why
  $bulk_storage->_dbi_connect_info->[0] .= ';bulkLogin=1';

  $self->_bulk_storage($bulk_storage);
}

for my $method (@also_proxy_to_extra_storages) {
  no strict 'refs';
  no warnings 'redefine';

  my $replaced = __PACKAGE__->can($method);

  *{$method} = Sub::Name::subname $method => sub {
    my $self = shift;
    $self->_writer_storage->$replaced(@_) if $self->_writer_storage;
    $self->_bulk_storage->$replaced(@_)   if $self->_bulk_storage;
    return $self->$replaced(@_);
  };
}

sub disconnect {
  my $self = shift;

# Even though we call $sth->finish for uses off the bulk API, there's still an
# "active statement" warning on disconnect, which we throw away here.
# This is due to the bug described in insert_bulk.
# Currently a noop because 'prepare' is used instead of 'prepare_cached'.
  local $SIG{__WARN__} = sub {
    warn $_[0] unless $_[0] =~ /active statement/i;
  } if $self->_is_bulk_storage;

# so that next transaction gets a dbh
  $self->_began_bulk_work(0) if $self->_is_bulk_storage;

  $self->next::method;
}

# Set up session settings for Sybase databases for the connection.
#
# Make sure we have CHAINED mode turned on if AutoCommit is off in non-FreeTDS
# DBD::Sybase (since we don't know how DBD::Sybase was compiled.) If however
# we're using FreeTDS, CHAINED mode turns on an implicit transaction which we
# only want when AutoCommit is off.
#
# Also SET TEXTSIZE for FreeTDS because LongReadLen doesn't work.
sub _run_connection_actions {
  my $self = shift;

  if ($self->_is_bulk_storage) {
# this should be cleared on every reconnect
    $self->_began_bulk_work(0);
    return;
  }

  if (not $self->using_freetds) {
    $self->_dbh->{syb_chained_txn} = 1;
  } else {
    # based on LongReadLen in connect_info
    $self->set_textsize;

    if ($self->_dbh_autocommit) {
      $self->_dbh->do('SET CHAINED OFF');
    } else {
      $self->_dbh->do('SET CHAINED ON');
    }
  }

  $self->next::method(@_);
}

=head2 connect_call_blob_setup

Used as:

  on_connect_call => [ [ 'blob_setup', log_on_update => 0 ] ]

Does C<< $dbh->{syb_binary_images} = 1; >> to return C<IMAGE> data as raw binary
instead of as a hex string.

Recommended.

Also sets the C<log_on_update> value for blob write operations. The default is
C<1>, but C<0> is better if your database is configured for it.

See
L<DBD::Sybase/Handling_IMAGE/TEXT_data_with_syb_ct_get_data()/syb_ct_send_data()>.

=cut

sub connect_call_blob_setup {
  my $self = shift;
  my %args = @_;
  my $dbh = $self->_dbh;
  $dbh->{syb_binary_images} = 1;

  $self->_blob_log_on_update($args{log_on_update})
    if exists $args{log_on_update};
}

sub _is_lob_type {
  my $self = shift;
  my $type = shift;
  $type && $type =~ /(?:text|image|lob|bytea|binary|memo)/i;
}

sub _is_lob_column {
  my ($self, $source, $column) = @_;

  return $self->_is_lob_type($source->column_info($column)->{data_type});
}

sub _prep_for_execute {
  my $self = shift;
  my ($op, $extra_bind, $ident, $args) = @_;

  my ($sql, $bind) = $self->next::method (@_);

  my $table = blessed $ident ? $ident->from : $ident;

  my $bind_info = $self->_resolve_column_info(
    $ident, [map $_->[0], @{$bind}]
  );
  my $bound_identity_col =
    first { $bind_info->{$_}{is_auto_increment} }
    keys %$bind_info
  ;

  my $columns_info = blessed $ident && $ident->columns_info;

