merge cmc/datastore/get_a_single_row (#590)

crates/re_arrow_store/benches/data_store.rs

@@ -1,7 +1,7 @@
 #[global_allocator]
 static GLOBAL: mimalloc::MiMalloc = mimalloc::MiMalloc;
 
-use arrow2::array::{Array, ListArray, StructArray};
+use arrow2::array::{Array, StructArray};
 use criterion::{criterion_group, criterion_main, Criterion};
 
 use re_arrow_store::{DataStore, TimeQuery, TimelineQuery};
@@ -89,9 +89,7 @@ fn query_messages(store: &mut DataStore) -> Box<dyn Array> {
     let mut results = store.get(&[component], &row_indices);
 
     let row = std::mem::take(&mut results[0]).unwrap();
-    let list = row.as_any().downcast_ref::<ListArray<i32>>().unwrap();
-    let rects = list.value(0);
-    let rects = rects.as_any().downcast_ref::<StructArray>().unwrap();
+    let rects = row.as_any().downcast_ref::<StructArray>().unwrap();
     assert_eq!(NUM_RECTS as usize, rects.len());
 
     row

crates/re_arrow_store/src/store_read.rs

@@ -1,7 +1,7 @@
 use std::sync::atomic::Ordering;
 
 use arrow2::{
-    array::{Array, Int64Array, MutableArray, UInt64Array, UInt64Vec},
+    array::{Array, Int64Array, ListArray, MutableArray, UInt64Array, UInt64Vec},
     datatypes::{DataType, TimeUnit},
 };
 
@@ -110,8 +110,7 @@ impl DataStore {
     ///             .map(|(&component, col)| Series::try_from((component, col)).unwrap())
     ///             .collect();
     ///
-    ///         let df = DataFrame::new(series).unwrap();
-    ///         df.explode(df.get_column_names()).unwrap()
+    ///         DataFrame::new(series).unwrap()
     ///     };
     ///
     ///     df
@@ -581,10 +580,15 @@ impl ComponentBucket {
         &self.name
     }
 
-    // Panics on out-of-bounds
+    /// Returns a shallow clone of the row data for the given `row_idx`.
     pub fn get(&self, row_idx: RowIndex) -> Box<dyn Array> {
         let row_idx = row_idx.as_u64() - self.row_offset.as_u64();
-        self.data.slice(row_idx as usize, 1)
+        let rows = self.data.slice(row_idx as usize, 1);
+        // This has to be safe to unwrap, otherwise it would never have made it past insertion.
+        rows.as_any()
+            .downcast_ref::<ListArray<i32>>()
+            .unwrap()
+            .value(0)
     }
 
     /// Returns the entire data Array in this component

crates/re_arrow_store/tests/data_store.rs

@@ -739,8 +739,7 @@ impl DataTracker {
                 })
                 .collect::<Vec<_>>();
 
-            let df = DataFrame::new(series).unwrap();
-            df.explode(df.get_column_names()).unwrap()
+            DataFrame::new(series).unwrap()
         };
 
         let series = expected
@@ -797,8 +796,7 @@ impl DataTracker {
                 .map(|(&component, col)| Series::try_from((component, col)).unwrap())
                 .collect();
 
-            let df = DataFrame::new(series).unwrap();
-            df.explode(df.get_column_names()).unwrap()
+            DataFrame::new(series).unwrap()
         };
 
         df

crates/re_query/src/query.rs

@@ -72,10 +72,7 @@ pub fn get_component_with_instances(
         .map(|(&component, col)| Series::try_from((component, col)))
         .collect();
 
-    let df = DataFrame::new(series?)?;
-    let exploded = df.explode(df.get_column_names())?;
-
-    Ok(exploded)
+    DataFrame::new(series?).map_err(Into::into)
 }
 
 /// If a `DataFrame` has no `Instance` column create one from the row numbers