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[hotfix] Add some guide to debug sql planner and code generator #480

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[hotfix] Add some guide to debug sql planner and code generator #480

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38 changes: 38 additions & 0 deletions contributing/code-style-and-quality-components.md
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Expand Up @@ -123,6 +123,44 @@ Avoid full integration tests
* Instead, use unit tests that validate the optimized plan which comes out of a planner. Or test the behavior of a runtime operator directly.


#### Debug the planner

When working on planner rules, It's useful to investigate which rules are applied, in which order and what transformation every rule generates.
In order to find out these details when running a planner test, you can enable the Calcite planner logging in debug mode adding the following lines to the log configuration in `flink-table/flink-table-planner/src/test/resources/log4j2-test.properties`:

```
loggers = testlogger
logger.testlogger.name = org.apache.calcite.plan
logger.testlogger.level = DEBUG
logger.testlogger.appenderRefs = TestLogger
```

This is a sample output:

```
[...]
3855 [main] DEBUG org.apache.calcite.plan.RelOptPlanner [] - call#1: Apply rule [FlinkJoinPushExpressionsRule] to [rel#40:LogicalJoin.NONE.any.None: 0.[NONE].[NONE](left=HepRelVertex#34,right=HepRelVertex#39,condition=AND(=($0, $5), >=($3, -($8, 3600000:INTERVAL HOUR)), <=($3, +($8, 3600000:INTERVAL HOUR))),joinType=inner)]
3855 [main] DEBUG org.apache.calcite.plan.AbstractRelOptPlanner.rule_execution_summary [] - Rule Attempts Info for HepPlanner
3856 [main] DEBUG org.apache.calcite.plan.AbstractRelOptPlanner.rule_execution_summary [] -
Rules Attempts Time (us)
FlinkJoinPushExpressionsRule 1 143
* Total 1 143
[...]
```


#### Debug the code generator

In a similar fashion to the planner debugging, you can debug the result of every code generation step enabling the logger, adding the following lines to the log configuration in `flink-table/flink-table-planner/src/test/resources/log4j2-test.properties`:

```
loggers = testlogger
logger.testlogger.name = org.apache.flink.table.planner.codegen
logger.testlogger.level = TRACE
logger.testlogger.appenderRefs = TestLogger
```


#### Compatibility

Don’t introduce physical plan changes in minor releases!
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