Move the facet extraction to dedicated modules

milli/src/update/new/extract/faceted/facet_document.rs

@@ -0,0 +1,51 @@
+use serde_json::Value;
+
+use crate::update::new::KvReaderFieldId;
+use crate::{FieldId, GlobalFieldsIdsMap, InternalError, Result, UserError};
+
+pub fn extract_document_facets(
+    attributes_to_extract: &[&str],
+    obkv: &KvReaderFieldId,
+    field_id_map: &mut GlobalFieldsIdsMap,
+    facet_fn: &mut impl FnMut(FieldId, &Value) -> Result<()>,
+) -> Result<()> {
+    let mut field_name = String::new();
+    for (field_id, field_bytes) in obkv {
+        let Some(field_name) = field_id_map.name(field_id).map(|s| {
+            field_name.clear();
+            field_name.push_str(s);
+            &field_name
+        }) else {
+            unreachable!("field id not found in field id map");
+        };
+
+        let mut tokenize_field = |name: &str, value: &Value| match field_id_map.id_or_insert(name) {
+            Some(field_id) => facet_fn(field_id, value),
+            None => Err(UserError::AttributeLimitReached.into()),
+        };
+
+        // if the current field is searchable or contains a searchable attribute
+        if perm_json_p::select_field(field_name, Some(attributes_to_extract), &[]) {
+            // parse json.
+            match serde_json::from_slice(field_bytes).map_err(InternalError::SerdeJson)? {
+                Value::Object(object) => perm_json_p::seek_leaf_values_in_object(
+                    &object,
+                    Some(attributes_to_extract),
+                    &[], // skip no attributes
+                    field_name,
+                    &mut tokenize_field,
+                )?,
+                Value::Array(array) => perm_json_p::seek_leaf_values_in_array(
+                    &array,
+                    Some(attributes_to_extract),
+                    &[], // skip no attributes
+                    field_name,
+                    &mut tokenize_field,
+                )?,
+                value => tokenize_field(field_name, &value)?,
+            }
+        }
+    }
+
+    Ok(())
+}