From e2e0d3edcba13ecfbe055cbe1ea43a2b35579971 Mon Sep 17 00:00:00 2001
From: jheer <jeffrey.heer@gmail.com>
Date: Tue, 21 Sep 2021 13:13:29 -0700
Subject: [PATCH] fix: Fix early termination for filtered table scans. (#235)

---
 src/table/table.js              |  2 +-
 test/table/column-table-test.js | 27 +++++++++++++++++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/src/table/table.js b/src/table/table.js
index b05c8532..8d4b94f1 100644
--- a/src/table/table.js
+++ b/src/table/table.js
@@ -440,7 +440,7 @@ export default class Table extends Transformable {
       }
     } else if (filter) {
       let c = n - i + 1;
-      for (i = filter.nth(i); --c; i = filter.next(i + 1)) {
+      for (i = filter.nth(i); --c && i > -1; i = filter.next(i + 1)) {
         fn(i, data, stop);
       }
     } else {
diff --git a/test/table/column-table-test.js b/test/table/column-table-test.js
index 48f0170b..d10cf0ea 100644
--- a/test/table/column-table-test.js
+++ b/test/table/column-table-test.js
@@ -104,6 +104,33 @@ tape('ColumnTable scan supports filtering and ordering', t => {
   t.end();
 });
 
+tape('ColumnTable scan supports early termination', t => {
+  const table = new ColumnTable({
+    a: ['a', 'a', 'a', 'b', 'b'],
+    b: [2, 1, 4, 5, 3]
+  });
+
+  let count;
+  const visitor = (row, data, stop) => { if (++count > 1) stop(); };
+
+  count = 0;
+  table.scan(visitor, true);
+  t.equal(count, 2, 'standard scan');
+
+  count = 0;
+  const filter = new BitSet(5);
+  [1, 2, 4].forEach(i => filter.set(i));
+  table.create({ filter }).scan(visitor, true);
+  t.equal(count, 2, 'filtered scan');
+
+  count = 0;
+  const order = (u, v, { b }) => b.get(u) - b.get(v);
+  table.create({ order }).scan(visitor, true);
+  t.equal(count, 2, 'ordered scan');
+
+  t.end();
+});
+
 tape('ColumnTable memoizes indices', t => {
   const ut = new ColumnTable({ v: [1, 3, 2] });
   const ui = ut.indices(false);