fix the field distribution when upgrading from the v1_12

crates/milli/src/update/upgrade/v1_12.rs

@@ -0,0 +1,29 @@
+use heed::RwTxn;
+
+use crate::{make_enum_progress, Result};
+
+use crate::{progress::Progress, Index};
+
+// The field distribution was not computed correctly in the v1.12 until the v1.12.3
+pub(super) fn v1_12_to_v1_12_3(
+    wtxn: &mut RwTxn,
+    index: &Index,
+    progress: Progress,
+) -> Result<bool> {
+    make_enum_progress! {
+        enum FieldDistribution {
+            RebuildingFieldDistribution,
+        }
+    };
+    progress.update_progress(FieldDistribution::RebuildingFieldDistribution);
+    crate::update::new::reindex::field_distribution(index, wtxn, &progress)?;
+    Ok(true)
+}
+
+pub(super) fn v1_12_3_to_v1_13(
+    _wtxn: &mut RwTxn,
+    _index: &Index,
+    _progress: Progress,
+) -> Result<bool> {
+    Ok(false)
+}