lib/PublicInbox/OverIdx.pm - pub/scm/infra/public-inbox - Git at Google

 # Copyright (C) all contributors <meta@public-inbox.org>
 # License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>

 # for XOVER, OVER in NNTP, and feeds/homepage/threads in PSGI
 # Unlike Msgmap, this is an _UNSTABLE_ cache which can be
 # tweaked/updated over time and rebuilt.
 #
 # Ghost messages (messages which are only referenced in References/In-Reply-To)
 # are denoted by a negative NNTP article number.
 package PublicInbox::OverIdx;
 use strict;
 use v5.10.1;
 use parent qw(PublicInbox::Over);
 use IO::Handle;
 use DBI qw(:sql_types); # SQL_BLOB
 use PublicInbox::MID qw/id_compress mids_for_index references/;
 use PublicInbox::Smsg qw(subject_normalized);
 use Compress::Zlib qw(compress);
 use Carp qw(croak);
 use bytes (); # length

 sub dbh_new {
 	my ($self) = @_;
 	my $dbh = $self->SUPER::dbh_new($self->{-no_fsync} ? 2 : 1);

 	# 80000 pages (80MiB on SQLite <3.12.0, 320MiB on 3.12.0+)
 	# was found to be good in 2018 during the large LKML import
 	# at the time.  This ought to be configurable based on HW
 	# and inbox size; I suspect it's overkill for many inboxes.
 	$dbh->do('PRAGMA cache_size = 80000');

 	create_tables($dbh);
 	$dbh;
 }

 sub new {
 	my ($class, $f) = @_;
 	my $self = $class->SUPER::new($f);
 	$self->{min_tid} = 0;
 	$self;
 }

 sub get_counter ($$) {
 	my ($dbh, $key) = @_;
 	my $sth = $dbh->prepare_cached(<<'', undef, 1);
 SELECT val FROM counter WHERE key = ? LIMIT 1

 	$sth->execute($key);
 	$sth->fetchrow_array;
 }

 sub adj_counter ($$$) {
 	my ($self, $key, $op) = @_;
 	my $dbh = $self->{dbh};
 	my $sth = $dbh->prepare_cached(<<"");
 UPDATE counter SET val = val $op 1 WHERE key = ?

 	$sth->execute($key);

 	get_counter($dbh, $key);
 }

 sub next_tid { adj_counter($_[0], 'thread', '+') }
 sub next_ghost_num { adj_counter($_[0], 'ghost', '-') }

 sub id_for ($$$$$) {
 	my ($self, $tbl, $id_col, $val_col, $val) = @_;
 	my $dbh = $self->{dbh};
 	my $in = $dbh->prepare_cached(<<"")->execute($val);
 INSERT OR IGNORE INTO $tbl ($val_col) VALUES (?)

 	if ($in == 0) {
 		my $sth = $dbh->prepare_cached(<<"", undef, 1);
 SELECT $id_col FROM $tbl WHERE $val_col = ? LIMIT 1

 		$sth->execute($val);
 		$sth->fetchrow_array;
 	} else {
 		$dbh->last_insert_id(undef, undef, $tbl, $id_col);
 	}
 }

 sub ibx_id {
 	my ($self, $eidx_key) = @_;
 	id_for($self, 'inboxes', 'ibx_id', eidx_key => $eidx_key);
 }

 sub sid {
 	my ($self, $path) = @_;
 	return unless defined $path && $path ne '';
 	id_for($self, 'subject', 'sid', 'path' => $path);
 }

 sub mid2id {
 	my ($self, $mid) = @_;
 	id_for($self, 'msgid', 'id', 'mid' => $mid);
 }

 sub delete_by_num {
 	my ($self, $num, $tid_ref) = @_;
 	my $dbh = $self->{dbh};
 	if ($tid_ref) {
 		my $sth = $dbh->prepare_cached(<<'', undef, 1);
 SELECT tid FROM over WHERE num = ? LIMIT 1

 		$sth->execute($num);
 		$$tid_ref = $sth->fetchrow_array; # may be undef
 	}
 	foreach (qw(over id2num)) {
 		$dbh->prepare_cached(<<"")->execute($num);
 DELETE FROM $_ WHERE num = ?

 	}
 }

 # this includes ghosts
 sub each_by_mid {
 	my ($self, $mid, $cols, $cb, @arg) = @_;
 	my $dbh = $self->{dbh};

 =over
 	I originally wanted to stuff everything into a single query:

 	SELECT over.* FROM over
 	LEFT JOIN id2num ON over.num = id2num.num
 	LEFT JOIN msgid ON msgid.id = id2num.id
 	WHERE msgid.mid = ? AND over.num >= ?
 	ORDER BY over.num ASC
 	LIMIT 1000

 	But it's faster broken out (and we're always in a
 	transaction for subroutines in this file)
 =cut

 	my $sth = $dbh->prepare_cached(<<'', undef, 1);
 SELECT id FROM msgid WHERE mid = ? LIMIT 1

 	$sth->execute($mid);
 	my $id = $sth->fetchrow_array;
 	defined $id or return;

 	push(@$cols, 'num');
 	$cols = join(',', map { $_ } @$cols);
 	my $lim = 10;
 	my $prev = get_counter($dbh, 'ghost');
 	while (1) {
 		$sth = $dbh->prepare_cached(<<"", undef, 1);
 SELECT num FROM id2num WHERE id = ? AND num >= ?
 ORDER BY num ASC
 LIMIT $lim

 		$sth->execute($id, $prev);
 		my $nums = $sth->fetchall_arrayref;
 		my $nr = scalar(@$nums) or return;
 		$prev = $nums->[-1]->[0];

 		$sth = $dbh->prepare_cached(<<"", undef, 1);
 SELECT $cols FROM over WHERE over.num = ? LIMIT 1

 		foreach (@$nums) {
 			$sth->execute($_->[0]);
 			# $cb may delete rows and invalidate nums
 			my $smsg = $sth->fetchrow_hashref // next;
 			$smsg = PublicInbox::Over::load_from_row($smsg);
 			$cb->($self, $smsg, @arg) or return;
 		}
 		return if $nr != $lim;
 	}
 }

 sub _resolve_mid_to_tid {
 	my ($self, $smsg, $tid) = @_;
 	my $cur_tid = $smsg->{tid};
 	if (defined $$tid) {
 		merge_threads($self, $$tid, $cur_tid);
 	} elsif ($cur_tid > $self->{min_tid}) {
 		$$tid = $cur_tid;
 	} else { # rethreading, queue up dead ghosts
 		$$tid = next_tid($self);
 		my $n = $smsg->{num};
 		if ($n > 0) {
 			$self->{dbh}->prepare_cached(<<'')->execute($$tid, $n);
 UPDATE over SET tid = ? WHERE num = ?