  my $identity_col =
    $columns_info &&
    first { $columns_info->{$_}{is_auto_increment} }
      keys %$columns_info
  ;

  if (($op eq 'insert' && $bound_identity_col) ||
      ($op eq 'update' && exists $args->[0]{$identity_col})) {
    $sql = join ("\n",
      $self->_set_table_identity_sql($op => $table, 'on'),
      $sql,
      $self->_set_table_identity_sql($op => $table, 'off'),
    );
  }

  if ($op eq 'insert' && (not $bound_identity_col) && $identity_col &&
      (not $self->{insert_bulk})) {
    $sql =
      "$sql\n" .
      $self->_fetch_identity_sql($ident, $identity_col);
  }

  return ($sql, $bind);
}

sub _set_table_identity_sql {
  my ($self, $op, $table, $on_off) = @_;

  return sprintf 'SET IDENTITY_%s %s %s',
    uc($op), $self->sql_maker->_quote($table), uc($on_off);
}

# Stolen from SQLT, with some modifications. This is a makeshift
# solution before a sane type-mapping library is available, thus
# the 'our' for easy overrides.
our %TYPE_MAPPING  = (
    number    => 'numeric',
    money     => 'money',
    varchar   => 'varchar',
    varchar2  => 'varchar',
    timestamp => 'datetime',
    text      => 'varchar',
    real      => 'double precision',
    comment   => 'text',
    bit       => 'bit',
    tinyint   => 'smallint',
    float     => 'double precision',
    serial    => 'numeric',
    bigserial => 'numeric',
    boolean   => 'varchar',
    long      => 'varchar',
);

sub _native_data_type {
  my ($self, $type) = @_;

  $type = lc $type;
  $type =~ s/\s* identity//x;

  return uc($TYPE_MAPPING{$type} || $type);
}

sub _fetch_identity_sql {
  my ($self, $source, $col) = @_;

  return sprintf ("SELECT MAX(%s) FROM %s",
    map { $self->sql_maker->_quote ($_) } ($col, $source->from)
  );
}

sub _execute {
  my $self = shift;
  my ($op) = @_;

  my ($rv, $sth, @bind) = $self->dbh_do($self->can('_dbh_execute'), @_);

  if ($op eq 'insert') {
    $self->_identity($sth->fetchrow_array);
    $sth->finish;
  }

  return wantarray ? ($rv, $sth, @bind) : $rv;
}

sub last_insert_id { shift->_identity }

# handles TEXT/IMAGE and transaction for last_insert_id
sub insert {
  my $self = shift;
  my ($source, $to_insert) = @_;

  my $columns_info = $source->columns_info;

  my $identity_col =
    (first { $columns_info->{$_}{is_auto_increment} }
      keys %$columns_info )
    || '';

  # check for empty insert
  # INSERT INTO foo DEFAULT VALUES -- does not work with Sybase
  # try to insert explicit 'DEFAULT's instead (except for identity, timestamp
  # and computed columns)
  if (not %$to_insert) {
    for my $col ($source->columns) {
      next if $col eq $identity_col;

      my $info = $source->column_info($col);

      next if ref $info->{default_value} eq 'SCALAR'
        || (exists $info->{data_type} && (not defined $info->{data_type}));

      next if $info->{data_type} && $info->{data_type} =~ /^timestamp\z/i;

      $to_insert->{$col} = \'DEFAULT';
    }
  }

  my $blob_cols = $self->_remove_blob_cols($source, $to_insert);

  # do we need the horrific SELECT MAX(COL) hack?
  my $dumb_last_insert_id =
       $identity_col
    && (not exists $to_insert->{$identity_col})
    && ($self->_identity_method||'') ne '@@IDENTITY';

  my $next = $self->next::can;

  # we are already in a transaction, or there are no blobs
  # and we don't need the PK - just (try to) do it
  if ($self->{transaction_depth}
        || (!$blob_cols && !$dumb_last_insert_id)
  ) {
    return $self->_insert (
      $next, $source, $to_insert, $blob_cols, $identity_col
    );
  }

