alamb opened a new issue, #10220:
URL: https://github.com/apache/datafusion/issues/10220
### Is your feature request related to a problem or challenge?
In InfluxDB we use `Dictionary(Int32, Utf8)` columns a lot.
Queries like this (with string constants) work great and are very fast
```sql
SELECT ... WHERE column = '1'
```
Queries like this (note `1` is an integer, not a `'1'`) the query goes very
slow
```sql
SELECT ... WHERE column = 1
```
@erratic-pattern and I tracked this down to an issue/ limitation in type
coercion:
## Reproducer
```
DataFusion CLI v37.1.0
> create table test as values (arrow_cast('1', 'Dictionary(Int32, Utf8)'));
0 row(s) fetched.
Elapsed 0.010 seconds.
> select arrow_typeof(column1) from test;
+----------------------------+
| arrow_typeof(test.column1) |
+----------------------------+
| Dictionary(Int32, Utf8) |
+----------------------------+
1 row(s) fetched.
Elapsed 0.002 seconds.
> explain SELECT * from test where column1 = 1;
+---------------+---------------------------------------------------+
| plan_type | plan |
+---------------+---------------------------------------------------+
| logical_plan | Filter: CAST(test.column1 AS Utf8) = Utf8("1") |
| | TableScan: test projection=[column1] |
| physical_plan | CoalesceBatchesExec: target_batch_size=8192 |
| | FilterExec: CAST(column1@0 AS Utf8) = 1 |
| | MemoryExec: partitions=1, partition_sizes=[1] |
| | |
+---------------+---------------------------------------------------+
2 row(s) fetched.
Elapsed 0.003 seconds.
```
I think this shows the core problem:
```
| logical_plan | Filter: CAST(test.column1 AS Utf8) = Utf8("1") |
```
It basically shows the column is being converted to a string, rather than
the constant being converted to th ecorrect type.
Not only does this mean the column is being un-encoded for the comparsion,
it also means that `PruningPredicate` doesn't work either
### Describe the solution you'd like
I would like the query to go fast lol
Specifically, I think the filter should look like this (no cast on the
column, and instead the constant type matches)
```
| logical_plan | Filter: test.column1 = Dictionary(Int32, Utf8("1")) |
```
Note this is what happens if you compare the dictionary column to a string
literal (
```sql
> explain SELECT * from test where column1 = '1';
+---------------+-----------------------------------------------------+
| plan_type | plan |
+---------------+-----------------------------------------------------+
| logical_plan | Filter: test.column1 = Dictionary(Int32, Utf8("1")) |
| | TableScan: test projection=[column1] |
| physical_plan | CoalesceBatchesExec: target_batch_size=8192 |
| | FilterExec: column1@0 = 1 |
| | MemoryExec: partitions=1, partition_sizes=[1] |
| | |
+---------------+-----------------------------------------------------+
2 row(s) fetched.
Elapsed 0.002 seconds.
>
```
### Describe alternatives you've considered
_No response_
### Additional context
_No response_
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