 		} elsif ($n < 0) {
 			push(@{$self->{-ghosts_to_delete}}, $n);
 		}
 	}
 	1;
 }

 # this will create a ghost as necessary
 sub resolve_mid_to_tid {
 	my ($self, $mid) = @_;
 	my $tid;
 	each_by_mid($self, $mid, ['tid'], \&_resolve_mid_to_tid, \$tid);
 	if (my $del = delete $self->{-ghosts_to_delete}) {
 		delete_by_num($self, $_) for @$del;
 	}
 	$tid // do { # create a new ghost
 		my $id = mid2id($self, $mid);
 		my $num = next_ghost_num($self);
 		$num < 0 or croak "BUG: ghost num is non-negative: $num\n";
 		$tid = next_tid($self);
 		my $dbh = $self->{dbh};
 		$dbh->prepare_cached(<<'')->execute($num, $tid);
 INSERT INTO over (num, tid) VALUES (?,?)

 		$dbh->prepare_cached(<<'')->execute($id, $num);
 INSERT INTO id2num (id, num) VALUES (?,?)

 		$tid;
 	};
 }

 sub merge_threads {
 	my ($self, $winner_tid, $loser_tid) = @_;
 	return if $winner_tid == $loser_tid;
 	my $dbh = $self->{dbh};
 	$dbh->prepare_cached(<<'')->execute($winner_tid, $loser_tid);
 UPDATE over SET tid = ? WHERE tid = ?

 }

 sub link_refs {
 	my ($self, $refs, $old_tid) = @_;
 	my $tid;

 	if (@$refs) {
 		# first ref *should* be the thread root,
 		# but we can never trust clients to do the right thing
 		my $ref = $refs->[0];
 		$tid = resolve_mid_to_tid($self, $ref);
 		merge_threads($self, $tid, $old_tid) if defined $old_tid;

 		# the rest of the refs should point to this tid:
 		foreach my $i (1..$#$refs) {
 			$ref = $refs->[$i];
 			my $ptid = resolve_mid_to_tid($self, $ref);
 			merge_threads($self, $tid, $ptid);
 		}
 	} else {
 		$tid = $old_tid // next_tid($self);
 	}
 	$tid;
 }

 # normalize subjects somewhat, they used to be ASCII-only but now
 # we use \w for UTF-8 support.  We may still drop it entirely and
 # rely on Xapian for subject matches...
 sub subject_path ($) {
 	my ($subj) = @_;
 	$subj = subject_normalized($subj);
 	$subj =~ s![^\w\.~/\-]+!_!g;
 	lc($subj);
 }

 sub ddd_for ($) {
 	my ($smsg) = @_;
 	my $dd = $smsg->to_doc_data;
 	utf8::encode($dd);
 	compress($dd);
 }

 sub add_overview {
 	my ($self, $eml, $smsg) = @_;
 	my $raw = $eml->body_raw;
 	$smsg->{lines} = $raw =~ tr!\n!\n!;
 	$smsg->{bytes} //= bytes::length $raw;
 	undef $raw;
 	my $mids = mids_for_index($eml);
 	my $refs = $smsg->parse_references($eml, $mids);
 	$mids->[0] //= do {
 		$smsg->{mid} //= '';
 		$eml->{-lei_fake_mid};
 	};
 	my $subj = $smsg->{subject};
 	my $xpath;
 	if ($subj ne '') {
 		$xpath = subject_path($subj);
 		$xpath = id_compress($xpath);
 	}
 	add_over($self, $smsg, $mids, $refs, $xpath, ddd_for($smsg));
 }

 sub _add_over {
 	my ($self, $smsg, $mid, $refs, $old_tid, $v) = @_;
 	my $cur_tid = $smsg->{tid};
 	my $n = $smsg->{num};
 	croak "BUG: num must not be zero for $mid" if !$n;
 	my $cur_valid = $cur_tid > $self->{min_tid};

 	if ($n > 0) { # regular mail
 		if ($cur_valid) {
 			$$old_tid //= $cur_tid;
 			merge_threads($self, $$old_tid, $cur_tid);
 		} else {
 			$$old_tid //= next_tid($self);
 		}
 	} elsif ($n < 0) { # ghost
 		$$old_tid //= $cur_valid ? $cur_tid : next_tid($self);
 		$$old_tid = link_refs($self, $refs, $$old_tid);
 		delete_by_num($self, $n);
 		$$v++;
 	}
 	1;
 }

 sub add_over {
 	my ($self, $smsg, $mids, $refs, $xpath, $ddd) = @_;
 	my $old_tid;
 	my $vivified = 0;
 	my $num = $smsg->{num};

 	begin_lazy($self);
 	delete_by_num($self, $num, \$old_tid);
 	$old_tid = undef if ($old_tid // 0) <= $self->{min_tid};
 	foreach my $mid (@$mids) {
 		my $v = 0;
 		each_by_mid($self, $mid, ['tid'], \&_add_over,
 				$mid, $refs, \$old_tid, \$v);
 		$v > 1 and warn "BUG: vivified multiple ($v) ghosts for $mid\n";
 		$vivified += $v;
 	}
 	$smsg->{tid} = $vivified ? $old_tid : link_refs($self, $refs, $old_tid);
 	$smsg->{sid} = sid($self, $xpath);
 	my $dbh = $self->{dbh};
 	my $sth = $dbh->prepare_cached(<<'');
 INSERT INTO over (num, tid, sid, ts, ds, ddd)
 VALUES (?,?,?,?,?,?)

 	my $nc = 1;
 	$sth->bind_param($nc, $num);
 	$sth->bind_param(++$nc, $smsg->{$_}) for (qw(tid sid ts ds));
 	$sth->bind_param(++$nc, $ddd, SQL_BLOB);
 	$sth->execute;
 	$sth = $dbh->prepare_cached(<<'');
 INSERT INTO id2num (id, num) VALUES (?,?)

 	foreach my $mid (@$mids) {
 		my $id = mid2id($self, $mid);
 		$sth->execute($id, $num);
 	}
 }

 sub _remove_oid {
 	my ($self, $smsg, $oid, $removed) = @_;
 	if (!defined($oid) || $smsg->{blob} eq $oid) {
 		delete_by_num($self, $smsg->{num});
 		push @$removed, $smsg->{num};
 	}
 	1;
 }

