[MINOR] Fix compression statistic logging for frames

Logging of frames statistics for compression is misleading when
samples are used to estimate the number of elements.
Therefore this commit change the logging message to reflect the
approximate nature of distinct counts

src/main/java/org/apache/sysds/runtime/frame/data/compress/ArrayCompressionStatistics.java

@@ -20,6 +20,8 @@
 package org.apache.sysds.runtime.frame.data.compress;
 
 import org.apache.sysds.common.Types.ValueType;
+import org.apache.sysds.conf.ConfigurationManager;
+import org.apache.sysds.conf.DMLConfig;
 import org.apache.sysds.runtime.frame.data.columns.ArrayFactory.FrameArrayType;
 
 public class ArrayCompressionStatistics {
@@ -48,8 +50,12 @@ public ArrayCompressionStatistics(int bytePerValue, int nUnique, boolean shouldC
 	@Override
 	public String toString() {
 		StringBuilder sb = new StringBuilder();
-		sb.append(String.format("Compressed Stats: size:%8d->%8d, Use:%10s, Unique:%6d, ValueType:%7s", originalSize,
-			compressedSizeEstimate, bestType == null ? "None" : bestType.toString(), nUnique, valueType));
+		if(ConfigurationManager.getDMLConfig().getDoubleValue(DMLConfig.COMPRESSED_SAMPLING_RATIO) < 1)
+			sb.append(String.format("Compressed Stats: size:%8d->%8d, Use:%10s, EstUnique:%6d, ValueType:%7s",
+				originalSize, compressedSizeEstimate, bestType == null ? "None" : bestType.toString(), nUnique, valueType));
+		else
+			sb.append(String.format("Compressed Stats: size:%8d->%8d, Use:%10s, Unique:%6d, ValueType:%7s", originalSize,
+				compressedSizeEstimate, bestType == null ? "None" : bestType.toString(), nUnique, valueType));
 		return sb.toString();
 	}
 }