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pbot/updates/lib4422/DualIndexSQLiteObject.pm
Pragmatic Software 3d97dc2c33 Rename "modules" to "applets"
"Applet" is a much better name for the external command-line
scripts and programs that can be loaded as PBot commands. They
will no longer be confused with Perl modules.

https://en.wikipedia.org/wiki/Applet
2021-11-19 18:05:50 -08:00

946 lines
26 KiB
Perl

# File: DualIndexSQLiteObject.pm
#
# Purpose: Provides a dual-indexed SQLite object with an abstracted API that includes
# setting and deleting values, caching, displaying nearest matches, etc. Designed to
# be as compatible as possible with DualIndexHashObject; e.g. get_keys, get_data, etc.
#
# This class is ideal if you don't want to store all of the data in working memory.
# Instead, the data is stored to and fetched from an SQLite database. To ensure
# lightning fast performance, data that is accessed will be temporarily cached
# in working memory. The caching TTL value can be adjusted via the
# `dualindexsqliteobject.cache_timeout` registry entry.
#
# Since this class does not store all the data in working memory, it provides
# iterator-based access via get_each, get_next and get_all.
#
# SPDX-FileCopyrightText: 2021 Pragmatic Software <pragma78@gmail.com>
# SPDX-License-Identifier: MIT
package lib4422::DualIndexSQLiteObject;
use warnings;
use strict;
use feature ':5.16';
use DBI;
use Text::Levenshtein::XS qw(distance);
sub new {
my ($class, %args) = @_;
Carp::croak("Missing pbot reference to " . __FILE__) unless exists $args{pbot};
my $self = bless {}, $class;
$self->{pbot} = delete $args{pbot};
$self->initialize(%args);
return $self;
}
sub initialize {
my ($self, %conf) = @_;
$self->{name} = $conf{name} // 'Dual Index SQLite object';
$self->{filename} = $conf{filename} // Carp::croak("Missing filename in " . __FILE__);
$self->{dbh} = undef;
$self->{cache} = {};
$self->begin;
}
sub begin {
my ($self) = @_;
$self->{pbot}->{logger}->log("Opening $self->{name} database ($self->{filename})\n");
$self->{dbh} = DBI->connect("dbi:SQLite:dbname=$self->{filename}", undef, undef,
{ AutoCommit => 0, RaiseError => 1, PrintError => 0, AutoInactiveDestroy => 1, sqlite_unicode => 1 }
) or die $DBI::errstr;
}
sub end {
my ($self) = @_;
$self->{pbot}->{logger}->log("Closing $self->{name} database ($self->{filename})\n");
if (defined $self->{dbh}) {
$self->{dbh}->commit;
$self->{dbh}->disconnect;
$self->{dbh} = undef;
}
}
sub load {
my ($self) = @_;
$self->create_database;
$self->create_cache;
}
sub save {
my ($self) = @_;
return if not $self->{dbh};
eval { $self->{dbh}->commit };
if ($@) {
$self->{pbot}->{logger}->log("Error saving $self->{name}: $@");
}
}
sub create_database {
my ($self) = @_;
eval {
$self->{dbh}->do(<<SQL);
CREATE TABLE IF NOT EXISTS Stuff (
index1 TEXT COLLATE NOCASE,
index2 TEXT COLLATE NOCASE
)
SQL
$self->{dbh}->do('CREATE INDEX IF NOT EXISTS idx1 ON Stuff (index1, index2)');
};
$self->{pbot}->{logger}->log("Error creating $self->{name} databse: $@") if $@;
}
sub create_cache {
my ($self) = @_;
$self->{cache} = {};
my ($index1_count, $index2_count) = (0, 0);
foreach my $index1 ($self->get_keys(undef, undef, 1)) {
my $lc_index1 = lc $index1;
$index1_count++;
foreach my $index2 ($self->get_keys($lc_index1, undef, 1)) {
my $lc_index2 = lc $index2;
$index2_count++;
$self->{cache}->{$lc_index1}->{$lc_index2} = {};
# _name contains original typographical case
if ($index1 ne $lc_index1) {
