From 0fb73ed6226f161efaa79ab750e28768997adaa6 Mon Sep 17 00:00:00 2001
From: Ganesh Vernekar <cs15btech11018@iith.ac.in>
Date: Wed, 14 Feb 2018 19:13:04 +0530
Subject: [PATCH] Changed recursion into iteration for removedPostings.Next()

---
 index/postings.go      | 43 +++++++++++++++++++++---------------------
 index/postings_test.go | 22 +++++++++++++++++++++
 2 files changed, 43 insertions(+), 22 deletions(-)

diff --git a/index/postings.go b/index/postings.go
index f942edaad..53449f341 100644
--- a/index/postings.go
+++ b/index/postings.go
@@ -445,32 +445,31 @@ func (rp *removedPostings) Next() bool {
 		rp.rok = rp.remove.Next()
 		rp.initialized = true
 	}
+	for {
+		if !rp.fok {
+			return false
+		}
 
-	if !rp.fok {
-		return false
-	}
-
-	if !rp.rok {
-		rp.cur = rp.full.At()
-		rp.fok = rp.full.Next()
-		return true
-	}
+		if !rp.rok {
+			rp.cur = rp.full.At()
+			rp.fok = rp.full.Next()
+			return true
+		}
 
-	fcur, rcur := rp.full.At(), rp.remove.At()
-	if fcur < rcur {
-		rp.cur = fcur
-		rp.fok = rp.full.Next()
+		fcur, rcur := rp.full.At(), rp.remove.At()
+		if fcur < rcur {
+			rp.cur = fcur
+			rp.fok = rp.full.Next()
 
-		return true
-	} else if rcur < fcur {
-		// Forward the remove postings to the right position.
-		rp.rok = rp.remove.Seek(fcur)
-	} else {
-		// Skip the current posting.
-		rp.fok = rp.full.Next()
+			return true
+		} else if rcur < fcur {
+			// Forward the remove postings to the right position.
+			rp.rok = rp.remove.Seek(fcur)
+		} else {
+			// Skip the current posting.
+			rp.fok = rp.full.Next()
+		}
 	}
-
-	return rp.Next()
 }
 
 func (rp *removedPostings) Seek(id uint64) bool {
diff --git a/index/postings_test.go b/index/postings_test.go
index 68553e357..9f8f71220 100644
--- a/index/postings_test.go
+++ b/index/postings_test.go
@@ -354,6 +354,28 @@ func TestRemovedPostings(t *testing.T) {
 
 }
 
+func TestRemovedNextStackoverflow(t *testing.T) {
+	var full []uint64
+	var remove []uint64
+
+	var i uint64
+	for i = 0; i < 1e7; i++ {
+		full = append(full, i)
+		remove = append(remove, i)
+	}
+
+	flp := newListPostings(full)
+	rlp := newListPostings(remove)
+	rp := newRemovedPostings(flp, rlp)
+	gotElem := false
+	for rp.Next() {
+		gotElem = true
+	}
+	
+	testutil.Ok(t, rp.Err())
+	testutil.Assert(t, !gotElem, "")
+}
+
 func TestRemovedPostingsSeek(t *testing.T) {
 	var cases = []struct {
 		a, b []uint64