jackwener commented on issue #3864:
URL:
https://github.com/apache/arrow-datafusion/issues/3864#issuecomment-1312516923
Datafusion only can propagate `EmptyRelation` just
`optimizer_config.max_passes` times. Because we depend on multi-passes
optimization to multiply elimination.
In other words, we currently don't have really `EmptyRelationPropagation`.
We can reproduce it.
After 3 optimizations, the plan can continue to be eliminated.
```sql
CREATE TABLE IF NOT EXISTS t1 AS VALUES(1,'HELLO'),(12,'DATAFUSION');
CREATE TABLE IF NOT EXISTS t2 AS VALUES(1,'HELLO'),(12,'DATAFUSION');
CREATE TABLE IF NOT EXISTS t3 AS VALUES(1,'HELLO'),(12,'DATAFUSION');
explain verbose select column1 from t1 join ( select column1 from t2 join
(select column1 from t3 where false ) as ta2 on t2.column1 = ta2.column1 ) as
ta1 on t1.column1 = ta1.column1;
```
The `root` cause is currently optimization is incomplete. We just have
top-down optimize, we don't have bottom-up optimize.
If we have bottom-up optimize, we can do `EmptyRelationPropagation` in once
optimization.
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