$self->{cache}->{$lc_index1}->{_name} = $index1;
}
if ($index2 ne $lc_index2) {
$self->{cache}->{$lc_index1}->{$lc_index2}->{_name} = $index2;
}
}
}
$self->{pbot}->{logger}->log("Cached $index2_count $self->{name} objects in $index1_count groups.\n");
}
sub cache_remove {
my ($self, $index1, $index2) = @_;
if (not defined $index2) {
# remove index1
delete $self->{cache}->{$index1};
} else {
# remove index2
delete $self->{cache}->{$index1}->{$index2};
# remove index1 if it has no more keys left (aside from _name)
if (not grep { $_ ne '_name' } keys %{$self->{cache}->{$index1}}) {
delete $self->{cache}->{$index1};
}
}
}
sub enqueue_decache {
my ($self, $index1, $index2) = @_;
}
sub create_metadata {
my ($self, $columns) = @_;
return if not $self->{dbh};
$self->{columns} = $columns;
eval {
my %existing = ();
foreach my $col (@{$self->{dbh}->selectall_arrayref("PRAGMA TABLE_INFO(Stuff)")}) {
$existing{$col->[1]} = $col->[2];
}
foreach my $col (sort keys %$columns) {
unless (exists $existing{$col}) {
$self->{dbh}->do("ALTER TABLE Stuff ADD COLUMN \"$col\" $columns->{$col}");
}
}
$self->{dbh}->commit;
};
if ($@) {
$self->{pbot}->{logger}->log("Error creating metadata for $self->{name}: $@");
$self->{dbh}->rollback;
}
}
sub load_metadata {
my ($self) = @_;
return if not $self->{dbh};
$self->{columns} = {};
eval {
my %existing = ();
foreach my $col (@{$self->{dbh}->selectall_arrayref("PRAGMA TABLE_INFO(Stuff)")}) {
$self->{columns}->{$col->[1]} = $col->[2];
}
};
if ($@) {
$self->{pbot}->{logger}->log("Error loading metadata for $self->{name}: $@");
}
}
sub levenshtein_matches {
my ($self, $index1, $index2, $distance, $strictnamespace) = @_;
$index1 //= '.*';
$distance //= 0.60;
my $output = 'none';
if (not $index2) {
my @matches;
my $length_a = length $index1;
foreach my $index (sort $self->get_keys) {
my $distance_result = distance($index1, $index, 20);
next if not defined $distance_result;
my $length_b = length $index;
my $length = $length_a > $length_b ? $length_a : $length_b;
if ($distance_result / $length < $distance) {
my $name = $self->get_data($index, '_name');
if ($name =~ / /) {
push @matches, "\"$name\"";
} else {
push @matches, $name;
}
}
}
$output = join ', ', @matches;
} else {
if (not $self->exists($index1)) {
return $output;
}
my %sections;
my $section;
my $length_a = length $index2;
foreach my $i1 (sort $self->get_keys) {
$section = $self->get_data($i1, '_name');
$section = 'global' if $section eq '.*';
if ($strictnamespace) {
next unless $i1 eq '.*' or lc $i1 eq lc $index1;
}
foreach my $i2 (sort $self->get_keys($i1)) {
my $distance_result = distance($index2, $i2, 20);
next if not defined $distance_result;
my $length_b = length $i2;
my $length = $length_a > $length_b ? $length_a : $length_b;
if ($distance_result / $length < $distance) {
my $name = $self->get_data($i1, $i2, '_name');
if ($name =~ / /) {
push @{$sections{$section}}, "\"$name\"";
} else {
push @{$sections{$section}}, $name;
}
}
}
}
$output = '';
foreach $section (sort keys %sections) {
$output .= "[$section] ";
$output .= join ', ', @{$sections{$section}};
$output .= '; ';
}
$output =~ s/; $//;
}
$output =~ s/(.*), /$1 or /;
$output = 'none' if not length $output;
return $output;
}
sub exists {
my ($self, $index1, $index2, $data_index) = @_;
return 0 if not defined $index1;
$index1 = lc $index1;
return 0 if not grep { $_ eq $index1 } $self->get_keys;
return 1 if not defined $index2;
$index2 = lc $index2;
