Emit core HNSW index properties in extract summary

README.md

@@ -20,6 +20,15 @@ Optional metadata join from `index_metadata.pickle`:
 - `user_id`
 - `seq_id`
 
+Extract summary also includes `index_properties` sourced from `header.bin`:
+
+- `m`
+- `ef_construction`
+- `cur_element_count`
+- `max_elements`
+- `persisted_version`
+- `word_size_bytes`
+
 Output format:
 
 - `parquet`
@@ -101,7 +110,15 @@ Parquet/Arrow exports.
     "scanned": 10000,
     "emitted": 8000,
     "deleted_skipped": 2000,
-    "dimension": 384
+    "dimension": 384,
+    "index_properties": {
+      "m": 16,
+      "ef_construction": 200,
+      "cur_element_count": 10000,
+      "max_elements": 12000,
+      "persisted_version": 1,
+      "word_size_bytes": 8
+    }
   }
 }
 ```

hnswtoolbox.go

@@ -44,11 +44,21 @@ type ExtractRequest struct {
 	BatchSize      int
 }
 
+type ExtractIndexProperties struct {
+	M                uint64 `json:"m"`
+	EfConstruction   uint64 `json:"ef_construction"`
+	CurElementCount  uint64 `json:"cur_element_count"`
+	MaxElements      uint64 `json:"max_elements"`
+	PersistedVersion int32  `json:"persisted_version"`
+	WordSizeBytes    uint32 `json:"word_size_bytes"`
+}
+
 type ExtractSummary struct {
-	Scanned        uint64 `json:"scanned"`
-	Emitted        uint64 `json:"emitted"`
-	DeletedSkipped uint64 `json:"deleted_skipped"`
-	Dimension      int    `json:"dimension"`
+	Scanned         uint64                 `json:"scanned"`
+	Emitted         uint64                 `json:"emitted"`
+	DeletedSkipped  uint64                 `json:"deleted_skipped"`
+	Dimension       int                    `json:"dimension"`
+	IndexProperties ExtractIndexProperties `json:"index_properties"`
 }
 
 type ExtractResponse struct {

hnswtoolbox_test.go

@@ -0,0 +1,51 @@
+package hnswtoolbox
+
+import (
+	"encoding/json"
+	"testing"
+)
+
+func TestExtractResponseUnmarshalIncludesIndexProperties(t *testing.T) {
+	raw := []byte(`{
+		"output_path": "/tmp/rebuilt.parquet",
+		"output_format": "parquet",
+		"summary": {
+			"scanned": 10000,
+			"emitted": 8000,
+			"deleted_skipped": 2000,
+			"dimension": 384,
+			"index_properties": {
+				"m": 16,
+				"ef_construction": 200,
+				"cur_element_count": 10000,
+				"max_elements": 12000,
+				"persisted_version": 1,
+				"word_size_bytes": 8
+			}
+		}
+	}`)
+
+	var response ExtractResponse
+	if err := json.Unmarshal(raw, &response); err != nil {
+		t.Fatalf("unmarshal extract response: %v", err)
+	}
+
+	if response.Summary.IndexProperties.M != 16 {
+		t.Errorf("M mismatch: got %d", response.Summary.IndexProperties.M)
+	}
+	if response.Summary.IndexProperties.EfConstruction != 200 {
+		t.Errorf("EfConstruction mismatch: got %d", response.Summary.IndexProperties.EfConstruction)
+	}
+	if response.Summary.IndexProperties.CurElementCount != 10000 {
+		t.Errorf("CurElementCount mismatch: got %d", response.Summary.IndexProperties.CurElementCount)
+	}
+	if response.Summary.IndexProperties.MaxElements != 12000 {
+		t.Errorf("MaxElements mismatch: got %d", response.Summary.IndexProperties.MaxElements)
+	}
+	if response.Summary.IndexProperties.PersistedVersion != 1 {
+		t.Errorf("PersistedVersion mismatch: got %d", response.Summary.IndexProperties.PersistedVersion)
+	}
+	if response.Summary.IndexProperties.WordSizeBytes != 8 {
+		t.Errorf("WordSizeBytes mismatch: got %d", response.Summary.IndexProperties.WordSizeBytes)
