kgyrtkirk opened a new pull request, #15552:
URL: https://github.com/apache/druid/pull/15552
I was looking into a query which was performing a bit poorly because the
`case_searched` was touching more than `1` columns (if there is only 1 column
there is a cache based evaluator).
While I was doing that I've noticed that there are a few simple things which
could help a bit:
* use a static `TRUE`/`FALSE` instead of creating a new object every time
* create the `ExprEval` early for `ConstantExpr` -s (except the one for
`BigInteger` which seem to have some odd contract)
* return early from type autodetection
these changes mostly reduce the amount of garbage the query creates during
`case_searched` evaluation; although `ExpressionSelectorBenchmark` shows some
improvements `~15%` - but my manual trials on the taxi dataset with 60M rows
showed more improvements - probably due to the fact that these changes mostly
only reduce gc pressure.
<details>
<summary>q1.3</summary>
```sql
SELECT
case when
LOOKUP("dropoff", 'look') = 'x' or
"max_temperature" = '125711' or min_temperature = '11' or min_temperature
= '112' or min_temperature = '1212' or min_temperature = '32' then
min_temperature end,
sum("total_amount"),
count(1)
FROM "trips_xaa"
group by 1
```
execution time improved from `6.69s` to `4.08s`
</details>
<details>
<summary>ExpressionSelectorBenchmark results</summary>
```diff
Benchmark (rowsPerSegment)
Mode Cnt Score Error Units
-ExpressionSelectorBenchmark.arithmeticOnLong 1000000
avgt 10 8.371 ± 0.100 ms/op
+ExpressionSelectorBenchmark.arithmeticOnLong 1000000
avgt 10 8.254 ± 0.041 ms/op
-ExpressionSelectorBenchmark.caseSearched1 1000000
avgt 10 9.612 ± 0.581 ms/op
+ExpressionSelectorBenchmark.caseSearched1 1000000
avgt 10 9.197 ± 0.033 ms/op
-ExpressionSelectorBenchmark.caseSearched2 1000000
avgt 10 275.416 ± 15.150 ms/op
+ExpressionSelectorBenchmark.caseSearched2 1000000
avgt 10 233.649 ± 4.713 ms/op
-ExpressionSelectorBenchmark.caseSearchedWithLookup 1000000
avgt 10 125.643 ± 6.343 ms/op
+ExpressionSelectorBenchmark.caseSearchedWithLookup 1000000
avgt 10 104.813 ± 1.242 ms/op
-ExpressionSelectorBenchmark.caseSearchedWithLookup2 1000000
avgt 10 132.319 ± 10.260 ms/op
+ExpressionSelectorBenchmark.caseSearchedWithLookup2 1000000
avgt 10 116.626 ± 2.644 ms/op
-ExpressionSelectorBenchmark.stringConcatAndCompareOnLong 1000000
avgt 10 8.355 ± 0.078 ms/op
+ExpressionSelectorBenchmark.stringConcatAndCompareOnLong 1000000
avgt 10 8.429 ± 0.119 ms/op
-ExpressionSelectorBenchmark.strlenUsingExpressionAsLong 1000000
avgt 10 9.236 ± 0.205 ms/op
+ExpressionSelectorBenchmark.strlenUsingExpressionAsLong 1000000
avgt 10 9.110 ± 0.084 ms/op
-ExpressionSelectorBenchmark.strlenUsingExpressionAsString 1000000
avgt 10 6.457 ± 0.129 ms/op
+ExpressionSelectorBenchmark.strlenUsingExpressionAsString 1000000
avgt 10 6.389 ± 0.077 ms/op
-ExpressionSelectorBenchmark.strlenUsingExtractionFn 1000000
avgt 10 3.499 ± 0.126 ms/op
+ExpressionSelectorBenchmark.strlenUsingExtractionFn 1000000
avgt 10 3.466 ± 0.041 ms/op
-ExpressionSelectorBenchmark.timeFloorUsingCursor 1000000
avgt 10 8.149 ± 0.035 ms/op
+ExpressionSelectorBenchmark.timeFloorUsingCursor 1000000
avgt 10 8.117 ± 0.052 ms/op
-ExpressionSelectorBenchmark.timeFloorUsingExpression 1000000
avgt 10 9.051 ± 0.106 ms/op
+ExpressionSelectorBenchmark.timeFloorUsingExpression 1000000
avgt 10 8.928 ± 0.058 ms/op
-ExpressionSelectorBenchmark.timeFloorUsingExtractionFn 1000000
avgt 10 7.765 ± 0.167 ms/op
+ExpressionSelectorBenchmark.timeFloorUsingExtractionFn 1000000
avgt 10 7.713 ± 0.125 ms/op
-ExpressionSelectorBenchmark.timeFormatUsingExpression 1000000
avgt 10 10.423 ± 0.158 ms/op
+ExpressionSelectorBenchmark.timeFormatUsingExpression 1000000
avgt 10 9.779 ± 0.167 ms/op
-ExpressionSelectorBenchmark.timeFormatUsingExtractionFn 1000000
avgt 10 7.752 ± 0.134 ms/op
+ExpressionSelectorBenchmark.timeFormatUsingExtractionFn 1000000
avgt 10 7.773 ± 0.103 ms/op
```
</details>
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