return 0 if not grep { $_ eq $index2 } $self->get_keys($index1);
return 1 if not defined $data_index;
return defined $self->get_data($index1, $index2, $data_index);
}
sub get_keys {
my ($self, $index1, $index2, $nocache) = @_;
my @keys;
if (not defined $index1) {
if (not $nocache) {
return keys %{$self->{cache}};
}
@keys = eval {
my $context = $self->{dbh}->selectall_arrayref('SELECT DISTINCT index1 FROM Stuff');
if (@$context) {
return map { $_->[0] } @$context;
} else {
return ();
}
};
if ($@) {
$self->{pbot}->{logger}->log($@);
return undef;
}
return @keys;
}
$index1 = lc $index1;
if (not defined $index2) {
if (not $nocache) {
return grep { $_ ne '_name' } keys %{$self->{cache}->{$index1}};
}
@keys = eval {
my $sth = $self->{dbh}->prepare('SELECT index2 FROM Stuff WHERE index1 = ?');
$sth->execute($index1);
my $context = $sth->fetchall_arrayref;
if (@$context) {
return map { $_->[0] } @$context;
} else {
return ();
}
};
if ($@) {
$self->{pbot}->{logger}->log($@);
return ();
}
return @keys;
}
$index2 = lc $index2;
if (not $nocache) {
@keys = grep { $_ ne '_name' } keys %{$self->{cache}->{$index1}->{$index2}};
return @keys if @keys;
}
@keys = eval {
my $sth = $self->{dbh}->prepare('SELECT * FROM Stuff WHERE index1 = ? AND index2 = ?');
$sth->execute($index1, $index2);
my $context = $sth->fetchall_arrayref({});
my @k = ();
return @k if not @{$context};
my ($lc_index1, $lc_index2) = (lc $index1, lc $index2);
foreach my $key (keys %{$context->[0]}) {
next if $key eq 'index1' or $key eq 'index2';
push @k, $key if defined $context->[0]->{$key};
$self->{cache}->{$lc_index1}->{$lc_index2}->{$key} = $context->[0]->{$key};
}
$self->enqueue_decache($lc_index1, $lc_index2);
return @k;
};
if ($@) {
$self->{pbot}->{logger}->log($@);
return ();
}
return @keys;
}
sub get_each {
my ($self, @opts) = @_;
my $sth = eval {
my $sql = 'SELECT ';
my @keys = ();
my @values = ();
my @where = ();
my @sort = ();
my $everything = 0;
foreach my $expr (@opts) {
my ($key, $op, $value) = $expr =~ /(.*?)\s+([!~=<>]+)\s+(.*)/;
if (not defined $key) {
$key = $expr;
}
if ($key eq '_everything') {
$everything = 1;
push @keys, '*';
next;
}
if ($key eq '_sort') {
if ($value =~ s/^\-//) {
push @sort, "$value DESC";
} else {
$value =~ s/^\+//; # optional
push @sort, "$value ASC";
}
next;
}
if (defined $op) {
my $prefix = 'AND';
if ($op eq '=' or $op eq '==') {
$op = '=';
} elsif ($op eq '!=' or $op eq '<>') {
$op = '!=';
} elsif ($op eq '~' or $op eq '~~') {
$op = 'LIKE';
}
if ($key =~ s/^(OR|AND)\s+//) {
$prefix = $1;
}
$prefix = '' if not @where;
push @where, [ $prefix, $key, $op ];
push @values, $value;
}
push @keys, $key unless $everything or grep { $_ eq $key } @keys;
}
$sql .= join ', ', @keys;
$sql .= ' FROM Stuff WHERE';
my $in_or = 0;
for (my $i = 0; $i < @where; $i++) {
my ($prefix, $key, $op) = @{$where[$i]};
my ($next_prefix, $next_key) = ('', '');
if ($i < @where - 1) {
($next_prefix, $next_key) = @{$where[$i + 1]};
}
if ($next_prefix eq 'OR' and $next_key eq $key) {
$sql .= "$prefix ";
$sql .= '(' if not $in_or;
$sql .= "\"$key\" $op ? ";
$in_or = 1;
} else {
$sql .= "$prefix \"$key\" $op ? ";
if ($in_or) {
$sql .= ') ';
$in_or = 0;
}
}
}
$sql .= ')' if $in_or;
$sql .= ' ORDER BY ' . join(', ', @sort) if @sort;
my $sth = $self->{dbh}->prepare($sql);
my $param = 0;
foreach my $value (@values) {
$sth->bind_param(++$param, $value);
}
$sth->execute;
return $sth;
};
if ($@) {
$self->{pbot}->{logger}->log("Error getting data: $@");
return undef;
}
return $sth;
}