  # otherwise use the _writer_storage to do the insert+transaction on another
  # connection
  my $guard = $self->_writer_storage->txn_scope_guard;

  my $updated_cols = $self->_writer_storage->_insert (
    $next, $source, $to_insert, $blob_cols, $identity_col
  );

  $self->_identity($self->_writer_storage->_identity);

  $guard->commit;

  return $updated_cols;
}

sub _insert {
  my ($self, $next, $source, $to_insert, $blob_cols, $identity_col) = @_;

  my $updated_cols = $self->$next ($source, $to_insert);

  my $final_row = {
    ($identity_col ?
      ($identity_col => $self->last_insert_id($source, $identity_col)) : ()),
    %$to_insert,
    %$updated_cols,
  };

  $self->_insert_blobs ($source, $blob_cols, $final_row) if $blob_cols;

  return $updated_cols;
}

sub update {
  my $self = shift;
  my ($source, $fields, $where, @rest) = @_;

  my $blob_cols = $self->_remove_blob_cols($source, $fields);

  my $table = $source->name;

  my $columns_info = $source->columns_info;

  my $identity_col =
    first { $columns_info->{$_}{is_auto_increment} }
      keys %$columns_info;

  my $is_identity_update = $identity_col && defined $fields->{$identity_col};

  return $self->next::method(@_) unless $blob_cols;

# If there are any blobs in $where, Sybase will return a descriptive error
# message.
# XXX blobs can still be used with a LIKE query, and this should be handled.

# update+blob update(s) done atomically on separate connection
  $self = $self->_writer_storage;

  my $guard = $self->txn_scope_guard;

# First update the blob columns to be updated to '' (taken from $fields, where
# it is originally put by _remove_blob_cols .)
  my %blobs_to_empty = map { ($_ => delete $fields->{$_}) } keys %$blob_cols;

# We can't only update NULL blobs, because blobs cannot be in the WHERE clause.

  $self->next::method($source, \%blobs_to_empty, $where, @rest);

# Now update the blobs before the other columns in case the update of other
# columns makes the search condition invalid.
  $self->_update_blobs($source, $blob_cols, $where);

  my @res;
  if (%$fields) {
    if (wantarray) {
      @res    = $self->next::method(@_);
    }
    elsif (defined wantarray) {
      $res[0] = $self->next::method(@_);
    }
    else {
      $self->next::method(@_);
    }
  }

  $guard->commit;

  return wantarray ? @res : $res[0];
}

sub insert_bulk {
  my $self = shift;
  my ($source, $cols, $data) = @_;

  my $columns_info = $source->columns_info;

  my $identity_col =
    first { $columns_info->{$_}{is_auto_increment} }
      keys %$columns_info;

  my $is_identity_insert = (first { $_ eq $identity_col } @{$cols}) ? 1 : 0;

  my @source_columns = $source->columns;

  my $use_bulk_api =
    $self->_bulk_storage &&
    $self->_get_dbh->{syb_has_blk};

  if ((not $use_bulk_api)
        &&
      (ref($self->_dbi_connect_info->[0]) eq 'CODE')
        &&
      (not $self->_bulk_disabled_due_to_coderef_connect_info_warned)) {
    carp <<'EOF';
Bulk API support disabled due to use of a CODEREF connect_info. Reverting to
regular array inserts.
EOF
    $self->_bulk_disabled_due_to_coderef_connect_info_warned(1);
  }

  if (not $use_bulk_api) {
    my $blob_cols = $self->_remove_blob_cols_array($source, $cols, $data);

# _execute_array uses a txn anyway, but it ends too early in case we need to
# select max(col) to get the identity for inserting blobs.
    ($self, my $guard) = $self->{transaction_depth} == 0 ?
      ($self->_writer_storage, $self->_writer_storage->txn_scope_guard)
      :
      ($self, undef);

    local $self->{insert_bulk} = 1;