 # returns number of removed messages in scalar context,
 # array of removed article numbers in array context.
 # $oid may be undef to match only on $mid
 sub remove_oid {
 	my ($self, $oid, $mid) = @_;
 	my $removed = [];
 	begin_lazy($self);
 	each_by_mid($self, $mid, ['ddd'], \&_remove_oid, $oid, $removed);
 	@$removed;
 }

 sub _num_mid0_for_oid {
 	my ($self, $smsg, $oid, $res) = @_;
 	my $blob = $smsg->{blob};
 	return 1 if (!defined($blob) || $blob ne $oid); # continue;
 	@$res = ($smsg->{num}, $smsg->{mid});
 	0; # done
 }

 sub num_mid0_for_oid {
 	my ($self, $oid, $mid) = @_;
 	my $res = [];
 	begin_lazy($self);
 	each_by_mid($self, $mid, ['ddd'], \&_num_mid0_for_oid, $oid, $res);
 	@$res, # ($num, $mid0);
 }

 sub create_tables {
 	my ($dbh) = @_;

 	$dbh->do(<<'');
 CREATE TABLE IF NOT EXISTS over (
 	num INTEGER PRIMARY KEY NOT NULL, /* NNTP article number == IMAP UID */
 	tid INTEGER NOT NULL, /* THREADID (IMAP REFERENCES threading, JMAP) */
 	sid INTEGER, /* Subject ID (IMAP ORDEREDSUBJECT "threading") */
 	ts INTEGER, /* IMAP INTERNALDATE (Received: header, git commit time) */
 	ds INTEGER, /* RFC-2822 sent Date: header, git author time */
 	ddd VARBINARY /* doc-data-deflated (->to_doc_data, ->load_from_data) */
 )

 	$dbh->do('CREATE INDEX IF NOT EXISTS idx_tid ON over (tid)');
 	$dbh->do('CREATE INDEX IF NOT EXISTS idx_sid ON over (sid)');
 	$dbh->do('CREATE INDEX IF NOT EXISTS idx_ts ON over (ts)');
 	$dbh->do('CREATE INDEX IF NOT EXISTS idx_ds ON over (ds)');

 	$dbh->do(<<'');
 CREATE TABLE IF NOT EXISTS counter (
 	key VARCHAR(8) PRIMARY KEY NOT NULL,
 	val INTEGER DEFAULT 0,
 	UNIQUE (key)
 )

 	$dbh->do("INSERT OR IGNORE INTO counter (key) VALUES ('thread')");
 	$dbh->do("INSERT OR IGNORE INTO counter (key) VALUES ('ghost')");

 	$dbh->do(<<'');
 CREATE TABLE IF NOT EXISTS subject (
 	sid INTEGER PRIMARY KEY AUTOINCREMENT,
 	path VARCHAR(40) NOT NULL, /* SHA-1 of normalized subject */
 	UNIQUE (path)
 )

 	$dbh->do(<<'');
 CREATE TABLE IF NOT EXISTS id2num (
 	id INTEGER NOT NULL, /* <=> msgid.id */
 	num INTEGER NOT NULL,
 	UNIQUE (id, num)
 )

 	# performance critical:
 	$dbh->do('CREATE INDEX IF NOT EXISTS idx_inum ON id2num (num)');
 	$dbh->do('CREATE INDEX IF NOT EXISTS idx_id ON id2num (id)');

 	$dbh->do(<<'');
 CREATE TABLE IF NOT EXISTS msgid (
 	id INTEGER PRIMARY KEY AUTOINCREMENT, /* <=> id2num.id */
 	mid VARCHAR(244) NOT NULL,
 	UNIQUE (mid)
 )

 }

 sub commit_lazy {
 	my ($self) = @_;
 	delete $self->{txn} or return;
 	$self->{dbh}->commit;
 	eval { $self->{dbh}->do('PRAGMA optimize') };
 }

 sub begin_lazy {
 	my ($self) = @_;
 	return if $self->{txn};
 	my $dbh = $self->dbh or return;
 	$dbh->begin_work;
 	# $dbh->{Profile} = 2;
 	$self->{txn} = 1;
 }

 sub rollback_lazy {
 	my ($self) = @_;
 	delete $self->{txn} or return;
 	$self->{dbh}->rollback;
 }

 sub dbh_close {
 	my ($self) = @_;
 	Carp::confess('BUG: in transaction') if $self->{txn};
 	$self->SUPER::dbh_close;
 }

 sub create {
 	my ($self) = @_;
 	my $fn = $self->{filename} // do {
 		croak('BUG: no {filename}') unless $self->{dbh};
 		return;
 	};
 	unless (-r $fn) {
 		require File::Path;
 		my ($dir) = ($fn =~ m!(.*?/)[^/]+\z!);
 		File::Path::mkpath($dir);
 	}
 	# create the DB:
 	PublicInbox::Over::dbh($self);
 	$self->dbh_close;
 }

 sub rethread_prepare {
 	my ($self, $opt) = @_;
 	return unless $opt->{rethread};
 	begin_lazy($self);
 	my $min = $self->{min_tid} = get_counter($self->{dbh}, 'thread') // 0;
 	my $pr = $opt->{-progress};
 	$pr->("rethread min THREADID ".($min + 1)."\n") if $pr && $min;
 }

 sub rethread_done {
 	my ($self, $opt) = @_;
 	return unless $opt->{rethread} && $self->{txn};
 	defined(my $min = $self->{min_tid}) or croak('BUG: no min_tid');
 	my $dbh = $self->{dbh} or croak('BUG: no dbh');
 	my $rows = $dbh->selectall_arrayref(<<'', { Slice => {} }, $min);
 SELECT num,tid FROM over WHERE num < 0 AND tid < ?

 	my $show_id = $dbh->prepare('SELECT id FROM id2num WHERE num = ?');
 	my $show_mid = $dbh->prepare('SELECT mid FROM msgid WHERE id = ?');
 	my $pr = $opt->{-progress};
 	my $total = 0;
 	for my $r (@$rows) {
 		my $exp = 0;
 		$show_id->execute($r->{num});
 		while (defined(my $id = $show_id->fetchrow_array)) {
 			++$exp;
 			$show_mid->execute($id);
 			my $mid = $show_mid->fetchrow_array;
 			if (!defined($mid)) {
 				warn <<EOF;
 E: ghost NUM=$r->{num} ID=$id THREADID=$r->{tid} has no Message-ID
 EOF
 				next;
 			}
 			$pr->(<<EOM) if $pr;
 # ghost $r->{num} <$mid> THREADID=$r->{tid} culled
 EOM
 		}
 		delete_by_num($self, $r->{num});
 	}
 	$pr->("# rethread culled $total ghosts\n") if $pr && $total;
 }