sub get_next {
my ($self, $sth) = @_;
my $data = eval {
return $sth->fetchrow_hashref;
};
if ($@) {
$self->{pbot}->{logger}->log("Error getting next: $@");
return undef;
}
return $data;
}
sub get_all {
my ($self, @opts) = @_;
my $sth = $self->get_each(@opts);
my $data = eval {
return $sth->fetchall_arrayref({});
};
if ($@) {
$self->{pbot}->{logger}->log("Error getting all data: $@\n");
return undef;
}
return @$data;
}
sub get_key_name {
my ($self, $index1, $index2) = @_;
my $lc_index1 = lc $index1;
if (not exists $self->{cache}->{$lc_index1}) {
return $lc_index1;
}
if (not defined $index2) {
if (exists $self->{cache}->{$lc_index1}->{_name}) {
return $self->{cache}->{$lc_index1}->{_name};
} else {
return $lc_index1;
}
}
my $lc_index2 = lc $index2;
if (not exists $self->{cache}->{$lc_index1}->{$lc_index2}) {
return $lc_index2;
}
if (exists $self->{cache}->{$lc_index1}->{$lc_index2}->{_name}) {
return $self->{cache}->{$lc_index1}->{$lc_index2}->{_name};
} else {
return $lc_index2;
}
}
sub get_data {
my ($self, $index1, $index2, $data_index) = @_;
my $lc_index1 = lc $index1;
my $lc_index2 = lc $index2;
if (not exists $self->{cache}->{$lc_index1}) {
return undef;
}
if (not exists $self->{cache}->{$lc_index1}->{$lc_index2} and $lc_index2 ne '_name') {
return undef;
}
if (not defined $data_index) {
# special case for compatibility with DualIndexHashObject
if ($lc_index2 eq '_name') {
if (exists $self->{cache}->{$lc_index1}->{_name}) {
return $self->{cache}->{$lc_index1}->{_name};
} else {
return $lc_index1;
}
}
my $data = eval {
my $sth = $self->{dbh}->prepare('SELECT * FROM Stuff WHERE index1 = ? AND index2 = ?');
$sth->execute($index1, $index2);
my $context = $sth->fetchall_arrayref({});
my $d = {};
foreach my $key (keys %{$context->[0]}) {
next if $key eq 'index1' or $key eq 'index2';
if (defined $context->[0]->{$key}) {
$self->{cache}->{$lc_index1}->{$lc_index2}->{$key} = $context->[0]->{$key};
$d->{$key} = $context->[0]->{$key};
}
}
$self->enqueue_decache($lc_index1, $lc_index2);
return $d;
};
if ($@) {
$self->{pbot}->{logger}->log("Error getting data for ($index1, $index2): $@\n");
return undef;
}
return $data;
}
# special case for compatibility with DualIndexHashObject
if ($data_index eq '_name') {
if (exists $self->{cache}->{$lc_index1}->{$lc_index2}->{_name}) {
return $self->{cache}->{$lc_index1}->{$lc_index2}->{_name};
} else {
return $lc_index2;
}
}
if (exists $self->{cache}->{$lc_index1}->{$lc_index2}->{$data_index}) {
return $self->{cache}->{$lc_index1}->{$lc_index2}->{$data_index};
}
my $value = eval {
my $sth = $self->{dbh}->prepare('SELECT * FROM Stuff WHERE index1 = ? AND index2 = ?');
$sth->execute($index1, $index2);
my $context = $sth->fetchall_arrayref({});
foreach my $key (keys %{$context->[0]}) {
next if $key eq 'index1' or $key eq 'index2';
$self->{cache}->{$lc_index1}->{$lc_index2}->{$key} = $context->[0]->{$key};
}
$self->enqueue_decache($lc_index1, $lc_index2);
return $context->[0]->{$data_index};
};
if ($@) {
$self->{pbot}->{logger}->log("Error getting data for ($index1, $index2, $data_index): $@\n");
return undef;
}
return $value;
}
sub add {
my ($self, $index1, $index2, $data, $quiet) = @_;
my $name1 = $self->get_data($index1, '_name') // $index1;
eval {
my $sth;
if (not $self->exists($index1, $index2)) {
$sth = $self->{dbh}->prepare('INSERT INTO Stuff (index1, index2) VALUES (?, ?)');
$sth->execute($name1, $index2);
}
my $sql = 'UPDATE Stuff SET ';
my $comma = '';
foreach my $key (sort keys %$data) {
