Fix: optimize projections for unnest logical plan. sqllogictest adapted

Author: Bert Vermeiren

datafusion/sqllogictest/test_files/push_down_filter.slt

@@ -39,9 +39,9 @@ physical_plan
 01)ProjectionExec: expr=[__unnest_placeholder(v.column2,depth=1)@0 as uc2]
 02)--UnnestExec
 03)----RepartitionExec: partitioning=RoundRobinBatch(4), input_partitions=1
-04)------ProjectionExec: expr=[column2@1 as __unnest_placeholder(v.column2), column1@0 as column1]
+04)------ProjectionExec: expr=[column2@0 as __unnest_placeholder(v.column2)]
 05)--------CoalesceBatchesExec: target_batch_size=8192
-06)----------FilterExec: column1@0 = 2
+06)----------FilterExec: column1@0 = 2, projection=[column2@1]
 07)------------DataSourceExec: partitions=1, partition_sizes=[1]
 
 query I
@@ -59,10 +59,9 @@ physical_plan
 02)--CoalesceBatchesExec: target_batch_size=8192
 03)----FilterExec: __unnest_placeholder(v.column2,depth=1)@0 > 3
 04)------RepartitionExec: partitioning=RoundRobinBatch(4), input_partitions=1
-05)--------ProjectionExec: expr=[__unnest_placeholder(v.column2,depth=1)@0 as __unnest_placeholder(v.column2,depth=1)]
-06)----------UnnestExec
-07)------------ProjectionExec: expr=[column2@1 as __unnest_placeholder(v.column2), column1@0 as column1]
-08)--------------DataSourceExec: partitions=1, partition_sizes=[1]
+05)--------UnnestExec
+06)----------ProjectionExec: expr=[column2@0 as __unnest_placeholder(v.column2)]
+07)------------DataSourceExec: partitions=1, partition_sizes=[1]
 
 query II
 select uc2, column1 from  (select unnest(column2) as uc2, column1 from v) where uc2 > 3 AND column1 = 2;