    $self->next::method(@_);

    if ($blob_cols) {
      if ($is_identity_insert) {
        $self->_insert_blobs_array ($source, $blob_cols, $cols, $data);
      }
      else {
        my @cols_with_identities = (@$cols, $identity_col);

        ## calculate identities
        # XXX This assumes identities always increase by 1, which may or may not
        # be true.
        my ($last_identity) =
          $self->_dbh->selectrow_array (
            $self->_fetch_identity_sql($source, $identity_col)
          );
        my @identities = (($last_identity - @$data + 1) .. $last_identity);

        my @data_with_identities = map [@$_, shift @identities], @$data;

        $self->_insert_blobs_array (
          $source, $blob_cols, \@cols_with_identities, \@data_with_identities
        );
      }
    }

    $guard->commit if $guard;

    return;
  }

# otherwise, use the bulk API

# rearrange @$data so that columns are in database order
  my %orig_idx;
  @orig_idx{@$cols} = 0..$#$cols;

  my %new_idx;
  @new_idx{@source_columns} = 0..$#source_columns;

  my @new_data;
  for my $datum (@$data) {
    my $new_datum = [];
    for my $col (@source_columns) {
# identity data will be 'undef' if not $is_identity_insert
# columns with defaults will also be 'undef'
      $new_datum->[ $new_idx{$col} ] =
        exists $orig_idx{$col} ? $datum->[ $orig_idx{$col} ] : undef;
    }
    push @new_data, $new_datum;
  }

# bcp identity index is 1-based
  my $identity_idx = exists $new_idx{$identity_col} ?
    $new_idx{$identity_col} + 1 : 0;

## Set a client-side conversion error handler, straight from DBD::Sybase docs.
# This ignores any data conversion errors detected by the client side libs, as
# they are usually harmless.
  my $orig_cslib_cb = DBD::Sybase::set_cslib_cb(
    Sub::Name::subname insert_bulk => sub {
      my ($layer, $origin, $severity, $errno, $errmsg, $osmsg, $blkmsg) = @_;

      return 1 if $errno == 36;

      carp
        "Layer: $layer, Origin: $origin, Severity: $severity, Error: $errno" .
        ($errmsg ? "\n$errmsg" : '') .
        ($osmsg  ? "\n$osmsg"  : '')  .
        ($blkmsg ? "\n$blkmsg" : '');

      return 0;
  });

  my $exception = '';
  try {
    my $bulk = $self->_bulk_storage;

    my $guard = $bulk->txn_scope_guard;

## XXX get this to work instead of our own $sth
## will require SQLA or *Hacks changes for ordered columns
#    $bulk->next::method($source, \@source_columns, \@new_data, {
#      syb_bcp_attribs => {
#        identity_flag   => $is_identity_insert,
#        identity_column => $identity_idx,
#      }
#    });
    my $sql = 'INSERT INTO ' .
      $bulk->sql_maker->_quote($source->name) . ' (' .
# colname list is ignored for BCP, but does no harm
      (join ', ', map $bulk->sql_maker->_quote($_), @source_columns) . ') '.
      ' VALUES ('.  (join ', ', ('?') x @source_columns) . ')';

## XXX there's a bug in the DBD::Sybase bulk support that makes $sth->finish for
## a prepare_cached statement ineffective. Replace with ->sth when fixed, or
## better yet the version above. Should be fixed in DBD::Sybase .
    my $sth = $bulk->_get_dbh->prepare($sql,
#      'insert', # op
      {
        syb_bcp_attribs => {
          identity_flag   => $is_identity_insert,
          identity_column => $identity_idx,
        }
      }
    );

    my @bind = do {
      my $idx = 0;
      map [ $_, $idx++ ], @source_columns;
    };

    $self->_execute_array(
      $source, $sth, \@bind, \@source_columns, \@new_data, sub {
        $guard->commit
      }
    );

    $bulk->_query_end($sql);
  } catch {
    $exception = shift;
  };

