diff --git a/atom b/atom
index d4aa334..01b32b1 100755
--- a/atom
+++ b/atom
@@ -1112,13 +1112,14 @@ unset count tagfiles
 echo '
 	CREATE TEMPORARY TABLE tasks(
 		id		INTEGER PRIMARY KEY,
-		unicity_check	TEXT	SECONDARY KEY,
+		key		TEXT	UNIQUE,
 		command_line	TEXT,
 		requires	INTEGER,
 		status		INTEGER NOT NULL,
 		FOREIGN KEY(requires) REFERENCES tasks(id)
 			ON DELETE SET NULL
-	);' >&3
+	);
+	CREATE INDEX tasks_by_key ON tasks ( key );' >&3
 
 echo '
 	SELECT	COUNT(DISTINCT source_files.id)
@@ -1192,27 +1193,32 @@ do
 		soxoptions_out+=" -c ${destinationchannels["$destination"]}"
 	fi
 	tmpfile="$fileid${soxoptions_in// /}${soxoptions_out// /}"
-	soxoptions_in+=' --single-threaded'
-	soxoptions_out+=" --temp \"$tempdir\""
-	decodetaskid=$(
-		InsertIfUnset tasks <<-EOInsert
-			unicity_check	$tmpfile
-			command_line	sox $soxoptions_in "$sourcepath/$filename" $soxoptions_out "$tempdir/$tmpfile.wav"
-			status		0
-		EOInsert
+	if ! decodetaskid=$(
+		Select tasks id <<<"key = $tmpfile"
 	)
-	case $(( ++count % 40 )) in
-		0) echo -ne '\b|' ;;
-		10) echo -ne '\b/' ;;
-		20) echo -en '\b-' ;;
-		30) echo -ne '\b\\' ;;
-		*) ;;
-	esac
-	if (( count % 1000 == 0 ))
 	then
-		echo 'COMMIT;BEGIN TRANSACTION;' >&3
-		(( debug ))	\
-		&& echo -e "\bCommitted $count tasks... "
+		soxoptions_in+=' --single-threaded'
+		soxoptions_out+=" --temp \"$tempdir\""
+		decodetaskid=$(
+			Insert tasks <<-EOInsert
+				key		$tmpfile
+				command_line	sox $soxoptions_in "$sourcepath/$filename" $soxoptions_out "$tempdir/$tmpfile.wav"
+				status		0
+			EOInsert
+		)
+		case $(( ++count % 40 )) in
+			0) echo -ne '\b|' ;;
+			10) echo -ne '\b/' ;;
+			20) echo -en '\b-' ;;
+			30) echo -ne '\b\\' ;;
+			*) ;;
+		esac
+		if (( count % 1000 == 0 ))
+		then
+			echo 'COMMIT;BEGIN TRANSACTION;' >&3
+			(( debug ))	\
+			&& echo -en "\bCommitted $count tasks...  "
+		fi
 	fi
 	unset			\
 		channels	\