 # used for cross-inbox search
 sub eidx_prep ($) {
 	my ($self) = @_;
 	$self->{-eidx_prep} // do {
 		my $dbh = $self->dbh;
 		$dbh->do(<<'');
 INSERT OR IGNORE INTO counter (key) VALUES ('eidx_docid')

 		$dbh->do(<<'');
 CREATE TABLE IF NOT EXISTS inboxes (
 	ibx_id INTEGER PRIMARY KEY AUTOINCREMENT,
 	eidx_key VARCHAR(255) NOT NULL, /* {newsgroup} // {inboxdir} */
 	UNIQUE (eidx_key)
 )

 		$dbh->do(<<'');
 CREATE TABLE IF NOT EXISTS xref3 (
 	docid INTEGER NOT NULL, /* <=> over.num */
 	ibx_id INTEGER NOT NULL, /* <=> inboxes.ibx_id */
 	xnum INTEGER NOT NULL, /* NNTP article number in ibx */
 	oidbin VARBINARY NOT NULL, /* 20-byte SHA-1 or 32-byte SHA-256 */
 	UNIQUE (docid, ibx_id, xnum, oidbin)
 )

 	$dbh->do('CREATE INDEX IF NOT EXISTS idx_docid ON xref3 (docid)');

 	# performance critical, this is not UNIQUE since we may need to
 	# tolerate some old bugs from indexing mirrors.  n.b. we used
 	# to index oidbin here, but leaving it out speeds up reindexing
 	# and "XHDR Xref <$MSGID>" isn't any slower w/o oidbin
 	$dbh->do('CREATE INDEX IF NOT EXISTS idx_reindex ON '.
 		'xref3 (xnum,ibx_id)');

 	$dbh->do('CREATE INDEX IF NOT EXISTS idx_oidbin ON xref3 (oidbin)');

 		$dbh->do(<<'');
 CREATE TABLE IF NOT EXISTS eidx_meta (
 	key VARCHAR(255) PRIMARY KEY,
 	val VARCHAR(255) NOT NULL
 )

 		# A queue of current docids which need reindexing.
 		# eidxq persists across aborted -extindex invocations
 		# Currently used for "-extindex --reindex" for Xapian
 		# data, but may be used in more places down the line.
 		$dbh->do(<<'');
 CREATE TABLE IF NOT EXISTS eidxq (docid INTEGER PRIMARY KEY NOT NULL)

 		$self->{-eidx_prep} = 1;
 	};
 }

 sub eidx_meta { # requires transaction
 	my ($self, $key, $val) = @_;

 	my $sql = 'SELECT val FROM eidx_meta WHERE key = ? LIMIT 1';
 	my $dbh = $self->{dbh};
 	defined($val) or return $dbh->selectrow_array($sql, undef, $key);

 	my $prev = $dbh->selectrow_array($sql, undef, $key);
 	if (defined $prev) {
 		$sql = 'UPDATE eidx_meta SET val = ? WHERE key = ?';
 		$dbh->do($sql, undef, $val, $key);
 	} else {
 		$sql = 'INSERT INTO eidx_meta (key,val) VALUES (?,?)';
 		$dbh->do($sql, undef, $key, $val);
 	}
 	$prev;
 }

 sub eidx_max {
 	my ($self) = @_;
 	get_counter($self->{dbh}, 'eidx_docid');
 }

 sub add_xref3 {
 	my ($self, $docid, $xnum, $oidhex, $eidx_key) = @_;
 	begin_lazy($self);
 	my $ibx_id = ibx_id($self, $eidx_key);
 	my $oidbin = pack('H*', $oidhex);
 	my $sth = $self->{dbh}->prepare_cached(<<'');
 INSERT OR IGNORE INTO xref3 (docid, ibx_id, xnum, oidbin) VALUES (?, ?, ?, ?)

 	$sth->bind_param(1, $docid);
 	$sth->bind_param(2, $ibx_id);
 	$sth->bind_param(3, $xnum);
 	$sth->bind_param(4, $oidbin, SQL_BLOB);
 	$sth->execute;
 }

 # for when an xref3 goes missing, this does NOT update {ts}
 sub update_blob {
 	my ($self, $smsg, $oidhex) = @_;
 	my $sth = $self->{dbh}->prepare(<<'');
 UPDATE over SET ddd = ? WHERE num = ?

 	$smsg->{blob} = $oidhex;
 	$sth->bind_param(1, ddd_for($smsg), SQL_BLOB);
 	$sth->bind_param(2, $smsg->{num});
 	$sth->execute;
 }

 sub merge_xref3 { # used for "-extindex --dedupe"
 	my ($self, $keep_docid, $drop_docid, $oidbin) = @_;
 	my $sth = $self->{dbh}->prepare_cached(<<'');
 UPDATE OR IGNORE xref3 SET docid = ? WHERE docid = ? AND oidbin = ?

 	$sth->bind_param(1, $keep_docid);
 	$sth->bind_param(2, $drop_docid);
 	$sth->bind_param(3, $oidbin, SQL_BLOB);
 	$sth->execute;

 	# drop anything that conflicted
 	$sth = $self->{dbh}->prepare_cached(<<'');
 DELETE FROM xref3 WHERE docid = ? AND oidbin = ?

 	$sth->bind_param(1, $drop_docid);
 	$sth->bind_param(2, $oidbin, SQL_BLOB);
 	$sth->execute;
 }

 sub eidxq_add {
 	my ($self, $docid) = @_;
 	$self->dbh->prepare_cached(<<'')->execute($docid);
 INSERT OR IGNORE INTO eidxq (docid) VALUES (?)

 }

 sub eidxq_del {
 	my ($self, $docid) = @_;
 	$self->dbh->prepare_cached(<<'')->execute($docid);
 DELETE FROM eidxq WHERE docid = ?

