From d0b87ae3b11188c386fdee1c2525d7431e7423a4 Mon Sep 17 00:00:00 2001
From: Naveen Michaud-Agrawal <naveen.michaudagrawal@gmail.com>
Date: Wed, 10 Oct 2018 23:50:44 -0400
Subject: [PATCH 1/2] Computed columns broken with delta updates on
 non-dependent columns

---
 packages/perspective/test/js/constructors.js | 27 ++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/packages/perspective/test/js/constructors.js b/packages/perspective/test/js/constructors.js
index a970f747b4..0d7b78dacb 100644
--- a/packages/perspective/test/js/constructors.js
+++ b/packages/perspective/test/js/constructors.js
@@ -362,6 +362,33 @@ module.exports = perspective => {
             expect(expected).toEqual(result);
         });
 
+        it("Computed column of arity 2 with updates on non-dependent columns", async function() {
+            var meta = {
+                w: "float",
+                x: "float",
+                y: "string",
+                z: "boolean"
+            };
+            var table = perspective.table(meta, {index: "y"});
+            let table2 = table.add_computed([
+                {
+                    column: "ratio",
+                    type: "float",
+                    func: (w, x) => w / x,
+                    inputs: ["w", "x"]
+                }
+            ]);
+
+            table2.update(data_3);
+
+            let delta_upd = [{y: "a", z: false}, {y: "b", z: true}, {y: "c", z: false}, {y: "d", z: true}];
+            table2.update(delta_upd);
+
+            let result = await table2.view({aggregate: [{op: "count", column: "y"}, {op: "count", column: "ratio"}]}).to_json();
+            let expected = [{y: "a", ratio: 1.5}, {y: "b", ratio: 1.25}, {y: "c", ratio: 1.1666666666666667}, {y: "d", ratio: 1.125}];
+            expect(expected).toEqual(result);
+        });
+
         it("String computed column of arity 1", async function() {
             var table = perspective.table(data);
 

From b3d7a498e53ea8b6e9cce59b8e255aeab5037821 Mon Sep 17 00:00:00 2001
From: Naveen Michaud-Agrawal <naveen.michaudagrawal@gmail.com>
Date: Thu, 11 Oct 2018 00:03:10 -0400
Subject: [PATCH 2/2] Don't compute if any dependencies are null

---
 packages/perspective/src/cpp/main.cpp | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/packages/perspective/src/cpp/main.cpp b/packages/perspective/src/cpp/main.cpp
index dc331fe34f..76f39b3b33 100644
--- a/packages/perspective/src/cpp/main.cpp
+++ b/packages/perspective/src/cpp/main.cpp
@@ -780,6 +780,9 @@ sort(t_ctx2_sptr ctx2, val j_sortby) {
  */
 val
 scalar_to_val(const t_tscalar scalar) {
+    if (!scalar.is_valid()) {
+        return val::null();
+    }
     switch (scalar.get_dtype()) {
         case DTYPE_BOOL: {
             if (scalar) {
@@ -934,7 +937,7 @@ table_add_computed_column(t_table_sptr table, t_str name, t_dtype dtype, val fun
 
     t_uindex size = table->size();
     for (t_uindex ridx = 0; ridx < size; ++ridx) {
-        val value = val::null();
+        val value = val::undefined();
 
         switch (arity) {
             case 0: {
@@ -943,20 +946,26 @@ table_add_computed_column(t_table_sptr table, t_str name, t_dtype dtype, val fun
             }
             case 1: {
                 i1 = scalar_to_val(icols[0]->get_scalar(ridx));
-                value = func(i1);
+                if (!i1.isNull()) {
+                    value = func(i1);
+                }
                 break;
             }
             case 2: {
                 i1 = scalar_to_val(icols[0]->get_scalar(ridx));
                 i2 = scalar_to_val(icols[1]->get_scalar(ridx));
-                value = func(i1, i2);
+                if (!i1.isNull() && !i2.isNull()) {
+                    value = func(i1, i2);
+                }
                 break;
             }
             case 3: {
                 i1 = scalar_to_val(icols[0]->get_scalar(ridx));
                 i2 = scalar_to_val(icols[1]->get_scalar(ridx));
                 i3 = scalar_to_val(icols[2]->get_scalar(ridx));
-                value = func(i1, i2, i3);
+                if (!i1.isNull() && !i2.isNull() && !i3.isNull()) {
+                    value = func(i1, i2, i3);
+                }
                 break;
             }
             case 4: {
@@ -964,7 +973,9 @@ table_add_computed_column(t_table_sptr table, t_str name, t_dtype dtype, val fun
                 i2 = scalar_to_val(icols[1]->get_scalar(ridx));
                 i3 = scalar_to_val(icols[2]->get_scalar(ridx));
                 i4 = scalar_to_val(icols[3]->get_scalar(ridx));
-                value = func(i1, i2, i3, i4);
+                if (!i1.isNull() && !i2.isNull() && !i3.isNull() && !i4.isNull()) {
+                    value = func(i1, i2, i3, i4);
+                }
                 break;
             }
             default: {
@@ -973,7 +984,9 @@ table_add_computed_column(t_table_sptr table, t_str name, t_dtype dtype, val fun
             }
         }
 
-        set_column_nth(out, ridx, value);
+        if (!value.isUndefined()) {
+            set_column_nth(out, ridx, value);
+        }
     }
 }