if (not exists $self->{columns}->{$key}) {
next;
}
$sql .= "$comma\"$key\" = ?";
$comma = ', ';
}
$sql .= ' WHERE index1 == ? AND index2 == ?';
$sth = $self->{dbh}->prepare($sql);
my $param = 1;
foreach my $key (sort keys %$data) {
next if not exists $self->{columns}->{$key};
$sth->bind_param($param++, $data->{$key});
}
$sth->bind_param($param++, $index1);
$sth->bind_param($param++, $index2);
$sth->execute();
# no errors updating SQL -- now we update cache
my ($lc_index1, $lc_index2) = (lc $index1, lc $index2);
if ($index1 ne $lc_index1 and not exists $self->{cache}->{$lc_index1}->{_name}) {
$self->{cache}->{$lc_index1}->{_name} = $index1;
}
if (grep { $_ ne '_name' } keys %{$self->{cache}->{$lc_index1}->{$lc_index2}}) {
foreach my $key (sort keys %$data) {
next if not exists $self->{columns}->{$key};
$self->{cache}->{$lc_index1}->{$lc_index2}->{$key} = $data->{$key};
}
} else {
$self->{cache}->{$lc_index1}->{lc $index2} = {}
}
if (not exists $self->{cache}->{$lc_index1}->{$lc_index2}->{_name} and $index2 ne $lc_index2) {
$self->{cache}->{$lc_index1}->{$lc_index2}->{_name} = $index2;
}
};
if ($@) {
$self->{pbot}->{logger}->log("Error adding $self->{name} $index2 to $index1: $@\n");
$self->{dbh}->rollback;
return "Error adding $index2 to $name1: $@\n";
}
$index1 = 'global' if $index1 eq '.*';
$index2 = "\"$index2\"" if $index2 =~ / /;
$self->{pbot}->{logger}->log("$self->{name}: [$index1]: $index2 added.\n") unless $quiet;
$self->save unless $quiet;
return "$index2 added to $name1.";
}
sub remove {
my ($self, $index1, $index2, $data_index, $dont_save) = @_;
if (not $self->exists($index1)) {
my $result = "$self->{name}: $index1 not found; similiar matches: ";
$result .= $self->levenshtein_matches($index1);
return $result;
}
my $name1 = $self->get_data($index1, '_name');
$name1 = 'global' if $name1 eq '.*';
my $lc_index1 = lc $index1;
if (not defined $index2) {
eval {
my $sth = $self->{dbh}->prepare("DELETE FROM Stuff WHERE index1 = ?");
$sth->execute($index1);
$self->cache_remove($index1);
};
if ($@) {
$self->{pbot}->{logger}->log("Error removing $index1 from $self->{name}: $@\n");
return "Error removing $name1: $@";
}
$self->save unless $dont_save;
return "$name1 removed.";
}
if (not $self->exists($index1, $index2)) {
my $result = "$self->{name}: [$name1] $index2 not found; similiar matches: ";
$result .= $self->levenshtein_matches($index1, $index2);
return $result;
}
my $name2 = $self->get_data($index1, $index2, '_name');
$name2 = "\"$name2\"" if $name2 =~ / /;
my $lc_index2 = lc $index2;
if (not defined $data_index) {
eval {
my $sth = $self->{dbh}->prepare("DELETE FROM Stuff WHERE index1 = ? AND index2 = ?");
$sth->execute($index1, $index2);
$self->cache_remove($index1, $index2);
};
if ($@) {
$self->{pbot}->{logger}->log("Error removing $self->{name}: [$name1] $name2: $@\n");
return "Error removing $name2 from $name1: $@";
}
$self->save unless $dont_save;
return "$name2 removed from $name1.";
}
if (not exists $self->{columns}->{$data_index}) {
return "$self->{name} have no such metadata $data_index.";
}
if (defined $self->get_data($lc_index1, $lc_index2, $data_index)) {
eval {
my $sth = $self->{dbh}->prepare("UPDATE Stuff SET '$data_index' = ? WHERE index1 = ? AND index2 = ?");
$sth->execute(undef, $index1, $index2);
$self->{cache}->{$index1}->{$index2}->{$data_index} = undef;
};
if ($@) {
$self->{pbot}->{logger}->log("Error unsetting $self->{name}: $name1.$name2: $@\n");