 }

 # returns true if we're vivifying a message for lei/store that was
 # previously external-metadata only
 sub vivify_xvmd {
 	my ($self, $smsg) = @_;
 	my @docids = $self->blob_exists($smsg->{blob});
 	my @vivify_xvmd;
 	for my $id (@docids) {
 		if (my $cur = $self->get_art($id)) {
 			# already indexed if bytes > 0
 			return if $cur->{bytes} > 0;
 			push @vivify_xvmd, $id;
 		} else {
 			warn "W: $smsg->{blob} #$id gone (bug?)\n";
 		}
 	}
 	$smsg->{-vivify_xvmd} = \@vivify_xvmd;
 }

 sub fork_ok {
 	state $fork_ok = eval("v$DBD::SQLite::sqlite_version") ge v3.8.3;
 	return 1 if $fork_ok;
 	my ($opt) = @_;
 	my @j = split(/,/, $opt->{jobs} // '');
 	state $warned;
 	grep { $_ > 1 } @j and $warned //= warn(<<EOM);
 DBD::SQLite version is v$DBD::SQLite::sqlite_version, need >= v3.8.3 for --jobs > 1
 EOM
 	$opt->{jobs} = '1,1';
 	undef;
 }

 1;
	# Copyright (C) all contributors <meta@public-inbox.org>
	# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>

	# for XOVER, OVER in NNTP, and feeds/homepage/threads in PSGI
	# Unlike Msgmap, this is an _UNSTABLE_ cache which can be
	# tweaked/updated over time and rebuilt.
	#
	# Ghost messages (messages which are only referenced in References/In-Reply-To)
	# are denoted by a negative NNTP article number.
	package PublicInbox::OverIdx;
	use strict;
	use v5.10.1;
	use parent qw(PublicInbox::Over);
	use IO::Handle;
	use DBI qw(:sql_types); # SQL_BLOB
	use PublicInbox::MID qw/id_compress mids_for_index references/;
	use PublicInbox::Smsg qw(subject_normalized);
	use Compress::Zlib qw(compress);
	use Carp qw(croak);
	use bytes (); # length

	sub dbh_new {
	my ($self) = @_;
	my $dbh = $self->SUPER::dbh_new($self->{-no_fsync} ? 2 : 1);

	# 80000 pages (80MiB on SQLite <3.12.0, 320MiB on 3.12.0+)
	# was found to be good in 2018 during the large LKML import
	# at the time. This ought to be configurable based on HW
	# and inbox size; I suspect it's overkill for many inboxes.
	$dbh->do('PRAGMA cache_size = 80000');

	create_tables($dbh);
	$dbh;
	}

	sub new {
	my ($class, $f) = @_;
	my $self = $class->SUPER::new($f);
	$self->{min_tid} = 0;
	$self;
	}

	sub get_counter ($$) {
	my ($dbh, $key) = @_;
	my $sth = $dbh->prepare_cached(<<'', undef, 1);
	SELECT val FROM counter WHERE key = ? LIMIT 1

	$sth->execute($key);
	$sth->fetchrow_array;
	}

	sub adj_counter ($$$) {
	my ($self, $key, $op) = @_;
	my $dbh = $self->{dbh};
	my $sth = $dbh->prepare_cached(<<"");
	UPDATE counter SET val = val $op 1 WHERE key = ?

	$sth->execute($key);

	get_counter($dbh, $key);
	}

	sub next_tid { adj_counter($_[0], 'thread', '+') }
	sub next_ghost_num { adj_counter($_[0], 'ghost', '-') }

	sub id_for ($$$$$) {
	my ($self, $tbl, $id_col, $val_col, $val) = @_;
	my $dbh = $self->{dbh};
	my $in = $dbh->prepare_cached(<<"")->execute($val);
	INSERT OR IGNORE INTO $tbl ($val_col) VALUES (?)

	if ($in == 0) {
	my $sth = $dbh->prepare_cached(<<"", undef, 1);
	SELECT $id_col FROM $tbl WHERE $val_col = ? LIMIT 1

	$sth->execute($val);
	$sth->fetchrow_array;
	} else {
	$dbh->last_insert_id(undef, undef, $tbl, $id_col);
	}
	}

	sub ibx_id {
	my ($self, $eidx_key) = @_;
	id_for($self, 'inboxes', 'ibx_id', eidx_key => $eidx_key);
	}

	sub sid {
	my ($self, $path) = @_;
	return unless defined $path && $path ne '';
	id_for($self, 'subject', 'sid', 'path' => $path);
	}

	sub mid2id {
	my ($self, $mid) = @_;
	id_for($self, 'msgid', 'id', 'mid' => $mid);
	}

	sub delete_by_num {
	my ($self, $num, $tid_ref) = @_;
	my $dbh = $self->{dbh};
	if ($tid_ref) {
	my $sth = $dbh->prepare_cached(<<'', undef, 1);
	SELECT tid FROM over WHERE num = ? LIMIT 1

	$sth->execute($num);
	$$tid_ref = $sth->fetchrow_array; # may be undef
	}
	foreach (qw(over id2num)) {
	$dbh->prepare_cached(<<"")->execute($num);
	DELETE FROM $_ WHERE num = ?

	}
	}

	# this includes ghosts
	sub each_by_mid {
	my ($self, $mid, $cols, $cb, @arg) = @_;
	my $dbh = $self->{dbh};

	=over
	I originally wanted to stuff everything into a single query:

	SELECT over.* FROM over
	LEFT JOIN id2num ON over.num = id2num.num
	LEFT JOIN msgid ON msgid.id = id2num.id
	WHERE msgid.mid = ? AND over.num >= ?
	ORDER BY over.num ASC
	LIMIT 1000

	But it's faster broken out (and we're always in a
	transaction for subroutines in this file)
	=cut

	my $sth = $dbh->prepare_cached(<<'', undef, 1);
	SELECT id FROM msgid WHERE mid = ? LIMIT 1

	$sth->execute($mid);
	my $id = $sth->fetchrow_array;
	defined $id or return;

	push(@$cols, 'num');
	$cols = join(',', map { $_ } @$cols);
	my $lim = 10;
	my $prev = get_counter($dbh, 'ghost');
	while (1) {
	$sth = $dbh->prepare_cached(<<"", undef, 1);
	SELECT num FROM id2num WHERE id = ? AND num >= ?
	ORDER BY num ASC
	LIMIT $lim

	$sth->execute($id, $prev);
	my $nums = $sth->fetchall_arrayref;
	my $nr = scalar(@$nums) or return;
	$prev = $nums->[-1]->[0];

	$sth = $dbh->prepare_cached(<<"", undef, 1);
	SELECT $cols FROM over WHERE over.num = ? LIMIT 1

	foreach (@$nums) {
	$sth->execute($_->[0]);
	# $cb may delete rows and invalidate nums
	my $smsg = $sth->fetchrow_hashref // next;
	$smsg = PublicInbox::Over::load_from_row($smsg);
	$cb->($self, $smsg, @arg) or return;
	}
	return if $nr != $lim;
	}
	}

	sub _resolve_mid_to_tid {
	my ($self, $smsg, $tid) = @_;
	my $cur_tid = $smsg->{tid};
	if (defined $$tid) {
	merge_threads($self, $$tid, $cur_tid);
	} elsif ($cur_tid > $self->{min_tid}) {
	$$tid = $cur_tid;
	} else { # rethreading, queue up dead ghosts
	$$tid = next_tid($self);
	my $n = $smsg->{num};
	if ($n > 0) {
	$self->{dbh}->prepare_cached(<<'')->execute($$tid, $n);
	UPDATE over SET tid = ? WHERE num = ?