  DBD::Sybase::set_cslib_cb($orig_cslib_cb);

  if ($exception =~ /-Y option/) {
    my $w = 'Sybase bulk API operation failed due to character set incompatibility, '
          . 'reverting to regular array inserts. Try unsetting the LANG environment variable'
    ;
    $w .= "\n$exception" if $self->debug;
    carp $w;

    $self->_bulk_storage(undef);
    unshift @_, $self;
    goto \&insert_bulk;
  }
  elsif ($exception) {
# rollback makes the bulkLogin connection unusable
    $self->_bulk_storage->disconnect;
    $self->throw_exception($exception);
  }
}

sub _dbh_execute_array {
  my ($self, $sth, $tuple_status, $cb) = @_;

  my $rv = $self->next::method($sth, $tuple_status);
  $cb->() if $cb;

  return $rv;
}

# Make sure blobs are not bound as placeholders, and return any non-empty ones
# as a hash.
sub _remove_blob_cols {
  my ($self, $source, $fields) = @_;

  my %blob_cols;

  for my $col (keys %$fields) {
    if ($self->_is_lob_column($source, $col)) {
      my $blob_val = delete $fields->{$col};
      if (not defined $blob_val) {
        $fields->{$col} = \'NULL';
      }
      else {
        $fields->{$col} = \"''";
        $blob_cols{$col} = $blob_val unless $blob_val eq '';
      }
    }
  }

  return %blob_cols ? \%blob_cols : undef;
}

# same for insert_bulk
sub _remove_blob_cols_array {
  my ($self, $source, $cols, $data) = @_;

  my @blob_cols;

  for my $i (0..$#$cols) {
    my $col = $cols->[$i];

    if ($self->_is_lob_column($source, $col)) {
      for my $j (0..$#$data) {
        my $blob_val = delete $data->[$j][$i];
        if (not defined $blob_val) {
          $data->[$j][$i] = \'NULL';
        }
        else {
          $data->[$j][$i] = \"''";
          $blob_cols[$j][$i] = $blob_val
            unless $blob_val eq '';
        }
      }
    }
  }

  return @blob_cols ? \@blob_cols : undef;
}

sub _update_blobs {
  my ($self, $source, $blob_cols, $where) = @_;

  my @primary_cols = try
    { $source->_pri_cols }
    catch {
      $self->throw_exception("Cannot update TEXT/IMAGE column(s): $_")
    };

# check if we're updating a single row by PK
  my $pk_cols_in_where = 0;
  for my $col (@primary_cols) {
    $pk_cols_in_where++ if defined $where->{$col};
  }
  my @rows;

  if ($pk_cols_in_where == @primary_cols) {
    my %row_to_update;
    @row_to_update{@primary_cols} = @{$where}{@primary_cols};
    @rows = \%row_to_update;
  } else {
    my $cursor = $self->select ($source, \@primary_cols, $where, {});
    @rows = map {
      my %row; @row{@primary_cols} = @$_; \%row
    } $cursor->all;
  }

  for my $row (@rows) {
    $self->_insert_blobs($source, $blob_cols, $row);
  }
}

sub _insert_blobs {
  my ($self, $source, $blob_cols, $row) = @_;
  my $dbh = $self->_get_dbh;

  my $table = $source->name;

  my %row = %$row;
  my @primary_cols = try
    { $source->_pri_cols }
    catch {
      $self->throw_exception("Cannot update TEXT/IMAGE column(s): $_")
    };

  $self->throw_exception('Cannot update TEXT/IMAGE column(s) without primary key values')
    if ((grep { defined $row{$_} } @primary_cols) != @primary_cols);

  for my $col (keys %$blob_cols) {
    my $blob = $blob_cols->{$col};

    my %where = map { ($_, $row{$_}) } @primary_cols;

    my $cursor = $self->select ($source, [$col], \%where, {});
    $cursor->next;
    my $sth = $cursor->sth;

    if (not $sth) {
      $self->throw_exception(
          "Could not find row in table '$table' for blob update:\n"
        . (Dumper \%where)
      );
    }

    try {
      do {
        $sth->func('CS_GET', 1, 'ct_data_info') or die $sth->errstr;
      } while $sth->fetch;

