dssysolyatin commented on PR #4491:
URL: https://github.com/apache/calcite/pull/4491#issuecomment-3164194589
@mihaibudiu @suibianwanwank Please rereview PR
Although I still believe the previous fix was correct in theory, but
`RelToSqlConverter` does some things that, in my opinion, it shouldn’t and such
things should be done by optimizer.
One of such things, that RelToSqlConverter tries to “merge projections” and
it is done using alias propogation which I restricted by my previous fix.
However, since RelToSqlConverter already has this behavior and some users rely
on it, I added a workaround instead. I don’t consider this a proper fix, but at
least it doesn’t break anything.
Some example
If I pass the following plan to `RelToSqlConverter`:
```
LogicalProject(EMPNO=[$0])
LogicalProject(EMPNO=[$0], ENAME=[$1], JOB=[$2], MGR=[$3], HIREDATE=[$4],
SAL=[$5], COMM=[$6], DEPTNO=[$7])
LogicalProject(EMPNO=[$0], ENAME=[$1], JOB=[$2], MGR=[$3],
HIREDATE=[$4], SAL=[$5], COMM=[$6], DEPTNO=[$7])
LogicalTableScan(table=[[scott, EMP]])
```
It generates the following SQL:
```
"SELECT \"EMP\".\"EMPNO\"\n"
+ "FROM \"scott\".\"EMP\" AS \"EMP\""
```
With my previous fix, it produced:
```
"SELECT \”t0\”.\”EMPNO\"\n"
+ "FROM \"scott\".\"EMP\" AS \"EMP\""
```
But t0 doesn’t exist — which is incorrect.
I’ve also added a couple of tests for these cases.
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