	} elsif ($n < 0) {
	push(@{$self->{-ghosts_to_delete}}, $n);
	}
	}
	1;
	}

	# this will create a ghost as necessary
	sub resolve_mid_to_tid {
	my ($self, $mid) = @_;
	my $tid;
	each_by_mid($self, $mid, ['tid'], \&_resolve_mid_to_tid, \$tid);
	if (my $del = delete $self->{-ghosts_to_delete}) {
	delete_by_num($self, $_) for @$del;
	}
	$tid // do { # create a new ghost
	my $id = mid2id($self, $mid);
	my $num = next_ghost_num($self);
	$num < 0 or croak "BUG: ghost num is non-negative: $num\n";
	$tid = next_tid($self);
	my $dbh = $self->{dbh};
	$dbh->prepare_cached(<<'')->execute($num, $tid);
	INSERT INTO over (num, tid) VALUES (?,?)

	$dbh->prepare_cached(<<'')->execute($id, $num);
	INSERT INTO id2num (id, num) VALUES (?,?)

	$tid;
	};
	}

	sub merge_threads {
	my ($self, $winner_tid, $loser_tid) = @_;
	return if $winner_tid == $loser_tid;
	my $dbh = $self->{dbh};
	$dbh->prepare_cached(<<'')->execute($winner_tid, $loser_tid);
	UPDATE over SET tid = ? WHERE tid = ?

	}

	sub link_refs {
	my ($self, $refs, $old_tid) = @_;
	my $tid;

	if (@$refs) {
	# first ref should be the thread root,
	# but we can never trust clients to do the right thing
	my $ref = $refs->[0];
	$tid = resolve_mid_to_tid($self, $ref);
	merge_threads($self, $tid, $old_tid) if defined $old_tid;

	# the rest of the refs should point to this tid:
	foreach my $i (1..$#$refs) {
	$ref = $refs->[$i];
	my $ptid = resolve_mid_to_tid($self, $ref);
	merge_threads($self, $tid, $ptid);
	}
	} else {
	$tid = $old_tid // next_tid($self);
	}
	$tid;
	}

	# normalize subjects somewhat, they used to be ASCII-only but now
	# we use \w for UTF-8 support. We may still drop it entirely and
	# rely on Xapian for subject matches...
	sub subject_path ($) {
	my ($subj) = @_;
	$subj = subject_normalized($subj);
	$subj =~ s![^\w\.~/\-]+!_!g;
	lc($subj);
	}

	sub ddd_for ($) {
	my ($smsg) = @_;
	my $dd = $smsg->to_doc_data;
	utf8::encode($dd);
	compress($dd);
	}

	sub add_overview {
	my ($self, $eml, $smsg) = @_;
	my $raw = $eml->body_raw;
	$smsg->{lines} = $raw =~ tr!\n!\n!;
	$smsg->{bytes} //= bytes::length $raw;
	undef $raw;
	my $mids = mids_for_index($eml);
	my $refs = $smsg->parse_references($eml, $mids);
	$mids->[0] //= do {
	$smsg->{mid} //= '';
	$eml->{-lei_fake_mid};
	};
	my $subj = $smsg->{subject};
	my $xpath;
	if ($subj ne '') {
	$xpath = subject_path($subj);
	$xpath = id_compress($xpath);
	}
	add_over($self, $smsg, $mids, $refs, $xpath, ddd_for($smsg));
	}

	sub _add_over {
	my ($self, $smsg, $mid, $refs, $old_tid, $v) = @_;
	my $cur_tid = $smsg->{tid};
	my $n = $smsg->{num};
	croak "BUG: num must not be zero for $mid" if !$n;
	my $cur_valid = $cur_tid > $self->{min_tid};

	if ($n > 0) { # regular mail
	if ($cur_valid) {
	$$old_tid //= $cur_tid;
	merge_threads($self, $$old_tid, $cur_tid);
	} else {
	$$old_tid //= next_tid($self);
	}
	} elsif ($n < 0) { # ghost
	$$old_tid //= $cur_valid ? $cur_tid : next_tid($self);
	$$old_tid = link_refs($self, $refs, $$old_tid);
	delete_by_num($self, $n);
	$$v++;
	}
	1;
	}

	sub add_over {
	my ($self, $smsg, $mids, $refs, $xpath, $ddd) = @_;
	my $old_tid;
	my $vivified = 0;
	my $num = $smsg->{num};

	begin_lazy($self);
	delete_by_num($self, $num, \$old_tid);
	$old_tid = undef if ($old_tid // 0) <= $self->{min_tid};
	foreach my $mid (@$mids) {
	my $v = 0;
	each_by_mid($self, $mid, ['tid'], \&_add_over,
	$mid, $refs, \$old_tid, \$v);
	$v > 1 and warn "BUG: vivified multiple ($v) ghosts for $mid\n";
	$vivified += $v;
	}
	$smsg->{tid} = $vivified ? $old_tid : link_refs($self, $refs, $old_tid);
	$smsg->{sid} = sid($self, $xpath);
	my $dbh = $self->{dbh};
	my $sth = $dbh->prepare_cached(<<'');
	INSERT INTO over (num, tid, sid, ts, ds, ddd)
	VALUES (?,?,?,?,?,?)

	my $nc = 1;
	$sth->bind_param($nc, $num);
	$sth->bind_param(++$nc, $smsg->{$_}) for (qw(tid sid ts ds));
	$sth->bind_param(++$nc, $ddd, SQL_BLOB);
	$sth->execute;
	$sth = $dbh->prepare_cached(<<'');
	INSERT INTO id2num (id, num) VALUES (?,?)

	foreach my $mid (@$mids) {
	my $id = mid2id($self, $mid);
	$sth->execute($id, $num);
	}
	}

	sub _remove_oid {
	my ($self, $smsg, $oid, $removed) = @_;
	if (!defined($oid) \|\| $smsg->{blob} eq $oid) {
	delete_by_num($self, $smsg->{num});
	push @$removed, $smsg->{num};
	}
	1;
	}

