Optimize selection functions for ID-only stores.

packages/vega-selections/src/constants.js

@@ -1,6 +1,11 @@
+import {field} from 'vega-util';
+
 export const Intersect = 'intersect';
 export const Union = 'union';
 export const VlMulti = 'vlMulti';
 export const VlPoint = 'vlPoint';
 export const Or = 'or';
 export const And = 'and';
+
+export const SelectionId = '_vgsid_';
+export const $selectionId = field(SelectionId);

packages/vega-selections/src/selectionResolve.js

@@ -1,5 +1,6 @@
-import {And, Or, Union, VlMulti, VlPoint} from './constants';
+import {intersection, union} from 'd3-array';
 import {array, toNumber} from 'vega-util';
+import {$selectionId, And, Or, SelectionId, Union, VlMulti, VlPoint} from './constants';
 
 /**
  * Resolves selection for use as a scale domain or reads via the API.
@@ -18,7 +19,7 @@ export function selectionResolve(name, op, isMulti, vl5) {
   var data = this.context.data[name],
     entries = data ? data.values.value : [],
     resolved = {}, multiRes = {}, types = {},
-    entry, fields, values, unit, field, res, resUnit, type, union,
+    entry, fields, values, unit, field, value, res, resUnit, type, union,
     n = entries.length, i = 0, j, m;
 
   // First union all entries within the same unit.
@@ -28,34 +29,51 @@ export function selectionResolve(name, op, isMulti, vl5) {
     fields = entry.fields;
     values = entry.values;
 
-    for (j = 0, m = fields.length; j < m; ++j) {
-      field = fields[j];
-      res = resolved[field.field] || (resolved[field.field] = {});
+    if (fields && values) { // Intentional selection stores
+      for (j = 0, m = fields.length; j < m; ++j) {
+        field = fields[j];
+        res = resolved[field.field] || (resolved[field.field] = {});
+        resUnit = res[unit] || (res[unit] = []);
+        types[field.field] = type = field.type.charAt(0);
+        union = ops[`${type}_union`];
+        res[unit] = union(resUnit, array(values[j]));
+      }
+
+      // If the same multi-selection is repeated over views and projected over
+      // an encoding, it may operate over different fields making it especially
+      // tricky to reliably resolve it. At best, we can de-dupe identical entries
+      // but doing so may be more computationally expensive than it is worth.
+      // Instead, for now, we simply transform our store representation into
+      // a more human-friendly one.
+      if (isMulti) {
+        resUnit = multiRes[unit] || (multiRes[unit] = []);
+        resUnit.push(array(values).reduce((obj, curr, j) => (obj[fields[j].field] = curr, obj), {}));
+      }
+    } else {  // Short circuit extensional selectionId stores which hold sorted IDs unique to each unit.
+      field = SelectionId;
+      value = $selectionId(entry);
+      res = resolved[field] || (resolved[field] = {});
       resUnit = res[unit] || (res[unit] = []);
-      types[field.field] = type = field.type.charAt(0);
-      union = ops[type + '_union'];
-      res[unit] = union(resUnit, array(values[j]));
-    }
+      resUnit.push(value);
 
-    // If the same multi-selection is repeated over views and projected over
-    // an encoding, it may operate over different fields making it especially
-    // tricky to reliably resolve it. At best, we can de-dupe identical entries
-    // but doing so may be more computationally expensive than it is worth.
-    // Instead, for now, we simply transform our store representation into
-    // a more human-friendly one.
-    if (isMulti) {
-      resUnit = multiRes[unit] || (multiRes[unit] = []);
-      resUnit.push(array(values).reduce((obj, curr, j) => (obj[fields[j].field] = curr, obj), {}));
+      if (isMulti) {
+        resUnit = multiRes[unit] || (multiRes[unit] = []);
+        resUnit.push({[SelectionId]: value});
+      }
     }
   }
 