      $sth->func('ct_prepare_send') or die $sth->errstr;

      my $log_on_update = $self->_blob_log_on_update;
      $log_on_update    = 1 if not defined $log_on_update;

      $sth->func('CS_SET', 1, {
        total_txtlen => length($blob),
        log_on_update => $log_on_update
      }, 'ct_data_info') or die $sth->errstr;

      $sth->func($blob, length($blob), 'ct_send_data') or die $sth->errstr;

      $sth->func('ct_finish_send') or die $sth->errstr;
    }
    catch {
      if ($self->using_freetds) {
        $self->throw_exception (
          "TEXT/IMAGE operation failed, probably because you are using FreeTDS: $_"
        );
      }
      else {
        $self->throw_exception($_);
      }
    }
    finally {
      $sth->finish if $sth;
    };
  }
}

sub _insert_blobs_array {
  my ($self, $source, $blob_cols, $cols, $data) = @_;

  for my $i (0..$#$data) {
    my $datum = $data->[$i];

    my %row;
    @row{ @$cols } = @$datum;

    my %blob_vals;
    for my $j (0..$#$cols) {
      if (exists $blob_cols->[$i][$j]) {
        $blob_vals{ $cols->[$j] } = $blob_cols->[$i][$j];
      }
    }

    $self->_insert_blobs ($source, \%blob_vals, \%row);
  }
}

=head2 connect_call_datetime_setup

Used as:

  on_connect_call => 'datetime_setup'

In L<connect_info|DBIx::Class::Storage::DBI/connect_info> to set:

  $dbh->syb_date_fmt('ISO_strict'); # output fmt: 2004-08-21T14:36:48.080Z
  $dbh->do('set dateformat mdy');   # input fmt:  08/13/1979 18:08:55.080

On connection for use with L<DBIx::Class::InflateColumn::DateTime>, using
L<DateTime::Format::Sybase>, which you will need to install.

This works for both C<DATETIME> and C<SMALLDATETIME> columns, although
C<SMALLDATETIME> columns only have minute precision.

=cut

{
  my $old_dbd_warned = 0;

  sub connect_call_datetime_setup {
    my $self = shift;
    my $dbh = $self->_get_dbh;

    if ($dbh->can('syb_date_fmt')) {
      # amazingly, this works with FreeTDS
      $dbh->syb_date_fmt('ISO_strict');
    } elsif (not $old_dbd_warned) {
      carp "Your DBD::Sybase is too old to support ".
      "DBIx::Class::InflateColumn::DateTime, please upgrade!";
      $old_dbd_warned = 1;
    }

    $dbh->do('SET DATEFORMAT mdy');

    1;
  }
}

sub datetime_parser_type { "DateTime::Format::Sybase" }

# ->begin_work and such have no effect with FreeTDS but we run them anyway to
# let the DBD keep any state it needs to.
#
# If they ever do start working, the extra statements will do no harm (because
# Sybase supports nested transactions.)

sub _dbh_begin_work {
  my $self = shift;

# bulkLogin=1 connections are always in a transaction, and can only call BEGIN
# TRAN once. However, we need to make sure there's a $dbh.
  return if $self->_is_bulk_storage && $self->_dbh && $self->_began_bulk_work;

  $self->next::method(@_);

  if ($self->using_freetds) {
    $self->_get_dbh->do('BEGIN TRAN');
  }

  $self->_began_bulk_work(1) if $self->_is_bulk_storage;
}

sub _dbh_commit {
  my $self = shift;
  if ($self->using_freetds) {
    $self->_dbh->do('COMMIT');
  }
  return $self->next::method(@_);
}

sub _dbh_rollback {
  my $self = shift;
  if ($self->using_freetds) {
    $self->_dbh->do('ROLLBACK');
  }
  return $self->next::method(@_);
}

