this.lock.readLock().lock();
try {
synchronized (filesCompacting) {
// First, see if coprocessor would want to override selection.
if (this.getCoprocessorHost() != null) {
List<StoreFile> candidatesForCoproc = compaction.preSelect(this.filesCompacting);
boolean override = this.getCoprocessorHost().preCompactSelection(
this, candidatesForCoproc, baseRequest);
if (override) {
// Coprocessor is overriding normal file selection.
compaction.forceSelect(new CompactionRequest(candidatesForCoproc));