andygrove commented on a change in pull request #923:
URL: https://github.com/apache/arrow-datafusion/pull/923#discussion_r694009745
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File path: datafusion/src/dataframe.rs
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@@ -223,6 +223,21 @@ pub trait DataFrame: Send + Sync {
/// ```
async fn collect(&self) -> Result<Vec<RecordBatch>>;
+ /// Print results.
+ ///
+ /// ```
+ /// # use datafusion::prelude::*;
+ /// # use datafusion::error::Result;
+ /// # #[tokio::main]
+ /// # async fn main() -> Result<()> {
+ /// let mut ctx = ExecutionContext::new();
+ /// let df = ctx.read_csv("tests/example.csv", CsvReadOptions::new())?;
+ /// df.show().await?;
+ /// # Ok(())
+ /// # }
+ /// ```
+ async fn show(&self) -> Result<()>;
Review comment:
Sorry to be a pain but this seems confusing to me and maybe it would be
better to revert to your original code and document that the user can limit
output by using `df.limit(20).show()`. Alternatively, we could add a
`show_limit(limit: usize)` alternate method where the user can specify how many
rows they would like.
The issue I have with this is that it shows 20 rows by default and if the
user wants more then they need to add a limit, which is counterintuitive
because limit normally reduces the number of rows. Also, this code only works
if the final operator is a limit, so it won't work constantly if the limit is
wrapped in a sort, for example.
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