# savepoint support using ASE syntax

sub _svp_begin {
  my ($self, $name) = @_;

  $self->_get_dbh->do("SAVE TRANSACTION $name");
}

# A new SAVE TRANSACTION with the same name releases the previous one.
sub _svp_release { 1 }

sub _svp_rollback {
  my ($self, $name) = @_;

  $self->_get_dbh->do("ROLLBACK TRANSACTION $name");
}

1;

=head1 Schema::Loader Support

As of version C<0.05000>, L<DBIx::Class::Schema::Loader> should work well with
most (if not all) versions of Sybase ASE.

=head1 FreeTDS

This driver supports L<DBD::Sybase> compiled against FreeTDS
(L<http://www.freetds.org/>) to the best of our ability, however it is
recommended that you recompile L<DBD::Sybase> against the Sybase Open Client
libraries. They are a part of the Sybase ASE distribution:

The Open Client FAQ is here:
L<http://www.isug.com/Sybase_FAQ/ASE/section7.html>.

Sybase ASE for Linux (which comes with the Open Client libraries) may be
downloaded here: L<http://response.sybase.com/forms/ASE_Linux_Download>.

To see if you're using FreeTDS check C<< $schema->storage->using_freetds >>, or run:

  perl -MDBI -le 'my $dbh = DBI->connect($dsn, $user, $pass); print $dbh->{syb_oc_version}'

Some versions of the libraries involved will not support placeholders, in which
case the storage will be reblessed to
L<DBIx::Class::Storage::DBI::Sybase::ASE::NoBindVars>.

In some configurations, placeholders will work but will throw implicit type
conversion errors for anything that's not expecting a string. In such a case,
the C<auto_cast> option from L<DBIx::Class::Storage::DBI::AutoCast> is
automatically set, which you may enable on connection with
L<DBIx::Class::Storage::DBI::AutoCast/connect_call_set_auto_cast>. The type info
for the C<CAST>s is taken from the L<DBIx::Class::ResultSource/data_type>
definitions in your Result classes, and are mapped to a Sybase type (if it isn't
already) using a mapping based on L<SQL::Translator>.

In other configurations, placeholders will work just as they do with the Sybase
Open Client libraries.

Inserts or updates of TEXT/IMAGE columns will B<NOT> work with FreeTDS.

=head1 INSERTS WITH PLACEHOLDERS

With placeholders enabled, inserts are done in a transaction so that there are
no concurrency issues with getting the inserted identity value using
C<SELECT MAX(col)>, which is the only way to get the C<IDENTITY> value in this
mode.

In addition, they are done on a separate connection so that it's possible to
have active cursors when doing an insert.

When using C<DBIx::Class::Storage::DBI::Sybase::ASE::NoBindVars> transactions
are disabled, as there are no concurrency issues with C<SELECT @@IDENTITY> as
it's a session variable.

=head1 TRANSACTIONS

Due to limitations of the TDS protocol, L<DBD::Sybase>, or both, you cannot
begin a transaction while there are active cursors, nor can you use multiple
active cursors within a transaction. An active cursor is, for example, a
L<ResultSet|DBIx::Class::ResultSet> that has been executed using C<next> or
C<first> but has not been exhausted or L<reset|DBIx::Class::ResultSet/reset>.

For example, this will not work:

  $schema->txn_do(sub {
    my $rs = $schema->resultset('Book');
    while (my $row = $rs->next) {
      $schema->resultset('MetaData')->create({
        book_id => $row->id,
        ...
      });
    }
  });

This won't either:

  my $first_row = $large_rs->first;
  $schema->txn_do(sub { ... });

Transactions done for inserts in C<AutoCommit> mode when placeholders are in use
are not affected, as they are done on an extra database handle.