   // Then resolve fields across units as per the op.
   op = op || Union;
-  Object.keys(resolved).forEach(field => {
-    resolved[field] = Object.keys(resolved[field])
-      .map(unit => resolved[field][unit])
-      .reduce((acc, curr) => acc === undefined ? curr : ops[types[field] + '_' + op](acc, curr));
-  });
+  if (resolved[SelectionId]) {
+    resolved[SelectionId] = ops[`${SelectionId}_${op}`](...Object.values(resolved[SelectionId]));
+  } else {
+    Object.keys(resolved).forEach(field => {
+      resolved[field] = Object.keys(resolved[field])
+        .map(unit => resolved[field][unit])
+        .reduce((acc, curr) => acc === undefined ? curr : ops[`${types[field]}_${op}`](acc, curr));
+    });
+  }
 
   entries = Object.keys(multiRes);
   if (isMulti && entries.length) {
@@ -69,6 +87,9 @@ export function selectionResolve(name, op, isMulti, vl5) {
 }
 
 var ops = {
+  [`${SelectionId}_union`]: union,
+  [`${SelectionId}_intersect`]: intersection,
+
   E_union: function(base, value) {
     if (!base.length) return value;
 

packages/vega-selections/src/selectionTest.js

@@ -1,9 +1,8 @@
 import {bisector} from 'd3-array';
-import {Intersect} from './constants';
+import {$selectionId, Intersect} from './constants';
 import {field, inrange, isArray, isDate, toNumber} from 'vega-util';
 
-const SELECTION_ID = '_vgsid_',
-    TYPE_ENUM = 'E',
+const TYPE_ENUM = 'E',
     TYPE_RANGE_INC = 'R',
     TYPE_RANGE_EXC = 'R-E',
     TYPE_RANGE_LE = 'R-LE',
@@ -105,8 +104,7 @@ export function selectionTest(name, datum, op) {
   return n && intersect;
 }
 
-const selectionId = field(SELECTION_ID),
-  bisect = bisector(selectionId),
+const bisect = bisector($selectionId),
   bisectLeft = bisect.left,
   bisectRight = bisect.right;
 
@@ -115,11 +113,11 @@ export function selectionIdTest(name, datum, op) {
       entries = data ? data.values.value : [],
       unitIdx = data ? data[UNIT_INDEX] && data[UNIT_INDEX].value : undefined,
       intersect = op === Intersect,
-      value = selectionId(datum),
+      value = $selectionId(datum),
       index = bisectLeft(entries, value);
 
   if (index === entries.length) return false;
-  if (selectionId(entries[index]) !== value) return false;
+  if ($selectionId(entries[index]) !== value) return false;
 
   if (unitIdx && intersect) {
     if (unitIdx.size === 1) return true;

packages/vega-selections/src/selectionTuples.js

@@ -1,14 +1,18 @@
 import {extend, field} from 'vega-util';
+import {$selectionId, SelectionId} from './constants';
 
 /**
  * Maps an array of scene graph items to an array of selection tuples.
  * @param {string} name  - The name of the dataset representing the selection.
- * @param {string} unit  - The name of the unit view.
+ * @param {string} base  - The base object that generated tuples extend.
  *
  * @returns {array} An array of selection entries for the given unit.
  */
 export function selectionTuples(array, base) {
-  return array.map(x => extend({
-    values: base.fields.map(f => (f.getter || (f.getter = field(f.field)))(x.datum))
-  }, base));
+  return array.map(x => extend(
+    base.fields ? {
+      values: base.fields.map(f => (f.getter || (f.getter = field(f.field)))(x.datum))
+    } : {
+      [SelectionId]: $selectionId(x.datum)
+    }, base));
 }

packages/vega-selections/src/selectionVisitor.js

@@ -23,4 +23,4 @@ export function selectionVisitor(name, args, scope, params) {
   if (!hasOwnProperty(params, dataName)) {
     params[dataName] = scope.getData(data).tuplesRef();
   }
-}
+}