From 309fc486c47d86776aeec07d86cd04b5d70d97a1 Mon Sep 17 00:00:00 2001
From: Phillip Cloud <417981+cpcloud@users.noreply.github.com>
Date: Mon, 24 Jul 2023 05:47:17 -0700
Subject: [PATCH] feat: expose offset in python API (#437)

---
 datafusion/tests/test_dataframe.py | 11 +++++++++++
 datafusion/tests/test_expr.py      |  8 ++++++++
 src/dataframe.rs                   |  5 +++--
 3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/datafusion/tests/test_dataframe.py b/datafusion/tests/test_dataframe.py
index 4df2061e..78cb50f1 100644
--- a/datafusion/tests/test_dataframe.py
+++ b/datafusion/tests/test_dataframe.py
@@ -115,6 +115,17 @@ def test_limit(df):
     assert len(result.column(1)) == 1
 
 
+def test_limit_with_offset(df):
+    # only 3 rows, but limit past the end to ensure that offset is working
+    df = df.limit(5, offset=2)
+
+    # execute and collect the first (and only) batch
+    result = df.collect()[0]
+
+    assert len(result.column(0)) == 1
+    assert len(result.column(1)) == 1
+
+
 def test_with_column(df):
     df = df.with_column("c", column("a") + column("b"))
 
diff --git a/datafusion/tests/test_expr.py b/datafusion/tests/test_expr.py
index 0c4869f2..73f7d087 100644
--- a/datafusion/tests/test_expr.py
+++ b/datafusion/tests/test_expr.py
@@ -81,6 +81,14 @@ def test_limit(test_ctx):
 
     plan = plan.to_variant()
     assert isinstance(plan, Limit)
+    assert plan.skip() == 0
+
+    df = test_ctx.sql("select c1 from test LIMIT 10 OFFSET 5")
+    plan = df.logical_plan()
+
+    plan = plan.to_variant()
+    assert isinstance(plan, Limit)
+    assert plan.skip() == 5
 
 
 def test_aggregate_query(test_ctx):
diff --git a/src/dataframe.rs b/src/dataframe.rs
index 00c12e85..b8d8ddc3 100644
--- a/src/dataframe.rs
+++ b/src/dataframe.rs
@@ -136,8 +136,9 @@ impl PyDataFrame {
         Ok(Self::new(df))
     }
 
-    fn limit(&self, count: usize) -> PyResult<Self> {
-        let df = self.df.as_ref().clone().limit(0, Some(count))?;
+    #[pyo3(signature = (count, offset=0))]
+    fn limit(&self, count: usize, offset: usize) -> PyResult<Self> {
+        let df = self.df.as_ref().clone().limit(offset, Some(count))?;
         Ok(Self::new(df))
     }