Revert "HBASE-28204 Canary can take lot more time If region starts with delete markers (#5522)"

This reverts commit ce9eabe.

Author: virajjasani

hbase-server/src/main/java/org/apache/hadoop/hbase/tool/CanaryTool.java

@@ -510,38 +510,38 @@ public Void call() {
 
     private Void readColumnFamily(Table table, ColumnFamilyDescriptor column) {
       byte[] startKey = null;
-      Scan scan = new Scan();
+      Get get = null;
+      Scan scan = null;
       ResultScanner rs = null;
       StopWatch stopWatch = new StopWatch();
       startKey = region.getStartKey();
       // Can't do a get on empty start row so do a Scan of first element if any instead.
       if (startKey.length > 0) {
-        // There are 4 types of region for any table.
-        // 1. Start and End key are empty. (Table with Single region)
-        // 2. Start key is empty. (First region of the table)
-        // 3. End key is empty. (Last region of the table)
-        // 4. Region with Start & End key. (All the regions between first & last region of the
-        // table.)
-        //
-        // Since Scan only takes Start and/or End Row and doesn't accept the region ID,
-        // we set the start row when Regions are of type 3 OR 4 as mentioned above.
-        // For type 1 and 2, We don't need to set this option.
-        scan.withStartRow(startKey);
+        get = new Get(startKey);
+        get.setCacheBlocks(false);
+        get.setFilter(new FirstKeyOnlyFilter());
+        get.addFamily(column.getName());
+      } else {
+        scan = new Scan();
+        LOG.debug("rawScan {} for {}", rawScanEnabled, region.getTable());
+        scan.setRaw(rawScanEnabled);
+        scan.setCaching(1);
+        scan.setCacheBlocks(false);
+        scan.setFilter(new FirstKeyOnlyFilter());
+        scan.addFamily(column.getName());
+        scan.setMaxResultSize(1L);
+        scan.setOneRowLimit();
       }
-      LOG.debug("rawScan {} for {}", rawScanEnabled, region.getTable());
-      scan.setRaw(rawScanEnabled);
-      scan.setCaching(1);
-      scan.setCacheBlocks(false);
-      scan.setFilter(new FirstKeyOnlyFilter());
-      scan.addFamily(column.getName());
-      scan.setMaxResultSize(1L);
-      scan.setOneRowLimit();
       LOG.debug("Reading from {} {} {} {}", region.getTable(), region.getRegionNameAsString(),
         column.getNameAsString(), Bytes.toStringBinary(startKey));
       try {
         stopWatch.start();
-        rs = table.getScanner(scan);
-        rs.next();
+        if (startKey.length > 0) {
+          table.get(get);
+        } else {
+          rs = table.getScanner(scan);
+          rs.next();
+        }
         stopWatch.stop();
         this.readWriteLatency.add(stopWatch.getTime());
         sink.publishReadTiming(serverName, region, column, stopWatch.getTime());