Some workarounds:

=over 4

=item * use L<DBIx::Class::Storage::DBI::Replicated>

=item * L<connect|DBIx::Class::Schema/connect> another L<Schema|DBIx::Class::Schema>

=item * load the data from your cursor with L<DBIx::Class::ResultSet/all>

=back

=head1 MAXIMUM CONNECTIONS

The TDS protocol makes separate connections to the server for active statements
in the background. By default the number of such connections is limited to 25,
on both the client side and the server side.

This is a bit too low for a complex L<DBIx::Class> application, so on connection
the client side setting is set to C<256> (see L<DBD::Sybase/maxConnect>.) You
can override it to whatever setting you like in the DSN.

See
L<http://infocenter.sybase.com/help/index.jsp?topic=/com.sybase.help.ase_15.0.sag1/html/sag1/sag1272.htm>
for information on changing the setting on the server side.

=head1 DATES

See L</connect_call_datetime_setup> to setup date formats
for L<DBIx::Class::InflateColumn::DateTime>.

=head1 TEXT/IMAGE COLUMNS

L<DBD::Sybase> compiled with FreeTDS will B<NOT> allow you to insert or update
C<TEXT/IMAGE> columns.

Setting C<< $dbh->{LongReadLen} >> will also not work with FreeTDS use either:

  $schema->storage->dbh->do("SET TEXTSIZE $bytes");

or

  $schema->storage->set_textsize($bytes);

instead.

However, the C<LongReadLen> you pass in
L<connect_info|DBIx::Class::Storage::DBI/connect_info> is used to execute the
equivalent C<SET TEXTSIZE> command on connection.

See L</connect_call_blob_setup> for a
L<connect_info|DBIx::Class::Storage::DBI/connect_info> setting you need to work
with C<IMAGE> columns.

=head1 BULK API

The experimental L<DBD::Sybase> Bulk API support is used for
L<populate|DBIx::Class::ResultSet/populate> in B<void> context, in a transaction
on a separate connection.

To use this feature effectively, use a large number of rows for each
L<populate|DBIx::Class::ResultSet/populate> call, eg.:

  while (my $rows = $data_source->get_100_rows()) {
    $rs->populate($rows);
  }

B<NOTE:> the L<add_columns|DBIx::Class::ResultSource/add_columns>
calls in your C<Result> classes B<must> list columns in database order for this
to work. Also, you may have to unset the C<LANG> environment variable before
loading your app, if it doesn't match the character set of your database.

When inserting IMAGE columns using this method, you'll need to use
L</connect_call_blob_setup> as well.

=head1 COMPUTED COLUMNS

If you have columns such as:

  created_dtm AS getdate()

represent them in your Result classes as:

  created_dtm => {
    data_type => undef,
    default_value => \'getdate()',
    is_nullable => 0,
  }

The C<data_type> must exist and must be C<undef>. Then empty inserts will work
on tables with such columns.

=head1 TIMESTAMP COLUMNS

C<timestamp> columns in Sybase ASE are not really timestamps, see:
L<http://dba.fyicenter.com/Interview-Questions/SYBASE/The_timestamp_datatype_in_Sybase_.html>.

They should be defined in your Result classes as:

  ts => {
    data_type => 'timestamp',
    is_nullable => 0,
    inflate_datetime => 0,
  }

The C<<inflate_datetime => 0>> is necessary if you use
L<DBIx::Class::InflateColumn::DateTime>, and most people do, and still want to
be able to read these values.

The values will come back as hexadecimal.

=head1 TODO

=over

=item *

Transitions to AutoCommit=0 (starting a transaction) mode by exhausting
any active cursors, using eager cursors.

=item *

Real limits and limited counts using stored procedures deployed on startup.

=item *

Adaptive Server Anywhere (ASA) support

=item *

Blob update with a LIKE query on a blob, without invalidating the WHERE condition.

=item *

bulk_insert using prepare_cached (see comments.)

=back

=head1 AUTHOR

See L<DBIx::Class/CONTRIBUTORS>.

=head1 LICENSE

You may distribute this code under the same terms as Perl itself.

=cut
# vim:sts=2 sw=2: