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Posted to gitbox@hive.apache.org by GitBox <gi...@apache.org> on 2022/10/05 20:01:39 UTC
[GitHub] [hive] kasakrisz commented on a diff in pull request #3588: HIVE-26524: Use Calcite to remove sections of a query plan known never produces rows
kasakrisz commented on code in PR #3588:
URL: https://github.com/apache/hive/pull/3588#discussion_r985560069
##########
ql/src/test/results/clientpositive/llap/float_equality.q.out:
##########
@@ -9,9 +9,7 @@ POSTHOOK: Input: _dummy_database@_dummy_table
1
PREHOOK: query: select 1 where -0.0<0.0
PREHOOK: type: QUERY
-PREHOOK: Input: _dummy_database@_dummy_table
Review Comment:
This was the original plan: empty result query is converted to a sub-query hence the the limit is not treated as global limit and the query is executed.
```
HiveProject(_o__c0=[1])
HiveSortLimit(fetch=[0])
HiveProject(DUMMY=[0])
HiveTableScan(table=[[_dummy_database, _dummy_table]], table:alias=[_dummy_table])
```
These is a TS on `_dummy_table`
```
STAGE PLANS:
Stage: Stage-0
Fetch Operator
limit: -1
Processor Tree:
TableScan
alias: _dummy_table
Row Limit Per Split: 1
Limit
Number of rows: 0
Select Operator
Select Operator
expressions: 1 (type: int)
outputColumnNames: _col0
ListSink
```
The new plan is just an empty values op.
```
HiveValues(tuples=[[]])
```
There is no TS,
```
STAGE PLANS:
Stage: Stage-0
Fetch Operator
limit: 0
Processor Tree:
ListSink
```
##########
ql/src/test/results/clientpositive/llap/fold_case.q.out:
##########
@@ -177,7 +180,7 @@ STAGE PLANS:
sort order:
Statistics: Num rows: 1 Data size: 8 Basic stats: COMPLETE Column stats: COMPLETE
value expressions: _col0 (type: bigint)
- Execution mode: vectorized, llap
+ Execution mode: llap
Review Comment:
The vectorization was lost because instead of a real table the `_dummy_table` with empty schema is scanned. It affects only this mapper. Rest of the plan (Reducer) is still vectorized.
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