[GitHub] [arrow-datafusion] francis-du opened a new pull request #942: [Python] - Support show function for DataFrame api of python library

[GitBox <gi...@apache.org>]

francis-du opened a new pull request #942:
URL: https://github.com/apache/arrow-datafusion/pull/942


   # Which issue does this PR close?
   
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   Closes #941
   
    # Rationale for this change
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   # What changes are included in this PR?
   <!--
   There is no need to duplicate the description in the issue here but it is sometimes worth providing a summary of the individual changes in this PR.
   -->
   
   Add `show` function for DataFrame api of python library
   
   # Are there any user-facing changes?
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   If there are user-facing changes then we may require documentation to be updated before approving the PR.
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   <!--
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   Users can directly print the query results by calling the show function.
   
   ```python
   import pyarrow as pa
   from datafusion import ExecutionContext
   
   ctx = ExecutionContext()
   
   batch = pa.RecordBatch.from_arrays(
       [pa.array([1, 2, 3]), pa.array([4, 5, 6])],
       names=["a", "b"],
   )
   
   df = ctx.create_dataframe([[batch]])
   df.show()
   
   ```
   
   Result
   
   ```
   +---+---+
   | a | b |
   +---+---+
   | 1 | 4 |
   | 2 | 5 |
   | 3 | 6 |
   +---+---+
   ```


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[GitHub] [arrow-datafusion] houqp merged pull request #942: [Python] - Support show function for DataFrame api of python library

[GitBox <gi...@apache.org>]

houqp merged pull request #942:
URL: https://github.com/apache/arrow-datafusion/pull/942


   


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[GitHub] [arrow-datafusion] andygrove commented on a change in pull request #942: [Python] - Support show function for DataFrame api of python library

[GitBox <gi...@apache.org>]

andygrove commented on a change in pull request #942:
URL: https://github.com/apache/arrow-datafusion/pull/942#discussion_r697431047



##########
File path: python/src/dataframe.rs
##########
@@ -139,6 +140,30 @@ impl DataFrame {
         to_py::to_py(&batches)
     }
 
+    /// Print the result, 20 lines by default
+    #[args(num = "20")]
+    fn show(&self, py: Python, num: usize) -> PyResult<()> {
+        let ctx = _ExecutionContext::from(self.ctx_state.clone());
+        let plan = ctx
+            .optimize(&self.limit(num)?.plan)
+            .map_err(|e| -> errors::DataFusionError { e.into() })?;
+        let plan = ctx
+            .create_physical_plan(&plan)
+            .map_err(|e| -> errors::DataFusionError { e.into() })?;

Review comment:
       You can chain these together to reduce the error handling code.
   
   ```suggestion
           let plan = ctx
               .optimize(&self.limit(num)?.plan)
               .and_then(|plan| ctx.create_physical_plan(&plan))
               .map_err(|e| -> errors::DataFusionError { e.into() })?;
   ```




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