	# returns number of removed messages in scalar context,
	# array of removed article numbers in array context.
	# $oid may be undef to match only on $mid
	sub remove_oid {
	my ($self, $oid, $mid) = @_;
	my $removed = [];
	begin_lazy($self);
	each_by_mid($self, $mid, ['ddd'], \&_remove_oid, $oid, $removed);
	@$removed;
	}

	sub _num_mid0_for_oid {
	my ($self, $smsg, $oid, $res) = @_;
	my $blob = $smsg->{blob};
	return 1 if (!defined($blob) \|\| $blob ne $oid); # continue;
	@$res = ($smsg->{num}, $smsg->{mid});
	0; # done
	}

	sub num_mid0_for_oid {
	my ($self, $oid, $mid) = @_;
	my $res = [];
	begin_lazy($self);
	each_by_mid($self, $mid, ['ddd'], \&_num_mid0_for_oid, $oid, $res);
	@$res, # ($num, $mid0);
	}

	sub create_tables {
	my ($dbh) = @_;

	$dbh->do(<<'');
	CREATE TABLE IF NOT EXISTS over (
	num INTEGER PRIMARY KEY NOT NULL, /* NNTP article number == IMAP UID */
	tid INTEGER NOT NULL, /* THREADID (IMAP REFERENCES threading, JMAP) */
	sid INTEGER, /* Subject ID (IMAP ORDEREDSUBJECT "threading") */
	ts INTEGER, /* IMAP INTERNALDATE (Received: header, git commit time) */
	ds INTEGER, /* RFC-2822 sent Date: header, git author time */
	ddd VARBINARY /* doc-data-deflated (->to_doc_data, ->load_from_data) */
	)

	$dbh->do('CREATE INDEX IF NOT EXISTS idx_tid ON over (tid)');
	$dbh->do('CREATE INDEX IF NOT EXISTS idx_sid ON over (sid)');
	$dbh->do('CREATE INDEX IF NOT EXISTS idx_ts ON over (ts)');
	$dbh->do('CREATE INDEX IF NOT EXISTS idx_ds ON over (ds)');

	$dbh->do(<<'');
	CREATE TABLE IF NOT EXISTS counter (
	key VARCHAR(8) PRIMARY KEY NOT NULL,
	val INTEGER DEFAULT 0,
	UNIQUE (key)
	)

	$dbh->do("INSERT OR IGNORE INTO counter (key) VALUES ('thread')");
	$dbh->do("INSERT OR IGNORE INTO counter (key) VALUES ('ghost')");

	$dbh->do(<<'');
	CREATE TABLE IF NOT EXISTS subject (
	sid INTEGER PRIMARY KEY AUTOINCREMENT,
	path VARCHAR(40) NOT NULL, /* SHA-1 of normalized subject */
	UNIQUE (path)
	)

	$dbh->do(<<'');
	CREATE TABLE IF NOT EXISTS id2num (
	id INTEGER NOT NULL, /* <=> msgid.id */
	num INTEGER NOT NULL,
	UNIQUE (id, num)
	)

	# performance critical:
	$dbh->do('CREATE INDEX IF NOT EXISTS idx_inum ON id2num (num)');
	$dbh->do('CREATE INDEX IF NOT EXISTS idx_id ON id2num (id)');

	$dbh->do(<<'');
	CREATE TABLE IF NOT EXISTS msgid (
	id INTEGER PRIMARY KEY AUTOINCREMENT, /* <=> id2num.id */
	mid VARCHAR(244) NOT NULL,
	UNIQUE (mid)
	)

	}

	sub commit_lazy {
	my ($self) = @_;
	delete $self->{txn} or return;
	$self->{dbh}->commit;
	eval { $self->{dbh}->do('PRAGMA optimize') };
	}

	sub begin_lazy {
	my ($self) = @_;
	return if $self->{txn};
	my $dbh = $self->dbh or return;
	$dbh->begin_work;
	# $dbh->{Profile} = 2;
	$self->{txn} = 1;
	}

	sub rollback_lazy {
	my ($self) = @_;
	delete $self->{txn} or return;
	$self->{dbh}->rollback;
	}

	sub dbh_close {
	my ($self) = @_;
	Carp::confess('BUG: in transaction') if $self->{txn};
	$self->SUPER::dbh_close;
	}

	sub create {
	my ($self) = @_;
	my $fn = $self->{filename} // do {
	croak('BUG: no {filename}') unless $self->{dbh};
	return;
	};
	unless (-r $fn) {
	require File::Path;
	my ($dir) = ($fn =~ m!(.*?/)[^/]+\z!);
	File::Path::mkpath($dir);
	}
	# create the DB:
	PublicInbox::Over::dbh($self);
	$self->dbh_close;
	}

	sub rethread_prepare {
	my ($self, $opt) = @_;
	return unless $opt->{rethread};
	begin_lazy($self);
	my $min = $self->{min_tid} = get_counter($self->{dbh}, 'thread') // 0;
	my $pr = $opt->{-progress};
	$pr->("rethread min THREADID ".($min + 1)."\n") if $pr && $min;
	}

	sub rethread_done {
	my ($self, $opt) = @_;
	return unless $opt->{rethread} && $self->{txn};
	defined(my $min = $self->{min_tid}) or croak('BUG: no min_tid');
	my $dbh = $self->{dbh} or croak('BUG: no dbh');
	my $rows = $dbh->selectall_arrayref(<<'', { Slice => {} }, $min);
	SELECT num,tid FROM over WHERE num < 0 AND tid < ?

	my $show_id = $dbh->prepare('SELECT id FROM id2num WHERE num = ?');
	my $show_mid = $dbh->prepare('SELECT mid FROM msgid WHERE id = ?');
	my $pr = $opt->{-progress};
	my $total = 0;
	for my $r (@$rows) {
	my $exp = 0;
	$show_id->execute($r->{num});
	while (defined(my $id = $show_id->fetchrow_array)) {
	++$exp;
	$show_mid->execute($id);
	my $mid = $show_mid->fetchrow_array;
	if (!defined($mid)) {
	warn <<EOF;
	E: ghost NUM=$r->{num} ID=$id THREADID=$r->{tid} has no Message-ID
	EOF
	next;
	}
	$pr->(<<EOM) if $pr;
	# ghost $r->{num} <$mid> THREADID=$r->{tid} culled
	EOM
	}
	delete_by_num($self, $r->{num});
	}
	$pr->("# rethread culled $total ghosts\n") if $pr && $total;
	}

	# used for cross-inbox search
	sub eidx_prep ($) {
	my ($self) = @_;
	$self->{-eidx_prep} // do {
	my $dbh = $self->dbh;
	$dbh->do(<<'');
	INSERT OR IGNORE INTO counter (key) VALUES ('eidx_docid')

