Impala Public Jenkins has submitted this change and it was merged. ( 
http://gerrit.cloudera.org:8080/22737 )

Change subject: IMPALA-13934: Do quick pointer comparison in 
IcebergDeleteBuilder
......................................................................

IMPALA-13934: Do quick pointer comparison in IcebergDeleteBuilder

Since IMPALA-13194 file paths are deduplicated in the serialized
position delete records. Therefore we can do a quick check pointer-based
comparison of subsequent position delete records instead of the costly
string compare.

If the pointers don't match we still need to check the strings for
equality because position records coming from different senders can be
coalesced into a single row batch by the EXCHANGE RECEIVER.

Measurements

Data table had ~1 Trillion data records and ~68 Billion position delete
records. Average time spent in the IcebergDeleteBuilder:
+------------+----------+-----------+
| Node count | Original | Optimized |
+------------+----------+-----------+
|          5 | 12m11s   | 9m47s     |
|         10 | 6m2s     | 5m        |
|         20 | 3m1s     | 2m30s     |
|         40 | 1m30s    | 1m15s     |
+------------+----------+-----------+

It's essential to optimize the builder as it blocks all the probe
threads of the IcebergDeleteNode.

Testing
 * no behaviour change, existing tests can be used

Change-Id: Ie171f912a5518b6e6a445efba9d39748ecec5a36
Reviewed-on: http://gerrit.cloudera.org:8080/22737
Reviewed-by: Impala Public Jenkins <impala-public-jenk...@cloudera.com>
Tested-by: Impala Public Jenkins <impala-public-jenk...@cloudera.com>
---
M be/src/exec/iceberg-delete-builder.cc
1 file changed, 1 insertion(+), 1 deletion(-)

Approvals:
  Impala Public Jenkins: Looks good to me, approved; Verified

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Gerrit-Project: Impala-ASF
Gerrit-Branch: master
Gerrit-MessageType: merged
Gerrit-Change-Id: Ie171f912a5518b6e6a445efba9d39748ecec5a36
Gerrit-Change-Number: 22737
Gerrit-PatchSet: 3
Gerrit-Owner: Zoltan Borok-Nagy <borokna...@cloudera.com>
Gerrit-Reviewer: Daniel Becker <daniel.bec...@cloudera.com>
Gerrit-Reviewer: Impala Public Jenkins <impala-public-jenk...@cloudera.com>

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