[BUG] Fix I32Array BW compat

rust/blockstore/src/arrow/block/value/int32array_value.rs

@@ -6,7 +6,7 @@ use crate::{
     key::KeyWrapper,
 };
 use arrow::{
-    array::{Array, ListArray, UInt32Array},
+    array::{Array, Int32Array, ListArray, UInt32Array},
     util::bit_util,
 };
 use std::{mem::size_of, sync::Arc};
@@ -50,12 +50,36 @@ impl<'referred_data> ArrowReadableValue<'referred_data> for &'referred_data [u32
         let list_array = array.as_any().downcast_ref::<ListArray>().unwrap();
         let start = list_array.value_offsets()[index] as usize;
         let end = list_array.value_offsets()[index + 1] as usize;
-        let u32array = list_array
-            .values()
-            .as_any()
-            .downcast_ref::<UInt32Array>()
-            .unwrap();
-        &u32array.values()[start..end]
+
+        // 9/17 In order to support backwards compatability before #2729 (https://github.com/chroma-core/chroma/pull/2729)
+        // which had this stored as a Int32Array, we first try to downcast to a UInt32Array and then if that fails
+        // we downcast to a Int32Array, if that fails we panic.
+        let u32array = list_array.values().as_any().downcast_ref::<UInt32Array>();
+        match u32array {
+            Some(u32array) => &u32array.values()[start..end],
+            None => {
+                let i32array = list_array.values().as_any().downcast_ref::<Int32Array>();
+                match i32array {
+                    Some(i32array) => {
+                        // &i32array.values()[start..end] as &[u32]
+                        // We are forced to use unsafe here because we are casting a &[i32] to a &[u32]
+                        // this is safe as of 9/17 ONLY because we use exclusively positive values here,
+                        // we should introduce versioning to the blockfile
+                        // to ensure that this sort of behavior is only done when needed.
+                        // (Yes this is not great :( )
+                        return unsafe {
+                            std::slice::from_raw_parts(
+                                i32array.values()[start..end].as_ptr() as *const u32,
+                                i32array.values()[start..end].len(),
+                            )
+                        };
+                    }
+                    None => panic!(
+                        "Expected UInt32Array or Int32Array (for legacy reasons) got neither"
+                    ),
+                }
+            }
+        }
     }
 
     fn add_to_delta<K: ArrowWriteableKey>(