return "Error unsetting $data_index from $name2: $@";
}
$self->save unless $dont_save;
return "$name2.$data_index unset.";
}
return "$name2.$data_index is not set.";
}
sub set {
my ($self, $index1, $index2, $key, $value, $dont_save) = @_;
if (not $self->exists($index1)) {
my $result = "$self->{name}: $index1 not found; similiar matches: ";
$result .= $self->levenshtein_matches($index1);
return $result;
}
if (not $self->exists($index1, $index2)) {
my $secondary_text = $index2 =~ / / ? "\"$index2\"" : $index2;
my $result = "$self->{name}: [" . $self->get_data($index1, '_name') . "] $secondary_text not found; similiar matches: ";
$result .= $self->levenshtein_matches($index1, $index2);
return $result;
}
my $name1 = $self->get_data($index1, '_name');
my $name2 = $self->get_data($index1, $index2, '_name');
$name1 = 'global' if $name1 eq '.*';
$name2 = "\"$name2\"" if $name2 =~ / /;
if (not defined $key) {
my $result = "[$name1] $name2 keys:\n";
my @metadata = ();
foreach my $key (sort $self->get_keys($index1, $index2)) {
my $value = $self->get_data($index1, $index2, $key);
push @metadata, "$key => $value" if defined $value;
}
if (not @metadata) {
$result .= "none";
} else {
$result .= join ";\n", @metadata;
}
return $result;
}
if (not exists $self->{columns}->{$key}) {
return "$self->{name} have no such metadata $key.";
}
if (not defined $value) {
$value = $self->get_data($index1, $index2, $key);
}
else {
eval {
my $sth = $self->{dbh}->prepare("UPDATE Stuff SET '$key' = ? WHERE index1 = ? AND index2 = ?");
$sth->execute($value, $index1, $index2);
my ($lc_index1, $lc_index2) = (lc $index1, lc $index2);
if (exists $self->{cache}->{$lc_index1}
and exists $self->{cache}->{$lc_index1}->{$lc_index2}
and exists $self->{cache}->{$lc_index1}->{$lc_index2}->{$key}) {
$self->{cache}->{$lc_index1}->{$lc_index2}->{$key} = $value;
}
$self->save unless $dont_save;
};
if ($@) {
$self->{pbot}->{logger}->log("Error setting $self->{name} $index1 $index2.$key: $@\n");
return "Error setting $name2.$key: $@";
}
}
return "[$name1] $name2.$key " . (defined $value ? "set to $value" : "is not set.");
}
sub unset {
my ($self, $index1, $index2, $key) = @_;
if (not $self->exists($index1)) {
my $result = "$self->{name}: $index1 not found; similiar matches: ";
$result .= $self->levenshtein_matches($index1);
return $result;
}
my $name1 = $self->get_data($index1, '_name');
$name1 = 'global' if $name1 eq '.*';
if (not $self->exists($index1, $index2)) {
my $result = "$self->{name}: [$name1] $index2 not found; similiar matches: ";
$result .= $self->levenshtein_matches($index1, $index2);
return $result;
}
my $name2 = $self->get_data($index1, $index2, '_name');
$name2 = "\"$name2\"" if $name2 =~ / /;
if (not exists $self->{columns}->{$key}) {
return "$self->{name} have no such metadata $key.";
}
eval {
my $sth = $self->{dbh}->prepare("UPDATE Stuff SET '$key' = ? WHERE index1 = ? AND index2 = ?");
$sth->execute(undef, $index1, $index2);
my ($lc_index1, $lc_index2) = (lc $index1, lc $index2);
if (exists $self->{cache}->{$lc_index1}
and exists $self->{cache}->{$lc_index1}->{$lc_index2}
and exists $self->{cache}->{$lc_index1}->{$lc_index2}->{$key}) {
$self->{cache}->{$lc_index1}->{$lc_index2}->{$key} = undef;
}
$self->save;
};
if ($@) {
$self->{pbot}->{logger}->log("Error unsetting key: $@\n");
return "Error unsetting key: $@";
}
return "[$name1] $name2.$key unset.";
}
# nothing to do here for SQLite
# kept for compatibility with DualIndexHashObject
sub clear { }
1;