	$dbh->do(<<'');
	CREATE TABLE IF NOT EXISTS inboxes (
	ibx_id INTEGER PRIMARY KEY AUTOINCREMENT,
	eidx_key VARCHAR(255) NOT NULL, /* {newsgroup} // {inboxdir} */
	UNIQUE (eidx_key)
	)

	$dbh->do(<<'');
	CREATE TABLE IF NOT EXISTS xref3 (
	docid INTEGER NOT NULL, /* <=> over.num */
	ibx_id INTEGER NOT NULL, /* <=> inboxes.ibx_id */
	xnum INTEGER NOT NULL, /* NNTP article number in ibx */
	oidbin VARBINARY NOT NULL, /* 20-byte SHA-1 or 32-byte SHA-256 */
	UNIQUE (docid, ibx_id, xnum, oidbin)
	)

	$dbh->do('CREATE INDEX IF NOT EXISTS idx_docid ON xref3 (docid)');

	# performance critical, this is not UNIQUE since we may need to
	# tolerate some old bugs from indexing mirrors. n.b. we used
	# to index oidbin here, but leaving it out speeds up reindexing
	# and "XHDR Xref <$MSGID>" isn't any slower w/o oidbin
	$dbh->do('CREATE INDEX IF NOT EXISTS idx_reindex ON '.
	'xref3 (xnum,ibx_id)');

	$dbh->do('CREATE INDEX IF NOT EXISTS idx_oidbin ON xref3 (oidbin)');

	$dbh->do(<<'');
	CREATE TABLE IF NOT EXISTS eidx_meta (
	key VARCHAR(255) PRIMARY KEY,
	val VARCHAR(255) NOT NULL
	)

	# A queue of current docids which need reindexing.
	# eidxq persists across aborted -extindex invocations
	# Currently used for "-extindex --reindex" for Xapian
	# data, but may be used in more places down the line.
	$dbh->do(<<'');
	CREATE TABLE IF NOT EXISTS eidxq (docid INTEGER PRIMARY KEY NOT NULL)

	$self->{-eidx_prep} = 1;
	};
	}

	sub eidx_meta { # requires transaction
	my ($self, $key, $val) = @_;

	my $sql = 'SELECT val FROM eidx_meta WHERE key = ? LIMIT 1';
	my $dbh = $self->{dbh};
	defined($val) or return $dbh->selectrow_array($sql, undef, $key);

	my $prev = $dbh->selectrow_array($sql, undef, $key);
	if (defined $prev) {
	$sql = 'UPDATE eidx_meta SET val = ? WHERE key = ?';
	$dbh->do($sql, undef, $val, $key);
	} else {
	$sql = 'INSERT INTO eidx_meta (key,val) VALUES (?,?)';
	$dbh->do($sql, undef, $key, $val);
	}
	$prev;
	}

	sub eidx_max {
	my ($self) = @_;
	get_counter($self->{dbh}, 'eidx_docid');
	}

	sub add_xref3 {
	my ($self, $docid, $xnum, $oidhex, $eidx_key) = @_;
	begin_lazy($self);
	my $ibx_id = ibx_id($self, $eidx_key);
	my $oidbin = pack('H*', $oidhex);
	my $sth = $self->{dbh}->prepare_cached(<<'');
	INSERT OR IGNORE INTO xref3 (docid, ibx_id, xnum, oidbin) VALUES (?, ?, ?, ?)

	$sth->bind_param(1, $docid);
	$sth->bind_param(2, $ibx_id);
	$sth->bind_param(3, $xnum);
	$sth->bind_param(4, $oidbin, SQL_BLOB);
	$sth->execute;
	}

	# for when an xref3 goes missing, this does NOT update {ts}
	sub update_blob {
	my ($self, $smsg, $oidhex) = @_;
	my $sth = $self->{dbh}->prepare(<<'');
	UPDATE over SET ddd = ? WHERE num = ?

	$smsg->{blob} = $oidhex;
	$sth->bind_param(1, ddd_for($smsg), SQL_BLOB);
	$sth->bind_param(2, $smsg->{num});
	$sth->execute;
	}

	sub merge_xref3 { # used for "-extindex --dedupe"
	my ($self, $keep_docid, $drop_docid, $oidbin) = @_;
	my $sth = $self->{dbh}->prepare_cached(<<'');
	UPDATE OR IGNORE xref3 SET docid = ? WHERE docid = ? AND oidbin = ?

	$sth->bind_param(1, $keep_docid);
	$sth->bind_param(2, $drop_docid);
	$sth->bind_param(3, $oidbin, SQL_BLOB);
	$sth->execute;

	# drop anything that conflicted
	$sth = $self->{dbh}->prepare_cached(<<'');
	DELETE FROM xref3 WHERE docid = ? AND oidbin = ?

	$sth->bind_param(1, $drop_docid);
	$sth->bind_param(2, $oidbin, SQL_BLOB);
	$sth->execute;
	}

	sub eidxq_add {
	my ($self, $docid) = @_;
	$self->dbh->prepare_cached(<<'')->execute($docid);
	INSERT OR IGNORE INTO eidxq (docid) VALUES (?)

	}

	sub eidxq_del {
	my ($self, $docid) = @_;
	$self->dbh->prepare_cached(<<'')->execute($docid);
	DELETE FROM eidxq WHERE docid = ?

	}

	# returns true if we're vivifying a message for lei/store that was
	# previously external-metadata only
	sub vivify_xvmd {
	my ($self, $smsg) = @_;
	my @docids = $self->blob_exists($smsg->{blob});
	my @vivify_xvmd;
	for my $id (@docids) {
	if (my $cur = $self->get_art($id)) {
	# already indexed if bytes > 0
	return if $cur->{bytes} > 0;
	push @vivify_xvmd, $id;
	} else {
	warn "W: $smsg->{blob} #$id gone (bug?)\n";
	}
	}
	$smsg->{-vivify_xvmd} = \@vivify_xvmd;
	}

	sub fork_ok {
	state $fork_ok = eval("v$DBD::SQLite::sqlite_version") ge v3.8.3;
	return 1 if $fork_ok;
	my ($opt) = @_;
	my @j = split(/,/, $opt->{jobs} // '');
	state $warned;
	grep { $_ > 1 } @j and $warned //= warn(<<EOM);
	DBD::SQLite version is v$DBD::SQLite::sqlite_version, need >= v3.8.3 for --jobs > 1
	EOM
	$opt->{jobs} = '1,1';
	undef;
	}

	1;