some progress

node_modules/mongoose/lib/helpers/indexes/getRelatedIndexes.js

@@ -0,0 +1,59 @@
+'use strict';
+
+function getRelatedSchemaIndexes(model, schemaIndexes) {
+  return getRelatedIndexes({
+    baseModelName: model.baseModelName,
+    discriminatorMapping: model.schema.discriminatorMapping,
+    indexes: schemaIndexes,
+    indexesType: 'schema'
+  });
+}
+
+function getRelatedDBIndexes(model, dbIndexes) {
+  return getRelatedIndexes({
+    baseModelName: model.baseModelName,
+    discriminatorMapping: model.schema.discriminatorMapping,
+    indexes: dbIndexes,
+    indexesType: 'db'
+  });
+}
+
+module.exports = {
+  getRelatedSchemaIndexes,
+  getRelatedDBIndexes
+};
+
+function getRelatedIndexes({
+  baseModelName,
+  discriminatorMapping,
+  indexes,
+  indexesType
+}) {
+  const discriminatorKey = discriminatorMapping && discriminatorMapping.key;
+  const discriminatorValue = discriminatorMapping && discriminatorMapping.value;
+
+  if (!discriminatorKey) {
+    return indexes;
+  }
+
+  const isChildDiscriminatorModel = Boolean(baseModelName);
+  if (isChildDiscriminatorModel) {
+    return indexes.filter(index => {
+      const partialFilterExpression = getPartialFilterExpression(index, indexesType);
+      return partialFilterExpression && partialFilterExpression[discriminatorKey] === discriminatorValue;
+    });
+  }
+
+  return indexes.filter(index => {
+    const partialFilterExpression = getPartialFilterExpression(index, indexesType);
+    return !partialFilterExpression || !partialFilterExpression[discriminatorKey];
+  });
+}
+
+function getPartialFilterExpression(index, indexesType) {
+  if (indexesType === 'schema') {
+    const options = index[1];
+    return options && options.partialFilterExpression;
+  }
+  return index.partialFilterExpression;
+}