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Posted to dev@phoenix.apache.org by "chenglei (JIRA)" <ji...@apache.org> on 2017/03/04 03:04:45 UTC
[jira] [Assigned] (PHOENIX-3705) SkipScanFilter may repeatedly copy
rowKey Columns to startKey
[ https://issues.apache.org/jira/browse/PHOENIX-3705?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
chenglei reassigned PHOENIX-3705:
---------------------------------
Resolution: Fixed
Assignee: chenglei
> SkipScanFilter may repeatedly copy rowKey Columns to startKey
> -------------------------------------------------------------
>
> Key: PHOENIX-3705
> URL: https://issues.apache.org/jira/browse/PHOENIX-3705
> Project: Phoenix
> Issue Type: Bug
> Affects Versions: 4.9.0
> Reporter: chenglei
> Assignee: chenglei
> Priority: Blocker
> Fix For: 4.10.0
>
> Attachments: PHOENIX-3705_v2.patch
>
>
> See following simple unit test first,the rowKey is composed of three PInteger columns,and the slots of SkipScanFilter are:
> [ [[1 - 4]], [5, 7], [[9 - 10]] ],
> When SkipScanFilter.filterKeyValue method is invoked on a KeyValue whose rowKey is [2,7,11], obviously SkipScanFilter.filterKeyValue
> returns ReturnCode.SEEK_NEXT_USING_HINT and SkipScanFilter.getNextCellHint returns [3,5,9], but unfortunately, SkipScanFilter.getNextCellHint actually returns [2,8,5,9] , a very strange value, the unit tests failed.
> {code}
> @Test
> public void testNavigate() {
> RowKeySchemaBuilder builder = new RowKeySchemaBuilder(3);
> for(int i=0;i<3;i++) {
> builder.addField(
> new PDatum() {
> @Override
> public boolean isNullable() {
> return false;
> }
> @Override
> public PDataType getDataType() {
> return PInteger.INSTANCE;
> }
> @Override
> public Integer getMaxLength() {
> return PInteger.INSTANCE.getMaxLength(null);
> }
> @Override
> public Integer getScale() {
> return PInteger.INSTANCE.getScale(null);
> }
> @Override
> public SortOrder getSortOrder() {
> return SortOrder.getDefault();
> }
> }, false, SortOrder.getDefault());
> }
>
> List<List<KeyRange>> rowKeyColumnRangesList=Arrays.asList(
> Arrays.asList(
> PInteger.INSTANCE.getKeyRange(PInteger.INSTANCE.toBytes(1), true, PInteger.INSTANCE.toBytes(4), true)),
> Arrays.asList(
> KeyRange.getKeyRange(PInteger.INSTANCE.toBytes(5)),
> KeyRange.getKeyRange(PInteger.INSTANCE.toBytes(7))),
> Arrays.asList(
> PInteger.INSTANCE.getKeyRange(PInteger.INSTANCE.toBytes(9), true, PInteger.INSTANCE.toBytes(10), true))
> );
>
> SkipScanFilter skipScanFilter=new SkipScanFilter(rowKeyColumnRangesList, builder.build());
>
> System.out.println(skipScanFilter);
>
> byte[] rowKey=ByteUtil.concat(
> PInteger.INSTANCE.toBytes(2),
> PInteger.INSTANCE.toBytes(7),
> PInteger.INSTANCE.toBytes(11));
> KeyValue keyValue=KeyValue.createFirstOnRow(rowKey);
> ReturnCode returnCode=skipScanFilter.filterKeyValue(keyValue);
> assertTrue(returnCode == ReturnCode.SEEK_NEXT_USING_HINT);
> Cell nextCellHint=skipScanFilter.getNextCellHint(keyValue);
> assertTrue(Bytes.toStringBinary(CellUtil.cloneRow(nextCellHint)).equals(
> "\\x80\\x00\\x00\\x03\\x80\\x00\\x00\\x05\\x80\\x00\\x00\\x09"));
> }
> {code}
> Let us see what's wrong, first column of rowKey [2,7,11 ] is 2, which is in SkipScanFilter's first slot range [1-4], so position[0] is 0 and we go to the second column 7, which match the second range [7] of SkipScanFilter's second slot [5, 7],so position[1] is 1 and we go to the third column 11, which is bigger than the third slot range [9 - 10],so position[2] is 0 and the {{SkipScanFilter.ptr}} which points to current column still stay on the third column. Now we begin to backtrack to second column, because the second range [7] of SkipScanFilter's second slot is singleKey and there is no more range,so position[1] is 0 and we continue to backtrack to first column, because the first slot range [1-4] is not singleKey so we stop backtracking at first column.
> Now the problem comes, in following line 448 of {{SkipScanFilter.navigate}} method,{{SkipScanFilter.setStartKey}} method is invoked,first copy rowKey columns before {{SkipScanFilter.ptr}} to {{SkipScanFilter.startKey}}, because now {{SkipScanFilter.ptr}} still point to the third column, so copy the first and second columns to {{SkipScanFilter.startKey}},{{SkipScanFilter.startKey}} is [2,7] after this step , then setStartKey method copy the lower bound {{SkipScanFilter.slots}} from {{j+1}} column, accoring to {{SkipScanFilter.position}} array,because now j is 0, and both position[1] and position[2] are 0, so {{SkipScanFilter.startKey}} becomes [2,7,5,9], and in following line 457, {{ByteUtil.nextKey}} is invoked on [2,7], [2,7] is incremented to [2,8], finally {{SkipScanFilter.startKey}} is [2,8,5,9].
> {code}
> 448 int currentLength = setStartKey(ptr, minOffset, j+1, nSlots, false);
> 449 // From here on, we use startKey as our buffer (resetting minOffset and maxOffset)
> 450 // We've copied the part of the current key above that we need into startKey
> 451 // Reinitialize the iterator to be positioned at previous slot position
> 452 minOffset = 0;
> 453 maxOffset = startKeyLength;
> 454 schema.iterator(startKey, minOffset, maxOffset, ptr, ScanUtil.getRowKeyPosition(slotSpan, j)+1);
> 455 // Do nextKey after setting the accessor b/c otherwise the null byte may have
> 456 // been incremented causing us not to find it
> 457 ByteUtil.nextKey(startKey, currentLength);
> {code}
> From above analysis, we can see the second column is repeatedly copied to {{SkipScanFilter.startKey}}, copy 7 to {{SkipScanFilter.startKey}} is error ,before {{SkipScanFilter.setStartKey}} method is invoked in line 448, we should first move {{SkipScanFilter.ptr}} to {{j+1}}, that is to say ,following code might be inserted before line 448:
> {code}
> schema.reposition(
> ptr,
> ScanUtil.getRowKeyPosition(slotSpan, i),
> ScanUtil.getRowKeyPosition(slotSpan, j+1),
> minOffset,
> maxOffset,
> slotSpan[j+1]);
> {code}
> Another problem is why the existing SkipScanFilter unit tests are ok? That is because in all existing unit test cases, backtrack column is just before current column which ptr points to, i.e. i==j+1, so the unit tests are ok.
> This issue may not affect the final query result , but obviously, it may lead to the erroneous startKey and cause the Skip Scan inefficient.
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