public static String updateCompactionHistory( String keyspaceName, String columnFamilyName, AbstractCompactionIterable ci, long startSize, long endSize) { long[] counts = ci.getMergedRowCounts(); StringBuilder mergeSummary = new StringBuilder(counts.length * 10); Map<Integer, Long> mergedRows = new HashMap<>(); for (int i = 0; i < counts.length; i++) { long count = counts[i]; if (count == 0) continue; int rows = i + 1; mergeSummary.append(String.format("%d:%d, ", rows, count)); mergedRows.put(rows, count); } SystemKeyspace.updateCompactionHistory( keyspaceName, columnFamilyName, System.currentTimeMillis(), startSize, endSize, mergedRows); return mergeSummary.toString(); }