From 1570a5127d35b2ab5b79e68dc939ea3d9f9a0d44 Mon Sep 17 00:00:00 2001
From: Thejas-bhat <thejas.orkombu@couchbase.com>
Date: Tue, 7 Nov 2023 09:47:02 +0530
Subject: [PATCH] index.Delete() to free up memory

---
 faiss_vector_posting.go       |  2 ++
 section_faiss_vector_index.go | 15 +++++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/faiss_vector_posting.go b/faiss_vector_posting.go
index 017c3101..59e193b6 100644
--- a/faiss_vector_posting.go
+++ b/faiss_vector_posting.go
@@ -334,6 +334,8 @@ func (sb *SegmentBase) SimilarVectors(field string, qVector []float32, k int64,
 				return nil, err
 			}
 
+			vecIndex.Delete()
+
 			// for every similar vector returned by the Search() API, add the corresponding
 			// docID and the score to the newly created vecPostingsList
 			for i := 0; i < len(ids); i++ {
diff --git a/section_faiss_vector_index.go b/section_faiss_vector_index.go
index 198a02c3..b22010a0 100644
--- a/section_faiss_vector_index.go
+++ b/section_faiss_vector_index.go
@@ -302,6 +302,8 @@ func (v *vectorIndexOpaque) mergeAndWriteVectorIndexes(fieldID int, sbs []*Segme
 			return err
 		}
 
+		index.Delete()
+
 		fieldStart, err := v.flushVectorSection(vecToDocID, mergedIndexBytes, w)
 		if err != nil {
 			return err
@@ -328,6 +330,8 @@ func (v *vectorIndexOpaque) mergeAndWriteVectorIndexes(fieldID int, sbs []*Segme
 		return err
 	}
 
+	freeReconstructedIndexes(vecIndexes)
+
 	fieldStart, err := v.flushVectorSection(vecToDocID, mergedIndexBytes, w)
 	if err != nil {
 		return err
@@ -336,6 +340,13 @@ func (v *vectorIndexOpaque) mergeAndWriteVectorIndexes(fieldID int, sbs []*Segme
 	return nil
 }
 
+// todo: can be parallelized.
+func freeReconstructedIndexes(vecIndexes []*faiss.IndexImpl) {
+	for _, index := range vecIndexes {
+		index.Delete()
+	}
+}
+
 // todo: is it possible to merge this resuable stuff with the interim's tmp0?
 func (v *vectorIndexOpaque) grabBuf(size int) []byte {
 	buf := v.tmp0
@@ -385,6 +396,10 @@ func (vo *vectorIndexOpaque) writeVectorIndexes(w *CountHashWriter) (offset uint
 			return 0, err
 		}
 
+		// safe to delete the index now since its been serialized and not
+		// referenced anymore
+		index.Delete()
+
 		fieldStart := w.Count()
 		// writing out two offset values to indicate that the current field's
 		// vector section doesn't have valid doc value content within it.