tshauck commented on code in PR #8546:
URL: https://github.com/apache/arrow-datafusion/pull/8546#discussion_r1428355818
##########
docs/source/library-user-guide/adding-udfs.md:
##########
@@ -432,3 +433,80 @@ Then, we can query like below:
```rust
let df = ctx.sql("SELECT geo_mean(a) FROM t").await?;
```
+
+## Adding a User-Defined Table Function
+
+A User-Defined Table Function (UDTF) is a function that takes parameters and
returns a `TableProvider`.
+
+Because we're returning a `TableProvider`, in this example we'll use the
`MemTable` data source to represent a table. This is a simple struct that holds
a set of RecordBatches in memory and treats them as a table. In your case, this
would be replaced with your own struct that implements `TableProvider`. See the
[example][4] for a working example that reads from a CSV file.
Review Comment:
Thanks for the feedback! I just pushed
[a090783](https://github.com/apache/arrow-datafusion/pull/8546/commits/a09078367caca6171afa8e9c542490f1f5ac8f80)
which expands a bit on why they're nice and adds the parquet metadata use-case
since it shows why they're nice for interactive analysis.
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