diff --git a/atom b/atom
index e7734bf..7e035f3 100755
--- a/atom
+++ b/atom
@@ -429,7 +429,7 @@ echo '
 	CREATE TEMPORARY TABLE tasks(
 		id		INTEGER PRIMARY KEY,
 		requires	INTEGER,
-		required	INTEGER,
+		required_by	INTEGER	DEFAULT 0,
 		status		INTEGER NOT NULL,
 		key		TEXT	UNIQUE,
 		rename_pattern	TEXT,
diff --git a/lib/decode/file b/lib/decode/file
index c91d7f0..ae33da8 100644
--- a/lib/decode/file
+++ b/lib/decode/file
@@ -165,6 +165,12 @@ decodeFile() {
 					Select tasks id <<<"key = $tmpfile"
 				)
 				then
+					parent_required=$(
+						Select tasks required_by			\
+							<<<"id = $decodetaskid"
+					)
+					Update tasks required_by $((++parent_required))	\
+						<<<"id = $decodetaskid"
 					soxtaskid=$(
 						Insert tasks <<-EOInsert
 							key		$tmpfile
@@ -176,7 +182,6 @@ decodeFile() {
 								done
 							)
 							requires	$decodetaskid
-							required	$decodetaskid
 							status		0
 							cleanup		$cleanup
 						EOInsert
diff --git a/lib/encode/mp3 b/lib/encode/mp3
index d0d6800..f2a91ee 100644
--- a/lib/encode/mp3
+++ b/lib/encode/mp3
@@ -52,7 +52,6 @@ encodeFile::mp3() {
 		Insert tasks <<-EOInsert
 			key		${fileid}lame$destination
 			requires	${soxtaskid:-$decodetaskid}
-			required	${soxtaskid:-$decodetaskid}
 			fileid		$destfileid
 			filename	$destdir/$destfile.mp3
 			$(
@@ -74,6 +73,12 @@ encodeFile::mp3() {
 			ascii		${destinationascii["$destination"]}
 		EOInsert
 	)
+	parent_required=$(
+		Select tasks required_by			\
+			<<<"id = ${soxtaskid:-$decodetaskid}"
+	)
+	Update tasks required_by $((++parent_required))	\
+		<<<"id = ${soxtaskid:-$decodetaskid}"
 	progressSpin
 	soxtaskid=''
 }
diff --git a/lib/encode/opus b/lib/encode/opus
index 2994190..d663339 100644
--- a/lib/encode/opus
+++ b/lib/encode/opus
@@ -20,7 +20,6 @@ encodeFile::opus() {
 		Insert tasks <<-EOInsert
 			key		${fileid}opusenc$destination
 			requires	${soxtaskid:-$decodetaskid}
-			required	${soxtaskid:-$decodetaskid}
 			fileid		$destfileid
 			filename	$destdir/$destfile.opus
 			$(
@@ -42,6 +41,12 @@ encodeFile::opus() {
 			ascii		${destinationascii["$destination"]}
 		EOInsert
 	)
+	parent_required=$(
+		Select tasks required_by			\
+			<<<"id = ${soxtaskid:-$decodetaskid}"
+	)
+	Update tasks required_by $((++parent_required))	\
+		<<<"id = ${soxtaskid:-$decodetaskid}"
 	progressSpin
 	soxtaskid=''
 }
diff --git a/lib/encode/vorbis b/lib/encode/vorbis
index a96523f..660fd5f 100644
--- a/lib/encode/vorbis
+++ b/lib/encode/vorbis
@@ -16,7 +16,6 @@ encodeFile::vorbis() {
 		Insert tasks <<-EOInsert
 			key		${fileid}oggenc$destination
 			requires	${soxtaskid:-$decodetaskid}
-			required	${soxtaskid:-$decodetaskid}
 			fileid		$destfileid
 			filename	$destdir/$destfile.ogg
 			$(
@@ -38,6 +37,12 @@ encodeFile::vorbis() {
 			ascii		${destinationascii["$destination"]}
 		EOInsert
 	)
+	parent_required=$(
+		Select tasks required_by			\
+			<<<"id = ${soxtaskid:-$decodetaskid}"
