feat(batch,optimizer): support column pruning for iceberg source #16429
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| if required_cols.is_empty() { | ||
| let mapping = ColIndexMapping::with_remaining_columns(required_cols, self.schema().len()); | ||
| // If reuqiured_cols is empty, we use the first column of iceberg to avoid the empty schema. | ||
| LogicalProject::with_mapping(self.clone_with_required_cols(&[0]).into() , mapping).into() |
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So iceberg scan does not support scan no fields? But the RW scan can do it (only the row count is meaningful in this case)
dev=> explain select 1 from t;
QUERY PLAN
-------------------------------------------
BatchExchange { order: [], dist: Single }
└─BatchProject { exprs: [1:Int32] }
└─BatchScan { table: t, columns: [] }
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This is a very corner case, but I am wondering if Iceberg supports creating a table without any columns. It should be possible in PG
postgres=# create table t();
CREATE TABLE
postgres=# \d+ t;
Table "public.t"
Column | Type | Collation | Nullable | Default | Storage | Compression | Stats target | Description
--------+------+-----------+----------+---------+---------+-------------+--------------+-------------
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So iceberg scan does not support scan no fields? But the RW scan can do it (only the row count is meaningful in this case)
Actually, the underlying sdk icelake doesn't handle the empty schema well and it will treat empty schema as all columns are required, so we need to make a trick here.
This is a very corner case, but I am wondering if Iceberg supports creating a table without any columns. It should be possible in PG
Iceberg doesn't support creating a table without any columns.
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What's changed and what's your intention?
Checklist
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