Add normalizedData option

docs/axes/cartesian/time.md

@@ -35,6 +35,7 @@ The following options are provided by the time scale. You may also set options p
 | `adapters.date` | `object` | `{}` | Options for adapter for external date library if that adapter needs or supports options
 | `distribution` | `string` | `'linear'` | How data is plotted. [more...](#scale-distribution)
 | `bounds` | `string` | `'data'` | Determines the scale bounds. [more...](#scale-bounds)
+| `normalizedData` | `boolean` | `false` | If true, the data is assumed to be unique, sorted, and consistent (i.e. each dataset / labels contain same index values).
 | `ticks.source` | `string` | `'auto'` | How ticks are generated. [more...](#ticks-source)
 | `time.displayFormats` | `object` | | Sets how different time units are displayed. [more...](#display-formats)
 | `time.isoWeekday` | `boolean` | `false` | If true and the unit is set to 'week', then the first day of the week will be Monday. Otherwise, it will be Sunday.

docs/general/performance.md

@@ -42,6 +42,10 @@ There are many approaches to data decimation and selection of an algorithm will
 
 Line charts are able to do [automatic data decimation during draw](#automatic-data-decimation-during-draw), when certain conditions are met. You should still consider decimating data yourself before passing it in for maximum performance since the automatic decimation occurs late in the chart life cycle.
 
+## Time Scale
+
+Provide data that is unique, sorted, and consistent (i.e. each dataset / labels contain same index values) and set `normalizedData: true`
+
 ## Line Charts
 
 ### Disable Bezier Curves

src/scales/scale.time.js

@@ -359,6 +359,7 @@ function ticksFromTimestamps(scale, values, majorUnit) {
 }
 
 function getDataTimestamps(scale) {
+	var options = scale.options;
 	var timestamps = scale._cache.data || [];
 	var i, ilen, metas;
 
@@ -367,6 +368,10 @@ function getDataTimestamps(scale) {
 	}
 
 	metas = scale._getMatchingVisibleMetas();
+	if (options.normalizedData && metas.length) {
+		return (scale._cache.data = metas[0].controller._getAllParsedValues(scale));
+	}
+
 	for (i = 0, ilen = metas.length; i < ilen; ++i) {
 		timestamps = timestamps.concat(metas[i].controller._getAllParsedValues(scale));
 	}
@@ -377,6 +382,7 @@ function getDataTimestamps(scale) {
 }
 
 function getLabelTimestamps(scale) {
+	var options = scale.options;
 	var timestamps = scale._cache.labels || [];
 	var i, ilen, labels;
 
@@ -390,10 +396,11 @@ function getLabelTimestamps(scale) {
 	}
 
 	// We could assume labels are in order and unique - but let's not
-	return (scale._cache.labels = arrayUnique(timestamps.sort(sorter)));
+	return (scale._cache.labels = options.normalizedData ? timestamps : arrayUnique(timestamps.sort(sorter)));
 }
 
 function getAllTimestamps(scale) {
+	var options = scale.options;
 	var timestamps = scale._cache.all || [];
 	var label, data;
 
@@ -403,12 +410,14 @@ function getAllTimestamps(scale) {
 
 	data = getDataTimestamps(scale);
 	label = getLabelTimestamps(scale);
-	if (data.length && label.length) {
+	if (label.length && (!data.length || options.normalizedData)) {
+		timestamps = label;
+	} else if (data.length && label.length) {
 		// If combining labels and data (data might not contain all labels),
 		// we need to recheck uniqueness and sort
 		timestamps = arrayUnique(data.concat(label).sort(sorter));
 	} else {
-		timestamps = data.length ? data : label;
+		timestamps = data;
 	}
 	timestamps = scale._cache.all = timestamps;
 
@@ -498,6 +507,11 @@ const defaultConfig = {
 	 */
 	bounds: 'data',
 
+	/**
+	 * If true, the data is assumed to be unique, sorted, and consistent (i.e. each dataset / labels contain same index values)
+	 */
+	normalizedData: false,
+
 	adapters: {},
 	time: {
 		parser: false, // false == a pattern string from https://momentjs.com/docs/#/parsing/string-format/ or a custom callback that converts its argument to a moment