+	}
+}

src/extractor.rs

@@ -31,12 +31,24 @@ pub struct ExtractOptions {
     pub metadata: Option<HashMap<u64, MetadataEntry>>,
 }
 
+#[derive(Debug, Clone, Serialize)]
+#[serde(rename_all = "snake_case")]
+pub struct ExtractIndexProperties {
+    pub m: u64,
+    pub ef_construction: u64,
+    pub cur_element_count: u64,
+    pub max_elements: u64,
+    pub persisted_version: i32,
+    pub word_size_bytes: u32,
+}
+
 #[derive(Debug, Clone, Serialize)]
 pub struct ExtractSummary {
     pub scanned: u64,
     pub emitted: u64,
     pub deleted_skipped: u64,
     pub dimension: usize,
+    pub index_properties: ExtractIndexProperties,
 }
 
 #[derive(Debug, Clone)]
@@ -131,6 +143,14 @@ where
         emitted: 0,
         deleted_skipped: 0,
         dimension: header.dimension(),
+        index_properties: ExtractIndexProperties {
+            m: header.m,
+            ef_construction: header.ef_construction,
+            cur_element_count: header.cur_element_count,
+            max_elements: header.max_elements,
+            persisted_version: header.persisted_version,
+            word_size_bytes: header.word_size.bytes() as u32,
+        },
     };
 
     let delete_marker_offset = header.delete_marker_offset();
@@ -506,6 +526,12 @@ mod tests {
         assert_eq!(summary.emitted, 2);
         assert_eq!(summary.deleted_skipped, 1);
         assert_eq!(summary.dimension, 3);
+        assert_eq!(summary.index_properties.m, 4);
+        assert_eq!(summary.index_properties.ef_construction, 100);
+        assert_eq!(summary.index_properties.cur_element_count, 3);
+        assert_eq!(summary.index_properties.max_elements, 3);
+        assert_eq!(summary.index_properties.persisted_version, 1);
+        assert_eq!(summary.index_properties.word_size_bytes, 8);
         assert_eq!(out.len(), 2);
         assert_eq!(out[0].label, 10);
         assert_eq!(out[1].label, 30);
@@ -683,6 +709,18 @@ mod tests {
                 summary_without_deleted.deleted_skipped,
                 fixture_records.len() as u64 - expected_non_deleted
             );
+            prop_assert_eq!(summary_without_deleted.index_properties.m, 4);
+            prop_assert_eq!(summary_without_deleted.index_properties.ef_construction, 100);
+            prop_assert_eq!(
+                summary_without_deleted.index_properties.cur_element_count,
+                fixture_records.len() as u64
+            );
+            prop_assert_eq!(
+                summary_without_deleted.index_properties.max_elements,
+                capacity as u64
+            );
+            prop_assert_eq!(summary_without_deleted.index_properties.persisted_version, 1);
+            prop_assert_eq!(summary_without_deleted.index_properties.word_size_bytes, 8);
 
             for exported in &exported_without_deleted {
                 let source = &fixture_records[exported.internal_id as usize];

src/lib.rs

@@ -7,8 +7,8 @@ pub mod metadata;
 
 pub use error::ExtractError;
 pub use extractor::{
-    extract_index, extract_index_to_columnar, ExtractOptions, ExtractSummary, ExtractedRecord,
-    OutputFormat,
+    extract_index, extract_index_to_columnar, ExtractIndexProperties, ExtractOptions,
+    ExtractSummary, ExtractedRecord, OutputFormat,
 };
 pub use header::{HeaderWordSize, PersistentHeader, HNSW_PERSISTENCE_VERSION};
 pub use importer::{