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#======================================================================
package DBD::SQLite::VirtualTable::FileContent;
#======================================================================
use strict;
use warnings;
use base 'DBD::SQLite::VirtualTable';
my %option_ok = map {($_ => 1)} qw/source content_col path_col
expose root get_content/;
my %defaults = (
content_col => "content",
path_col => "path",
expose => "*",
get_content => "DBD::SQLite::VirtualTable::FileContent::get_content",
);
#----------------------------------------------------------------------
# object instanciation
#----------------------------------------------------------------------
sub NEW {
my $class = shift;
my $self = $class->_PREPARE_SELF(@_);
local $" = ", "; # for array interpolation in strings
# initial parameter check
!@{$self->{columns}}
or die "${class}->NEW(): illegal options: @{$self->{columns}}";
$self->{options}{source}
or die "${class}->NEW(): missing (source=...)";
my @bad_options = grep {!$option_ok{$_}} keys %{$self->{options}};
!@bad_options
or die "${class}->NEW(): bad options: @bad_options";
# defaults ... tempted to use //= but we still want to support perl 5.8 :-(
foreach my $k (keys %defaults) {
defined $self->{options}{$k}
or $self->{options}{$k} = $defaults{$k};
}
# get list of columns from the source table
my $src_table = $self->{options}{source};
my $sql = "PRAGMA table_info($src_table)";
my $dbh = ${$self->{dbh_ref}}; # can't use method ->dbh, not blessed yet
my $src_info = $dbh->selectall_arrayref($sql, {Slice => [1, 2]});
@$src_info
or die "${class}->NEW(source=$src_table): no such table in database";
# associate each source colname with its type info or " " (should eval true)
my %src_col = map { ($_->[0] => $_->[1] || " ") } @$src_info;
# check / complete the exposed columns
my @exposed_cols;
if ($self->{options}{expose} eq '*') {
@exposed_cols = map {$_->[0]} @$src_info;
}
else {
@exposed_cols = split /\s*,\s*/, $self->{options}{expose};
my @bad_cols = grep { !$src_col{$_} } @exposed_cols;
die "table $src_table has no column named @bad_cols" if @bad_cols;
}
for (@exposed_cols) {
die "$class: $self->{options}{content_col} cannot be both the "
. "content_col and an exposed col" if $_ eq $self->{options}{content_col};
}
# build the list of columns for this table
$self->{columns} = [ "$self->{options}{content_col} TEXT",
map {"$_ $src_col{$_}"} @exposed_cols ];
# acquire a coderef to the get_content() implementation, which
# was given as a symbolic reference in %options
no strict 'refs';
$self->{get_content} = \ &{$self->{options}{get_content}};
bless $self, $class;
}
sub _build_headers {
my $self = shift;
my $cols = $self->sqlite_table_info;
# headers : names of columns, without type information
$self->{headers} = [ map {$_->{name}} @$cols ];
}
#----------------------------------------------------------------------
# method for initiating a search
#----------------------------------------------------------------------
sub BEST_INDEX {
my ($self, $constraints, $order_by) = @_;
$self->_build_headers if !$self->{headers};
my @conditions;
my $ix = 0;
foreach my $constraint (grep {$_->{usable}} @$constraints) {
my $col = $constraint->{col};
# if this is the content column, skip because we can't filter on it
next if $col == 0;
# for other columns, build a fragment for SQL WHERE on the underlying table
my $colname = $col == -1 ? "rowid" : $self->{headers}[$col];
push @conditions, "$colname $constraint->{op} ?";
$constraint->{argvIndex} = $ix++;
$constraint->{omit} = 1; # SQLite doesn't need to re-check the op
}
# TODO : exploit $order_by to add ordering clauses within idxStr
my $outputs = {
idxNum => 1,
idxStr => join(" AND ", @conditions),
orderByConsumed => 0,
estimatedCost => 1.0,
estimatedRows => undef,
};
return $outputs;
}
#----------------------------------------------------------------------
# method for preventing updates
#----------------------------------------------------------------------
sub _SQLITE_UPDATE {
my ($self, $old_rowid, $new_rowid, @values) = @_;
die "attempt to update a readonly virtual table";
