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https://issues.apache.org/jira/browse/PHOENIX-7106?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17806140#comment-17806140
 ] 

ASF GitHub Bot commented on PHOENIX-7106:
-----------------------------------------

kadirozde commented on code in PR #1736:
URL: https://github.com/apache/phoenix/pull/1736#discussion_r1450753169


##########
phoenix-core-server/src/main/java/org/apache/phoenix/coprocessor/IndexerRegionScanner.java:
##########
@@ -435,12 +437,33 @@ public boolean next(List<Cell> results) throws 
IOException {
                 mutations.clear();
             }
         }
-        byte[] rowCountBytes = PLong.INSTANCE.toBytes(Long.valueOf(rowCount));
+        byte[] rowCountBytes = PLong.INSTANCE.toBytes((long) rowCount);
         final Cell aggKeyValue;
         if (lastCell == null) {
-            aggKeyValue = 
PhoenixKeyValueUtil.newKeyValue(UNGROUPED_AGG_ROW_KEY,
-                SINGLE_COLUMN_FAMILY,
-                    SINGLE_COLUMN, AGG_TIMESTAMP, rowCountBytes,0, 
rowCountBytes.length);
+            byte[] rowKey;
+            byte[] startKey = scan.getStartRow().length > 0 ? 
scan.getStartRow() :
+                    region.getRegionInfo().getStartKey();
+            byte[] endKey = scan.getStopRow().length > 0 ? scan.getStopRow() :
+                    region.getRegionInfo().getEndKey();
+            final boolean isIncompatibleClient =
+                    
ScanUtil.isIncompatibleClientForServerReturnValidRowKey(scan);
+            if (!isIncompatibleClient) {
+                rowKey = ByteUtil.getLargestPossibleRowKeyInRange(startKey, 
endKey);
+                if (rowKey == null) {
+                    if (scan.includeStartRow()) {

Review Comment:
   If lastCell is null then there is no row left to scan. Why do we need to 
worry about the start row here? 





> Data Integrity issues due to invalid rowkeys returned by various coprocessors
> -----------------------------------------------------------------------------
>
>                 Key: PHOENIX-7106
>                 URL: https://issues.apache.org/jira/browse/PHOENIX-7106
>             Project: Phoenix
>          Issue Type: Improvement
>    Affects Versions: 5.2.0, 5.1.4
>            Reporter: Viraj Jasani
>            Assignee: Viraj Jasani
>            Priority: Blocker
>             Fix For: 5.2.0, 5.1.4
>
>
> HBase scanner interface expects server to perform scan of the cells from 
> HFile or Block cache and return consistent data i.e. rowkey of the cells 
> returned should stay in the range of the scan boundaries. When a region moves 
> and scanner needs reset, or if the current row is too large and the server 
> returns partial row, the subsequent scanner#next is supposed to return 
> remaining cells. When this happens, cell rowkeys returned by servers i.e. any 
> coprocessors is expected to be in the scan boundary range so that server can 
> reliably perform its validation and return remaining cells as expected.
> Phoenix client initiates serial or parallel scans from the aggregators based 
> on the region boundaries and the scan boundaries are sometimes adjusted based 
> on where optimizer provided key ranges, to include tenant boundaries, salt 
> boundaries etc. After the client opens the scanner and performs scan 
> operation, some of the coprocs return invalid rowkey for the following cases:
>  # Grouped aggregate queries
>  # Some Ungrouped aggregate queries
>  # Offset queries
>  # Dummy cells returned with empty rowkey
>  # Update statistics queries
>  # Uncovered Index queries
>  # Ordered results at server side
>  # ORDER BY DESC on rowkey
>  # Global Index read-repair
>  # Paging region scanner with HBase scanner reopen
>  # ORDER BY on non-pk column(s) with/without paging
>  # GROUP BY on non-pk column(s) with/without paging
> Since many of these cases return reserved rowkeys, they are likely not going 
> to match scan or region boundaries. It has potential to cause data integrity 
> issues in certain scenarios as explained above. Empty rowkey returned by 
> server can be treated as end of the region scan by HBase client.
> With the paging feature enabled, if the page size is kept low, we have higher 
> chances of scanners returning dummy cell, resulting in increased num of RPC 
> calls for better latency and timeouts. We should return only valid rowkey in 
> the scan range for all the cases where we perform above mentioned operations 
> like complex aggregate or offset queries etc.



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