+	)
+	Update tasks required_by $((++parent_required))	\
+		<<<"id = ${soxtaskid:-$decodetaskid}"
 	progressSpin
 	soxtaskid=''
 }
diff --git a/lib/tasks/gettaskinfos b/lib/tasks/gettaskinfos
index 5a51657..648e4ab 100644
--- a/lib/tasks/gettaskinfos
+++ b/lib/tasks/gettaskinfos
@@ -4,7 +4,6 @@ gettaskinfos() {
 		SELECT
 			id,
 			source_file,
-			required,
 			cleanup,
 			fileid,
 			filename
@@ -16,8 +15,6 @@ gettaskinfos() {
 	rest="${line#*::AtOM:SQL:Sep::}::AtOM:SQL:Sep::"
 	sourcefileid=${rest%%::AtOM:SQL:Sep::*}
 	rest=${rest#*::AtOM:SQL:Sep::}
-	required=${rest%%::AtOM:SQL:Sep::*}
-	rest=${rest#*::AtOM:SQL:Sep::}
 	cleanup=${rest%%::AtOM:SQL:Sep::*}
 	rest=${rest#*::AtOM:SQL:Sep::}
 	destfileid=${rest%%::AtOM:SQL:Sep::*}
diff --git a/lib/workers/check b/lib/workers/check
index fa52afb..7da7f36 100644
--- a/lib/workers/check
+++ b/lib/workers/check
@@ -1,5 +1,9 @@
 #!/bin/bash
 checkworkers() {
+	local			\
+		taskid		\
+		parent_required	\
+		parent_task
 	for key in ${!workers[@]}
 	do
 		if ! kill -0 ${workers[key]} 2>/dev/null
@@ -14,6 +18,19 @@ checkworkers() {
 				failedtasks+=($taskid)
 				(( ++failed ))
 			fi
+			parent_task=$(
+				Select tasks requires	\
+					<<<"id = $taskid"
+			)
+			if (( parent_task ))
+			then
+				parent_required=$(
+					Select tasks required_by	\
+						<<<"id = $parent_task"
+				)
+				Update tasks required_by $((--parent_required))	\
+					<<<"id = $parent_task"
+			fi
 			unset workertasks[key]
 		fi
 	done
diff --git a/lib/workers/cleaner b/lib/workers/cleaner
index b72a53e..08f3c60 100644
--- a/lib/workers/cleaner
+++ b/lib/workers/cleaner
@@ -1,26 +1,23 @@
 #!/bin/bash
 cleaner() {
+	local			\
+		key		\
+		faildepends	\
+		taskid		\
+		count
 	for key in ${!failedtasks[@]}
 	do
 		taskid=${failedtasks[key]}
 		gettaskinfos $taskid
 		faildepends=$(
-			Select tasks 'COUNT(*)' <<-EOWhere
-				requires = $taskid
+			Select tasks required_by <<-EOWhere
+				id = $taskid
 			EOWhere
 		)
 		(( failed+=faildepends ))
 		(( ran+=faildepends ))
 		Update tasks status 2 <<<"id = $taskid"
-		echo "SELECT	COUNT(*)
-			FROM	tasks
-			WHERE	( status = 0 OR status = 1 )
-			AND	required = $taskid;">&3
-		read -u4 count
-		if (( count == 0 ))
-		then
-			rm -f "$cleanup"
-		fi
+		rm -f "$cleanup"
 		unset failedtasks[key]
 	done
 	for key in ${!finishedtasks[@]}
@@ -60,11 +57,7 @@ cleaner() {
 			"WHERE  id=$destfileid;"			\
 			>&3
 		fi
-		echo "SELECT	COUNT(*)
-			FROM	tasks
-			WHERE	( status = 0 OR status = 1 )
-			AND	required = $taskid;">&3
-		read -u4 count
+		count=$(Select tasks required_by <<<"id = $taskid")
 		if (( count == 0 ))
 		then
 			rm -f "$cleanup"
diff --git a/lib/workers/master b/lib/workers/master
index 449bc05..efe0155 100644
--- a/lib/workers/master
+++ b/lib/workers/master
@@ -17,7 +17,6 @@ master() {
 			SELECT
 				id,
 				source_file,
-				required,
 				cmd_arg0,
 				cmd_arg1,
 				cmd_arg2,