}
#----------------------------------------------------------------------
# file slurping function (not a method!)
#----------------------------------------------------------------------
sub get_content {
my ($path, $root) = @_;
$path = "$root/$path" if $root;
my $content = "";
if (open my $fh, "<", $path) {
local $/; # slurp the whole file into a scalar
$content = <$fh>;
close $fh;
}
else {
warn "can't open $path";
}
return $content;
}
#======================================================================
package DBD::SQLite::VirtualTable::FileContent::Cursor;
#======================================================================
use strict;
use warnings;
use base "DBD::SQLite::VirtualTable::Cursor";
sub FILTER {
my ($self, $idxNum, $idxStr, @values) = @_;
my $vtable = $self->{vtable};
# build SQL
local $" = ", ";
my @cols = @{$vtable->{headers}};
$cols[0] = 'rowid'; # replace the content column by the rowid
push @cols, $vtable->{options}{path_col}; # path col in last position
my $sql = "SELECT @cols FROM $vtable->{options}{source}";
$sql .= " WHERE $idxStr" if $idxStr;
# request on the index table
my $dbh = $vtable->dbh;
$self->{sth} = $dbh->prepare($sql)
or die DBI->errstr;
$self->{sth}->execute(@values);
$self->{row} = $self->{sth}->fetchrow_arrayref;
return;
}
sub EOF {
my ($self) = @_;
return !$self->{row};
}
sub NEXT {
my ($self) = @_;
$self->{row} = $self->{sth}->fetchrow_arrayref;
}
sub COLUMN {
my ($self, $idxCol) = @_;
return $idxCol == 0 ? $self->file_content : $self->{row}[$idxCol];
}
sub ROWID {
my ($self) = @_;
return $self->{row}[0];
}
sub file_content {
my ($self) = @_;
my $root = $self->{vtable}{options}{root};
my $path = $self->{row}[-1];
my $get_content_func = $self->{vtable}{get_content};
return $get_content_func->($path, $root);
}
1;
__END__
=head1 NAME
DBD::SQLite::VirtualTable::FileContent -- virtual table for viewing file contents
=head1 SYNOPSIS
Within Perl :
$dbh->sqlite_create_module(fcontent => "DBD::SQLite::VirtualTable::FileContent");
Then, within SQL :
CREATE VIRTUAL TABLE tbl USING fcontent(
source = src_table,
content_col = content,
path_col = path,
expose = "path, col1, col2, col3", -- or "*"
root = "/foo/bar"
get_content = Foo::Bar::read_from_file
);
SELECT col1, path, content FROM tbl WHERE ...;
=head1 DESCRIPTION
A "FileContent" virtual table is bound to some underlying I<source
table>, which has a column containing paths to files. The virtual
table behaves like a database view on the source table, with an added
column which exposes the content from those files.
This is especially useful as an "external content" to some
fulltext table (see L<DBD::SQLite::Fulltext_search>) : the index
table stores some metadata about files, and then the fulltext engine
can index both the metadata and the file contents.
=head1 PARAMETERS
Parameters for creating a C<FileContent> virtual table are
specified within the C<CREATE VIRTUAL TABLE> statement, just
like regular column declarations, but with an '=' sign.
Authorized parameters are :
=over
=item C<source>
The name of the I<source table>.
This parameter is mandatory. All other parameters are optional.
=item C<content_col>
The name of the virtual column exposing file contents.
The default is C<content>.
=item C<path_col>
The name of the column in C<source> that contains paths to files.
The default is C<path>.
=item C<expose>
A comma-separated list (within double quotes) of source column names
to be exposed by the virtual table. The default is C<"*">, which means
all source columns.
=item C<root>
An optional root directory that will be prepended to the I<path> column
when opening files.
=item C<get_content>
Fully qualified name of a Perl function for reading file contents.
The default implementation just slurps the entire file into a string;
but this hook can point to more sophisticated implementations, like for
example a function that would remove html tags. The hooked function is
called like this :
$file_content = $get_content->($path, $root);
=back
=head1 AUTHOR
Laurent Dami E<lt>dami@cpan.orgE<gt>
=head1 COPYRIGHT AND LICENSE
Copyright Laurent Dami, 2014.
This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.
=cut